Timing of Serum Parathyroid Hormone Levels May Predict Postoperative Hypocalcemia

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Of the total patients, 25 developed postoperative hypocalcemia; the onset of hypocalcemia was less than 24 hours in 19 patients.
Of the total patients, 25 developed postoperative hypocalcemia; the onset of hypocalcemia was less than 24 hours in 19 patients.

Serum intact parathyroid hormone measured at 4 hours and 1 day postoperation may serve as accurate predictors of postoperative hypocalcemia, but with different laboratory cutoff point values, according to a study published in Endocrine.

Researchers conducted a prospective study of 101 patients at a tertiary care hospital in southern Brazil who underwent a thyroidectomy (partial or total) between January and November 2015, to determine the most accurate time and cutoff points of intact parathyroid hormone (iPTH) postsurgery that would allow clinicians to predict the risk for postoperative hypocalcemia.

Study results found total thyroidectomies, longer surgery duration, parathyroid gland-related surgical complications, and lower iPTH at 4 hours and 1 day postoperatively were associated with the development of postoperative hypocalcemia (all P < .005).

Researchers found that the cutoff times for iPTH at 4 hours and 1 day postoperation were 19.55 and 14.35 pg/mL, respectively. Sensibility, specificity, positive predictive value, and negative predictive values at 4 hours postoperation were 86.9%, 94.2%, 83.3%, and 95.6%, respectively, and at 1 day postoperation were 88%, 98.6%, 95.6%, and 96.1%, respectively. When comparing the difference between the 2 points of evaluation (4 hours and 1 day postoperation), no significant differences in predictive value were found (area under the curve, 0.935 vs 0.940; P =.415).

Researchers concluded that serum iPTH values at 4 hours and 1 day postoperation were both accurate to predict postoperative hypocalcemia. Therefore, clinicians should consider selecting and implementing serum iPTH level checks at either 4 hours or 1 day postoperation to assess the risk of developing postoperative hypocalcemia in postthyroidectomy patients.

Reference

Filho, EBY, Machry RV, Mesquita R, Scheffel RS, Maia AL. The timing of parathyroid hormone measurement defines the cutoff values to accurately predict postoperative hypocalcemia: a prospective study [published online May 2, 2018]. Endocrine. doi: 10.1007/s12020-018-1601-9

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