The Predictive Value Of Parathyroid Hormone Level And Decline Rate For Postoperative Hypocalcemia Of Thyroid Papillary Carcinoma

Objective To investigate the predictive value of parathyroid hormone(PTH)level on postoperative day 1 and the decline percentage for postoperative hypocalcemia of thyroid papillary carcinoma.Material and methods We retrospectively analyzed the clinical data of 64 patients with thyroid papillary carcinoma and divided the patients into two groups,hypocalcemia group and non-hypocalcemia group,according to the minimum postoperative serum calcium level within a week.The lowest postoperative serum calcium level in peripheral blood of the hypocalcemia group was less than 2.00 m m o l/L,while non-hypocalcemia group was more than 2.00 mmo l/L.The level of serum calcium and PTH in peripheral blood were measured before surgery and on postoperative day 1,and the decline rate of PTH(ΔPTH%)=(The preoperative level of serum PTH in peripheral blood-the level of PTH on postoperative day 1)/The preoperative level of serum PTH in peripheral blood,were calculated.Remeasured the level of postoperative serum calcium in peripheral blood within a week.Analyses were performed using SPSS20.The gender information was analyzed byχ~2 test.The preoperative level of serum calcium and PTH in peripheral blood,the level of serum calcium and PTH on postoperative day 1 andΔPTH%were analyzed by independent sample t-test.Box figure showed the difference distribution of the level of PTH on postoperative day 1 andΔPTH%;Receiver-operating characteristic(ROC)curve of the level of serum calcium and PTH on postoperative day 1 andΔPTH%was drawed,analyzed the accuracy of hypocalcemia prediction according to the area under the curve(AUC),analyzed the coordinates of the curve,and determined the sensitivity,the specificity,calculated the misdiagnosis rate and the missed diagnosis rate of postoperative hypocalcemia predictive according to the cut-off value.Results Among the total 64 cases there were 18 cases in hypocalcemia group and46 cases in non-hypocalcemia group.There was no significant difference between the two groups in terms of gender,age,the preoperative level of serum calcium and PTH in peripheral blood.The P values of the level of serum calcium and PTH on postoperative day 1 andΔPTH%were lower than 0.001,and there were significant difference between the two groups.For the hypocalcemia group,the average level of PTH in peripheral blood on postoperative day 1 was 8.10(±3.28)mmol/L,for the non-hypocalcemia group the average was 28.12(±11.24)mmol/L,for the hypocalcemia group the average ofΔPTH%was 77.55(±10.57)%,for the non-hypocalcemia group the average was 17.24(±38.05)%,the distribution difference of the level of PTH on postoperative day 1 andΔPTH%were showed remarkable by box figure.The ROC curve of the level of serum calcium on the postoperative day 1 showed the area under the curve(AUC)was 0.835,analyzed the coordinates of the curve,the cut-off value was 2.175 m m o l/L,the sensitivity was 77.8%,the specificity was 71.7%;the ROC curve of the level of PTH on the postoperative day 1 showed the AUC was 0.981,analyzed the coordinates of the curve,the cut-off value was 13.765 p g/m L,the sensitivity was 100%,the specificity was93.5%;the ROC curve ofΔPTH%showed the AUC was 0.989,analyzed the coordinates of the curve,the cut-off value was 59.15 p g/m L,the sensitivity was 100%,the specificity was 95.7%.When predicting the occurrence of postoperative hypocalcemia by the level of serum calcium on postoperative day 1 was less than 2.175 mmol/L,the misdiagnosis rate was 28.3%,the missed diagnosis rate was 22.2%;when predicting the occurrence of postoperative hypocalcemia by the level of PTH on postoperative day 1was less than 13.765pg/m L,the misdiagnosis rate was 6.5%,the missed diagnosis rate was 0%;when predicting the occurrence of postoperative hypocalcemia by theΔPTH%on postoperative day 1 was more than 59.15%,the misdiagnosis rate was 4.3%,the missed diagnosis rate was 0%;when predicting the occurrence of postoperative hypocalcemia by the level of PTH on postoperative day 1 was less than 13.765pg/m L and theΔPTH%on postoperative day 1 was more than 59.15%,the misdiagnosis rate was2.2%,the missed diagnosis rate was 0%.Conclusion Combining the level of serum calcium andΔPTH%on the postoperative day 1 had the highest predictive accuracy for postoperative hypocalcemia of thyroid papillary carcinoma.