Efficacy and limitations of a web-based native adult knee septic arthritis calculator in urban trauma care.

Abstract

Septic arthritis of the knee presents significant diagnostic challenges. Traditional diagnostic methods demonstrate limited sensitivity and specificity, whereas delayed intervention risks irreversible joint damage. A web-based septic arthritis calculator offers quantifiable risk assessment, but its performance requires validation. We evaluated (1) diagnostic accuracy of a web-based septic arthritis calculator in a tertiary referral center and (2) optimal risk thresholds for recommending surgical intervention and for confidently excluding septic arthritis. We retrospectively analyzed 121 consults for suspected septic arthritis of the knee including arthrocentesis in adult patients at a tertiary referral center from 2018 to 2023. Newman criteria served as the diagnostic gold standard for septic arthritis. We calculated risk probabilities using the web-based tool incorporating 6 clinical and laboratory variables. Receiver operating characteristic analysis identified optimal thresholds for surgical intervention and assessed diagnostic performance. The calculator demonstrated excellent discrimination between septic (n = 75) and nonseptic (n = 46) joints (area under the curve of 0.97 [95% confidence interval 0.95-0.99; <i>P</i> < .001). Median calculated probabilities for sepsis were 80% vs 4% for nonseptic cases. Optimal thresholds included 58% for recommending surgical intervention (sensitivity 89%, specificity 98%, positive predictive value 99%) and 24.6% for excluding septic arthritis (sensitivity 96%, specificity 87%, negative predictive value 93%). Both thresholds achieved 93% correct classification. The web-based calculator provides excellent diagnostic accuracy and clinically relevant thresholds derived from ROC analysis: ≥58% for recommending surgical intervention and <24.6% for confidently excluding septic arthritis. These findings support systematic implementation in tertiary referral centers to enhance diagnostic precision and optimize resource allocation, although prospective validation remains essential. III.