Use of combined search criteria improved validity of rare disease (craniopharyngioma) diagnosis in a national registry

Mapping three versions of the international classification of diseases to categories of chronic conditions

INTRODUCTION

Administrative health data capture diagnoses using the International Classification of Diseases (ICD), which has multiple versions over time. To facilitate longitudinal investigations using these data, we aimed to map diagnoses identified in three ICD versions - ICD-8 with adaptations (ICDA-8), ICD-9 with clinical modifications (ICD-9-CM), and ICD-10 with Canadian adaptations (ICD-10-CA) - to mutually exclusive chronic health condition categories adapted from the open source Clinical Classifications Software (CCS).

METHODS

We adapted the CCS crosswalk to 3-digit ICD-9-CM codes for chronic conditions and resolved the one-to-many mappings in ICD-9-CM codes. Using this adapted CCS crosswalk as the reference and referring to existing crosswalks between ICD versions, we extended the mapping to ICDA-8 and ICD-10-CA. Each mapping step was conducted independently by two reviewers and discrepancies were resolved by consensus through deliberation and reference to prior research. We report the frequencies, agreement percentages and 95% confidence intervals (CI) from each step.

RESULTS

We identified 354 3-digit ICD-9-CM codes for chronic conditions. Of those, 77 (22%) codes had one-to-many mappings; 36 (10%) codes were mapped to a single CCS category and 41 (12%) codes were mapped to combined CCS categories. In total, the codes were mapped to 130 adapted CCS categories with an agreement percentage of 92% (95% CI: 86%-98%). Then, 321 3-digit ICDA-8 codes were mapped to CCS categories with an agreement percentage of 92% (95% CI: 89%-95%). Finally, 3583 ICD-10-CA codes were mapped to CCS categories; 111 (3%) had a fair or poor mapping quality; these were reviewed to keep or move to another category (agreement percentage = 77% [95% CI: 69%-85%]).

CONCLUSIONS

We developed crosswalks for three ICD versions (ICDA-8, ICD-9-CM, and ICD-10-CA) to 130 clinically meaningful categories of chronic health conditions by adapting the CCS classification. These crosswalks will benefit chronic disease studies spanning multiple decades of administrative health data.

The incidence of Cushing's disease: a nationwide Swedish study

BACKGROUND

Studies on the incidence of Cushing's disease (CD) are few and usually limited by a small number of patients. The aim of this study was to assess the annual incidence in a nationwide cohort of patients with presumed CD in Sweden.

METHODS

Patients registered with a diagnostic code for Cushing's syndrome (CS) or CD, between 1987 and 2013 were identified in the Swedish National Patient Registry. The CD diagnosis was validated by reviewing clinical, biochemical, imaging, and histopathological data.

RESULTS

Of 1317 patients identified, 534 (41%) had confirmed CD. One-hundred-and-fifty-six (12%) patients had other forms of CS, 41 (3%) had probable but unconfirmed CD, and 334 (25%) had diagnoses unrelated to CS. The mean (95% confidence interval) annual incidence between 1987 and 2013 of confirmed CD was 1.6 (1.4-1.8) cases per million. 1987-1995, 1996-2004, and 2005-2013, the mean annual incidence was 1.5 (1.1-1.8), 1.4 (1.0-1.7) and 2.0 (1.7-2.3) cases per million, respectively. During the last time period the incidence was higher than during the first and second time periods (P < 0.05).

CONCLUSION

The incidence of CD in Sweden (1.6 cases per million) is in agreement with most previous reports. A higher incidence between 2005 and 2013 compared to 1987-2004 was noticed. Whether this reflects a truly increased incidence of the disease, or simply an increased awareness, earlier recognition, and earlier diagnosis can, however, not be answered. This study also illustrates the importance of validation of the diagnosis of CD in epidemiological research.

