Any link of gout disease control among hypertensive patients and onset of end-stage renal disease? Results from a population-based study

Agreement Between Administrative Database and Medical Chart Review for the Prediction of Chronic Kidney Disease G category

Background

Chronic kidney disease (CKD) is a major health issue and cardiovascular risk factor. Validity assessment of administrative data for the detection of CKD in research for drug benefit and risk using real-world data is important. Existing algorithms have limitations and we need to develop new algorithms using administrative data, giving the importance of drug benefit/risk ratio in real world.

Objective

The aim of this study was to validate a predictive algorithm for CKD GFR category 4-5 (eGFR < 30 mL/min/1.73 m² but not receiving dialysis or CKD G4-5ND) using the administrative databases of the province of Quebec relative to estimated glomerular filtration rate (eGFR) as a reference standard.

Design

This is a retrospective cohort study using chart collection and administrative databases.

Setting

The study was conducted in a community outpatient medical clinic and pre-dialysis outpatient clinic in downtown Montreal and rural area.

Patients

Patient medical files with at least 2 serum creatinine measures (up to 1 year apart) between September 1, 2013, and June 30, 2015, were reviewed consecutively (going back in time from the day we started the study). We excluded patients with end-stage renal disease on dialysis. The study was started in September 2013.

Measurement

Glomerular filtration rate was estimated using the CKD Epidemiological Collaboration (CKD-EPI) from each patient's file. Several algorithms were developed using 3 administrative databases with different combinations of physician claims (diagnostics and number of visits) and hospital discharge data in the 5 years prior to the cohort entry, as well as specific drug use and medical intervention in preparation for dialysis in the 2 years prior to the cohort entry.

Methods

Chart data were used to assess eGFR. The validity of various algorithms for detection of CKD groups was assessed with sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results

A total of 434 medical files were reviewed; mean age of patients was 74.2 ± 10.6 years, and 83% were older than 65 years. Sensitivity of algorithm #3 (diagnosis within 2-5 years and/or specific drug use within 2 years and nephrologist visit ≥4 within 2-5 years) in identification of CKD G4-5ND ranged from 82.5% to 89.0%, specificity from 97.1% to 98.9% with PPV and NPV ranging from 94.5% to 97.7% and 91.1% to 94.2%, respectively. The subsequent subgroup analysis (diabetes, hypertension, and <65 and ≥65 years) and also the comparisons of predicted prevalence in a cohort of older adults relative to published data emphasized the accuracy of our algorithm for patients with severe CKD (CKD G4-5ND).

Limitations

Our cohort comprised mostly older adults, and results may not be generalizable to all adults. Participants with CKD without 2 serum creatinine measurements up to 1 year apart were excluded.

Conclusions

The case definition of severe CKD G4-5ND derived from an algorithm using diagnosis code, drug use, and nephrologist visits from administrative databases is a valid algorithm compared with medical chart reviews in older adults.

Association of Chronic Kidney Disease With Allopurinol Use in Gout Treatment

IMPORTANCE

Clinicians are often cautious about use of allopurinol in patients with gout when renal function declines.

OBJECTIVE

To assess the association of allopurinol use in gout with the risk of developing chronic kidney disease stage 3 or higher.

DESIGN, SETTING, AND PARTICIPANTS

A time-stratified propensity score-matched, population-based, prospective cohort study of individuals with newly diagnosed gout who initiated allopurinol (≥300 mg/d) compared with those who did not initiate allopurinol, using the Health Improvement Network (THIN), a United Kingdom general practitioner electronic health records database, was carried out. The data were analyzed using Cox proportional hazards regression. Among adults aged 18 to 89 years with newly diagnosed gout, we propensity score matched 4760 initiators of allopurinol (≥300 mg/d) to the same number of noninitiators of allopurinol, excluding those with chronic kidney disease stage 3 or higher or urate-lowering therapy use before their gout diagnosis.

EXPOSURES

Allopurinol initiation at a dose of 300 mg or more per day.

MAIN OUTCOMES AND MEASURES

Development of chronic kidney disease stage 3 or higher.

RESULTS

Of the 4760 allopurinol initiators (3975 men, 785 women) and same number of noninitiators (3971 men, 789 women), 579 and 623, respectively, developed chronic kidney disease stage 3 or higher, with a mean follow-up time of 5 and 4 years, mean age of 57 years, and mean body mass index (calculated as weight in kilograms divided by height in meters squared) of 30 for both groups. Use of allopurinol of at least 300 mg/d was associated with lower risk of developing chronic kidney disease stage 3 or higher compared with nonusers, with a hazard ratio (HR) of 0.87 (95% CI, 0.77-0.97). Allopurinol initiation at less than 300 mg/d was not associated with renal function decline (HR, 1.00; 95% CI, 0.91-1.09).

CONCLUSIONS AND RELEVANCE

In this large cohort, allopurinol initiation of at least 300 mg/d was associated with a lower risk of renal function deterioration. Because allopurinol does not appear to be associated with renal function decline, clinicians should consider evaluating other potential causes when patients with gout experience renal function decline.