(A) A ROC curve for the synovial WBC count is shown with an AUC of 98%. A cutoff value of 12,800 cells/μL demonstrates 89% sensitivity, 100% specificity, 100% PPV, 88% NPV, and 94% accuracy. (B) A ROC curve for %PMN is shown with an AUC of 91%. A cutoff value of 89% demonstrates 81% sensitivity, 90% specificity, 91% PPV, 79% NPV, and 85% accuracy. (C) A ROC curve for the serum CRP levels is shown with an AUC of 93%. A cutoff value of 93 mg/L demonstrates 88% sensitivity, 100% specificity, 100% PPV, 83% NPV, and 92% accuracy. (D) A ROC curve for the serum ESR is shown with an AUC of 73%. A cutoff value of 44 mm/hr demonstrates 92% sensitivity, 53% specificity, 76% PPV, 80% NPV, and 77% accuracy. PPV = positive predictive value; NPV = negative predictive value; CI = confidence interval.