title: Do low preoperative vitamin D levels reduce the accuracy of quick parathyroid hormone in predicting postthyroidectomy hypocalcemia?
abstract: BACKGROUND
  Although some studies have suggested that low preoperative 25-hydroxyvitamin D (25-OHD) levels may increase the risk of hypocalcemia and decrease the accuracy of single quick parathyroid hormone in predicting hypocalcemia after total thyroidectomy, the literature remains scarce and inconsistent. Our study aimed to address these issues.
  
  
  METHODS
  Of the 281 consecutive patients who underwent a total/completion total thyroidectomy, 244 (86.8%) did not require any oral calcium and/or calcitriol supplements (group 1), while 37 (13.2%) did (group 2) at hospital discharge. 25-OHD level was checked 1 day before surgery, and postoperative quick parathyroid hormone (PTH) was checked at skin closure (PTH-SC). Postoperative serum calcium was checked regularly. Hypocalcemia was defined by the presence of symptoms or adjusted calcium of <1.90 mmol/L. Significant factors for hypocalcemia were determined by univariate and multivariate analyses. The accuracy of PTH-SC in predicting hypocalcemia was measured by area under a receiver operating characteristic curve (AUC), and the AUC of PTH-SC was compared between patients with preoperative 25-OHD <15 and ≥15 ng/mL via bootstrapping.
  
  
  RESULTS
  Preoperative 25-OHD level was not significantly different between groups 1 and 2 (13.1 vs. 12.5 ng/mL, p = 0.175). After adjusting for other significant factors, PTH-SC (odds ratio 2.49, 95% confidence interval 1.52-4.07, p < 0.001) and parathyroid autotransplantation (odds ratio 3.23, 95% confidence interval 1.22-8.60, p = 0.019) were the two independent factors for hypocalcemia. The AUC of PTH-SC was similar between those with 25-OHD <15 and ≥15 ng/mL (0.880 vs. 0.850, p = 0.61)
  
  
  CONCLUSIONS
  Low 25-OHD was not a significant factor for hypocalcemia and did not lower the accuracy of quick PTH in predicting postthyroidectomy hypocalcemia.
authors.affiliation: Division of Endocrine Surgery, Department of Surgery, University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong SAR, China. blang@hku.hk
authors.forename: Brian Hung-Hin
authors.initials: BH
authors.lastname: Lang
authors.forename: Kai Pun
authors.initials: KP
authors.lastname: Wong
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
authors.forename: Yuen Ki
authors.initials: YK
authors.lastname: Fong
authors.forename: Desmond Kwan-Kit
authors.initials: DK
authors.lastname: Chan
authors.forename: Grace Kin-Yee
authors.initials: GK
authors.lastname: Hung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D002118:Calcium / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006996:Hypocalcemia / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D011184:Postoperative Period; D011300:Preoperative Care; D011379:Prognosis; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000150:complications / Q000601:surgery*; D013965:Thyroidectomy; D014807:Vitamin D / Q000097:blood*; D055815:Young Adult
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; D002118:Calcium