Pheochromocytoma in Denmark during 1977-2016: validating diagnosis codes and creating a national cohort using patterns of health registrations

Background

Pheochromocytoma and catecholamine-secreting paraganglioma (PPGL) are rare but potentially life-threatening tumors. We aimed to validate diagnosis codes for PPGL in the Danish National Patient Registry, the Danish National Pathology Registry, and the Danish Registry of Causes of Death and to create a national cohort of incident PPGL patients by linking these three registries.

Patients and methods

We obtained data from the three abovementioned registries for all individuals registered with pheochromocytoma or catecholamine hypersecretion in Denmark during 1977–2016 (average population 5.30 million). We then reviewed health records for all individuals living in the North Denmark Region and Central Denmark Region (average population 1.75 million) to validate the diagnosis of PPGL. We tested a number of algorithms for accurately identifying true cases of PPGL to maximize positive predictive values (PPVs) and completeness. The best algorithm was subsequently validated in an external sample.

Results

We identified 2626 individuals with a PPGL diagnosis code in Denmark, including 787 (30.0%) in the North Denmark Region and Central Denmark Region. In this subsample, we retrieved the health records of 771/787 (98.0%) individuals and confirmed 198 incident PPGL patients (25.3%). The PPV of PPGL diagnosis codes was 21.7% in the Danish National Patient Registry, 50.0% in the Danish Registry of Causes of Death, and 79.5% in the Danish National Pathology Registry. By combining patterns of registrations in the three registries, we could increase the PPV to 93.1% (95% confidence interval [CI]: 88.5–96.3) and completeness to 88.9% (95% CI: 83.7–92.9), thus creating a national PPGL cohort of 588 patients. PPV for the optimal algorithm was 95.3% (95% CI: 88.5–98.7) in the external validation sample.

Conclusion

Diagnosis codes for pheochromocytoma had low PPV in several individual health registries. However, with a combination of registries we were able to identify a near-complete national cohort of PPGL patients in Denmark, as a valuable source for epidemiological research.

Incidence of malignant tumours in patients with a non-functioning pituitary adenoma

Whether patients with non-functioning pituitary adenoma (NFPA) are at increased risk of developing malignant tumours has been sparsely studied and is a matter of debate. In this study, we have investigated the incidence of malignant tumours in a large and unselected group of patients with NFPA. The study was nationwide and included all patients diagnosed with NFPA between 1987 and 2011 (n = 2795) in Sweden, identified in the National Patient Register. Malignant tumours, occurring after the NFPA diagnosis, were identified in the Swedish Cancer Register between 1987 and 2014. Standardised incidence ratios (SIRs) for malignant tumours with 95% confidence intervals (CI) were calculated using the Swedish population as reference. In total, 448 malignant tumours were detected in 386 patients with NFPA, as compared to 368 expected malignancies in the general population (SIR 1.22 (95% CI 1.11-1.33)). The incidence of neoplasms of the brain was increased (SIR 5.83 (95% CI 4.03-8.14)). When analysing the total incidence of malignancies excluding neoplasms of the brain, the overall SIR was still increased (SIR 1.14 (95% CI 1.03-1.26)). The incidence of malignant neoplasm of skin other than malignant melanoma (SIR 1.99 (95% CI 1.55-2.52)) and malignant melanoma (SIR 1.62 (95% CI 1.04-2.38)) were increased, whereas the incidence of breast cancer (SIR 0.65 (95% CI 0.42-0.97)) was decreased. The incidence of other types of malignancies did not differ significantly from the expected incidence in the general population. In conclusion, patients with NFPA have an increased overall risk of developing malignancies. To what extent these findings are due to more frequent medical surveillance, genetic predisposition or endocrine changes, remains unknown.

Time trends of mortality in patients with non-functioning pituitary adenoma: a Swedish nationwide study

PURPOSE

Patients with non-functioning pituitary adenomas (NFPA), especially women, have increased mortality. The aim of this study was to investigate whether mortality in NFPA patients has changed during the last two decades.

