Diagnostic efficacy of ([Ca]×[Cl])/P combined with ALP in the diagnosis and subtype differentiation of primary hyperparathyroidism.

Objective: To evaluate the diagnostic performance of the calcium-chloride/phosphorus ratio (([Ca]×[Cl])/P) combined with alkaline phosphatase (ALP) in primary hyperparathyroidism (PHPT) and its subtypes-hypercalcemic PHPT (HPHPT) and normocalcemic PHPT (NPHPT)-for accurate clinical differentiation. Methods: Clinical data of 135 surgically confirmed patients with PHPT (77 HPHPT, 58 NPHPT) and 135 age- and sex-matched healthy controls from Taizhou Enze Medical Center (Jan 2017-Dec 2024) were retrospectively analyzed. Serum ALP, Ca/P, Cl/P, and ([Ca]×[Cl])/P were measured; ROC curves assessed the diagnostic performance of single and combined indicators. Results: Most patients with PHPT were female. Adenoma prevalence was higher in the HPHPT group (83.12%) than in the NPHPT group (60.34%). ALP, parathyroid hormone (PTH), Ca/P, Cl/P, and ([Ca]×[Cl])/P levels were elevated in the HPHPT group compared with both the NPHPT and control groups, while serum phosphorus was lower (P<0.001). The area under the ROC curve (AUC) for ([Ca]×[Cl])/P in diagnosing PHPT was 0.960. Combined detection of ([Ca]×[Cl])/P (250.67 mmol/L) and ALP (93.50 U/L) yielded an AUC of 0.983 (sensitivity: 94.8%, specificity: 98.5%, accuracy: 95.0%), comparable to that of PTH (AUC = 0.997). The AUC for differentiating HPHPT from NPHPT was 0.881, and for distinguishing adenomas from hyperplasia was 0.677, demonstrating superior subtype discrimination compared with other indicators, including PTH. Conclusion: The combination of ([Ca]×[Cl])/P and ALP demonstrates favorable sensitivity and specificity for the diagnosis of PHPT and the differentiation of HPHPT from NPHPT, and exhibits clinical practicality. In addition, it provides supplementary value in distinguishing parathyroid adenoma from hyperplasia.