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Positive predictive value of first-time rheumatoid arthritis diagnoses and their serological subtypes in the Danish National Patient Registry

Authors Linauskas A, Overvad K, Johansen MB, Stengaard-Pedersen K, de Thurah A

Received 19 June 2018

Accepted for publication 11 September 2018

Published 21 November 2018 Volume 2018:10 Pages 1709—1720


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 3

Editor who approved publication: Professor Henrik Toft Sørensen

Asta Linauskas,1,2 Kim Overvad,3 Martin Berg Johansen,4 Kristian Stengaard-Pedersen,1,5 Annette de Thurah1,5

1Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark; 2Department of Rheumatology, North Denmark Regional Hospital, Hjoerring, Denmark; 3Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark; 4Unit of Clinical Biostatistics, Aalborg University Hospital, Aalborg, Denmark; 5Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

To assess whether the positive predictive value (PPV) of first-time rheumatoid arthritis (RA) diagnosis registration in the Danish National Patient Registry increases when data are linked to the RA treatment codes and to assess the PPV of first-time RA diagnoses according to RA serological subtypes.
Methods: Participants from the Danish Diet, Cancer, and Health cohort with at least one RA diagnosis, registered at one of the Central Denmark Region hospitals in the Danish National Patient Registry during the period 1977–2016, were identified. Register-based RA diagnoses were verified by scrutinizing medical records against RA classification criteria or clinical case RA. PPVs for overall RA, seropositive RA, and other RA were calculated for two models: first-time RA diagnosis registration ever in the Danish National Patient Registry and first-time RA diagnosis registration ever where subsequently a prescription had been redeemed for a synthetic disease-modifying antirheumatic drug.
Results: Overall, 205 of 311 first-time register-based RA diagnoses were verified (PPV: 61.9%; 95% CI: 56.9–67.0). Regarding RA serological subtypes, 93 of 150 register-based seropositive RA (PPV: 62.0; 95% CI: 53.9–69.5) and 36 of 144 other RA (PPV: 25.0; 95% CI: 18.5–32.8) were confirmed. When register-based RA diagnosis codes were linked to RA treatment codes, the PPVs increased substantially: the PPV for overall RA was 87.7% (95% CI: 82.5–91.5), the PPV for seropositive RA was 80.2% (95% CI: 71.6–86.7), and the PPV for other RA was 41.1% (95% CI: 30.2–52.9).
Conclusion: The first-time RA diagnoses in the Danish National Patient Registry should be used with caution in epidemiology research. However, linking registry-based RA diagnoses to the subsequent RA treatment codes increases the probability of identifying true RA diagnoses, especially overall RA and seropositive RA.

Keywords: administrative database research, Danish National Prescription Registry, Anatomical Therapeutic Chemical codes, seropositive rheumatoid arthritis, Denmark

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