METHODS

This was a nationwide population-based study including 2795 patients (1502 men, 1293 women) diagnosed with NFPA between 1997 and 2011. Patients were identified and followed in Swedish National Health Registries. Standardized mortality ratios (SMRs) with 95 % confidence intervals were calculated for three time periods at first NFPA diagnosis using the general population as reference.

RESULTS

Mean (±SD) age at NFPA diagnosis was 58.9 ± 16.8 years. Mean (range) follow-up time was 8.3 (0-18) years, resulting in 20,517 patient-years at risk. Surgical treatment and radiotherapy were used in 53 and 5 %, respectively. The prevalence of hypopituitarism was 64 % during the first time period of diagnosis and then declined gradually during the study period (P value for trend <0.0001). The use of pituitary surgery and radiotherapy remained stable. In women, mortality was increased for patients diagnosed between 1997 and 2006 but not for those diagnosed between 2007 and 2011. The SMR in men remained stable throughout the study and did not differ from the general population. During the last time period, 2007-2011, the SMR between men and women did not differ.

CONCLUSIONS

While mortality in men with NFPA remains normal and stable during the last two decades, mortality in women has declined. Decreasing prevalence of pituitary insufficiency may be a plausible explanation for this positive development.

Evaluation of ICD-10 algorithms to identify hypopituitary patients in the Danish National Patient Registry

Objective

Routinely collected health data may be valuable sources for conducting research. This study aimed to evaluate the validity of algorithms detecting hypopituitary patients in the Danish National Patient Registry (DNPR) using medical records as reference standard.

Study design and setting

Patients with International Classification of Diseases (10th edition [ICD-10]) diagnoses of hypopituitarism, or other diagnoses of pituitary disorders assumed to be associated with an increased risk of hypopituitarism, recorded in the DNPR during 2000–2012 were identified. Medical records were reviewed to confirm or disprove hypopituitarism.

Results

Hypopituitarism was confirmed in 911 patients. In a candidate population of 1,661, this yielded an overall positive predictive value (PPV) of 54.8% (95% confidence interval [CI]: 52.4–57.3). Using algorithms searching for patients recorded at least one, three or five times with a diagnosis of hypopituitarism (E23.0x) and/or at least once with a diagnosis of postprocedural hypopituitarism (E89.3x), PPVs gradually increased from 73.3% (95% CI: 70.6–75.8) to 83.3% (95% CI: 80.7–85.7). Completeness for the same algorithms, however, decreased from 90.8% (95% CI: 88.7–92.6) to 82.9% (95% CI: 80.3–85.3) respectively. Including data of hormone replacement in the same algorithms PPVs increased from 73.2% (95% CI: 70.6–75.7) to 82.6% (95% CI: 80.1–84.9) and completeness decreased from 94.3% (95% CI: 92.6–95.7) to 89.7% (95% CI: 87.5–91.6) with increasing records of E23.0x.

Conclusion

The DNPR is a valuable data source to identify hypopituitary patients using a search criteria of at least five records of E23.0x and/or at least one record of E89.3x. Completeness is increased when including hormone replacement data in the algorithm. The consequences of misclassification must, however, always be considered.

Validation of diagnostic codes for Charcot-Marie-Tooth disease in the Danish National Patient Registry

Purpose

To validate the diagnostic codes for Charcot–Marie–Tooth disease (CMT) in the Danish National Patient Registry (DNPR) using positive predictive value (PPV) as a measure of validity.

Patients and methods

We used the DNPR to identify all patients diagnosed with at least one primary CMT diagnosis at a specialized department in the Central Denmark Region during the period 1977–2012. From this population, we randomly selected 123 patients for the validation study. Medical files were reviewed and used as reference standard. We estimated the PPV of the CMT diagnoses and stratified the analysis according to age at diagnosis, gender, and calendar time.

Results

In the DNPR, 275 patients were identified. We were able to retrieve 96 medical files from the random sample of 123 patients, and 85 CMT diagnoses were confirmed. The average age at diagnosis was 42.5 years, and 34% were female. The PPV was 88.5% (95% confidence interval: 80.4–94.1).

