Early biomarkers of hypocalcemia following total thyroidectomy

Hypocalcemia is the most frequent major complication following total thyroidectomy (TT), delaying timely hospital demission. We prospectively evaluated the diagnostic utility of parathyroid hormone (PTH) measured one hour after TT and the delta (post-minus pre-surgery) PTH in order to determine which biomarker best predicted post-surgery hypocalcemia. Ninety-six consecutive patients, with either plurinodular goiter, Graves' disease or cervico-mediastinal goiter (22 (23%) men and 74 (77%) women, mean age 48.5 ± 15.2 and 47.9 ± 13.2 years, respectively), scheduled to undergo TT were enrolled. PTH was measured prior and one hour after surgery. Delta PTH was defined as one-hour post-surgery values minus pre-surgery PTH level. Hypocalcemia was defined as a calcemia under 8.0 mg/dL. Receiver operating characteristic (ROC) analysis was used to evaluate the Area Under Curve (AUC), sensibility and specificity of the two biomarkers for the occurrence of hypocalcemia. Forty-nine (51%) patients presented biochemical values under the cut-off but only 17 (18%) had clinical symptoms. Both variables yielded statistically significant AUC (PTH one-hour post surgery: 0.654; p = 0.0403; 95%CI: 0.519-0.773 and delta PTH: 0.659; p = 0.0263; 95%CI: 0.527-0.776). Although comparison of the two ROC curves did not yield significant differences, delta PTH yielded a better sensitivity and PTH one-hour post-TT yielded a marginally better specificity (sensitivity of 50% and 87% and specificity of 76% and 67% for cut-offs of <39.8 pg/dl and <54.5 pg/dl, respectively). Both biomarkers have similar diagnostic accuracy for hypocalcemia, and can be used to indicate when supplemental therapy should be implemented in order to favor a timely discharge.