Serum Calcium to Phosphorous (Ca/P) Ratio Is a Simple, Inexpensive, and Accurate Tool in the Diagnosis of Primary Hyperparathyroidism

Abstract

Primary hyperparathyroidism (PHPT) diagnosis is challenging and is based on serum calcium (Ca) and parathyroid hormone (PTH). Because serum Ca and phosphorous (P) are inversely related in PHPT, we investigated the diagnostic value of the serum Ca/P ratio in the diagnosis of PHPT. We report a single‐center, case‐controlled, retrospective study including 97 patients with documented PHPT and compared them with those of 96 controls (C). The main outcome measures were: serum PTH, 25‐OH vitamin D, Ca, P, albumin, and creatinine. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the serum Ca/P ratio were calculated. The results were verified using an independent, anonymous set of data extracted from a laboratory database containing over 900 million entries. A total of 35 (36.1%) PHPT patients had normocalcemic PHPT (NCHPT). Ca and PTH were significantly higher in PHPT than in C (p < 0.0001). P was significantly lower in PHPT than in C (p < 0.0001). The Ca/P ratio was significantly higher in PHPT than in C (p < 0.0001). Receiver‐operating characteristic (ROC) curves analyses identified a cutoff of 2.71 (3.5 if Ca and P are expressed in mg/dL) for Ca/P ratio with a sensitivity and specificity of 86% and 87%, respectively (p < 0.0001), confirmed by the independent, big data approach. In conclusion, Ca/P is a valuable tool for the diagnosis of PHPT and is of superior value compared to serum Ca alone, especially in NCPHT. Because Ca/P is simple, inexpensive, and easily accessible worldwide, this ratio is useful for PHPT diagnosis, especially in laboratory/medical settings relying on limited resources, such as low‐income countries. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

New parathyroid function index for the differentiation of primary and secondary hyperparathyroidism: a case-control study

“…However, this index was not used for differential diagnosis, but rather was used to help surgeons determine whether to explore the neck further or wait for PTH results after minimally invasive parathyroidectomy. In another study by Madeo et al, a Ca/P ratio of 2.71 was considered valuable for the diagnosis of PHPT [14], consistent with our study. However, in our study, the diagnostic power of the PFindex was stronger than those of the Ca/P Ratio and Wisconsin Index (Tables 2, 3).…”

Normocalcemic Hyperparathyroidism: A Heterogeneous Disorder Often Misdiagnosed?

“…Both relied on the evaluation of serum phosphorus (P). In a single‐center, case–controlled, retrospective study including 97 patients with biochemically and histologically documented PHPT, Madeo and colleagues ( 13 ) proposed a specific cut‐point for the albumin‐adjusted Ca/P ratio to easily identify subjects with PHPT without requiring measurement of PTH. A ratio cut‐point above 3.5, when Ca and P were measured in mg/dL, had a sensitivity of 89% and specificity of 91% for detecting patients in the cohort with either PHPT or NHPT.…”

Health status of Polychrus gutturosus based on physical examination, hematology and biochemistry parameters in Costa Rica

“…A correlation was found between calcium to phosphorus (Ca/P) ratio and weight in females but not in males. Ca and P homeostasis are directly interrelated because serum Ca interplays with serum P through the modulation of several hormones, such that serum concentration is approximately inversely related (a high Ca/P ratio means higher Ca than P) ( Madeo et al, 2018 ). Calcium increases proportionally greater than P, resulting in a higher value of Ca/P.…”