The alpha defensin lateral flow test is effective in predicting eradication of periprosthetic joint infection after surgical debridement.

The primary aim of this study was to assess the utility of the alpha defensin lateral flow (ADLF) test for predicting the eradication of PJI after surgical debridement. The secondary aim was to describe the reliability of ADLF test in diagnosis of PJI intra- operatively. A prospective observational study was conducted in three independent orthopaedic centres. Twenty-two patients undergoing revision surgery (debridement, antibiotics and implant retention (DAIR), single or two-stage revision) for PJI were recruited, 13 female and 9 male with an average age of 64 years. Samples were collected intra-operatively at the start of the first surgical procedure and then at the completion of debridement or prior to reimplantation depending on the operation performed. These samples were tested using ADLF and then sent for microbiological analysis. The ADLF result was then compared to the corresponding culture result in order to determine the diagnostic predictive accuracy. The reliability of ADLF test to predict eradication of infection after debridement of PJI was excellent for specificity and positive predictive value (PPV) of which both where 100%, but had a poor sensitivity (14.3%) and negative predictive value (NPV) (62.5%). The reliability of ADLF test to predict PJI was poor with only a 50% sensitivity and specificity. The ADLF test has a high specificity and PPV for diagnosing eradication of infection after debridement. In contrast the ADLF testing appears to have poor diagnostic accuracy for PJI when used on intra-operative samples, prior to surgical intervention.