The Danish health care system and epidemiological research: from health care contacts to database records

The mediating role of effective treatments in the relationship between income level and survival in patients with heart failure: a sex- and cohabitation-stratified study

AIMS 

Patients with heart failure and low income have a high mortality risk. We examined whether lower survival among low-income patients with heart failure could be explained by different use of β -blockers, renin-angiotensin system inhibitors (RASi), and implanted devices compared with high-income patients.

METHODS AND RESULTS 

We linked Danish national registries to identify patients with new-onset heart failure between 2005 and 2016. A total of 18 308 patients was included in the main analysis. We collected information on medical treatment and device therapy after discharge. We investigated the remaining income disparity if everybody had the same probability of treatment as the high-income patients. We used causal mediation analysis to examine to what extent treatment differences mediate the association between income and 1-year mortality in strata defined by sex and cohabitation status. If low-income patients had the same probability of initiating β-blockers and RASi treatment as high-income patients, low-income men who lived alone would increase initiation of treatment by 12.4% (CI: 10.0% to 14.9%) and as a result reduce their absolute 1-year mortality by 1.0% (CI: -1.4% to -0.5%). If low-income patients had the same probability of not having breaks in medical treatment and getting device therapy, as high-income patients, low-income patients would increase the probability of not having breaks in treatment between 1.8% and 5.8% and increase the probability of getting device therapy between 1.0% and 3.8%, across strata of sex and cohabitation status.

CONCLUSION 

Lower rates of treatment initiation appear to mediate the poorer survival seen among patients with heart failure and low income, but only in males living alone.

Existing Data Sources in Clinical Epidemiology: The Danish COVID-19 Cohort

Background

To facilitate research on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a prospective cohort of all Danish residents tested for SARS-CoV-2 in Denmark is established.

Data Structure

All Danish residents tested by reverse transcriptase polymerase chain reactions (RT-PCR) for SARS-CoV-2 in Denmark are included. The cohort is identified using the Danish Microbiology Database. Individual-level record linkage between administrative and health-care registries is facilitated by the Danish Civil Registration System. Information on outcomes related to SARS-CoV-2 infection includes hospital admission, intensive care unit admission, mechanical ventilation, and death and is retrieved from the five administrative Danish regions, the Danish National Patient Registry, and the Danish Register of Causes of Death. The Patient Registry further provides a complete hospital contact history of somatic and psychiatric conditions and procedures. Data on all prescriptions filled at community pharmacies are available from the Danish National Prescription Registry. Health-care authorization status is obtained from the Danish Register of Healthcare Professionals. Finally, selected laboratory values are obtained from the Register of Laboratory Results for Research. The cohort is governed by a steering committee with representatives from the Danish Medicines Agency, Statens Serum Institut, the Danish Health Authority, the Danish Health Data Authority, Danish Patients, the Faculties of Health Sciences at the Danish universities, and Danish regions. The steering committee welcomes suggestions for research studies and collaborations. Research proposals will be prioritized based on timeliness and potential clinical and public health implications. All research protocols assessing specific hypotheses for medicines will be made publicly available using the European Union electronic Register of Post-Authorisation Studies.

Conclusion

The Danish COVID-19 cohort includes all Danish residents with an RT-PCR test for SARS-CoV-2. Through individual-level linkage with existing Danish health and administrative registries, this is a valuable data source for epidemiological research on SARS-CoV-2.

Inequalities in heart failure care in a tax-financed universal healthcare system: a nationwide population-based cohort study

Aims

Data on socioeconomic‐related differences in heart failure (HF) care are sparse. Inequality in care may potentially contribute to a poor clinical outcome. We examined socioeconomic‐related differences in quality of HF care among patients with incident HF with reduced ejection fraction (EF) (HFrEF).

Methods and results

We conducted a nationwide population‐based cohort study among patients with HFrEF (EF ≤40%) registered from January 2008 to October 2015 in the Danish Heart Failure Registry, a nationwide registry of patients with a first‐time primary HF diagnosis. Associations between individual‐level socioeconomic factors (cohabitation status, education, and family income) and the quality of HF care defined by six guideline‐recommended process performance measures [New York Heart Association (NYHA) classification, treatment with angiotensin‐converting‐enzyme inhibitors (ACEI)/angiotensin receptor blockers (ARB), beta‐blockers and mineralocorticoid receptor antagonists, exercise training, and patient education] were assessed using multiple imputation and multivariable logistic regression controlling for potential confounders. Among 17 122 HFrEF patients included, 15 290 patients had data on all six process performance measures. Living alone was associated with lower odds of NYHA classification [adjusted OR (aOR) 0.81; 95% confidence interval (CI): 0.72–0.90], prescription of ACEI/ARB (aOR 0.76; 95% CI: 0.68–0.88) and beta‐blockers (aOR 0.84; 95% CI: 0.76–0.93), referral to exercise training (aOR 0.75; 95% CI: 0.69–0.81), and patient education (aOR 0.73; 95% CI: 0.67–0.80). Compared with high‐level education, low‐level education was associated with lower odds of NYHA classification (aOR 0.93; 95% CI: 0.79–1.11), treatment with ACEI/ARB (aOR 0.99; 95% CI: 0.81–1.20) and beta‐blockers (aOR 0.93; 95% CI: 0.79–1.09), referral to exercise training (aOR 0.73; 95% CI: 0.65–0.82), and patient education (aOR 0.86, 95% CI: 0.75–0.98). An income in the lowest tertile was associated with lower odds of NYHA classification (aOR 0.67; 95% CI: 0.58–0.79), prescription of ACEI/ARB (aOR 0.80, 95% CI: 0.67–0.95) and beta‐blockers (aOR 0.88, 95% CI: 0.86–1.01), referral to exercise training (aOR 0.59, 95% CI: 0.53–0.64), and patient education (aOR 0.66; 95% CI: 0.59–0.74) compared with an income in the highest tertile. Overall, no systematic differences were seen when the analyses were stratified by sex and age groups.

Conclusions

Living alone, low‐level education, and income in the lowest tertile were associated with reduced use of recommended processes of HF care among Danish HFrEF patients with a first‐time primary HF diagnosis. Efforts are warranted to ensure guideline‐recommended HF care to all HFrEF patients, irrespective of socioeconomic background.

Trends of anti-reflux surgery in Denmark 2000-2017: a nationwide registry-based cohort study

BACKGROUND

The utilisation of laparoscopic fundoplication peaked internationally around 2000. Perioperative morbidity, mortality, and length of stay initially declined as the use of laparoscopic technique increased. Studies indicate that complication rates have increased over time, probably as a consequence of rising age and level of comorbidity. None of these previous studies is nationwide. Therefore, this study aimed to investigate trends in the utilisation of anti-reflux surgery in the entire Danish population from 2000 to 2017.

METHODS

Nationwide Danish health registries were utilised to include all Danish patients undergoing anti-reflux surgery 2000-2017. The utilisation of anti-reflux surgery in procedures per 100.000 inhabitants was compared to the utilisation of proton-pump inhibitors for each year. Postoperative complications, mortality, and length of stay per year, including yearly changes, were also calculated.

RESULTS

The use of anti-reflux surgery peaked in 2001 with 5.9 procedures per 100,000 inhabitants and reached its lowest point in 2008 with 2.8 procedures per 100,000 inhabitants. The use of proton-pump inhibitors increased from 3,370 users per 100,000 inhabitants in 2000 to 10,284 users per 100,000 inhabitants in 2017. The 30-day and 90-day mortality ranged from 0 to 1.2%. The 30-day hospital-registered complications were 1.3-6.1%, and the 90-day hospital-registered complications were 2.4-8.3%. Length of stay was consistently low, with a median of 2 days in 2000 reduced to a median of 1 day by 2017.

CONCLUSION

The utilisation of anti-reflux surgery in Denmark from 2000 to 2017 declined, and the use of PPI increased dramatically. Age, comorbidity, and postoperative complications increased, while the use of laparoscopic technique remained high, and mortality was consistently low.

The Danish Hip Arthroscopy Registry: Registration Completeness and Patient Characteristics Between Responders and Non-Responders

Purpose

To report completeness of registered surgeries in the Danish hip arthroscopy registry (DHAR) and proportion of patients completing patient-reported outcome measures (PROMs) prior to surgery and at 1-year follow-up.

Patients and Methods

Completeness was determined as the number of surgeries registered in DHAR in comparison with the number of surgeries registered in the Danish National Patient Registry database (DNPR). The number of patients self-reporting pre-surgical PROMs was compared to the total number of surgeries registered in DHAR. Further, we evaluated potential differences in baseline characteristics between the groups of responders and non-responders at 1-year follow-up. Patient characteristics included age, sex, activity levels measured by the hip sports activity scale (HSAS), and PROMs (Copenhagen Hip and Groin Outcome Score, EQ-5D-3L and general hip status). Age was stratified in three groups (<25, 25–39, ≥40).

Results

From February 2012 to September 2018, 5565 arthroscopic hip surgeries were registered in DNPR, and 4937 were registered in DHAR (89%). The yearly rate of registrations in DHAR compared to DNPR increased from 77% in 2012 to 85% in 2018 and peaking in 2015 at 94%. A total of 3294 DHAR-registered patients (67%) had self-reported their pre-surgical outcome scores, and of those, 2886 (58%) completed PROMs at 1-year follow-up. More males (45 vs 41%, p = 0.002) and individuals younger than 25 years of age (24% vs 18%, p<0.001) had not completed follow-up questionnaire. The PROM baseline scores of the responders at follow-up did not differ from the non-responders.

Conclusion

The proportion of arthroscopic hip surgeries registered in the Danish Hip Arthroscopy Registry and the proportion of self-reporting PROM scores have increased to acceptable levels, whereas the proportion of patients with follow-up data is comparably low. For further quality improvement, more attention should be given to patients completing PROMs, focusing on younger males and follow-up PROMs.

Association of Neighborhood Disadvantage With Cardiovascular Risk Factors and Events Among Refugees in Denmark

IMPORTANCE

Refugees are among the most disadvantaged individuals in society, and they often have elevated risks of cardiovascular risk factors and events. Evidence is limited regarding factors that may worsen cardiovascular health among this vulnerable group.

