Endocrine Abstracts

Introduction: The diagnosis of primary hyperparathyroidism and hypoparathyroidism is still challenging because of the increasing frequency of non-classical presentations. The calcium-to-phosphorus ratio (Ca/P) (CPR) is an inexpensive biochemical marker that could be useful to diagnose parathyroid disorders.

Aim: The aim of this study was to assess the performances of CPR in the diagnosis of primary hyperparathyroidism and hypoparathyroidism.

Methods: This was a single-center, cross-sectional study including 32 patients with PHPT, 32 patients with hypoparathyroidism, and 32 controls. Total serum calcium (mg/l), serum phosphorus (mg/l), and parathyroid hormone (PTH) (ng/l) levels were recorded for all the participants. The diagnostic performance of the CPR was evaluated using the receiver operating characteristic (ROC) curve to define cut-off points. Sensitivity and specificity were calculated.

Results: The mean CPR was 1.58±0.39 in patients with hypoparathyroidism, 5.37±1.28 in patients with primary hyperparathyroidism, and 2.94±0.49 in controls (P<10-3). It was positively correlated with the PTH level (r=0.618, p <10-3). However, CPR was not correlated with age, body weight, and body mass index. CPR had an area under the ROC curve of 0.977 (95%-confidence interval: 0.941-1) in the diagnosis of primary hyperparathyroidism with an optimum cut-off level of 3.70, providing a sensitivity of 94% and a specificity of 100%. The area under the ROC curve of CPR in the diagnosis of hypoparathyroidism was 0.987 (95%-confidence interval: 0.969-1). A CPR level below 1.99 was defined to identify patients with hypoparathyroidism with a sensitivity of 97% and a specificity of 91%.

Conclusion: Our results demonstrated the accuracy of CPR as a reliable tool for the diagnosis of both primary hyperparathyroidism and hypoparathyroidism.