Uso del factor reumatoide en atención primaria en España: estudio de cohortes poblacionales incluyendo 4,8 millones de participantes y casi medio millón de mediciones

Morsley, Klara, Miller, Anne, Luqmani, Raashid, Fina-Aviles, Francesc, Javaid, Muhammad Kassim, Edwards, Christopher J., Pinedo-Villanueva, Rafael, Medina, Manuel, Calero, Sebastian, Cooper, Cyrus, Arden, Nigel and Prieto-Alhambra, Daniel (2018) Uso del factor reumatoide en atención primaria en España: estudio de cohortes poblacionales incluyendo 4,8 millones de participantes y casi medio millón de mediciones. Reumatologia Clinica. (doi:10.1016/j.reuma.2017.11.001).

Abstract

Objective: Rheumatoid factor (RF) testing is used in primary care in the diagnosis of rheumatoid arthritis (RA); however a positive RF may occur without RA. Incorrect use of RF testing may lead to increased costs and delayed diagnoses. The aim was to assess the performance of RF as a test for RA and to estimate the costs associated with its use in a primary care setting. Material and methods: A retrospective cohort study using the Information System for the Development of Research in Primary Care database (contains primary care records and laboratory results of >80% of the Catalonian population, Spain). Participants were patients ≥18 years with ≥1 RF test performed between 01/01/2006 and 31/12/2011, without a pre-existing diagnosis of RA. Outcome measures were an incident diagnosis of RA within 1 year of testing, and the cost of testing per case of RA. Results: 495,434/4,796,498 (10.3%) patients were tested at least once. 107,362 (21.7%) of those tested were sero-positive of which 2768 (2.6%) were diagnosed with RA within 1 year as were 1141/388,072 (0.3%) sero-negative participants. The sensitivity of RF was 70.8% (95% CI 69.4–72.2), specificity 78.7% (78.6–78.8), and positive and negative predictive values 2.6% (2.5–2.7) and 99.7% (99.6–99.7) respectively. Approximately €3,963,472 was spent, with a cost of €1432 per true positive case. Conclusions: Although 10% of patients were tested for RF, most did not have RA. Limiting testing to patients with a higher pre-test probability would significantly reduce the cost of testing.

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Contributors

Author: Cyrus Cooper

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