A retrospective, monocentric, cross-sectional study was conducted. Sociodemographic and clinical data on patients admitted to the OD with suspected SA between April 2014 and September 2019 were collected.
One-hundred and ten patients were included. In the overall sample, most patients were male (n=61; 55.5%) with a median age of 70 (IQR=20) years old. Thirty-six patients (32.7%) had a previous history of hyperuricemia or gout, or had this diagnosis established at the time of their hospital admission. Monoarthritis was the most common form of presentation (n=106; 96.4%), with the knee being the most frequently involved joint (n=60; 54.5%). S. aureus was the most representative microorganism in synovial fluid (SF) cultures (n=33; 30.6%). SF cultures did not allow the identification of a causative microorganism in 53 cases submitted to arthrotomy (50.5%). Serum C-reactive protein (CRP) was a predictive factor for microorganism identification in SF cultures, with values ≥ 17.6 mg/dl presenting a sensibility and specificity of 60.8% and 77.4%, respectively [CI 95% (0.52 – 0.80)]. Patients with a diagnosis of hyperuricemia or gout presented a higher risk for a negative SF culture result (OR = 4.7 [CI 95% =1.9 – 11.5]).
Elderly subjects with multiple comorbidities, namely cardiovascular risk factors, seem more prone to SA. Serum CRP appears to be a predictive factor for the identification of a causative microorganism. The higher risk of a negative SF culture in patients with hyperuricemia or gout should alert us for the possibility of misdiagnosis of SA in patients with an acute gout attack.