• Nagihan Bestepe, Fatma Neslihan Cuhaci, Burcak Polat, Berna Evranos Ogmen, Didem Ozdemir, Reyhan Ersoy, and Bekir Cakir.
• Ankara City Hospital, Department of Endocrinology and Metabolism - Ankara, Turkey.
• Rev Assoc Med Bras (1992). 2022 Jan 1; 68 (12): 166816741668-1674.

ObjectivePrimary hyperparathyroidism is a common endocrine disease and most cases are asymptomatic. Currently, in a hypercalcemic patient, the first laboratory investigation is serum primary hyperparathyroidism measurement. However, the primary hyperparathyroidism level cannot be measured in many primary healthcare centers in our country. In addition, serum calcium levels are normal in normocalcemic primary hyperparathyroidism patients, even if most centers have serum calcium levels measured. Therefore, a simple and inexpensive laboratory biochemical marker is required for the diagnosis of primary hyperparathyroidism. Recently, the calcium/phosphorus ratio has been proposed as a suitable tool for diagnosing primary hyperparathyroidism. This study aimed to investigate the diagnostic value of serum calcium/phosphorus ratio in primary hyperparathyroidism screening.MethodsA total of 462 patients followed in our clinic with a diagnosis of primary hyperparathyroidism were reviewed in this retrospective study. Out of these patients, 148 with normal levels of serum parathyroid hormone, calcium, and phosphorus were selected as the control group. Serum calcium, corrected calcium, phosphorus, albumin, parathyroid hormone, 25-hydroxyvitamin D, and creatinine were evaluated. The diagnostic accuracy of the calcium/phosphorus ratio was investigated using receiver operating characteristic curve analysis.ResultsThere were 404 (87.4%) females and 58 (12.6%) males in the primary hyperparathyroidism group. Calcium, parathyroid hormone, and calcium/phosphorus ratio were significantly higher in primary hyperparathyroidism than in controls (p<0.001 for each). Receiver operating characteristic curve analyses identified a cutoff value of 2.59 (3.35 if calcium and phosphorus are measured in mg/dL) for the calcium/phosphorus ratio, with a sensitivity of 90.5% and specificity of 93.2% (p<0.001).ConclusionThe calcium/phosphorus ratio is a simple and inexpensive method for primary hyperparathyroidism screening when a cutoff value of 2.59 is used.

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