Timing of intraoperative baseline parathormone estimation at the time of parathyroidectomy.
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The objectives of this study were two-fold, firstly to determine the best tool to confirm completion of resection of all hypercellular parathyroid tissue. Secondly, to assess the optimal time for drawing baseline parathyroid hormone (PTH) sample on the day of surgery. 190 consecutive patients who underwent parathyroidectomy for sporadic primary hyperparathyroidism at a single tertiary care center between January 1, 2008 and May 31, 2012 were included in this largely retrospective study. Conventionally, a single baseline intraoperative PTH (ioPTH) measurement is collected; however, in a subset of these patients, we opted to collect two baseline samples in order to strengthen the data and create matched pairs. As part of the prospective arm of this study, 30 patients had both pre- and post-induction ioPTH levels measured; their mean PTH level pre-induction was 202 ng/L and mean PTH level post-induction was 292 ng/L. A paired-samples t-test demonstrated a statistically significant difference between the two means (p-value = 0.045). Mean percent change in ioPTH level from baseline to post-excision sample was also evaluated. Mean percent change in PTH from pre-induction to post-excision was 59.4% and from post-induction to post-excision was 68.0%. A paired-samples t-test demonstrated a statistically significant difference between the two means (p-value = 0.032). The clinical implication of these results is rooted in surgical decision-making. In 4 of the 30 cases, the Miami criterion was satisfied only with the post-induction measurement as baseline; if the pre-induction PTH measurement had served as a baseline, surgery would’ve continued needlessly.