Physician Variability in Time to Kidney Biopsy and Glucocorticoid Prescription in IgA Nephropathy: A Population-Based...

Similar patients experienced almost three-fold differences in biopsy timing depending on which physician they saw. Glucocorticoid prescribing varied meaningfully by physician after adjustment for clinical and biopsy features.

Practice patterns in the management of IgA nephropathy (IgAN) vary but the extent of physician-level variability in key decisions, such as kidney biopsy and glucocorticoid use, is unknown. Understanding variability in clinical practice provides essential context for knowledge translation as new evidence and guidelines emerge for the treatment of IgAN. We hypothesized that time to biopsy and likelihood of glucocorticoid use would vary significantly by physician.

We conducted a population-based cohort study of adults with biopsy-proven IgAN in Manitoba, Canada (2002-2021). Linear mixed-effects models were used to examine factors associated with time from urinary abnormality to kidney biopsy, and logistic mixed models were used to assess the likelihood of glucocorticoid prescription. Models included random intercepts for physician to quantify between-physician variability using the intraclass correlation coefficient (ICC), median time ratio, and median odds ratio.

Among 380 patients managed by 38 physicians, the physician-level ICC for time to biopsy was 0.31, indicating that nearly one third of the total variability in time to biopsy was attributable to between-physician differences. The corresponding median time ratio was 2.65, representing a nearly three-fold difference in time to biopsy between two otherwise similar patients managed by different physicians. For glucocorticoid prescription, the ICC was 0.07, indicating 7% of the variability was attributable to physician practice. The median odds ratio was 1.59, indicating that two otherwise similar patients could have 59% different odds of being prescribed glucocorticoids depending on which physician managed their care.

This is one of the first studies to quantify between-physician variability in IgAN care. Substantial between-physician variability exists in the timing of biopsy and use of immunosuppression in IgAN. These findings highlight opportunities for targeted knowledge translation to promote timely, equitable, and evidence-aligned care.