We employed inpatient and outpatient billing data from Medicaid patients at Brigham and Women's Hospital in Boston to identify lupus nephritis cases. We identified Medicaid patients seen 2000-2007 with > 2 claims for lupus (ICD9 710.0) and compared four separate ICD9-based strategies: 1: greater than 2 claims for any combination of acute or chronic glomerulonephritis (including lupus glomerulonephritis), acute or chronic renal failure, nephritis or nephrotic syndrome (including lupus nephrotic syndrome), renal failure or proteinuria (ICD-9 codes 580.-586. and 791.0), 2: greater than 2 claims for visit to a nephrologist, 3: either strategy 1 or strategy 2 and 4: both strategy 1 and strategy 2.
Independently and blinded to these results, two board-certified rheumatologists performed medical record reviews to validate lupus and lupus nephritis according to American College of Rheumatology Criteria for Systemic Lupus Erythematosus14 (link), 15 (link). To validate the presence of lupus nephritis, we employed the ACR criteria14 (link), 15 (link) referring to the presence of nephritis (persistent proteinuria > 0.5 gms/day, or > 3+ on urinalysis, or cellular casts), AND/OR biopsy-proven renal disease attributed to lupus and classified as Class-III-IV or V (focal or diffuse glomerulonephritis or membranous nephropathy) according to the World Health Organization classification16 (link) for subjects identified by each algorithm. We calculated the positive predictive value (PPV) for each strategy. PPV is calculated as the number with confirmed lupus nephritis divided by the total number subjects within that strategy.
Independently and blinded to these results, two board-certified rheumatologists performed medical record reviews to validate lupus and lupus nephritis according to American College of Rheumatology Criteria for Systemic Lupus Erythematosus14 (link), 15 (link). To validate the presence of lupus nephritis, we employed the ACR criteria14 (link), 15 (link) referring to the presence of nephritis (persistent proteinuria > 0.5 gms/day, or > 3+ on urinalysis, or cellular casts), AND/OR biopsy-proven renal disease attributed to lupus and classified as Class-III-IV or V (focal or diffuse glomerulonephritis or membranous nephropathy) according to the World Health Organization classification16 (link) for subjects identified by each algorithm. We calculated the positive predictive value (PPV) for each strategy. PPV is calculated as the number with confirmed lupus nephritis divided by the total number subjects within that strategy.
