P32: POST-OPERATIVE RELATIVE PARATHORMONE DECLINE (ΔPTH%) AND ABSOLUTE PARATHORMONE DECLINE (ΔPTH) LEVELS ARE BETTER MARKERS OF SYMPTOMATIC HYPOCALCEMIA FOLLOWING TOTAL THYROIDECTOMY THAN POST-OPERATIVE PTH ALONE

Abstract

Introduction: Hypocalcemia is a frequent complication following thyroidectomy which can delay discharge and increase overall treatment expenditure. We aimed to assess the predictive value of absolute and relative intact Parathormone(iPTH) decline levels as reliable markers of post-operative hypocalcemia. Method: This prospective study included 95 consecutive patients at our tertiary care centre. Patients underwent either Total Thyroidectomy(TT), TT+Central Neck Dissection(CND) or TT+CND+Modified Radical Neck Dissection(MRND). iPTH levels were measured four hours after surgery and the following morning after surgery(POD 1). iPTH, absolute iPTH decline(ΔPTH) and relative iPTH decline(ΔPTH%) were calculated and correlated with hypocalcemia. Comparisons between groups were measured by chi-square test, Fischer's exact test and Mann-Whitney U test. Result: Of the 95 patients, 59 had malignant disease, while 36 patients had benign histopathology. TT was performed in 69 patients, TT+CCLND in 7, and TT+CCLND+MRND in 19. 32.6% of patients(n=31) had biochemical hypocalcemia and 20%(n=19) had symptomatic hypocalcemia. The mean calcium of the cohort on Post-operative day(POD)-1 was 8.3±0.66(range=6.5-9.9) and POD-3 was 8.4±0.69(range=6.3–10.7). Median PTH, measured 4 hours after surgery was 24pg/ml(IQR–23.4;range 2.5–85.5), and measured on POD-1 was 28pg/ml(IQR–27.6;range=2-79). The ΔPTH(U=206;p<0.001) & ΔPTH% (U=127;p<0.001) were significantly higher in patients with symptomatic hypocalcemia. A ΔPTH% of 20%(sensitivity=84%;specificity=91%) and ΔPTH of 3.75 pg/ml(sensitivity = 74%; specificity=87%) were good predictors of symptomatic hypocalcemia. Conclusion: Post-operative ΔPTH and ΔPTH% are reliable predictors of hypocalcemia following thyroid surgery and have the potential to facilitate a safe early discharge for patients undergoing TT. 20% fall in the PTH level(ΔPTH%) can be useful as a marker of hypocalcemia. Take-home message: Post-operative ΔPTH and ΔPTH% are better predictors of hypocalcemia following thyroid surgery than a single value of post-operative PTH alone.