AB1001 Misdiagnosing osteoarthritis as rheumatoid arthritis, clinical implications and costs related
Authors: P. Santos-Moreno, J.M. Bello, M. Cubides, L. Amador, D. Zambrano, L. Villarreal, A. Urbina
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> There are many patients with osteoarthritis (OA) that are misdiagnosed as rheumatoid arthritis (RA) in general practice in Colombia. False positive diagnosis of RA is made on the basis of proximal or distal compromise in hands associated with low level positive rheumatoid factor. As a result, they are treated with disease modifying anti-rheumatic drugs (DMARDs), leading to higher economic costs for health system. <h3>Objectives</h3> The aim of this study was to calculate the possible direct economic costs of care of OA patients misdiagnosed as RA in a 12 month period in a cohort of patients derived to a specialized RA center in Colombia. <h3>Methods</h3> A descriptive cross sectional study was performed. Patients derived during a 12 month period to a RA specialized center with presumptive diagnosis of this disease and found finally diagnosed with OA were included in analysis. For confirmation or ruling-out RA diagnosis was followed a standardized protocol by a rheumatologist. Percentages and averages were calculated for demographic and clinical characteristics of the cohort of patients in which final diagnosis of OA was made. We described the direct costs in colombian pesos (COP) of their care assuming an average of 4 visits/year to general practitioner (6.000 COP/consultation), 2 visits/year for physiatrist and orthopedics (16.000 COP/consultation) and 4 set/year of conventional laboratories (40.000 COP/set). Cost of medication doses were calculated for an average use of methotrexate, sulfasalazine, chloroquine and prednisolone (103.000 COP/monthly). Indirect costs were not calculated. <h3>Results</h3> From 2841 patients evaluated, in 1511 patients (53.2%) diagnosis of RA was confirmed, the remaining 1330 patients (46.8%) had a wrong diagnosis of RA. Between incorrect differential diagnosis were found: osteoarthritis in 896 patients (67.36%), systemic lupus erythematosus in 104 patients (7.81%), Sjögren syndrome in 50 patients (3.75%), spondyloarthropathies in 45 patients (3.38%), gout in 28 patients (2.1%) and other diagnoses in 15.56% of the remaining population. As above mentioned, 896 patients (67.36% of misdiagnosed patients) had finally OA. Of this patients, 629 (76.2%) were women and 267 (29.79%) men, with an average age of 59.5 years (range between 9-92 years). For each patient we calculated 24.000 COP/year for general practitioner visits, 64.000 COP/year for specialized medicine visits, 160.000 COP/year for laboratory sets and 1'236.000 COP/year for medications. This leads to a total cost of 1'484.000 COP/year per patient. From a total of 896 misdiagnosed patients the cost rises to 1'329'664.000 COP. These patients had an average of 4.5 years of wrong treatment for their misdiagnosis, making the cost rise up to 5'983'488.000 COP (3 million US dollars). <h3>Conclusions</h3> There is an important economic implication of the misdiagnosis of OA as RA, being this the most frequent mistake in the diagnosis of this disease. The implementation of educational programs for health care primary physicians and specialized RA centers could save this amount of money for the health system in Colombia. <h3>Disclosure of Interest</h3> None Declared.