Is There a Threshold Value of Hemoglobin A1c That Predicts Risk of Infection Following Primary Total Hip Arthroplasty?

BACKGROUND There remains little evidence to support a perioperative hemoglobin A1c (HbA1c) level that could serve as a threshold for a significantly increased risk of deep postoperative infection in patients with diabetes mellitus (DM) following total hip arthroplasty (THA). METHODS A national administrative database was queried for patients who underwent primary THA with DM. Patients with an HbA1c level within 3 months of surgery were identified and were stratified based on HbA1c level in 0.5 mg/dL increments. The incidence of deep infection requiring operative intervention within 1 year for each group was identified and a receiver operating characteristic (ROC) and area under the curve (AUC) analysis was performed to determine a threshold value of the HbA1c. RESULTS A total of 7736 patients who underwent THA with a perioperative HbA1c level were included. The rate of infection ranged from 0.7% to 5.9%. The inflection point of the ROC curve corresponded to an HbA1c level between 7.0 and 7.5 mg/dL (P = .001, specificity = 69%, sensitivity = 47%). The AUC for the ROC was 0.68. Patients with an HbA1c level of 7.5 mg/dL or greater had a significantly higher risk of deep infection compared to patients below this threshold (odds ratio, 2.6; 95% CI, 1.9-3.4; P < .0001). CONCLUSION The risk of infection in patients with DM increases as the perioperative HbA1c increases. However, in the present study, the HbA1c threshold level calculated demonstrated low discrimination based on our AUC value, suggesting the HbA1c test is poorly predictive of periprosthetic joint infection following THA in patients with DM.