A number of immunologic markers and demographic factors are strongly predictive of risk for incident proteinuria in patients with systemic lupus erythematosus (SLE), according to the results of a recent cohort analysis published in Lupus Science & Medicine.
The study investigators sought to identify fixed and time-varying predictors of incident proteinuria in patients with SLE. The analysis was based on individuals with no history of diabetes who had not experienced a prior episode of renal involvement. They defined an incident case of proteinuria as ≥2 measures of urine protein to creatinine ratio (or 24-hour protein measures) >0.5 in 2 visits separated by >30 days and <180 days. Rates of incident proteinuria were estimated in subgroups of patients with SLE defined by time-invariant and time-variant predictors.
A total of 895 patients were included in the analysis. Overall, 94% were women, 58% were white, and 34% were black. The mean patient age at the beginning of follow-up was 42. Over 4669 person-years of follow-up, 57 cases of incident proteinuria were reported. The overall rate of incident proteinuria was 12.2 per 1000 person-years.
The incidence rate of proteinuria was significantly higher in patients younger than 40 compared with patients age 40 to 49 (rate ratio [RR], 0.4; P =.0041), patients age 50 to 59 (RR, 0.2; P =.0002), and patients older than 60 (RR, 0.1; P =.0015). Moreover, the incidence rate was also significantly higher in black patients (RR, 2.9; P =.0003); other non-white patients had significantly higher rates than white patients (RR, 3.7; P =.0019).
In patients with a low C3 measure in a prior cohort visit, the rate of incident proteinuria was increased by a factor of 16.1 (P <.0001) and in patients with a low C4 measure the rate was increased by a factor of 16.3 (P <.0001).
Regarding associations between prior and current medication use, patients who had used hydroxychloroquine (HCQ) in the past but were not current users (RR, 4.8; P <.05) and patients who used HCQ for <6 months (RR, 4.8; P < .05) had a higher incidence of proteinuria compared with patients who had never used HCQ .The rate of proteinuria reported in patients receiving angiotensin-converting enzyme inhibitors and angiotensin receptor blockers was similar to that in patients not receiving these agents.
The investigators concluded that older patients with SLE are at a low risk for the development of proteinuria. The highest rates of proteinuria reported in this analysis were in patients with recent low complement levels.
Duarte-García A, Barr E, Magder LS, Petri M. Predictors of incident proteinuria among patients with SLE. Lupus Sci Med. 2017;4(1):e000200.