Improved immunoassay for the detection of severe combined immunodeficiency.

not an accurate predictor of post-thyroidectomy hypocalcemia in patients with vitamin D deficiency. Vitamin D deficiency is associated with increased serum PTH. Therefore the decline in serum PTH to an absolute cutoff value may take longer in these patients. We measured serum PTH at 8 –10 h postthyroidectomy. Further studies should assess the value of PTH measured at a later time point in predicting postthyroidec-tomy hypocalcemia in vitamin D– deficient patients. A limitation of this pilot study was the small number of patients with vitamin D deficiency , which may have had an effect on the area under the ROC curve in this group. Absolute concentrations of PTH are commonly used to predict postthyroidectomy hypocal-cemia. Our results confirm that a serum PTH concentration measured 8 –10 h after total thyroid-ectomy predicts the development of hypocalcemia, but only in the absence of vitamin D deficiency. Further studies are required to investigate whether percentage decrease in serum PTH (rather than absolute concentration) is a better predictor of postthyroid-ectomy hypocalcemia in vitamin D– deficient patients. A decrease in PTH of 60% coupled with a simultaneous decrease in calcium of 10% that occurs 5– 6 h postthy-roidectomy has been reported to have a sensitivity and specificity of 100% for predicting hypocal-cemia (4). Serum PTH did not accurately predict the occurrence of hypocal-cemia in vitamin D– deficient patients. It is therefore important to recognize this limitation of serum PTH, given the high prevalence of vitamin D deficiency in patients undergoing total thyroidectomy. It has been shown that the Liaison immunoassay is less accurate than liquid chromatography– tandem mass spectrometry for measuring concentrations of 25-hydroxyvitamin D (5). It would therefore be desirable to use liquid chromatography–tandem mass spectrometry for measuring 25-hydroxyvitamin D in future studies. Preoperative measurement of 25-hydroxyvitamin D and vitamin D replacement before surgery, where possible, may increase the reliability of PTH as a predictor of postthyroid-ectomy hypocalcemia. Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article. Role of Sponsor: The funding organizations played no role in the design of study, choice of enrolled patients, review and interpretation of data, or preparation or approval of manuscript. The …