PTH and Hypocalcemia: Sam et al [20] demonstrated that the area under the ROC curve for postoperative serum PTH to predict hypocalcemia in patients without VDD was 0.93 (95% CI: 0.86 –1.00; P = 0.0001), but that of patients with VDD was 0.68 (95% CI: 0.39–0.97; P = 0.23).