Abstract
Intra-operative parathyroid hormone (PTH) levels have successfully been used to assess surgical ablation of parathyroid adenomas, the use of this same test to predict preservation of viable gland has not been widely used. to test the sensitivity and specificity of intraoperative rapid PTH assay test in predicting permanent postoperative hypoparathyroidism, and applicability to guide the search for inadvertently removed parathyroid glands for possible auto transplantation. 52 patients undergoing total thyroidectomy for non-malignant thyroid diseases were included. Intraoperative rapid PTH assay test was performed. If levels were reduced, or less than 3 parathyroid glands were detected, removed thyroid gland was examined for unintentionally removed parathyroid tissue for possible auto transplantation. There was a strong correlation between intraoperative rapid PTH assays and those taken 24 hours after surgery, 16 out of 52 patients had reduction of the PTH intraoperatively to levels below 25 pg/ml, of them, 11 patients (who had values between 15-24 pg/ml) recovered to normal PTH levels within 4 weeks, while the 5 patients with intraoperative PTH levels below 15 pg/ml failed to regain normal PTH levels up to 12 weeks postoperatively, even in those patients where parathyroid tissue was auto transplantated. The 4 patients who had parathyroid tissue reimplanted intraoperatively restored some of their parathyroid function as indicated by relative rise of their PTH levels, but did not reach even the low normal levels. (ROC) curve for prediction of early hypoparathyroidism using intraoperative rapid PTH assay was statistically highly significant with optimal cutoff value for predicting early hypocalcaemia level <27 pg/ml, (sensitivity 100%, specificity 68.2%). (ROC) curves for predicting permanent hypoparathyroidism using intraoperative rapid PTH assay or standard PTH assay taken 24 hours after surgery were statistically significant with optimal cutoff value PTH level <12 pg/ml on the intraoperative PTH curve or <15 pg/ml on the postoperative PTH curve (sensitivity 100%, specificity 100%). Intraoperative PTH assay may allow intraoperative monitoring of parathyroid function, predicting postoperative outcomes, may identify patients at risk of developing postoperative hypoparathyroidism, guiding surgeons to re-examine removed specimens for inadvertently removed parathyroid tissue with possible auto transplantation, or more practically a guide to early replacement therapy to prevent hypocalcaemia, leading to safe and early hospital discharge. Limitations in our study to be reconsidered in further studies, are relative small sample size, inability for randomisation, and the variable values reported for the cut off value of PTH causing hypocalcaemic symptoms needing intervention.
Highlights
In non-neoplastic thyroid diseases, total thyroidectomy is sometimes indicated for cases such as multinodular goiter, obstructive symptoms; retrosternal goiter, even in the absence of obstruction; primary hyperthyroidism or Grave’s disease; recurrent or secondary hyperthyroidism, etc. [1]
The 4 patients who had parathyroid tissue reimplanted intraoperatively restored some of their parathyroid function as indicated by relative rise of their parathyroid hormone (PTH) levels, but did not reach even the low normal levels. (ROC) curve for prediction of early hypoparathyroidism using intraoperative rapid PTH assay was statistically highly significant with optimal cutoff value for predicting early hypocalcaemia level
By using the receiver operating characteristic (ROC) curves for prediction of permanent hypoparathyroidism via comparing the intraoperative rapid PTH assay with the standard PTH assay taken 24 hours after surgery, we found that both curves had an AUC of 1.0 (SE = 0, 95% CI = 0.932 – 1.0, P
Summary
In non-neoplastic thyroid diseases, total thyroidectomy is sometimes indicated for cases such as multinodular goiter, obstructive symptoms; retrosternal goiter, even in the absence of obstruction; primary hyperthyroidism or Grave’s disease (that is unresponsive to medical management); recurrent or secondary hyperthyroidism, etc. [1]. Permanent hypoparathyroidism and recurrent laryngeal nerve damage are two major morbidities of thyroid surgery, accounting for most medical litigation [2]. Despite these applications, occasionally postoperative hypoparathyroidism and subsequent hypocalcaemia ensue; causes of such a drop of parathyroid levels may be due to several reasons, such as inadvertent excision of a parathyroid gland(s), which according to Lin et al (2002)’s study occurred in 9% of patients undergoing thyroidectomy [4], as the majority of patients (95%) had two or less parathyroid glands in their excised specimens, in addition to induced capsular bleeding due to inadvertent incision which commonly occurred [5,6,7], or indirect injury to the glands by a very meticulous homeostasis technique, with subsequent avascular necrosis. One potential additional application of this tool is to select patients for parathyroid autotransplantation during thyroidectomy [19]
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