OBJECTIVE

To test the hypothesis that refugee placement in socioeconomically disadvantaged neighborhoods is associated with increased cardiovascular risk.

DESIGN, SETTING, AND PARTICIPANTS

The study population of this quasi-experimental, registry-based cohort study included 49 305 adults 18 years and older who came to Denmark as refugees from other countries during the years of Denmark's refugee dispersal policy from 1986 to 1998. Refugees were dispersed to neighborhoods with varying degrees of socioeconomic disadvantage in an arbitrary manner conditional on observed characteristics. The association of neighborhood disadvantage on arrival with several cardiovascular outcomes in subsequent decades was evaluated using regression models that adjusted for individual, family, and municipal characteristics. Health outcomes were abstracted from the inpatient register, outpatient specialty clinic register, and prescription drug register through 2016. Data analysis was conducted from May 2018 to July 2019.

EXPOSURES

A composite index of neighborhood disadvantage was constructed using 8 neighborhood-level socioeconomic characteristics derived from Danish population register data.

MAIN OUTCOMES AND MEASURES

Primary study outcomes included hypertension, hyperlipidemia, type 2 diabetes, myocardial infarction, and stroke. Before data analysis commenced, it was hypothesized that higher levels of neighborhood disadvantage were associated with an increased risk of cardiovascular risk factors and events.

RESULTS

A total of 49 305 participants were included (median [interquartile range] age, 30.5 [24.9-39.8] years; 43.3% women). Participant region of origin included 6318 from Africa (12.8%), 7253 from Asia (14.7%), 3446 from Eastern Europe (7.0%), 5416 from Iraq (11.0%), 6206 from Iran (12.6%), 5558 from Palestine (via Lebanon, Israel, Occupied Palestinian Territories; 11.3%), and 15 108 from Yugoslavia (30.6%). Adjusted models revealed an association between placement in disadvantaged neighborhoods and increased risk of hypertension (0.71 [95% CI, 0.30-1.13] percentage points per unit of disadvantage index; P < .01), hyperlipidemia (0.44 [95% CI, 0.06-0.83] percentage points; P = .01), diabetes (0.45 [95% CI, 0.09-0.81] percentage points; P = .01), and myocardial infarction (0.14 [95% CI, 0.03-0.25] percentage points; P = .01). No association was found for stroke. Individuals who arrived in Denmark before age 35 years had an increased risk of hyperlipidemia (1.16 [95% CI, 0.41-1.92] percentage points; P < .01), and there were no differences by sex.

CONCLUSIONS AND RELEVANCE

In this quasi-experimental cohort study, neighborhood disadvantage was associated with increased cardiovascular risk in a relatively young population of refugees. Neighborhood characteristics may be an important consideration when refugees are placed by resettlement agencies and host countries. Future work should examine additional health outcomes as well as potential mediating pathways to target future interventions (eg, neighborhood ease of walking, employment opportunities).

Comorbidity and risk of venous thromboembolism after hospitalization for first-time myocardial infarction: A population-based cohort study

BACKGROUND

Myocardial infarction (MI) is a risk factor for venous thromboembolism (VTE). Although comorbidities affect MI prognosis, it is unclear whether they affect VTE risk after MI.

OBJECTIVES

We examined the impact of comorbidity on VTE risk after MI.

METHODS

We used nationwide population-based registries to identify first-time hospitalizations for MI and subsequent occurrence of VTE in Denmark (1995-2013). We included a comparison cohort from the general population matched 5:1 with MI patients by sex, age, and comorbidities. We computed 30-day and 1- to 12-month cumulative risks, rates, and hazard ratios of VTE. We also assessed the interaction between MI and comorbidity, defined as excess VTE risk in patients with both MI and comorbidity, by computing interaction contrasts and attributable fractions relating to the interaction.

RESULTS

Thirty-day and 1- to 12-month VTE risks were 0.6% and 0.5% in the MI cohort (n = 160 338) and 0.03% and 0.3% in the comparison cohort (n = 792 384). The 30-day hazard ratio for VTE in the MI cohort was 23 (95% confidence interval, 20-27), which decreased during 1-year follow-up. Thirty days after MI, interactions between MI and comorbidity accounted for 16% and 39% of VTE rates in MI patients with low-to-moderate and high comorbidity, respectively. The interactions were driven primarily by hemiplegia and cancer.

CONCLUSIONS

Thirty-day VTE risk was substantially increased after MI compared with the general population. Although the absolute VTE risk was low, comorbidity substantially increased this risk, especially hemiplegia and cancer. VTE prophylaxis might be indicated in such high-risk patients but warrants further investigation.

How patients in Denmark acquire their medicines: overview, data sources and implications for pharmacoepidemiology

The means by which patients acquire their medications differ between countries, and a knowledge of this is essential when conducting and interpreting pharmacoepidemiological studies. The aim of this paper is to provide an overview of how patients obtain medicines in Denmark, to relate these to nationwide registries available for research and to discuss the implications for research. Health services are predominantly tax-funded in Denmark, with dentistry and some medicine bought at community pharmacies being exceptions, involving partial reimbursement of charges. The paper gives an overview of prescription medicines acquired from community pharmacies (including magistral preparations), over-the-counter medicines, vaccinations and in-hospital medicine including so-called "free medicine" (in Danish: "vederlagsfri medicin"). "Free medicine" is medicines for a defined list of diseases and indications that is provided free of charge to patients in outpatient clinics. The paper also describes the content of the various Danish data sources about medicine use, summarizes their strengths and limitations, and exemplifies the ways of evaluating their completeness. An example is provided of the regional variation in the means by which medicines are acquired.

Registrations of Patients with Renal Cell Carcinoma in the Nationwide Danish Renal Cancer Database versus the Danish Cancer Registry: Data Quality, Completeness and Survival (DaRenCa Study-3)

Background

The Danish multidisciplinary renal cancer group (DaRenCa) established the nationwide database DaRenCaData in 2010. The Danish Cancer Registry (DCR) has been considered the golden standard. In contrast to DCR, DaRenCaData required the diagnosis to be histologically or cytologically verified. DaRenCaData and DCR have not previously been compared.

Patients and Methods

We included patients with renal cell carcinoma registered in DaRenCaData and/or DCR from August 1st 2010 to December 31st 2015. We computed completeness and positive predictive value (PPV) of a diagnosis in DaRenCaData compared with DCR, 1-year, 3-year and 5-year mortality rate ratios, and relative survival.

Results

We identified 4890 patients in the two registries. Of these, 4326 were registered in DaRenCaData and 4714 in DCR. Completeness of DaRenCaData was 88% [95% CI, 87–89%] and increased during the period from 82% to 94%. The PPV was 96% [95% CI, 95–97%]. A total of 4150 patients (85%) were found in both registries, 4% (176 patients) in DaRenCaData only, and 12% (564 patients) in DCR only. The relative survival was higher for patients in DaRenCaData vs DCR; the 1-year and 5-year relative survival was 85% vs 81% and 65% vs 59%, respectively. Compared with patients registered in both registries, the mortality rates were higher in patients registered in DaRenCaData only (1-year hazard ratio (HR)=2.84 [95% CI, 2.20–3.68]) or DCR only (1-year HR=4.29 [95% CI, 3.72–4.93]). Observed in both registries, survival improved over time with a 7% yearly reduction in death based on estimations of 1-year mortality rate ratios.

Conclusion

DaRenCaData had high and increasing completeness and high PPV, establishing it as a high-quality research database. Observed in both registries, renal cell carcinoma mortality declined over time; patients only registered in DCR or DaRenCaData had poorer outcomes. This study points to the importance of assessing the inclusion criteria when interpreting registry-based studies.

Long-Term Survival, Morbidity, Social Functioning and Risk of Disability in Patients with a Herpes Simplex Virus Type 1 or Type 2 Central Nervous System Infection, Denmark, 2000-2016

Background

The long-term prognosis following herpes simplex virus (HSV) central nervous system (CNS) infection is still debated.

Patients and Methods

We examined outcomes in all Danish residents who, during 2000–2016, tested PCR positive for HSV-1 (n=208) or HSV-2 (n=283) in the cerebrospinal fluid, compared to comparison cohorts from the general population (n=2080 and n=2830).

Results

One-year mortality was increased among HSV-1 patients (difference 19.3%; 95% CI: 13.6% to 25.0%) and HSV-2 patients (difference 5.3%; 95% CI: 2.5% to 8.1%), but thereafter mortality was not increased. After exclusion of persons diagnosed with cancer prior to study inclusion, one-year mortality difference for HSV-2 patients was 1.7% (−0.1% to 3.5%). After five years, HSV-1 patients had lower employment (difference −19.8%; 95% CI: −34.7% to −4.8%) and higher disability pension rates (difference 22.2%; 95% CI: 8.4% to 36.0%) than the comparison cohort, but similar number of inpatient days, outpatient visits, and sick leave. HSV-2 patients had employment and disability pension rates comparable to the comparison cohort, but more inpatient days (difference 1.5/year; 95% CI: −0.2 to 3.2), outpatient visits (difference 1.3/year; 95% CI: 0.3 to 3.2), and sick leave days (difference 9.1/year; 95% CI: 7.9 to 10.4).

Conclusion

HSV-1 and HSV-2 CNS infections differ substantially with respect to prognosis. HSV-1 CNS infection is followed by increased short-term mortality and long-term risk of disability. HSV-2 CNS infection has no substantial impact on mortality or working capability but is associated with increased morbidity.

Association of Angiotensin-Converting Enzyme Inhibitor or Angiotensin Receptor Blocker Use With COVID-19 Diagnosis and Mortality

IMPORTANCE

It has been hypothesized that angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) may make patients more susceptible to coronavirus disease 2019 (COVID-19) and to worse outcomes through upregulation of the functional receptor of the virus, angiotensin-converting enzyme 2.

OBJECTIVE

To examine whether use of ACEI/ARBs was associated with COVID-19 diagnosis and worse outcomes in patients with COVID-19.