Conclusion

The CMT diagnoses in the DNPR have high validity. The DNPR can be used as a data source for epidemiologic research on CMT.

Higher incidence of morbidity in women than men with non-functioning pituitary adenoma: a Swedish nationwide study

OBJECTIVE

Increased mortality rates are found in women and young adults with non-functioning pituitary adenomas (NFPAs). This nationwide study aimed to investigate the burden of comorbidities in patients with NFPA and to examine whether gender influences the outcome.

DESIGN

NFPA patients were identified and followed-up from National Registries in Sweden. It was a nationwide, population-based study.

METHOD

Standardised incidence ratios (SIRs) for comorbidities with 95% confidence intervals (CI). Comorbidities were analysed in all patients, both patients with and without hypopituitarism.

RESULTS

Included in the analysis were 2795 patients (1502 men, 1293 women), diagnosed with NFPA between 1987 and 2011. Hypopituitarism was reported in 1500 patients (54%). Mean patient-years at risk per patient was 7 (range 0-25). Both men (SIR 2.2, 95% CI: 1.8-2.5; P<0.001) and women (2.9, 2.4-3.6; P<0.001) had a higher incidence of type 2 diabetes mellitus (T2DM) than the general population, with women having a higher incidence compared with men (P=0.02). The incidence of myocardial infarction was increased in women (1.7, 1.3-2.1; P<0.001), but not in men. Both men (1.3, 1.1-1.6; P=0.006) and women (2.3; 1.9-2.8; P<0.001) had an increased incidence of cerebral infarction, with women having a higher incidence than men (P<0.001). The incidence of sepsis was increased for both genders. The incidence of fractures was increased in women (1.8, 1.5-1.8; P<0.001), but not for men.

CONCLUSIONS

This nationwide study shows excessive morbidity due to T2DM, cerebral infarction and sepsis in all NFPA patients. Women had higher incidence of T2DM, myocardial infarction, cerebral infarction and fracture in comparison to both the general population and to men.

The Danish National Patient Registry: a review of content, data quality, and research potential

Background

The Danish National Patient Registry (DNPR) is one of the world’s oldest nationwide hospital registries and is used extensively for research. Many studies have validated algorithms for identifying health events in the DNPR, but the reports are fragmented and no overview exists.

Objectives

To review the content, data quality, and research potential of the DNPR.

Methods

We examined the setting, history, aims, content, and classification systems of the DNPR. We searched PubMed and the Danish Medical Journal to create a bibliography of validation studies. We included also studies that were referenced in retrieved papers or known to us beforehand. Methodological considerations related to DNPR data were reviewed.

Results

During 1977–2012, the DNPR registered 8,085,603 persons, accounting for 7,268,857 inpatient, 5,953,405 outpatient, and 5,097,300 emergency department contacts. The DNPR provides nationwide longitudinal registration of detailed administrative and clinical data. It has recorded information on all patients discharged from Danish nonpsychiatric hospitals since 1977 and on psychiatric inpatients and emergency department and outpatient specialty clinic contacts since 1995. For each patient contact, one primary and optional secondary diagnoses are recorded according to the International Classification of Diseases. The DNPR provides a data source to identify diseases, examinations, certain in-hospital medical treatments, and surgical procedures. Long-term temporal trends in hospitalization and treatment rates can be studied. The positive predictive values of diseases and treatments vary widely (<15%–100%). The DNPR data are linkable at the patient level with data from other Danish administrative registries, clinical registries, randomized controlled trials, population surveys, and epidemiologic field studies – enabling researchers to reconstruct individual life and health trajectories for an entire population.

Conclusion

The DNPR is a valuable tool for epidemiological research. However, both its strengths and limitations must be considered when interpreting research results, and continuous validation of its clinical data is essential.

