Validity of clinical psoriatic arthritis diagnoses made by rheumatologists in the Swedish National Patient Register

Abstract

Objectives

: Knowledge of the correspondence between clinical ICD diagnoses and classification criteria fulfilment is crucial to interpret studies identifying cases via ICD codes. We assessed the degree to which patients registered with ICD-10 diagnoses of psoriatic arthritis (PsA) in the Swedish National Patient Register (NPR) fulfil established PsA classification criteria.

Method

Four hundred patients with at least one outpatient visit to one of five rheumatology or internal medicine departments (three university/two county departments across Sweden) in 2013–2015, with a main ICD-10 diagnosis of PsA (L40.5, M07.0–M07.3), were randomly selected (80 cases/site). Through a structured medical record review, positive predictive values (PPVs) for fulfilment of the following classification criteria were assessed: CASPAR, Moll and Wright, Vasey and Espinoza, and modified ESSG criteria for PsA. A subset analysis regarding CASPAR fulfilment was also performed among cases with available rheumatoid factor and peripheral X-ray status (central CASPAR items; n = 227).

Results

Of the 400 patients with a main ICD-10 diagnosis of PsA, 343 (86%) fulfilled at least one of the four PsA classification criteria. PPVs for the different criteria were: CASPAR 69% (82% in the subset analysis), Moll and Wright 51%, Vasey and Espinoza 76%, and modified ESSG 64%. Overall, only 6.5% of the 400 PsA diagnoses were judged as clearly incorrect by the medical record reviewers.

Conclusion

The validity of rheumatologist-made, clinical ICD-10 diagnoses for PsA in the Swedish NPR is good, with PPVs of 69–82% for CASPAR fulfilment and 86% for meeting any established PsA classification criteria.

Acknowledgement

Special thanks to our patient representative Britt Nilsson for her valuable input.

Disclosure statement

JKW: consultant for AbbVie, Amgen, Celgene, Eli Lilly, and Novartis. EK: speakers’ bureaux for Eli Lilly; consultant for Novartis; grant/research support from Roche. VS: consultant for Astra Zeneca, Novartis, and Sanofi. SE: consultant for AbbVie, Janssen and Novartis. JA: grant/research support for the Swedish biologics register ARTIS from AbbVie, BMS, Eli Lilly, Merck, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB. LTHJ: consultant for AbbVie, Eli Lilly, Janssen, Novartis, and Pfizer. No potential conflicts of interest were reported by the remaining authors (GMA, SW, UL, and DDG).

Authors contributions

JKW contributed to study conception and design, acquisition of data, analysis and interpretation of data, and drafting of the manuscript. GMA, EK, VS, SW, and DDG contributed to study conception and design, acquisition and interpretation of data, and critically revised the manuscript, making intellectual contribution to its content. SE, UL, JA, and LTHJ contributed to study concept and design, interpretation of data and critically revised the manuscript, making intellectual contribution to its content. All authors read and approved the final manuscript.

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03009742.2022.2066807.