SAT0354 Validity of Gout Diagnosis in Swedish Primary and Secondary Care

Abstract

BackgroundTo diagnose gout, the golden standard is detection of monosodium urate (MSU) crystals in synovial fluid [1,2]. However, while some gout classification criteria include this variable, most gout diagnoses are based on clinical features [3,4]. This discrepancy between clinical practice and classification criteria hampers gout epidemiological studies.ObjectivesThe objective was to validate gout diagnoses (ICD-10 gout codes) in primary care (PC) and secondary care relative to five classification criteria (Rome [5], New York [6], ARA [7], Mexico [8], and Netherlands [9]). The frequency with which MSU crystal identification was used to establish a gout diagnosis was also determined.MethodsIn total, 394 patients with ≥1 ICD-10 gout diagnoses in 2009–2013 in Gothenburg, Sweden were identified from medical records of two PCs (n=262) and one secondary care center (n=132). Medical records were assessed for all classification criteria.ResultsPC patients met criteria cut-offs more frequently when ≥2 gout diagnoses were made. However, even then, few PC patients met the Rome and New York cut-offs (19% and 8%, respectively). ARA, Mexico, and Netherlands cut-offs were met more frequently by PC patients with ≥2 gout diagnoses (54%, 81%, and 80%, respectively). Mexico and Netherlands cut-offs were met frequently by the rheumatology department patients even when patients with only 1 gout diagnosis were included (80% and 71%, respectively). MSU crystal analysis served to establish gout diagnosis in only 27% and 2% of rheumatology department and PC cases, respectively.ConclusionsIf a patient is deemed to have gout when ≥2 PC or ≥1 rheumatology-center visits associate with an ICD-10 gout code, the positive predictive value of this variable relative to the Mexico and Netherlands classification criteria was ≥80% in both PC and rheumatology care settings in Sweden. MSU crystal identification was rarely used to establish gout diagnoses.ReferencesMcCarty DJ et al: Identification of urate crystals in gouty synovial fluid. Ann Intern Med 1961, 54:452-460.Pascual E et al: Synovial fluid analysis for diagnosis of intercritical gout. Ann Intern Med 1999, 131(10):756-759.Choi HK et al: Alcohol intake and risk of incident gout in men: a prospective study. Lancet 2004, 363(9417):1277-1281.Choi HK et al: Obesity, weight change, hypertension, diuretic use, and risk of gout in men: the health professionals follow-up study. Arch Intern Med 2005, 165(7):742-748.Kellgren J H JM et al: The epidomiology of chronic rheumatism. Oxford: Blackwell Scientific 1963.Decker J: Report from the subcommittee on diagnostic criteria for gout. In: Bennett PH, Wood PHN, eds. Population studies of the rheumatic diseases. Proceedings of the Third International Symposium, New York, June 5-10, 1966. Amsterdam: Excerpta Medica Foundation, 1968, 1968:385-387.Wallace SL et al: Preliminary criteria for the classification of the acute arthritis of primary gout. Arthritis Rheum 1977, 20(3):895-900.Pelaez-Ballestas I et al: Diagnosis of chronic gout: evaluating the american...