AB0846 HIGH DEGREE OF CLASSIFICATION CRITERIA FULFILLMENT AMONG PATIENTS WITH CLINICAL PSORIATIC ARTHRITIS DIAGNOSES IN SWEDEN

Abstract

Background:The clinical diagnosis of psoriatic arthritis (PsA) may be challenging. In Sweden, the vast majority of PsA cases are diagnosed within rheumatology or internal medicine (IM). Knowledge of the correspondence between clinical ICD diagnoses and classification criteria fulfillment is crucial to interpret studies identifying cases based on ICD codes.Objectives:To assess the degree to which patients with clinical PsA diagnoses in Sweden fulfill established PsA classification criteria.Methods:Four hundred patients with ≥1 outpatient physician visit to one of five rheumatology or IM departments (3 university/2 county departments, spread across Sweden) 2013-2015 with a main ICD-10 diagnosis of PsA (L40.5/M07.0-M07.3), were randomly selected from the Swedish National Patient Register (80 cases/site). Based on a structured medical record review, positive predictive values (PPV) of a clinical PsA diagnosis (i.e. ≥1 visit with a PsA ICD-10 code) for fulfillment of the following classification criteria were assessed: CASPAR,[1] Moll & Wright,[2] Vasey & Espinoza,[3] and Modified ESSG criteria for PsA,[4] respectively (as well as for any of these); ASAS criteria for peripheral or axial spondyloarthritis (SpA) [5]; and the 1987 ACR criteria for rheumatoid arthritis (RA).[6] Subanalyses regarding CASPAR fulfillment were also performed restricted to patients with available rheumatoid factor and peripheral X-ray status (central CASPAR items; n=227), and among patients with ≥2 ICD codes for PsA, of which ≥1 from a rheumatology/IM department (n=353).Results:Out of 400 clinically diagnosed PsA patients, 343 (86%) fulfilled any of the 4 PsA classification criteria, with a PPV for CASPAR fulfillment of 69% (rising to 73-82% in the subanalyses;Figure 1). Substantial overlap was seen regarding fulfillment of the 4 PsA criteria (Figure 2A). Moreover, 86% fulfilled the ASAS peripheral or axial SpA criteria, while the 1987 ACR definition of RA was met by 27% – in both cases with the great majority also classifiable as PsA (Figure 2B). Most patients not fulfilling any PsA criteria had either no verified arthritis or polyarticular disease (Table). Overall, only 6.5% of the clinical PsA diagnoses were judged as clearly wrong by the rheumatologists performing the medical record assessments.Conclusion:The validity of clinical ICD-10 diagnoses for PsA in the Swedish National Patient Register is good, with a PPV of 86% for the fulfillment of established PsA classification criteria.