Background: Post-operative parathyroid hormone (postopPTH) testing is variably employed by surgeons performing total thyroidectomy to identify patients at-risk for subsequent hypocalcemia, and to guide prophylactic calcium and vitamin-D supplementation to prevent clinically significant hypocalcemia and related complications. Whether postopPTH testing can guide management that improves patient outcomes remains of interest to clinicians caring for patients undergoing thyroidectomy.
Objectives: To assess the association of postopPTH testing-based management strategy on frequency of significant hypocalcemia following total thyroidectomy.
Methods: The National Surgical Quality Improvement Program Procedure Targeted dataset for the year 2016 identified 1900 patients who underwent total thyroidectomy, with or without postopPTH. Patients with postopPTH testing (n= 865) were compared to those managed without postopPTH testing (n= 1035).
The primary outcome of interest was frequency of significant hypocalcemia events within 30-days following index procedure, based on utilization or non-utilization of postopPTH testing to guide management. Secondary outcomes of interest included frequency of clinically severe hypocalcemia-related events, length of hospital stay (LoS) and readmission. Pearson chi-square tests were used to analyze differences in outcomes stratified by use of postopPTH. Fisher’s exact test, Kruskal-Wallis test and Wilcoxon ranksum test were used to test for differences in readmissions and LoS.
Results: A total of 865 (45.5%) of patients who underwent total thyroidectomy received postopPTH testing. The frequency of significant postoperative hypocalcemia within 30-days of index surgery was higher in patients tested for postopPTH versus those managed without postopPTH testing (10% [n=84] vs. 6% [n=61], p=0.002). The frequency of clinically severe hypocalcemia-related events (6% vs. 5%, p=0.34) and readmission (4% vs. 3%, p=0.33) were similar between groups. LoS for postopPTH group (1.28 days [SD 1.76]) was statistically longer than the group without postopPTH testing (1.09 days [1.25]) (p=0.011), however, this difference may not be clinically significant.
Within the group of patients with postopPTH testing after total thyroidectomy, 179 patients received no postoperative oral calcium or vitamin-D supplements, 371 received both medications, 216 received oral calcium, and 50 patients received vitamin-D supplementation. In the group of patients that were treated with oral calcium and vitamin-D following postopPTH testing, the frequency of significant hypocalcemia within 30-days and clinically severe hypocalcemia-related events were 14% (n=53) and 10% (n=37), respectively. In comparison, patients in the group where postopPTH was not available to determine management, and where calcium and vitamin-D were empirically supplemented, frequency of significant hypocalcemia within 30-days and clinically severe hypocalcemia-related events were 9% (n=34) and 7% (n=29), respectively.
Clinical Implications: In this analysis of multi-institutional pooled data, PostopPTH testing after total thyroidectomy was not associated with improvements in outcomes, including frequency of significant hypocalcemia events within 30-days, clinically severe hypocalcemia-related events, LoS and hospital readmission. The higher frequency of significant hypocalcemia and related clinically severe events in patients managed with postopPTH compared to those managed empirically should encourage critical reassessment of clinical response when patients at-risk for hypocalcemia are identified with postopPTH testing. Inability to identify critical postopPTH thresholds and/or inappropriate calcium and vitamin-D replacement patterns may handicap the value of postopPTH testing following total thyroidectomy.