Excess mortality and morbidity in patients with craniopharyngioma, especially in patients with childhood onset: a population-based study in Sweden

CONTEXT

Craniopharyngiomas (CPs) in adults have been associated with excess mortality.

OBJECTIVE

The aim of the study was to investigate mortality and morbidity in patients with childhood-onset and adult-onset CP.

METHODS

PATIENTS with CP were identified and followed in Swedish national health registries, 1987 through 2011. The inclusion criteria for the CP diagnosis were internally validated against patient records in 28% of the study population.

SETTINGS

This was a nationwide population-based study.

PATIENTS

A total of 307 patients (151 men and 156 women) were identified and included (mean follow-up, 9 years; range, 0-25 years). The inclusion criteria had a positive predictive value of 97% and a sensitivity of 92%.

INTERVENTION

There were no interventions.

MAIN OUTCOME MEASURES

Standardized mortality ratios (SMRs) and standardized incidence ratios (SIRs) with 95% confidence intervals were calculated using the Swedish population as the reference.

RESULTS

During the study, 54 patients died compared with the expected number of 14.1, resulting in an SMR of 3.2 (2.2-4.7) for men and 4.9 (3.2-7.2) for women. PATIENTS with childhood-onset (n = 106) and adult-onset (n = 201) CP had SMRs of 17 (6.3-37) and 3.5 (2.6-4.6), respectively. PATIENTS with hypopituitarism (n = 250), diabetes insipidus (n = 110), and neither of these (n = 54) had SMRs of 4.3 (3.1-5.8), 6.1 (3.5-9.7), and 2.7 (1.4-4.6), respectively. The SMR due to cerebrovascular diseases was 5.1 (1.7-12). SIRs were 5.6 (3.8-8.0) for type 2 diabetes mellitus, 7.1 (5.0-9.9) for cerebral infarction, 0.7 (0.2-1.7) for myocardial infarction, 2.1 (1.4-3.0) for fracture, and 5.9 (3.4-9.4) for severe infection. The SIR for all malignant tumors was 1.3 (0.8-2.1).

CONCLUSIONS

This first nationwide population-based study of patients with CP demonstrated excess mortality that was especially marked in patients with childhood-onset disease and among women. Death due to cerebrovascular diseases was increased 5-fold. Hypopituitarism and diabetes insipidus were negative prognostic factors for mortality and morbidity. PATIENTS with CP had increased disease burden related to type 2 diabetes mellitus, cerebral infarction, fracture, and severe infection.

Acute presentation of craniopharyngioma in children and adults in a Danish national cohort

We aimed to study the occurrence of acute-onset symptoms at initial presentation in a national Danish cohort of patients with childhood- or adult-onset craniopharyngioma, and to investigate potential risk factors for acute presentation. Medical records of 189 consecutive patients (39 children, 150 adults) presenting with craniopharyngioma during the period 1985-2004 were reviewed, and data regarding initial symptoms, neuroimaging results, vision and pituitary function were systematically collected. Acute symptoms preceding hospital admission were noted. Subgroup analyses were based on age, gender and calendar year period. Potential risk factors for acute presentation were analysed through uni- and multivariate analyses. Acute symptoms were reported in 24 (13%) patients. Acute visual symptoms, headache, nausea or vomiting were most frequently reported, and acute symptoms were more frequent among children (28%) than among adults (9%) (P < 0.01). There were no differences according to sex or calendar year period. Hydrocephalus was present in half of childhood cases and one-fifth of adult patients (P < 0.001). Intra-tumour haemorrhage was seen in two cases. Acute symptoms were more frequent among patients with tumours occupying the third ventricle (P < 0.01), radiologic signs of calcification (P < 0.05) or hydrocephalus (P < 0.01). In multivariate analysis, however, only childhood onset (P < 0.05) and calcification (P < 0.05) were independent risk factors for acute presentation. Craniopharyngioma presented with acute symptoms in 13% of patients. Childhood onset and radiologic signs of calcification were independent risk factors for acute presentation. Intra-tumour haemorrhage was rare.