Hypertension, proteinuria, and RAAS inhibition use in children with systemic lupus erythematosus: Data from a multi-institutional pediatric learning health system

Objectives: To assess the potential of a multi-institutional pediatric learning health system for comparative effectiveness research in pediatric-onset systemic lupus erythematosus (SLE), we characterized renin angiotensin aldosterone system (RAAS) inhibitor utilization and the feasibility of ascertaining key treatment indications and outcomes, including hypertension and proteinuria. Methods: We identified children with SLE and lupus nephritis (LN) at 6 PEDSnet institutions using previously developed computable phenotypes. A reference population of controls without SLE was randomly sampled from the same rheumatology/nephrology clinics (N = 200 controls per site). We evaluated data completeness, plausibility, and conformance related to RAAS inhibitor treatment indications and outcomes: (a) percent of encounters with blood pressure (BP) readings, (b) percent of BP readings with paired height, (c) percent of patients with ≥1 urinalysis within 7 days of SLE diagnosis, (d) urinalyses for which proteinuria could be classified as normal or abnormal, and (e) RAAS inhibitor use. Results: There were 1303 patients with SLE, including 457 with LN. BP measurements were available at 62% of encounters, of which 96% were paired with a height within 90 days. BP distributions were higher in patients with SLE and LN compared to controls without SLE. One third of SLE patients had a hypertension diagnosis. 60%–83% of patients at each site had a urinalysis protein measurement within 7 days of SLE diagnosis. A normal or abnormal result for proteinuria could be derived for 96% of measurements, and nearly all patients with LN had ≥1 abnormal result (range 94%–100% by site). RAAS inhibitors were prescribed to 31% of SLE and 71% of LN patients (range 60%–84% by site). Hypertension, elevated BP or proteinuria was identified in 90% of SLE cases at the time of RAAS inhibitor initiation. Conclusion: We demonstrated the feasibility of ascertaining health measurement data relevant to pediatric lupus treatment and outcomes in a pediatric learning health system, as well as hospital-level variation in RAAS inhibitor use. This work will facilitate more efficient multi-institutional comparative effectiveness research and also highlights opportunities for increased treatment standardization.