Development and Validation of a Nomogram for Post-Parathyroidectomy Hypocalcemia in Secondary Hyperparathyroidism

Severe hypocalcemia (SH) is a common and serious complication after parathyroidectomy (PTX) in patients with secondary hyperparathyroidism (SHPT). However, accurately predicting high-risk patients remains challenging. This study aimed to develop and validate a linear predictive model to identify these patients preoperatively.

From January 2013 to May 2025, 755 total parathyroidectomy (TPTX) or TPTX with autotransplantation (TPTX-AT) were performed by a single surgical team at the 960th Hospital of the PLA Joint Logistics Support Force. After applying inclusion and exclusion criteria, 685 patients were enrolled and randomly divided (7:3) into training and validation cohorts. Variables associated with serum calcium levels on the first postoperative day (POD1 Ca) were identified through linear regression analysis in the training cohort. Model validity was assessed using ten-fold and leave-one-out cross-validation. Bland-Altman plots and paired t-tests evaluated agreement within groups. Model performance in the validation cohort was measured using bias, precision, and accuracy metrics.

Significant predictors of POD1 Ca included TPTX-AT (β [95% confidence interval (CI)]: -0.055 [-0.119, -0.001]), parathyroid hormone (PTH) (-0.078 [-0.115, -0.041], ng/mL), C-terminal cross-linked telopeptide of type I collagen (CTX) (-0.147 [-0.198, -0.096], μg/L), preoperative serum calcium (0.626 [0.516, 0.736], mmol/L), and alkaline phosphatase (ALP) (-0.018 [-0.024, -0.012], μkat/L). Bland-Altman analysis showed good agreement in the validation cohort (bias <0.001, 95% limits of agreement [LoA]: -0.507, 0.566).

The nomogram provides an accurate, individualized prediction of postoperative hypocalcemia risk after parathyroidectomy, supporting tailored clinical management of SHPT patients.