DESIGN, SETTING, AND PARTICIPANTS

To examine outcomes among patients with COVID-19, a retrospective cohort study using data from Danish national administrative registries was conducted. Patients with COVID-19 from February 22 to May 4, 2020, were identified using ICD-10 codes and followed up from day of diagnosis to outcome or end of study period (May 4, 2020). To examine susceptibility to COVID-19, a Cox regression model with a nested case-control framework was used to examine the association between use of ACEI/ARBs vs other antihypertensive drugs and the incidence rate of a COVID-19 diagnosis in a cohort of patients with hypertension from February 1 to May 4, 2020.

EXPOSURES

ACEI/ARB use was defined as prescription fillings 6 months prior to the index date.

MAIN OUTCOMES AND MEASURES

In the retrospective cohort study, the primary outcome was death, and a secondary outcome was a composite outcome of death or severe COVID-19. In the nested case-control susceptibility analysis, the outcome was COVID-19 diagnosis.

RESULTS

In the retrospective cohort study, 4480 patients with COVID-19 were included (median age, 54.7 years [interquartile range, 40.9-72.0]; 47.9% men). There were 895 users (20.0%) of ACEI/ARBs and 3585 nonusers (80.0%). In the ACEI/ARB group, 18.1% died within 30 days vs 7.3% in the nonuser group, but this association was not significant after adjustment for age, sex, and medical history (adjusted hazard ratio [HR], 0.83 [95% CI, 0.67-1.03]). Death or severe COVID-19 occurred in 31.9% of ACEI/ARB users vs 14.2% of nonusers by 30 days (adjusted HR, 1.04 [95% CI, 0.89-1.23]). In the nested case-control analysis of COVID-19 susceptibility, 571 patients with COVID-19 and prior hypertension (median age, 73.9 years; 54.3% men) were compared with 5710 age- and sex-matched controls with prior hypertension but not COVID-19. Among those with COVID-19, 86.5% used ACEI/ARBs vs 85.4% of controls; ACEI/ARB use compared with other antihypertensive drugs was not significantly associated with higher incidence of COVID-19 (adjusted HR, 1.05 [95% CI, 0.80-1.36]).

CONCLUSIONS AND RELEVANCE

Prior use of ACEI/ARBs was not significantly associated with COVID-19 diagnosis among patients with hypertension or with mortality or severe disease among patients diagnosed as having COVID-19. These findings do not support discontinuation of ACEI/ARB medications that are clinically indicated in the context of the COVID-19 pandemic.

Association between male sex and outcomes of Coronavirus Disease 2019 (Covid-19) - a Danish nationwide, register-based study

BACKGROUND AND OBJECTIVES

Male sex has been associated with severe Coronavirus disease 2019 (Covid-19) infection. We examined the association between male sex and severe Covid-19 infection and if an increased risk remains after adjustment for age and comorbidities.

METHODS

Nationwide register-based follow-up study of Covid-19 patients in Denmark until May 16, 2020. Average risk ratio comparing 30-day composite outcome of all-cause death, severe Covid-19 diagnosis or intensive care unit (ICU) admission for men versus women standardized to the age and comorbidity distribution of all patients were derived from multivariable Cox regression. Included covariates were age, hypertension, diagnoses including obesity, alcohol, sleep apnea, diabetes, chronic obstructive pulmonary disease, previous myocardial infarction (MI), ischemic heart disease (IHD), heart failure (HF), atrial fibrillation (AF), stroke, peripheral artery disease, cancer, liver-, rheumatic-, and chronic kidney disease (CKD).

RESULTS

Of 4,842 Covid-19 patients, 2,281 (47.1%) were men. Median age was 57 [25%-75% 43-73] for men versus 52 [38-71] for women (P<0.001); however, octogenarians had equal sex distribution. Alcohol diagnosis, diabetes, hypertension, sleep apnea, prior MI and IHD (all P<0.001) as well as AF, stroke and HF (all P=0.01) were more often seen in men, and so was CKD (P=0.03). Obesity diagnosis (P<0.001) were more often seen in women. Other comorbidity differences were insignificant (P>0.05). The fully adjusted average risk ratio was 1.63 [95% CI 1.44-1.84].

CONCLUSIONS

Men with Covid-19 infection have >50% higher risk of all-cause death, severe Covid-19 infection, or ICU admission than women. The excess risk was not explained by age and comorbidities.

Network and Systems Medicine: Position Paper of the European Collaboration on Science and Technology Action on Open Multiscale Systems Medicine

Introduction: Network and systems medicine has rapidly evolved over the past decade, thanks to computational and integrative tools, which stem in part from systems biology. However, major challenges and hurdles are still present regarding validation and translation into clinical application and decision making for precision medicine. Methods: In this context, the Collaboration on Science and Technology Action on Open Multiscale Systems Medicine (OpenMultiMed) reviewed the available advanced technologies for multidimensional data generation and integration in an open-science approach as well as key clinical applications of network and systems medicine and the main issues and opportunities for the future. Results: The development of multi-omic approaches as well as new digital tools provides a unique opportunity to explore complex biological systems and networks at different scales. Moreover, the application of findable, applicable, interoperable, and reusable principles and the adoption of standards increases data availability and sharing for multiscale integration and interpretation. These innovations have led to the first clinical applications of network and systems medicine, particularly in the field of personalized therapy and drug dosing. Enlarging network and systems medicine application would now imply to increase patient engagement and health care providers as well as to educate the novel generations of medical doctors and biomedical researchers to shift the current organ- and symptom-based medical concepts toward network- and systems-based ones for more precise diagnoses, interventions, and ideally prevention. Conclusion: In this dynamic setting, the health care system will also have to evolve, if not revolutionize, in terms of organization and management.

Inflammatory bowel disease and pancreatic cancer: a Scandinavian register-based cohort study 1969-2017

BACKGROUND

Patients with inflammatory bowel disease (IBD) have an increased risk of cancer.

AIM

To assess the risk of pancreatic cancer in IBD compared to the general population.

METHODS

Patients with incident IBD 1969-2017 were identified in Danish and Swedish National Patient Registers and through biopsy data, and were matched to IBD-free reference individuals by sex, age, place of residence and year of IBD diagnosis. We linked data to Cancer and Causes of Death Registers and examined the absolute and relative risks of pancreatic cancer and pancreatic cancer death.

RESULTS

Among 161 926 patients followed for 2 000 951 person years, 442 (0.27%) were diagnosed with pancreatic cancer compared to 3386 (0.21%) of the 1 599 024 reference individuals. The 20-year cumulative incidence was 0.34% (95% confidence interval 0.30-0.38) vs 0.29% (0.28-0.30). The incidence rate was 22.1 (20.1-24.2)/100 000 person years in the patients (excluding the first year of follow-up: 20.8 [18.8-23.0]), and 16.6 (16.0-17.2) in the reference individuals. The hazard ratio (HR) for pancreatic cancer was increased overall: 1.43 (1.30-1.58), in subtypes (Crohn's disease: 1.44 [1.18-1.74]; ulcerative colitis: 1.35 [1.19-1.53]; IBD unclassified: 1.99 [1.50-2.64]) and especially in IBD patients with primary sclerosing cholangitis: 7.55 (4.94-11.5). Patients and reference individuals with pancreatic cancer did not differ in cancer stage (P = 0.17) or pancreatic cancer mortality (HR 1.07 [0.95-1.21]).

CONCLUSIONS

Patients with IBD had an excess risk of pancreatic cancer, in particular patients with primary sclerosing cholangitis. However, the cumulative incidence difference after 20 years was small: 0.05%, that is, one extra pancreatic cancer per 2000 IBD patients.

Incident psychiatric comorbidity following stress disorder diagnoses in Danish school-aged children: prospective population-based study

BACKGROUND

Prospective population-based studies of psychiatric comorbidity following trauma and severe stress exposure in children are limited.

AIMS

To examine incident psychiatric comorbidity following stress disorder diagnoses in Danish school-aged children using Danish national healthcare system registries.

METHOD

Children (6-15 years of age) with a severe stress or adjustment disorder (ICD-10) between 1995 and 2011 (n = 11 292) were followed prospectively for an average of 5.8 years. Incident depressive, anxiety and behavioural disorder diagnoses were examined relative to an age- and gender-matched comparison cohort (n = 56 460) using Cox proportional hazards regression models. Effect modification by gender was examined through stratified analyses.

RESULTS

All severe stress and adjustment disorder diagnoses were associated with increased rates for all incident outcome disorders relative to the comparison cohort. For instance, adjustment disorders were associated with higher rates of incident depressive (rate ratio RR = 6.8; 95% CI 6.0-7.7), anxiety (RR = 5.3; 95% CI 4.5-6.4), and behavioural disorders (RR = 7.9; 95% CI 6.6-9.3). Similarly, PTSD was also associated with higher rates of depressive (RR = 7.4; 95% CI 4.2-13), anxiety (RR = 7.1; 95% CI 3.5-14) and behavioural disorder (RR = 4.9; 95% CI 2.3-11) diagnoses. There was no evidence of gender-related differences.

CONCLUSIONS

Stress disorders varying in symptom constellation and severity are associated with a range of incident psychiatric disorders in children. Transdiagnostic assessments within a longitudinal framework are needed to characterise the course of post-trauma or severe stressor psychopathology.

Prescriber responsibility, predictors for initiation, and 20-year trends in use of non-aspirin non-steroidal anti-inflammatory drugs in patients with cardiovascular contraindications: a nationwide cohort study

AIMS

To examine whether prescription patterns complied with recommendations not to use nonsteroidal anti-inflammatory drugs (NSAIDs) in patients with cardiovascular contraindications. Moreover, we examined predictors for initiation and prescriber responsibility.

