Validation of new medication use algorithms as proxies for worsening disease activity in patients with juvenile idiopathic arthritis

Abstract

PurposeTo facilitate claims‐based research on populations with juvenile idiopathic arthritis (JIA), we sought to validate an algorithm of new medication use as a proxy for worsening JIA disease activity.MethodsUsing electronic health record data from three pediatric centers, we defined new JIA medication use as (re)initiation of disease‐modifying antirheumatic drugs or glucocorticoids (oral or intra‐articular). Data were collected from 201 randomly selected subjects with (101) or without (100) new medication use. We assessed the positive predictive value (PPV) and negative predictive value (NPV) based on a reference standard of documented worsening of JIA disease activity. The algorithm was refined to optimize test characteristics.ResultsOverall, the medication‐based algorithm had suboptimal performance in representing worsening JIA disease activity (PPV 69.3%, NPV 77.1%). However, algorithm performance improved for definitions specifying longer times after JIA diagnosis (≥1‐year post‐diagnosis: PPV 82.9%, NPV 80.0%) or after initiation of prior JIA treatment (≥1‐year post‐treatment: PPV 89.7%, NPV 80.0%).ConclusionAn algorithm for new JIA medication use appears to be a reasonable proxy for worsening JIA disease activity, particularly when specifying new use ≥1 year since initiating a prior JIA medication. This algorithm will be valuable for conducting research on JIA populations within administrative claims databases.