Glomerulonephritis (GN) is associated with an increased likelihood of progression to end-stage renal disease (ESRD) and death, researchers concluded.
James B. Wetmore, MD, MS, and colleagues from the Chronic Disease Research Group in Minneapolis examined the incidence and period prevalence of GN and resultant ESRD and death rates in a 20% Medicare sample (5,442,495 individuals) and an Optum Clinformatics Employer Group Health Plan (EGHP) sample of 13,712,946 individuals.
The Medicare and EGHP cohorts had 31,409 and 5,246 patients with incident GN, respectively. The mean ages of these patients were 75.9 and 54.6 years, respectively.
The incidence rates of primary and secondary GN, per 100,000 patient-years, were 57 and 134, respectively, in the Medicare cohort and 20 and 10 in the health plan cohort, respectively, Dr. Wetmore’s group reported online ahead of print in Kidney International. The period prevalence, per 100,000 individuals, was 306 and 917 in the Medicare cohort and 70 and 52 in the health plan cohort, respectively. The death rates in incident Medicare patients were 2.7-fold higher for primary GN compared with no GN.
In the Medicare cohort, women with incident secondary GN had a significant 30% and 18% decreased likelihood of progressing to ESRD and death, respectively, than men. Black patients with primary or secondary GN had a significant 1.6-fold greater likelihood of progressing to ESRD than white patients, but they were not more likely to progress to death.
In the Medicare cohort, the rate of progression to ESRD, per 1000 patient-years, was 72.9 and 24.1 for patients with primary and secondary GN, respectively, compared with 2.2 for non-GN patients, according to the investigators. In the EGHP cohort, the rates were 46.2 and 19.5 for those with primary and secondary GN, respectively, compared with 0.2 for non-GN patients.
“In addition to highlighting the additional risks GN confers for ESRD,” the investigators wrote, “our findings raise the possibility that incident primary GN may be more likely to result in ESRD than secondary GN, as primary GN was over twice as likely to result in ESRD in the EGHP cohort and about 3 times as likely in the Medicare cohort.”
Using their approach, Dr Wetmore’s group noted, it cannot be determined definitively whether incident primary GN is more likely than secondary GN to lead to ESRD because the higher death rate among patients with secondary rather than primary GN would yield an underestimate of the former’s rate of ESRD.
The researchers discussed some potential reasons why patients with primary GN may have a higher ESRD rate. For example, treatment for secondary GN, which conventionally consists of treating the underlying systemic disorder, may be more successful, on average, than treatment of primary GN, the investigators stated. Another possibility, they noted, is that physicians may be more likely to prescribe potent immunosuppressive drugs to patients with systemic disorders and take a more conservative approach in renal-limited disease. However, the researchers cautioned that “GN is, fundamentally, a biopsy-proven diagnosis, [so] a study such as ours cannot render definitive estimates of incidence and period prevalence because the specific pathological findings resulting from a biopsy cannot reliably be deduced from claims data.”