METHODS AND RESULTS

We identified first-time cardiovascular diseases from medical databases (1996-2017). We assessed standardized prevalence proportions, predictors from logistic regression, and prescriber identifiers. 1-year prevalence of NSAID initiation increased 3.4% from 1996 (19.4%) to 2001 (22.7%) and declined by 2.7% thereafter until 2017 (13.5%). Trends were independent of age, sex, and disease subtype, although larger annual declines occurred for heart failure (3.9%) and ischemic heart disease (3.5%) since 2002. One-year prevalence remained highest among patients with venous thromboembolism (16.6%) and angina (13.8%), and lowest for ST-segment elevation myocardial infarction (7.0%) and heart failure (8.8%). Initiators were predominantly prescribed ibuprofen (59%), diclofenac (23%) and etodolac (6%). Diclofenac and coxib use declined, while ibuprofen and naproxen use increased. Median prescribed pill dose of ibuprofen declined after 2008 from moderate/high (600 mg) to low (400 mg). Treatment duration declined for all NSAIDs, except celecoxib. Rheumatic, obesity, and pain-related conditions predicted NSAID initiation. General practitioners issued 86-91% of all NSAID prescriptions, followed by hospital prescribers (7.3-12%).

CONCLUSIONS

Initiation of NSAIDs in patients with cardiovascular disease declined since 2002. Shorter treatment duration, declining COX-2 inhibition, and increasing use of naproxen and low-dose ibuprofen suggest adherence to guidelines when NSAIDs cannot be avoided. Still, NSAID use remained prevalent despite cardiovascular contraindications, warranting awareness of appropriateness of use among general practitioners in particular.

Validity of First-Time Diagnoses of Inherited Ichthyosis in the Danish National Patient Registry and the Danish Pathology Registry

Purpose

Inherited ichthyosis is a monogenetic disease characterized by hyperkeratosis and scaling of the skin, with large interindividual variation in severity. It can affect quality of life for patients and their families. Population-based data on inherited ichthyosis are lacking, which hampers studies into its epidemiology.

Patients and Methods

Based on medical record review, we validated diagnoses of inherited ichthyosis in two nationwide population-based registries commonly used for epidemiological research: The Danish National Patient Registry and the Danish Pathology Registry. The study period was January 1, 1977, through December 31, 2015. Validation samples were taken from one regional hospital without a specialized dermatological department and two specialized dermatological departments. Positive predictive values (PPVs) were estimated overall and for each coding system (ICD-8, ICD-10 and SNOMED), including for specific ICD-10 codes.

Results

We identified 1772 first-time diagnoses of inherited ichthyosis; 363 patients were diagnosed at the departments selected for validation, and 307 of these patients (84.6%) had medical records enabling validation. We observed an overall PPV of 73.3% (95% CI: 68.1-77.9). For ICD-8, ICD-10, and SNOMED diagnoses, the PPVs were 73.2% (95% CI: 58.1-84.3), 74.7% (95% CI: 69.0-79.7), and 46.2% (95% CI: 22.1-71.7), respectively. In analyses for ICD-10 diagnoses, we observed much higher validity of diagnoses from the specialized departments (PPV 79.7%; 95% CI: 74.1-84.3) than the regional hospital (PPV 5.9%; 95% CI: 0.6-24.3). The PPVs for specific diagnoses were 80.1% for ichthyosis vulgaris and 96.6% for X-linked ichthyosis but below 45% for remaining, rarer, subtypes.

Conclusion

The PPV of first-time diagnosis of inherited ichthyosis made at specialized dermatological departments in the Danish National Patient Registry is approximately 80%. Diagnoses from the Danish Pathology Registry had low PPVs precluding their use for research.

Grief symptoms and primary care use: a prospective study of family caregivers

BACKGROUND

Family caregivers to patients who are severely ill have high use of primary health care and psychotropic medication. However, it remains sparsely investigated whether healthcare services target the most vulnerable caregivers.

AIM

This study aimed to examine associations between family caregivers' grief trajectories of persistent high-grief symptom level (high-grief trajectory) versus persistent low-grief symptom level (low-grief trajectory), as well as early contacts with GPs or psychologists and the use of psychotropic medication.

DESIGN & SETTING

A population-based cohort study of family caregivers (n = 1735) in Denmark was undertaken.

METHOD

The Prolonged Grief-13 (PG-13) scale measured family caregivers' grief symptoms at inclusion (during the patient's terminal illness), 6 months after bereavement, and 3 years after bereavement. Multinomial regression was used to analyse register-based information on GP consultations, psychologist sessions, and psychotropic medication prescriptions in the 6 months before inclusion.

RESULTS

A total of 1447 (83.4%) family caregivers contacted their GP, and 91.6% of participants in the high-grief trajectory had GP contact. Compared with family caregivers in the low-grief trajectory, family caregivers in the high-grief trajectory had ≥4 face-to-face GP consultations (odds ratio [OR] = 2.6; 95% confidence interval [CI] = 1.3 to 5.0), more GP talk therapy (OR =4.4; 95% CI = 1.9 to 10.0), and more psychotropic medication, but not significantly more psychologist sessions (OR = 1.7; 95% CI = 0.5 to 6.6).

CONCLUSION

Family caregivers in the high-grief trajectory had more contact with their GP, but their persisting grief symptoms suggest that primary care interventions for family caregivers should be optimised. Future research is warranted in such interventions and in the referral patterns to specialised mental health care.

Readmission of older acutely admitted medical patients after short-term admissions in Denmark: a nationwide cohort study

Background

Knowledge of unplanned readmission rates and prognostic factors for readmission among older people after early discharge from emergency departments is sparse. The aims of this study were to examine the unplanned readmission rate among older patients after short-term admission, and to examine risk factors for readmission including demographic factors, comorbidity and admission diagnoses.

Methods

This cohort study included all medical patients aged ≥65 years acutely admitted to Danish hospitals between 1 January 2013 and 30 June 2014 and surviving a hospital stay of ≤24 h. Data on readmission within 30 days, comorbidity, demographic factors, discharge diagnoses and mortality were obtained from the Danish National Registry of Patients and the Danish Civil Registration System. We examined risk factors for readmission using a multivariable Cox regression to estimate adjusted hazard ratios (aHR) with 95% confidence intervals (CI) for readmission.

Results

A total of 93,306 patients with a median age of 75 years were acutely admitted and discharged within 24 h, and 18,958 (20.3%; 95% CI 20.1 - 20.6%) were readmitted with a median time to readmission of 8 days (IQR 3 - 16 days). The majority were readmitted with a new diagnosis. Male sex (aHR 1.15; 1.11 - 1.18) and a Charlson Comorbidity Index ≥3 (aHR 2.28; 2.20 - 2.37) were associated with an increased risk of readmission. Discharge diagnoses associated with increased risk of readmission were heart failure (aHR 1.26; 1.12 - 1.41), chronic obstructive pulmonary disease (aHR 1.33; 1.25 - 1.43), dehydration (aHR 1.28; 1.17 - 1.39), constipation (aHR 1.26; 1.14 - 1.39), anemia (aHR 1.45; 1.38 - 1.54), pneumonia (aHR 1.15; 1.06 - 1.25), urinary tract infection (aHR 1.15; 1.07 - 1.24), suspicion of malignancy (aHR 1.51; 1.37 - 1.66), fever (aHR 1.52; 1.33 - 1.73) and abdominal pain (aHR 1.12; 1.05 - 1.19).

Conclusions

One fifth of acutely admitted medical patients aged ≥65 were readmitted within 30 days after early discharge. Male gender, the burden of comorbidity and several primary discharge diagnoses were risk factors for readmission.

Evaluating the Representativeness of US Centricity Electronic Medical Records With Reports From the Centers for Disease Control and Prevention: Comparative Study on Office Visits and Cardiometabolic Conditions

Background

Electronic medical record (EMR)–based clinical and epidemiological research has dramatically increased over the last decade, although establishing the generalizability of such big databases for conducting epidemiological studies has been an ongoing challenge. To draw meaningful inferences from such studies, it is essential to fully understand the characteristics of the underlying population and potential biases in EMRs.

Objective

This study aimed to assess the generalizability and representativity of the widely used US Centricity Electronic Medical Record (CEMR), a primary and ambulatory care EMR for population health research, using data from the National Ambulatory Medical Care Surveys (NAMCS) and the National Health and Nutrition Examination Surveys (NHANES).

Methods

The number of office visits reported in the NAMCS, designed to meet the need for objective and reliable information about the provision and the use of ambulatory medical care services, was compared with similar data from the CEMR. The distribution of major cardiometabolic diseases in the NHANES, designed to assess the health and nutritional status of adults and children in the United States, was compared with similar data from the CEMR.

Results

Gender and ethnicity distributions were similar between the NAMCS and the CEMR. Younger patients (aged <15 years) were underrepresented in the CEMR compared with the NAMCS. The number of office visits per 100 persons per year was similar: 277.9 (95% CI 259.3-296.5) in the NAMCS and 284.6 (95% CI 284.4-284.7) in the CEMR. However, the number of visits for males was significantly higher in the CEMR (CEMR: 270.8 and NAMCS: 239.0). West and South regions were underrepresented and overrepresented, respectively, in the CEMR. The overall prevalence of diabetes along with age and gender distribution was similar in the CEMR and the NHANES: overall prevalence, 10.1% and 9.7%; male, 11.5% and 10.8%; female, 9.1% and 8.8%; age 20 to 40 years, 2.5% and 1.8%; and age 40 to 60 years, 9.4% and 11.1%, respectively. The prevalence of obesity was similar: 42.1% and 39.6%, with similar age and female distribution (41.5% and 41.1%) but different male distribution (42.7% and 37.9%). The overall prevalence of high cholesterol along with age and female distribution was similar in the CEMR and the NHANES: overall prevalence, 12.4% and 12.4%; and female, 14.8% and 13.2%, respectively. The overall prevalence of hypertension was significantly higher in the CEMR (33.5%) than in the NHANES (95% CI: 27.0%-31.0%).

Conclusions

The distribution of major cardiometabolic diseases in the CEMR is comparable with the national survey results. The CEMR represents the general US population well in terms of office visits and major chronic conditions, whereas the potential subgroup differences in terms of age and gender distribution and prevalence may differ and, therefore, should be carefully taken care of in future studies.

Reoperation after antireflux surgery: a population-based cohort study

Background

Antireflux surgery for gastro-oesophageal reflux disease (GORD) and/or hiatal hernia is effective. Between 10 and 20 per cent of patients undergo reoperation for recurrent symptoms. Most studies are undertaken in a single centre and possibly underestimate the rate of reoperation. The aim of this nationwide population-based cohort study was to investigate long-term reoperation rates after antireflux surgery.

