Do routine hospital data accurately record comorbidity in advanced kidney disease populations? A record linkage cohort study

BACKGROUND

Routine healthcare datasets capturing clinical and administrative information are increasingly being used to examine health outcomes. The accuracy of such data is not clearly defined. We examine the accuracy of diagnosis recording in individuals with advanced chronic kidney disease using a routine healthcare dataset in England with comparison to information collected by trained research nurses.

METHODS

We linked records from the Access to Transplant and Transplant Outcome Measures study to the Hospital Episode Statistics dataset. International Classification of Diseases (ICD-10) and Office for Population Censuses and Surveys Classification of Interventions and Procedures (OPCS-4) codes were used to identify medical conditions from hospital data. The sensitivity, specificity, positive and negative predictive values were calculated for a range of diagnoses.

RESULTS

Comorbidity information was available in 96% of individuals prior to starting kidney replacement therapy. There was variation in the accuracy of individual medical conditions identified from the routine healthcare dataset. Sensitivity and positive predictive values ranged from 97.7 and 90.4% for diabetes and 82.6 and 82.9% for ischaemic heart disease to 44.2 and 28.4% for liver disease.

CONCLUSIONS

Routine healthcare datasets accurately capture certain conditions in an advanced chronic kidney disease population. They have potential for use within clinical and epidemiological research studies but are unlikely to be sufficient as a single resource for identifying a full spectrum of comorbidities.

Temporal Trends and Factors Associated with Home Hemodialysis Technique Survival in Canada

BACKGROUND AND OBJECTIVES

The last 15 years has seen growth in home hemodialysis (HD) utilization in Canada owing to reports of improved outcomes relative to patients on conventional in-center HD. What effect growth has had on home HD technique and patient survival during this period is not known.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

We compared the risk of home HD technique failure, mortality, and the composite outcome among three incident cohorts of patients on home HD in Canada: 1996-2002, 2003-2007, and 2008-2012. A multivariable piece-wise exponential model was used to evaluate all outcomes using inverse probability of treatment and censoring weights.

RESULTS

A total of 1869 incident patients on home HD were identified from the Canadian Organ Replacement Register. Relative to those treated between 2003 and 2007 (n=568), the risk of home HD technique failure was similar between patients treated between 1996 and 2002 (n=233; adjusted hazard ratio [AHR], 1.39; 95% confidence interval [95% CI], 0.78 to 2.46) but higher among incident patients on home HD treated between 2008 and 2012 (n=1068; AHR, 1.51; 95% CI, 1.06 to 2.15). Relative to patients treated between 2003 and 2007, adjusted mortality was similar among those treated between 2008 and 2012 (AHR, 0.83; 95% CI, 0.58 to 1.19) and those treated between 1996 and 2002 (AHR, 0.67; 95% CI, 0.38 to 1.21). The risk of the composite outcome of death and technique failure was similar across cohorts, as was the risk of receiving a kidney transplant. Increasing age, diabetes as a comorbidity, and smoking status were associated with an increased risk of death as well as the composite outcome. Medium-sized facilities had a lower risk of death, technique failure, and the composite outcome compared with larger facilities.

CONCLUSIONS

A higher risk of technique failure was seen in the most contemporary era. Further characterization of the risk factors for, and causes of technique failure is needed to develop strategies to improve patient retention on home HD.

Peritoneal dialysis catheter implantation by nephrologists is associated with higher rates of peritoneal dialysis utilization: a population-based study

BACKGROUND

The likelihood of peritoneal dialysis (PD) utilization following a PD catheter insertion attempt is poorly described. We explored the risk factors for PD nonuse, focusing on the method of PD catheter implantation.

METHODS

This population-based retrospective cohort study employed Ontario administrative health data to identify 3886 predialysis adults who had an incident PD catheter implantation between 2002 and 2010. The impact of the method of catheter implantation including open-surgical (open, n = 1884), surgical-laparoscopic (laparoscopic, n = 1154), nephrology-percutaneous (nephrology, n = 498) and radiology-percutaneous (radiology, n = 350) on rates of PD utilization (defined as four consecutive weeks of PD) was examined.

