SAT0355 The validity of gout diagnosis in primary and secondary care – results from a patients survey

Abstract

Background: Gout affects 1%-2% of adults worldwide being the most common inflammatory arthritis and usually managed in primary care. The gold standard for definitive diagnosis of gout is the presence of monosodium urate crystals (MSU) in joints or tissues and the latest classification criteria from ACR-EULAR also have this as a central item. Microscopy is however seldom performed in primary care today. Although not intended as diagnostic there are several classification criteria, such as the Mexico and the Netherlands criteria that do not include microscopy. Objectives: The aim of this study was to validate the diagnosis of gout in primary and secondary care according to the Mexico and the Netherlands criteria and items thereof through a patient survey. Methods: All patients above 18 with an ICD10-diagnosis of gout at a visit in primary and secondary careJan 2015 through February 2017) were identified from 12 primary care centres and one rheumatology clinic within the Western Sweden Health Care Region. They were sent a questionnaire regarding comorbidities, demographics and gout characteristics. To test the validity of their gout diagnosis, questions of the two gout classification criteria Mexico and the Netherlands were posed. Self-reported knowledge about having gout, was included as an anchor point for the diagnosis. Positive predictive values (PPV) were calculated for these definitions. Structured telephone interviews collecting similar information were performed in 10% of non-responders. The ACR/EULAR criteria was not used, since it includes identification of MSU crystals and imaging as central items. Results: 1589 individuals with a gout diagnosis were identified. 868 (54.6%) individuals responded. Mean age was 71 years and the proportion of men was 80%. 89% of secondary care patients had ever been treated with Allopurinol compared to 71% in primary care. The PPVs ranged from 78.5% to 94%, in secondary care, being lowest for the Netherlands criteria and highest for self-reported gout (table 1). Corresponding PPVs were marginally lower in primary care (but still over 70% for all criteria). Similar results were found among those interviewed by telephone (not shown). Conclusions: The majority of patients diagnosed with gout in both primary and secondary care have had clinical symptoms compatible with the Netherlands and Mexico criteria for gout. Diagnoses of gout identified through health care registers is therefore a valid and useful tool for epidemiological research. Patients with gout in secondary care reported more features of gout than patients in primary care.