Methods

This study included patients who underwent antireflux surgery between 2000 and 2017 in Denmark, and were registered in the Danish nationwide health registries. Reoperation rates were calculated for 1, 5, 10 and 15 years after the primary antireflux operation for GORD and/or hiatal hernia. Duration of hospital stay, 30- and 90-day mortality and morbidity, and use of endoscopic pneumatic dilatation were assessed.

Results

This study included a total of 4258 antireflux procedures performed in 3717 patients. Some 3252 patients had only primary antireflux surgery and 465 patients underwent reoperation. The 1-, 5-, 10- and 15-year rates of repeat antireflux surgery were 3·1, 9·3, 11·7 and 12·8 per cent respectively. Thirty- and 90-day mortality rates were similar for primary surgery (0·4 and 0·6 per cent respectively) and reoperations. The complication rate was higher for repeat antireflux surgery (7·0 and 8·3 per cent at 30 and 90 days respectively) than primary operation (3·4 and 4·8 per cent). A total of 391 patients (10·5 per cent of all patients) underwent endoscopic dilatation after primary antireflux surgery, of whom 95 (24·3 per cent) had repeat antireflux surgery.

Conclusion

In this population-based study in Denmark, the reoperation rate 15 years after antireflux surgery was 12·8 per cent. Reoperations were associated with more complications.

Incidence of New-Onset and Worsening Heart Failure Before and After the COVID-19 Epidemic Lockdown in Denmark: A Nationwide Cohort Study

BACKGROUND

The Danish government ordered a public lockdown on March 12, 2020, because of the coronavirus disease 2019 (COVID-19) pandemic. We investigated the immediate consequences of such a lockdown for patients with heart failure (HF).

METHODS

Using the Danish nationwide administrative databases, we investigated the incidence of new-onset HF and hospitalizations for worsening HF before and after the lockdown (January 1 to March 11 versus March 12 to March 31) in 2020 versus 2019. We also investigated the mortality for all patients with HF and in COVID-19-infected patients with HF.

RESULTS

Rates of new-onset HF between January 1 and March 11 were comparable for 2020 and 2019 (1.83 versus 1.78 per 10 000 person-years; P=0.19), while hospitalizations for worsening HF were slightly higher in 2020 versus 2019 (1.04 versus 0.93 per 1000 person-years; P=0.02). In the lockdown period, rates of new-onset HF diagnoses (1.26 versus 2.25 per 1000 person-years) and of hospitalizations for worsening HF (0.63 versus 0.99 per 1000 person-years) were significantly lower in 2020 versus 2019 (P for both, <0.0001). Mortality was similar before and after the national lockdown for the population with HF. We observed 90 HF patients with diagnosed COVID-19 infection, of whom 37% (95% CI, 23%-50%) died within 15 days.

CONCLUSIONS

The number of patients hospitalized with worsening HF or diagnosed with new-onset HF was markedly reduced after lockdown but has not yet impacted mortality in HF patients at a population-based level. However, these data raise concerns for a potential undertreatment of HF currently that may impact prognosis in the longer term.

Pediatric Guillain-Barré Syndrome in a 30-Year Nationwide Cohort

BACKGROUND

Guillain-Barré syndrome is the most common cause of acute flaccid paresis in childhood. Few validated large-scale population-based data are available concerning pediatric Guillain-Barré syndrome, including incidence, risk factors, and initial clinical characteristics.

METHODS

In the Danish National Patient Registry, we identified all children aged below 16 years (N = 212) diagnosed with Guillain-Barré syndrome and admitted to any Danish department of pediatrics between 1987 and 2016. A total of 145 (68%) medical files could be retrieved and reviewed, enabling classification of patients with true Guillain-Barré syndrome. The nationwide Guillain-Barré syndrome incidence rate was calculated and stratified by age, gender, time periods, and season. Risk factors and initial Guillain-Barré syndrome characteristics were assessed by medical record review.

RESULTS

The positive predictive value of Guillain-Barré syndrome diagnosis codes was 86%. The crude Guillain-Barré syndrome incidence rate was 0.69 per 100,000 person years and peaked at two years of age. The incidence rate was higher among men (0.80) than women (0.58) and was relatively stable over the 30-year period. No seasonal difference of the incidence rate was found. Of the 125 Guillain-Barré syndrome cases, 63% were preceded by infection, whereas none were preceded by surgery or malignant disease. Medically treated pain was documented in 70%, mainly confined to the lower extremities.

CONCLUSIONS

Pediatric Guillain-Barré syndrome diagnoses in the Danish National Patient Registry have high validity, the incidence peaks at age two years, and is preceded by infection in two-thirds of children. Lower extremity pain is a common clinical presentation in the acute setting.

The Copenhagen Primary Care Laboratory Pregnancy (CopPreg) database

PURPOSE

The Copenhagen Primary Care Laboratory Pregnancy (CopPreg) database was established based on data from The Danish Medical Birth Register and the Copenhagen Primary Care Laboratory (CopLab) database. The aim was to provide a biomedical and epidemiological data resource for research in early disease programming (eg, parental clinical biomarker levels and pregnancy/ birth outcomes or long-term health in the offspring).

PARTICIPANTS

The cohort consisted in total of 203 608 women (with 340 891 pregnancies) who gave birth to 348 248 children and with 200 590 related fathers. In this paper, we focused on women and fathers who had clinical test requisitions prior to and during pregnancy, and on all children. Thus, the cohort in focus consisted of 203 054 pregnancies with requisitions on 147 045 pregnant women, 39 815 fathers with requisitions during periconception and 65 315 children with requisitions.

FINDINGS TO DATE

In addition to information on pregnancy and birth health status and general socio-demographic data, over 2.2 million clinically relevant test results were available for pregnancies with requisitions, over 1.5 million for children and over 600 000 test results were available for the fathers with requisitions during periconception. These were ordered by general practitioners in the primary care setting only and included general blood tests, nutritional biomarkers (macronutrients and micronutrients) and hormone tests. Information on tests related to infections, allergies, heart and lung function and sperm analyses (fathers) were also available.

FUTURE PLANS

The CopPreg database provides ready to use and valid data from already collected, objectively measured and analysed clinical tests. With several research projects planned, we further invite national and international researchers to use this vast data resource. In a coming paper, we will explore and discuss the indication bias in our cohort.

Increasing Incidence and Prevalence of Acquired Hemolytic Anemias in Denmark, 1980-2016

Background

Acquired hemolytic disorders—autoimmune hemolytic anemia (AIHA), cold agglutinin disease (CAD), paroxysmal nocturnal hemoglobinuria (PNH), drug-induced hemolysis (DIHA), and acquired hemolysis not otherwise specified (AHNOS)—are considered rare. Despite their potentially major health implications, data regarding their incidence and prevalence are scarce.

Methods

To fill this gap we collected data regarding all patients with acquired hemolytic disorder diagnoses in 1977–2016 from the Danish National Patient Register. These data were linked with vital and migration status information from the Danish Civil Registration System. From these data combined with annual demographic data for the background population, we calculated age- and sex-specific incidence rates and prevalence proportions of acquired hemolytic disorders for specified time periods.

Results

Our analysis included 5868 patients with acquired hemolytic disorders (2715 with AIHA, 112 CAD, 397 DIHA, 116 PNH, and 2154 AHNOS). The incidence rates per 100 000 person-years in 1980–1993 and 2008–2016 were 0.81 and 1.77 for AIHA, 0.31 and 0.12 for DIHA, and 0.04 and 0.08 for PNH, respectively. The 2008–2016 CAD incidence rate was 0.18/100 000 person-years, CAD diagnosis code was not defined before 1994. All incidence rates increased with age. The prevalence proportion per 100 000 persons in 1980 and 2015 was 2.52 and 17.01 for AIHA, 0.80 and 1.50 for DIHA, and 0.18 and 1.04 for PNH. CAD prevalence in 2015 was 1.04/100 000 persons.

Conclusion

Acquired hemolytic anemia incidence rates and prevalence proportions with the exception of DIHA are markedly increasing.

Prevalence of Congenital Hemolytic Disorders in Denmark, 2000-2016

Background

Congenital red blood cell (RBC) disorders, such as hemoglobinopathies, are frequent worldwide but with large geographical variation. Growing migration has increased the number of patients with RBC disorders in formerly low prevalence countries, eg, Denmark. However, accurate prevalences are unknown.

Methods

Patients with a registered diagnosis of congenital hemolysis in the Danish National Patient Register between 1977 and 2016 were linked to a national laboratory database of RBC disorders and the Danish civil registration system. We calculate annual age- and sex-specific prevalences of the congenital hemolytic disorders from 2000 to 2016.

Results

Prevalences of all subtypes of congenital hemolytic disorders increased during the study period. The prevalence of hereditary spherocytosis increased 1.73 times between 2000 and 2015, from 10.2/10⁵ persons to 17.7/10⁵ persons. Alpha thalassemia trait had a prevalence of 0.5/10⁵ persons in 2000, but increased 41 times to 19.2/10⁵ persons in 2015. Beta thalassemia minor increased eightfold from 4.5/10⁵ persons in 2000 to 34.9/10⁵ persons in 2015. Likewise, sickle cell trait increased 11 times from 0.7/10⁵ persons in 2000 to 8.1/10⁵ persons in 2015, whereas sickle cell disease increased from 0.5/10⁵ persons to 2.7/10⁵ persons in 2015, a fivefold increase.

Conclusion

The prevalence of congenital RBC disorders in Denmark is increasing. The hemoglobinopathy traits now have prevalences as high as hereditary spherocytosis. These estimates of congenital hemolytic disorders in Denmark emphasize that inborn hemoglobin disorders are a public health concern, even in some formerly low prevalence countries.

