Development of a simple diagnostic tool predicting the aseptic nature of a joint effusion: a pragmatic pilot study.

Objectives: Among all of the swollen joints undergoing an aspiration in primary care, approximately 92 % are of nonseptic cause. This study therefore sought to develop a predictive model, based on simple clinical and paraclinical data, with the aim of predicting the aseptic nature of joint effusion.

Methods: This is a cohort, prospective, monocentric study. Some explanatory variables were predetermined on the basis of the literature review. A predictive model has been established based on these variables. In order to prioritise the negative predictive value, a cut-off point considering the best specificity for an observed sensitivity greater than or equal to 98 % was retained.

Results: A total of 328 participants, 49.1 % of whom were women, were included in this study, with a median age of 69 years. The median duration of evolution of joint effusion before the puncture was 30 days. Joint fluid had inflammatory characteristics in 46.0 % of cases and 8 septic arthritis were identified. The area under the receiver operating characteristic (ROC) curve of the predictive model was evaluated at 0.93. The model includes the maximum temperature, the polyarticular nature of the clinical picture and the macroscopic appearance of the joint fluid.

Conclusions: This study made it possible to develop a simple and easily accessible predictive model in a primary care setting. This tool could make it possible to exclude a priori the septic aetiology of one out of four native joint effusions. Its performances remain to be determined on an independent population in a subsequent study (confirmation cohort in progress).