RESULTS

Eighty-three percent of study patients received PD. After adjustment, relative to patients with openly inserted catheters, PD utilization was greater for those with nephrology-inserted catheters [adjusted hazard ratio (aHR) 1.59, 95% confidence interval (CI) 1.29-1.95] and similar for radiology-inserted catheters [aHR 1.16, 95% CI 0.94-1.43] or laparoscopic-inserted catheters [aHR 0.97 (95% CI 0.86-1.09)]. Among PD nonusers, death occurred in 10% of the open group, 6% of the laparoscopic group, 27% of the radiology group and in fewer than 3% of the nephrology group. Sixty-nine percent received hemodialysis in the open group, 63% in the laparoscopic group, 61% in the radiology group and 88% in the nephrology group. Those remaining predialysis comprised 12% of the open group, 22% of the laparoscopic group, 11% of the radiology group and <3% of the nephrology group.

CONCLUSIONS

Nephrology insertion resulted in lower overall rates of PD nonuse, particularly due to death or remaining predialysis. Greater use may be related to insertion timing, technique or greater commitment on the part of nephrologists to the success of PD.

The impact of transfer from hemodialysis on peritoneal dialysis technique survival

BACKGROUND

A significant proportion of peritoneal dialysis (PD) patients receive an initial period of hemodialysis (HD) before transitioning to PD ("PD-switch"). We sought to better understand the risks of PD technique failure (TF) and mortality for those patients compared with patients starting with PD as their first dialysis modality ("PD-first").

METHODS

Using Canadian Organ Replacement Register data, we compared the risk of PD TF between PD-first and PD-switch patients within the first year after HD initiation. In a secondary analysis, the PD-switch patients were stratified into three groups based on timing of the switch from initial HD to PD as follows: 0 - 90 days, 91 - 180 days, and 181 - 365 days. Each group was compared with PD-first patients for risk of PD TF and death.

RESULTS

Between 2001 and 2010, 9404 patients initiated PD as their first renal replacement therapy, and 3757 switched from HD to PD. After multivariable adjustment, the risk of PD TF was higher among PD-switch patients than among PD-first patients [adjusted hazard ratio (AHR): 1.37; 95% confidence interval (CI): 1.26 to 1.49], particularly within the first year after the switch from HD to PD (AHR: 1.51; 95% CI: 1.36 to 1.68). There was no association between time on HD within the first year and subsequent risk of PD TF. For all the stratified PD-switch groups, death rates were higher than those for PD-first patients.

CONCLUSIONS

Compared with patients who start renal replacement therapy with PD, those who transfer from HD to PD within the first year on dialysis experience higher rates of PD TF and death, with the highest risk being observed in the initial year after the switch to PD.

End stage renal disease in Brunei Darussalam - report from the first Brunei Dialysis Transplant Registry (BDTR)

The Brunei Dialysis and Transplant Registry (BDTR) was established in 2011 to collect data from patients undergoing renal replacement therapy (RRT) in Brunei Darussalam. The chief aims of the registry are to obtain general demographic data for RRT patients and to determine disease burden attributable to End Stage Renal Disease (ESRD). The registry population comprises of all ESRD patients treated in Brunei Darussalam. Data domains include general demographic data, medical history, ESRD etiological causes, laboratory investigations, dialysis treatment and outcomes. There were 545 prevalent RRT patients in Brunei at the end of 2011. The incidence and prevalence of ESRD were 265 and 1250 per million population. Hemodialysis (HD), Peritoneal Dialysis (PD) and Transplant comprised of 83%, 11% and 6% of the RRT population, respectively. Diabetes mellitus accounted for 57% of all new incident cases. The mean serum hemoglobin, phosphate, calcium and iPTH were 11.0 ± 1.6 g/dL, 1.9 ± 0.5 mmol/L, 2.3 ± 0.2 mmol/L and 202.5 ± 323.4 ng/mL. Dialysis adequacy for HD and PD were 65.1 (urea reduction ratio) and 2.0 ± 0.3 (Kt/v). 71 % of all prevalent HD had functioning AV fistulae and the peritonitis incidence was one in 24.5 patient-month/episode. The first BDTR has identified some deficiencies in the renal services in Brunei. However, it signals an important milestone for the establishment of benchmarked renal practice in the country. We hoped to maintain and improve our registry for years to come and will strive to align our standards to acceptable international practice.

Changes in patient and technique survival over time among incident peritoneal dialysis patients in Canada

BACKGROUND AND OBJECTIVES

In the last 15 years in Canada, there have been less stringent guidelines for peritoneal dialysis (PD) adequacy, availability of novel PD solutions, and lower PD-related peritonitis rates. Effects of these changes on outcomes of incident patients treated with PD during this period are unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Risk of PD technique failure and mortality were compared among three incident cohorts of PD patients who initiated dialysis during the following periods: 1995-2000, 2001-2005, and 2006-2009. A multivariable model was used to evaluate time to PD technique failure using inverse probability of treatment and censoring weights accounting for changing survival and transplantation rates.