Existing Data Sources in Clinical Epidemiology: Laboratory Information System Databases in Denmark

Routine biomarker results from hospital laboratory information systems, covering hospitals and general practitioners, in Denmark are available to researchers through access to the regional Clinical Laboratory Information System Research Database at Aarhus University and the nationwide Register of Laboratory Results for Research. This review describes these two data sources. The laboratory databases have different geographical and temporal coverage. They both include individual-level biomarker results that are electronically transferred from laboratory information systems. The biomarker results can be linked to all other Danish registries at the individual level, using the unique identifier, the CPR number. The databases include variables such as the CPR number, date and time (hour and minute) of sampling, NPU code, and name of the biomarker, identification code for the laboratory and the requisitioner, the test result with the corresponding unit, and the lower and upper reference limits. Access to the two databases differs since they are hosted by two different institutions. Data cannot be transferred outside Denmark, and direct access is provided only to Danish institutions. It is concluded that access to data on routine biomarkers expands the detailed biological and clinical information available on patients in the Danish healthcare system. The full potential is enabled through linkage to other Danish healthcare registries.

Different Strategies to Execute Multi-Database Studies for Medicines Surveillance in Real-World Setting: A Reflection on the European Model

Although postmarketing studies conducted in population‐based databases often contain information on patients in the order of millions, they can still be underpowered if outcomes or exposure of interest is rare, or the interest is in subgroup effects. Combining several databases might provide the statistical power needed. A multi‐database study (MDS) uses at least two healthcare databases, which are not linked with each other at an individual person level, with analyses carried out in parallel across each database applying a common study protocol. Although many MDSs have been performed in Europe in the past 10 years, there is a lack of clarity on the peculiarities and implications of the existing strategies to conduct them. In this review, we identify four strategies to execute MDSs, classified according to specific choices in the execution: (A) local analyses, where data are extracted and analyzed locally, with programs developed by each site; (B) sharing of raw data, where raw data are locally extracted and transferred without analysis to a central partner, where all the data are pooled and analyzed; (C) use of a common data model with study‐specific data, where study‐specific data are locally extracted, loaded into a common data model, and processed locally with centrally developed programs; and (D) use of general common data model, where all local data are extracted and loaded into a common data model, prior to and independent of any study protocol, and protocols are incorporated in centrally developed programs that run locally. We illustrate differences between strategies and analyze potential implications.

Associations between adjustment disorder and hospital-based infections in the Danish population

OBJECTIVE

There is some evidence that posttraumatic stress disorder (PTSD) is associated with increased risk of infections, and it is unknown whether adjustment disorder is as well. We assessed the association between adjustment disorder and subsequent infections, and assessed additive interaction with sex.

METHODS

The study population included a nationwide cohort of all Danish-born residents of Denmark diagnosed with adjustment disorder between 1995 and 2011, and an age- and sex-matched general population comparison cohort. We compared rates of infections requiring inpatient or outpatient hospitalization in the two cohorts. We fit Cox proportional hazards models to compute adjusted hazard ratios (aHR) for the associations between adjustment disorder and 32 types of infections, and calculated interaction contrasts to assess interaction between adjustment disorder and sex.

RESULTS

Adjustment disorder was associated with increased rates of infections overall (n = 19,838 infections, aHR = 1.8, 95% confidence interval = 1.8. 1.9), and increased rates of each individual infection type (aHRs for 30 infections ranged from 1.5 to 2.3), adjusting for baseline psychiatric and somatic comorbidities and marital status. For many infection types (e.g., skin infections, pneumonia), interaction contrasts indicated rate differences were greater among men than women, while for two (urinary tract infections and sexually transmitted infections), rate differences were greater for women.

CONCLUSIONS

These findings are consistent with studies examining the relationship between psychological stress and infections, and between PTSD and infections. They may be explained by a combination of the triggering of unhealthy behaviors as well as immune responses to stress.

Restriction of non-opioid analgesics sold over-the-counter in Denmark: A national study of impact on poisonings

OBJECTIVE

Self-poisoning with non-opioid analgesics presents a growing challenge to health care providers. We aimed to assess the impact of an 18-year age restriction of OTC sales and a pack size restriction of non-opioid analgesics sold OTC in pharmacies on hospital-treated poisonings and poisoning severity measured using biomarkers.

METHODS

We applied a before and after design using interrupted time series analysis. Data on all poisonings recorded as hospital admissions were obtained during 2002-2015 and biochemical parameters from laboratory databases during 2011-2015, both covering the entire Danish population.

RESULTS

The age restriction was followed by a 17% level reduction in admissions for non-opioid analgesic poisoning among young people age 10-17 years (RR 0.830; 95% CI 0.697-0.988; p < 0.036). After the pack size restriction, an instant level reduction of 18.5% (RR 0.815; 95% CI 0.729-0.912; p < 0.001) was observed for the entire population. A 27% decrease in the number of poisonings with alanine transaminase levels (ALT) ≥ 210 U/L was observed (RR 0.734; 95% CI 0.579-0.931; p = 0.011) followed by 40% decrease in biomarkers indicative of liver failure (RR 0.597; 95% CI 0.421-0.847; p = 0.004). We also observed similar reductions for other poisonings such as psychotropics.

LIMITATIONS

Although declines in poisonings were observed after implementation of means restrictive measures, a causal link cannot be inferred.

CONCLUSION

Age and pack size restriction were assiociated with a reduction in the numbers of poisonings. This was also observed for pharmaceutical poisonings in general, which might suggest a non-specific or spill-over effect.

Validity and reliability of State-Trait Anxiety Inventory in Danish women aged 45 years and older with abnormal cervical screening results

Background

State Trait Anxiety Inventory (STAI) scale was developed in the 1980’s and has been widely used both in clinical settings and in research. However the Danish version of STAI has not been validated. The aim of this study was to assess the validity and reliability of STAI - state anxiety scale in Danish women aged 45 years and older with abnormal cervical cancer screening results.

Methods

Women ≥45 years referred with an abnormal cervical cytology and healthy volunteers (n = 12) underwent cognitive interview after completing STAI. Further, STAI was sent out in an electronic questionnaire to women (n = 109) seen at the gynecological department with abnormal cervical cancer screening test during 2018. Validity and reliability of STAI was evaluated according to the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist by examining internal consistency, test-retest reliability, measurement error, floor and ceiling, construct validity and content validity.

Results

In the cognitive interviews the content validity was evaluated to be very good. The internal consistency of the scale was excellent with Cronbach’s α = 0.93. Test-retest reliability was good with an intra-class correlation coefficient of 0.80 and the systematic difference between test-retest results was negligible. The construct validity was good.

Conclusion

To our best knowledge, this is the first validation study of the Danish translation of STAI-state anxiety scale. This version of STAI demonstrates an acceptable reliability and validity when used in a gynecological setting.

Association of CHA2 DS2 -VASc Score with Stroke, Thromboembolism, and Death in Hip Fracture Patients

OBJECTIVES

Patients undergoing hip fracture surgery have a 10 times increased risk of stroke compared with the general population. We aimed to evaluate the association between the CHA₂ DS₂ -VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, previous stroke/TIA [transient ischemic attack]/systemic embolism (2 points), vascular disease, age 65-74 years, and female sex) score and the risk of stroke, thromboembolism, and all-cause mortality in patients with hip fracture with or without atrial fibrillation (AF).

DESIGN

Nationwide prospective cohort study.

SETTING

Danish hospitals.

PARTICIPANTS

Subjects were all incident hip fracture patients in Denmark age 65 years and older with surgical repair procedures between 2004 and 2016 (n = 78,096). Participants were identified using the Danish Multidisciplinary Hip Fracture Registry.

MEASUREMENTS

We calculated incidence rates, cumulative incidences, and hazard ratios (HRs) with 95% confidence intervals (CIs) by CHA₂ DS₂ -VASc score, stratified on AF history.

RESULTS

The cumulative incidence of ischemic stroke 1 year after hip fracture increased with ascending CHA₂ DS₂ -VASc score, and it was 1.9% for patients with a score of 1 and 8.6% for patients with a score above 5 in the AF group. Corresponding incidences in the non-AF group were 1.6% and 7.6%. Compared with a CHA₂ DS₂ -VASc score of 1, adjusted HRs were 5.53 (95% CI = 1.37-22.24) among AF patients and 4.91 (95% CI = 3.40-7.10) among non-AF patients with a score above 5. A dose-response-like association was observed for all cardiovascular outcomes. All-cause mortality risks and HRs were substantially higher for all CHA₂ DS₂ -VASc scores above 1 in both the AF group and the non-AF group.

CONCLUSION

Among patients with hip fracture, a higher CHA₂ DS₂ -VASc score was associated with increased risk of stroke, thromboembolism, and death. This finding applied both to patients with and without AF. Patients with high CHA₂ DS₂ -VASc scores had almost similar absolute risks for cardiovascular outcomes, irrespective of AF. J Am Geriatr Soc 68:1698-1705, 2020.

Evans syndrome in children below 13 years of age - A nationwide population-based cohort study

Evans syndrome is defined by autoimmune haemolytic anaemia and immune thrombocytopenia occurring in the same patient. Although known to be rare the frequency and prognosis of Evans syndrome in children is unknown, and only few registry-based studies are available. The epidemiology and prognosis of Evans syndrome in patients above 13 years of age has recently been investigated. In this age group both incidence and prevalence of Evans syndrome increased during the study period and median survival was just 7.2 years. Using Danish health registries and the same approach, we identified 21 children below 13 years of age with Evans syndrome during 1981–2015. Patients with Evans syndrome were age–and sex matched with children both from the general population, and with patients with either autoimmune haemolytic anaemia or immune thrombocytopenia. The incidence of Evans syndrome ranged between 0.5 and 1.2/1,000,000 person-years. Prevalence was 6.7 and 19.3/1,000,000 in 1990 and 2015 respectively. Hazard ratio for death was 22 fold higher for children with ES compared to matched children from general population, and was also elevated compared to children with autoimmune haemolytic anaemia or immune thrombocytopenia. We conclude that pediatric ES is very rare and associated with elevated mortality. However, despite the nationwide study and a long and complete follow-up, results are imprecise due to the rarity of this disorder.

Geographical variation in palliative cancer care in a tax-based healthcare system: drug reimbursement in Denmark

BACKGROUND

In Denmark, a tax-based universal healthcare setting, drug reimbursement for terminal illness (DRTI) should be equally accessible for all terminally ill patients. Examining DRTI status by regions provides new knowledge on inequality in palliative care provision and associated factors. This study aims to investigate geographical variation in DRTI among terminally ill cancer patients.

