Validation of finger test for necrotising soft tissue infection

Abstract

Background: Necrotising soft tissue infection (NSTI) is rare but fatal. Andreasen proposed finger test as an early diagnostic tool to differentiate NSTI from other soft tissue infections. We aim to evaluate the accuracy and reproducibility of the test for the diagnosis of NSTI. Methods: Patients who were admitted to our department from 2012 to 2016 with suspicion of NSTI and finger test done were retrospectively reviewed. Finger test was done and interpreted as described by Andreasen. Definitive diagnosis of NSTI was confirmed with surgical and pathological findings. Results: Among the 35 patients included in the study, NSTI was confirmed in 10 cases. Finger test had a sensitivity of 100%, a specificity of 80%, positive predictive value of 66.7%, negative predictive value of 100% and an overall accuracy of 85.7%. There was no difference in demographics or comorbidities between NSTI and non-NSTI groups. Surgeons involved had 76.7% agreement and moderate reproducibility (kappa = 0.48) on the diagnostic criteria of finger test. Conclusion: A negative finger test was reliable to exclude NSTI and a positive test suggested further surgical exploration. Yet, clinical judgement was still of paramount importance to treat NSTI promptly.