RESULTS

Between 1995 and 2009,13,120 incident adult PD patients were identified from the Canadian Organ Replacement Register. Compared with the 1995-2000 cohort (n=5183), the risk of PD technique failure was lower among patients between 2001 and 2005 (n=4316) but similar among incident patients between 2006 and 2009 (n=3621). Cause-specific PD technique failure revealed no difference in PD peritonitis-related technique failure over time. PD technique failure due to inadequate PD was initially higher in the 2001-2005 cohort but lower in the 2006-2009 cohort compared with the 1995-2000 cohort. Relative to incident patients between 1995 and 2000, adjusted mortality was lower among incident patients between 2001 and 2005 and 2006 and 2009.

CONCLUSIONS

Survival on PD continues to improve with only modest changes in PD technique failure. Peritonitis remains an ongoing and modifiable source of PD technique failure.

UK Renal Registry 13th Annual Report (December 2010): Chapter 4: comorbidities and current smoking status amongst patients starting renal replacement therapy in England, Wales and Northern Ireland from 2008 to 2009

INTRODUCTION

Comorbidity is an important determinant of survival for renal replacement therapy patients and impacts other care processes such as dialysis access creation and transplant wait-listing. The prevalence of comorbidities in incident patients on renal replacement therapy (RRT) changes with age and varies between ethnic groups. This study describes these associations and the independent effect of comorbidities on outcomes.

METHODS

Incident patients reported to the UK Renal Registry (UKRR) with comorbidity data in 2008 and 2009 (n = 5,617) were included in analyses exploring the association of comorbidity with patient demographics, treatment modality, haemoglobin and renal function at start of RRT. For analyses examining comorbidity and survival, adult patients starting RRT between 2004 and 2009 in centres reporting to the UKRR with comorbidity data (n = 16,527) were included. The relationship between comorbidities and mortality at 90 days and one year after 90 days from start of RRT was explored using Cox regression.

RESULTS

Completeness of comorbidity data was 44.4% in 2009 compared with 52.1% in 2004. Of patients with data, 56.5% had one or more comorbidities. Diabetes mellitus and ischaemic heart disease were the most common conditions seen in 32.9% and 22.5% of patients respectively. Current smoking was recorded for 12.4% of incident RRT patients in the 2-year period. The presence of comorbidities in patients <75 years became more common with increasing age in all ethnic groups. In multivariable survival analysis, malignancy and the presence of ischaemic/neuropathic ulcers were the strongest independent predictors of poor survival at 1 year after 90 days from the start of RRT in patients <65 years.

CONCLUSION

Differences in prevalence rates of comorbid illnesses in incident RRT patients may reflect variation in access to health care or competing risk prior to commencing treatment. The interpretation of analyses continues to be limited by poor data completeness.

Hemodialysis vascular access modifies the association between dialysis modality and survival

Several comparisons of peritoneal dialysis (PD) and hemodialysis (HD) in incident patients with ESRD demonstrate superior survival in PD-treated patients within the first 1 to 2 years. These survival differences may be due to higher HD-related mortality as a result of high rates of incident central venous catheter (CVC) use or due to an initial survival advantage conferred by PD. We compared the survival of incident PD patients with those who initiated HD with a CVC (HD-CVC) or with a functional arteriovenous fistula or arteriovenous graft (HD-AVF/AVG). We used multivariable piece-wise exponential nonproportional and proportional hazards models to evaluate early (1 year) mortality as well as overall mortality during the period of observation using an intention-to-treat approach. We identified 40,526 incident adult dialysis patients from the Canadian Organ Replacement Register (2001 to 2008). Compared with the 7412 PD patients, 1-year mortality was similar for the 6663 HD-AVF/AVG patients but was 80% higher for the 24,437 HD-CVC patients (adjusted HR, 1.8; 95% confidence intervals [CI], 1.6 to 1.9). During the entire period of follow-up, HD-AVF/AVG patients had a lower risk for death, and HD-CVC patients had a higher risk for death compared with patients on PD. In conclusion, the use of CVCs in incident HD patients largely accounts for the early survival benefit seen with PD.