METHODS

We linked socioeconomic and medical data from 135 819 Danish cancer decedents in the period 2007-15 to regional healthcare characteristics. We analyzed associations between region of residence and DRTI. Prevalence ratios (PR) for DRTI were estimated using generalized linear models adjusted for patient factors (age, gender, comorbidity and socioeconomic profile) and multilevel models adjusted for both patient factors and regional healthcare capacity (patients per general practitioner, numbers of hospital and hospice beds).

RESULTS

DRTI allocation differed substantially across Danish regions. Healthcare capacity was associated with DRTI with a higher probability of DRTI among patients living in regions with high compared with low hospice bed supply (PR 1.13, 95% CI 1.10-1.17). Also, the fully adjusted PR of DRTI was 0.94 (95% CI 0.91-0.96) when comparing high with low number of hospital beds. When controlled for both patient and regional healthcare characteristics, the PR for DRTI was 1.17 (95% CI 1.14-1.21) for patients living in the Central Denmark Region compared with the Capital Region.

CONCLUSION

DRTI status varied across regions in Denmark. The variation was associated with the distribution of healthcare resources. These findings highlight difficulties in ensuring equal access to palliative care even in a universal healthcare system.

Reduced survival of total knee arthroplasty after previous unicompartmental knee arthroplasty compared with previous high tibial osteotomy: a propensity-score weighted mid-term cohort study based on 2,133 observations from the Danish Knee Arthroplasty Registry

Background and purpose - Both medial unicompartmental knee arthroplasties (UKA) and high tibial osteotomies (HTO) are reliable treatments for isolated medial knee osteoarthritis. However, both may with time need conversion to a total knee arthroplasty (TKA). We conducted the largest nationwide registry comparison of the survival of TKA following UKA with TKA following HTO.Patients and methods - From the Danish Knee Arthroplasty Registry, aseptic conversions to TKA from UKA and TKA converted from HTO within the period of 1997-2018 were retrieved. The Kaplan-Meier method and the Cox proportional hazards regression were used to estimate the survival and hazard ratio (HR) for revision, considering confounding by indication utilizing propensity-score based inverse probability of treatment weighting (PS-IPTW).Results - PS-IPTW yielded a well-balanced pseudo-cohort (standard mean difference (SMD) < 0.1 for all covariates, except implant supplementation) of 963.8 TKAs following UKA and 1139.1 TKAs following HTO. The survival of TKA following UKA was significantly less than that of TKA following HTO with a 5-year estimated survival of 0.88 (95% confidence interval (CI) 0.85-0.90) and 0.94 (CI 0.93-0.96), respectively. The differences in survival corresponded to an implant-supplementation adjusted HR of 2.7 (CI 2.4-3.1) for TKA following UKA compared with TKA following HTO.Interpretation - Previous UKA more than doubled the revision risk of a subsequent TKA compared with previous HTO. This potential risk should be considered in the shared treatment decision of patients who are candidates for both UKA and HTO.

Time-dependent incidence and risk for myocardial infarction in patients with alcoholic cirrhosis

BACKGROUND

It remains unsettled whether alcoholic cirrhosis is a risk factor for myocardial infarction (MI).

METHODS

We used data from nationwide healthcare registries to study all Danes diagnosed with alcoholic cirrhosis in 1996-2014, and five controls were matched to each of them on gender and age. We excluded everyone with ischaemic heart disease and used Cox regression to estimate the incidence rate ratio of MI adjusted for potential cardiovascular confounders. Further, we described the MI-risk with non-MI death as a competing risk.

RESULTS

We included 22 867 patients (67% men) with a median age of 57 years. During the first year of follow-up, their incidence rate ratio of MI was increased to 1.24 (95% CI: 0.94-1.62), driven by the effect among women (2.13, 95% CI: 1.17-3.87) and those with most severe cirrhosis (1.32, 95% CI: 0.91-1.90). After the first year, the overall incidence rate ratio fell to (0.89, 95% CI: 0.76-1.05). Patients were more likely to die from non-MI causes (33.7% vs 1.0%), which protected them against MI. The overall 1-year MI-risk was similar in patients and controls: 0.38% (95% CI: 0.30-0.47%) vs 0.34% (95% CI: 0.31-0.38%). After five years of follow-up, male patients had lower MI-risk than their controls, whereas women with cirrhosis had an increased MI-risk throughout follow-up.

CONCLUSIONS

The incidence rate of MI was increased the first year following a diagnosis of alcoholic cirrhosis, in particular in women and those with most severe liver disease. Due to the competing risk of non-MI mortality, the MI-risk was not increased.

Alanine Aminotransferase and 20-Year Risk of Major Chronic Diseases and Death in a Healthy Cohort Aged 30 to 49 Years

Purpose

Alanine aminotransferase is the most frequently used marker of liver cell injury. We examined the association between alanine aminotransferase levels and long-term absolute risks of morbidity and mortality in healthy Danish people aged 30-49 years.

Patients and Methods

We divided 671 healthy participants from the Ebeltoft Health Promotion Project into four categories based on their baseline alanine aminotransferase values: low (≤10U/l), medium-low (men: 11-34U/l, women: 11-22U/l), medium-high (men: 35-69U/l, women: 23-44U/l) and high (men: ≥70U/l, women: ≥45U/l), and followed them through Danish healthcare registries for up to 20 years. We examined mortality and absolute risks of liver disease, overall cancer, ischemic heart disease, and diabetes.

Results

The risk of any cancer was highest for participants with "low alanine aminotransferase" or "high alanine aminotransferase" (20-year risk: 17.2% [95% confidence interval (CI): 6.3-32.7%] and 18.2% [95% CI: 5.7-36.3%], respectively). The risk of diabetes was highest for participants with "medium-high alanine aminotransferase" or "high alanine aminotransferase" (20-year risk: 12.1% [95% CI: 7.3-18.3%] and 9.1% [95% CI: 1.6-25.1%], respectively). Participants with "high alanine aminotransferase" had the highest 20-year risk of liver disease (20-year risk: 13.6% [95% CI: 3.4-30.9%], while it was 1.0% or less in the other groups). The chance of being alive after 20 years without having been diagnosed with liver disease, cancer, ischemic heart disease, or diabetes was lowest in the "high alanine aminotransferase" group (50% [95% CI: 28-68%]) and 72-79% in the other groups.

Conclusion

Our findings suggest that persons with high or abnormally low alanine aminotransferase measurements are at increased long-term risk of several chronic diseases.

The Validity of Registered Synchronous Peritoneal Metastases from Colorectal Cancer in the Danish Medical Registries

Introduction

Treatment options for peritoneal metastases (PM) from colorectal cancer (CRC) have increased, their efficiency should be monitored. For this purpose, register-based data on PM can be used, if valid.

Purpose

We aimed to evaluate the completeness and positive predictive value (PPV) of synchronous peritoneal metastases (S-PM) registered among CRC patients in the Danish National Patient Register (DNPR) and/or the Danish National Pathology Register (the DNPatR) using the Danish Colorectal Cancer Group database (DCCG) as a reference.

Patients and Methods

We identified Danish patients with newly diagnosed primary CRC in the DCCG during 2014–2015. S-PM were routinely registered in the DCCG. We excluded patients with non-CRC cancers and identified S-PM using all three registries. We estimated the completeness and the PPV of registered S-PM in the DNPR, the DNPatR and the DNPR and/or the DNPatR (DNPR/DNPatR) in combination using the DCCG as the reference. We stratified by age, gender, WHO performance status, tumour location and distant metastases to liver and/or lungs.

Results

We identified 9142 patients with CRC in DCCG. In DCCG, 366 patients were registered with S-PM, among whom 213 in DCCG only, whereas 153 in DCCG and in at least one of DNPR and/or DNPatR. In DNPR/DNPatR, S-PM was registered with a completeness of 42% [95% CI: 37–47] and a PPV of 60% [95% CI: 54–66]. In the DNPR only, the completeness was 32% [95% CI: 27–37] and the PPV 57% [95% CI: 50–64]. The completeness in the DNPatR was 19% [95% CI: 15–23] and the PPV was 76% [95% CI: 68–85]. In the DNPR/DNPatR patients aged <60 years (57% [95% CI: 46–69]), patients with WHO performance status 0 (46% [95% CI: 37–54]) and patients with no distant metastases (58% [95% CI: 50–65]) were registered with a higher completeness.

Conclusion

Our algorithm demonstrates that the DNPR/DNPatR captures less than half of CRC patients with S-PM. Potential candidates for curative treatment options are registered with a higher completeness. Clinicians should be encouraged to register the presence of S-PM to increase the validity of register-based S-PM data.

Neonatal Vitamin D Status and Risk of Asthma in Childhood: Results from the D-Tect Study

Background: low vitamin D status in pregnancy can influence the offspring’s lung function and contribute to childhood asthma development. The objective of this study was to examine the influence of neonatal vitamin D status on the development of asthma among children age 3–9 years in a large population sample. Method: in a case-cohort study utilizing a Danish biobank and register data we examined the association between neonatal 25-hydroxyvitamin D₃ (25(OH)D₃) concentrations and incidence of asthma among children aged 3–9 years. Cases of asthma (n = 911) were randomly selected among all cases of asthma in the Danish National Patient Register from children born between 1992 and 2002. The sub-cohort (n = 1423) was randomly selected among all children born in the same period. We used a weighted Cox proportional hazard model assessing the hazard of first asthma diagnoses by quintiles of 25(OH)D₃. Results: the median 25(OH)D3 (interquartile range) for asthma cases was 23 nmol/L (14–35) and the sub-cohort 25 nmol/L (14–40). The hazard ratio for developing asthma between ages 3 and 9 years was lower for children in the fifth quintile of neonatal 25(OH)D₃ compared to children in the first quintile, both in the unadjusted (0.61 95% CI: 0.46–0.80) and adjusted (0.55 95% CI: 0.39–0.77) analyses. Conclusion: the results from our study suggest that higher neonatal vitamin D concentration may reduce the risk of developing childhood asthma at ages 3–9 years, indicating that neonatal vitamin D status as a proxy of vitamin D status during the prenatal period is important for normal immune- and lung development.

