Fig. 1A–B.

Receiver operating curves for predicting periprosthetic infection are illustrated. An area under the curve of 1 demonstrates an ideal test with a 100% sensitivity and specificity, while an area under the curve less than 0.5 indicates that the diagnostic has poor discriminatory value. (A) The cutoff value for optimal accuracy in diagnosis of PJI was 1100 cells/μL for fluid leukocyte count. (B) The cutoff value for optimal accuracy for fluid neutrophil differential was 64%. When both tests yielded results below their cutoff values, the negative predictive value of the combination increased to 99.6%, while if both tests were greater than their cutoff values the positive predictive value improved to 100%.