Patterns and effects of missing comorbidity data for patients starting renal replacement therapy in England, Wales and Northern Ireland

BACKGROUND

Renal Registries play a key role in assessing quality of care and outcomes of renal replacement therapy and comparisons of outcomes between groups should adjust for differences in comorbidities. This study aimed to describe patterns of missing comorbidity data and differences in survival between patients with comorbidity data returned and those with missing comorbidity data.

METHODS

Trends in comorbidity data returns by year (1998-2006) and within centres were examined using descriptive statistics. Survival of patients was described using Kaplan-Meier graphs (log-rank tests) and hazard ratios were calculated using Cox proportional hazard models. Last follow-up was at 31 December 2007. A range of sensitivity analyses were carried out, including multiple imputation.

RESULTS

Among 34,059 patients, there were 62% who had no comorbidity data. The completeness of comorbidity data increased markedly from 17% in 1998 to 47% in 2003, but had fallen back to 37% by the year 2006. Those with a missing comorbidity generally do considerably worse than those without the comorbidity and in most cases more closely follow the survival curve of those with the comorbidity. Multiple imputation analysis suggested that those with missing information on comorbidity have higher prevalence of comorbidity than seen in those with available data. Treating missing comorbidity entries as indication of absent comorbidity (i.e. a tick only if yes policy) would lead to an attenuation of the effect of comorbidity on survival.

CONCLUSIONS

Missing data lead to difficulties in performing between centre comparisons. A 'tick if present policy' in comorbidity data collection should be discouraged. Much more work is needed to fully understand why levels of missing comorbidity data are so high and to identify strategies to improve recording.

A validation study of the Canadian Organ Replacement Register

BACKGROUND AND OBJECTIVES

Accurate and complete documentation of patient characteristics and comorbidities in renal registers is essential to control bias in the comparison of outcomes across groups of patients or dialysis facilities. The objectives of this study were to assess the quality of data collected in the Canadian Organ Replacement Register (CORR) compared with the patient's medical charts.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This cohort study of a representative sample of adult, incident patients registered in CORR in 2005 to 2006 examined the prevalence, sensitivity, specificity, positive and negative predictive values, and κ of comorbid conditions and agreement in coding of patient demographics and primary renal disease between CORR and the patient's medical record. The effect of coding variation on patient survival was evaluated.

RESULTS

Medical records on 1125 patients were reviewed. Agreement exceeded 97% for health card number, date of birth, and sex and 71% (range 46.6 to 89.1%) for the primary renal disease. Comorbid conditions were under-reported in CORR. Sensitivities ranged from 0.89 (95% confidence interval 0.80, 0.92) for hypertension to 0.47 (0.38, 0.55) for peripheral vascular disease. Specificity was >0.93 for all comorbidities except hypertension. Hazard ratios for death were similar whether calculated using data from CORR or the medical record.

CONCLUSIONS

Comorbid conditions are under-reported in CORR; however, the associated risks of mortality were similar whether using the CORR data or the medical record data, suggesting that CORR data can be used in clinical research with minimal concern for bias.

Impact of dialysis modality on survival after kidney transplant failure

BACKGROUND AND OBJECTIVES

An increasing number of patients are returning to dialysis after allograft loss (DAGL). These patients are at a higher mortality risk compared with incident ESRD patients. Among transplant-naïve patients, those treated with peritoneal dialysis (PD) enjoy an early survival advantage compared with those treated with hemodialysis (HD), but this advantage is not sustained over time. Whether a similar time-dependent survival advantage exists for PD-treated patients after allograft loss is unclear and may impact dialysis modality selection in these patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We identified 2110 adult patients who initiated dialysis after renal transplant failure between January 1991 and December 2005 from The Canadian Organ Replacement Register. Multivariable regression analysis was used to evaluate the impact of initial dialysis modality on early (2 years), late (after 2 years), and overall mortality using an intention-to-treat approach.

RESULTS

After adjustment, there was no difference in overall survival between HD- and PD-treated patients (hazard ratio((HD:PD)), 1.05; 95% confidence interval, 0.85 to 1.31), with similar results seen for both early and late survival. Superior survival was seen in more contemporary cohorts of patients returning to DAGL.

CONCLUSIONS

The use of PD compared with HD is associated with similar early and overall survival among patients initiating DAGL. Differences in both patient characteristics and predialysis management between patients returning to DAGL and transplant-naive incident dialysis patients may be responsible for the absence of an early survival advantage with the use of PD in DAGL patients.