Long-term patient satisfaction and durability of laparoscopic anti-reflux surgery in a large Danish cohort: study protocol for a retrospective cohort study with development of a novel scoring system for patient selection

INTRODUCTION

Laparoscopic anti-reflux surgery is standard of care in surgical treatment of gastro-oesophageal reflux disease and is not without risks of adverse effects, including disruption of the fundoplication and postfundoplication dysphagia, in some cases leading to reoperation. Non-surgical factors such as pre-existing anxiety or depression influence postoperative satisfaction and symptom relief. Previous studies have focused on a short-term follow-up or only certain aspects of disease, such as reoperation or postoperative quality of life. The aim of this study is to evaluate long-term patient-satisfaction and durability of laparoscopic anti-reflux surgery in a large Danish cohort using a comprehensive multimodal follow-up, and to develop a clinically applicable scoring system usable in selecting patients for anti-reflux surgery.

METHODS AND ANALYSIS

The study is a retrospective cohort study utilising data from patient records and follow-up with patient-reported quality of life as well as registry-based data. The study population consists of all adult patients having undergone laparoscopic anti-reflux surgery at The Department of Surgery, Kolding Hospital, a part of Lillebaelt Hospital Denmark in an 11-year period. From electronic records; patient characteristics, preoperative endoscopic findings, reflux disease characteristics and details on type of surgery, will be identified. Disease-specific quality of life and dysphagia will be collected from a patient-reported follow-up. From Danish national registries, data on comorbidity, reoperative surgery, use of pharmacological anti-reflux treatment, mortality and socioeconomic factors will be included. Primary outcome of this study is treatment success at follow-up.

ETHICS AND DISSEMINATION

Study approval has been obtained from The Danish Patient Safety Agency, The Danish Health Data Authority and Statistics Denmark, complying to Danish and EU legislation. Inclusion in the study will require informed consent from participating subjects. The results of the study will be published in peer-reviewed medical journals regardless of whether these are positive, negative or inconclusive.

TRIAL REGISTRATION NUMBER

Clinicaltrials.gov (NCT03959020).

Application of the Adaptive Validation Substudy Design to Colorectal Cancer Recurrence

Background

Among men and women diagnosed with colorectal cancer (CRC), 20-50% will develop a cancer recurrence. Cancer recurrences are not routinely captured by most population-based registries; however, linkage across Danish registries allows for the development of predictive models to detect recurrence. Successful application of such models in population-based settings requires validation against a gold standard to ensure the accuracy of recurrence identification.

Objective

We apply a recently developed validation study design for prospectively collected validation data to validate predicted CRC recurrences against gold standard diagnoses from medical records in an actively followed cohort of CRC patients in Denmark.

Methods

We use a Bayesian monitoring framework, traditionally used in clinical trials, to iteratively update classification parameters (positive and negative predictive values, and sensitivity and specificity) in an adaptive validation substudy design. This design allows determination of the sample size necessary to estimate the corresponding parameters and to identify when validation efforts can cease based on predefined criteria for parameter values and levels of precision.

Results

Among 355 men and women diagnosed with CRC in Denmark and actively followed semi-annually, there were 63 recurrences diagnosed by active follow-up and 70 recurrences identified by a predictive algorithm. The adaptive validation design met stopping criteria for the classification parameters after 120 patients had their recurrence information validated. This stopping point yielded parameter estimates for the classification parameters similar to those obtained when the entire cohort was validated, with 66% less patients needed for the validation study.

Conclusion

In this proof of concept application of the adaptive validation study design for outcome misclassification, we demonstrated the ability of the method to accurately determine when sufficient validation data have been collected. This method serves as a novel validation substudy design for prospectively collected data with simultaneous implementation of a validation study.

The Positive Predictive Value of Hip Fracture Diagnoses and Surgical Procedure Codes in the Danish Multidisciplinary Hip Fracture Registry and the Danish National Patient Registry

Aim

The health-care databases may be a valuable source for epidemiological research in hip fracture surgery, if the diagnoses are valid. We examined the validity of hip fracture diagnoses and surgical procedure codes in the Danish Multidisciplinary Hip Fracture Registry (DMHFR) and the Danish National Patient Registry (DNPR) by calculating the positive predictive value (PPV).

Methods

We identified a random sample of 750 hip fracture patients registered in the DMHFR between 2014 and 2017. Diagnoses have been coded by the 10^th revision of the International Classification of Diseases, while procedures have been coded by the Nordic Medico-Statistical Committee classification in the DNPR and directly transferred to the DMHFR. Using the surgical procedure description from the medical record as gold standard, we estimated the PPV of the hip fracture diagnoses and surgical procedure codes in the DMHFR and the DNPR with 95% confidence interval (CIs).

Results

The PPV was 90% (95% CI: 86%-93%) for fracture of the neck of femur, 92% (95% CI: 87%-95%) for trochanteric fracture, and 83% (95% CI: 78%-88%) for subtrochanteric fracture. Joining trochanteric and subtrochanteric fracture resulted in a PPV of 97% (95% CI: 95%-98%). Procedure codes had a PPV of 100% for primary prosthetic replacement and internal fixation with intramedullary nail, 96% (95% CI: 85%-99%) for internal fixation using screws alone, 91% (95% CI: 84%-96%) for internal fixation using plates and screws, and 89% (95% CI: 83%-94%) for internal fixation with other or combined methods. Stratifying by age group, gender, hospital type and calendar year of surgery showed similar results as the overall PPV estimates.

Conclusion

Our findings indicate a high quality of the hip fracture diagnoses and corresponding procedure codes in the DMHFR and the DNPR, with a majority of PPVs above 90%. Thus, the DMHFR and the DNPR are a valuable data source on hip fracture for epidemiological research.

Syncope as a sign of occult cancers: a population-based cohort study

BACKGROUND

We examined if syncope was a marker of an occult cancer by comparing the risk in patients with a syncope episode with that of the general population.

METHODS

Using Danish population-based medical registries, we identified all patients diagnosed with syncope during 1994-2013 and followed them until a cancer diagnosis, emigration, death or end of follow-up, whichever came first. We computed cumulative risks and standardised incidence ratios (SIR) with 95% confidence intervals (CI).

RESULTS

Among 208,361 patients with syncope, 20,278 subsequent cancers were observed. The 6-month cumulative risk of any cancer was 1.2%, increasing to 17.9 % for 1-20 years of follow-up. The highest cumulative risks after 6 months of follow-up were lung cancer (0.2%), colorectal cancer (0.2%), prostate cancer (0.1%) and brain cancer (0.1%). The 6-month SIR were 2.7 (95% CI: 2.4-3.0) for lung cancer, 2.0 (95% CI: 1.8-2.2) for colorectal cancer, 1.7 (95% CI: 1.5-1.9) for prostate cancer and 10.0 (95% CI: 8.6-11.4) for brain cancer.

CONCLUSIONS

Syncope was a weak marker of an occult cancer. In short-term the highest cumulative risks were observed for lung, colorectal, prostate and brain cancers. An aggressive search for occult cancer in a patient with syncope is probably not warranted.

The interaction effect of cardiac and non-cardiac comorbidity on myocardial infarction mortality: A nationwide cohort study

BACKGROUND

Whether the prognostic impact of comorbidity on myocardial infarction (MI) mortality is due to comorbidity alone or/and its interaction effect is unknown.

METHODS

We used Danish medical registries to conduct a nationwide cohort study of all first-time MIs during 1995-2016 (n = 179,515) and a comparison cohort matched on age, sex, and individual comorbidities (n = 880,347). We calculated age-standardized 5-year all-cause mortality rates. Interaction was examined on an additive scale by calculating interaction contrasts (difference in rate differences).

RESULTS

Among individuals without comorbidity, the 30-day mortality rate per 1000 person-years was 1851 (95% CI: 1818-1884) for MI patients and 22 (21-24) for comparison cohort members (rate difference = 1829). For individuals with low comorbidity, corresponding baseline mortality rates were 2498 (2436-2560) in the MI and 54 (50-57) in the comparison cohort (rate difference = 2444). The interaction contrast (616) indicated that the interaction accounted for 25% (616/2498) of the total 30-day mortality rate in MI patients with low comorbidity. This percentage increased further for moderate (35%) and severe (45%) comorbidity levels. Absolute and relative interaction effects were largest within the first 30 days and younger individuals. Dose-response patterns were also observed during 31-365 days and 1-5 years of follow-up (p-values for trends<0.002). The interaction differed substantially between individual types of cardiac and non-cardiac comorbidities.

CONCLUSION

Cardiac and non-cardiac comorbidities interact with MI to increase short- and long-term mortality beyond that explained by their additive effects. The interaction had a dose-response relation with comorbidity burden and a magnitude of clinical importance.

The Danish Multidisciplinary Hip Fracture Registry 13-Year Results from a Population-Based Cohort of Hip Fracture Patients

AIM OF THE REGISTRY

The aim of the Danish Multidisciplinary Hip Fracture Registry (DMHFR) is to collect data on processes of treatment, nursing care and rehabilitation as well as outcomes for patients with hip fracture in Denmark, and thereby monitor and improve the quality.

STUDY POPULATION

Hip fracture patients at age 65 or older that have undergone surgery with arthroplasty or internal fixation since 2004.

MAIN VARIABLES

DMHFR collects quality indicators and descriptive variables. Quality indicators include eight process performance measures within treatment, nursing care and rehabilitation, reflecting recommendations from the national clinical guideline for hip fracture patients, and three outcome measures including survival within 30-days, unplanned acute readmission within 30 days and reoperation within 2 years. Descriptive variables include a number of patient- and surgery-related characteristics. All data are collected prospectively.

RESULTS

By the end of 2018, the DMHFR included 86,438 hip fracture patients. Since 2006, all hospital departments in Denmark, treating patients with hip fracture, have reported improvement in quality of care and improvement in survival, and reoperation over time as well as high completeness of variables registration.

CONCLUSION

The DMHFR is a well-established nationwide clinical registry, which plays a key role for monitoring and improving hip fracture care in Denmark. The registry can further be linked to a range of other nationwide registries in order to answer a number of relevant clinical research questions.