Diagnostic performance of the calcium/phosphate ratio for primary hyperparathyroidism in southwest China

The Ca∗Cl/P Ratio: A Novel and More Appropriate Screening Tool for Normocalcaemic or Overt Primary Hyperparathyroidism

OBJECTIVE

The main purpose of this study was to explore the diagnostic performance of the Ca∗Cl/P ratio for primary hyperparathyroidism (PHPT), especially normocalcaemic PHPT (NPHPT), to assist health care providers in making reliable and rapid clinical identifications.

METHODS

From January 1, 2013, to March 31, 2023, 230 PHPT patients, including 65 with NPHPT and 230 sex- and age-matched controls, were enrolled in this retrospective study. Differences between hypercalcaemic PHPT (HPHPT) and NPHPT and between them and their respective controls were analyzed. The diagnostic accuracy of the Ca∗Cl/P ratio, Ca/P ratio, Cl/P ratio and albumin-corrected calcium was assessed by the area under the receiver operating characteristic curve.

RESULTS

Compared with corresponding controls, NPHPT and HPHPT patients both had significantly higher Ca ∗ Cl/P ratios (271.64 ± 51.74 vs 192.71 ± 26; 419.91 ± 139.11 vs 199.14 ± 36.75, P < .001). In the overall cohort, the ROC-AUC of the Ca∗Cl/P ratio (0.964, 95% CI = 0.943-0.979) for diagnosis of PHPT patients was superior to albumin-corrected calcium (0.959, 95% CI = 0.934-0.973), the Ca/P ratio (0.956, 95% CI = 0.934-0.973), and the Cl/P ratio (0.923, 95% CI = 0.895-0.946). A Ca ∗ Cl/P ratio above 239.17 mmol/L, with sensitivity (0.952), specificity (0.922), PPV (0.924), NPV (0.951) and accuracy (0.937), can distinguish PHPT patients from healthy individuals. Furthermore, the Ca ∗ Cl/P ratio yielded a sensitivity of 0.831, specificity of 0.938, PPV of 0.931, NPV of 0.847 and accuracy of 0.885 for NPHPT.

CONCLUSION

The Ca∗Cl/P ratio provides excellent diagnostic power for diagnosis of PHPT, especially NPHPT.

Application of calcium-to-phosphorus (Ca/P) ratio in the diagnosis of pseudohypoparathyroidism: another piece in the puzzle of diagnosis of Ca-P metabolism disorders

Objective

The serum calcium (Ca)-to-phosphorus (P) ratio has been proposed to identify patients with primary hyperparathyroidism and chronic hypoparathyroidism (HPT), but it has never been tested in pseudohypoparathyroidism (PHP). The aim of this study was to test the performance of Ca/P ratio in PHP diagnosis compared with that in healthy subjects and patients with HPT for differential diagnosis.

Design

A retrospective, cross-sectional, and observational study was carried out.

Methods

Serum Ca, P, creatinine, parathyroid hormone (PTH), and albumin were collected. Ca and P were expressed in mmol/L. Ca/P diagnostic performance was evaluated by receiver operating characteristic curve, sensitivity, specificity, and accuracy.

Results

A total of 60 patients with PHP, 60 patients with HPT, and 120 controls were enrolled. The Ca/P ratio was lower in patients with PHP and HPT than that in controls (p < 0.0001). The cutoff of 1.78 (2.32 if Ca and P measured in mg/dL) for Ca/P ratio could identify patients with PHP and HPT among the entire cohort (sensitivity and specificity of 76%). No valid cutoff of Ca/P was found to distinguish patients with PHP from patients with HPT; in this case, PTH above 53.0 ng/dL identified patients with PHP (sensitivity and specificity of 100%). The index (Ca/P × PTH) above 116 ng/L recognized patients with PHP from controls (sensitivity of 84.7% and specificity of 87.4%), whereas (Ca/P × PTH) below 34 ng/L recognized patients with HPT from controls (sensitivity of 88.9% and specificity of 90.8%).

Conclusions

The Ca/P ratio below 1.78 (2.32 CU) is highly accurate to identify patients with PHP and HPT, although it is not reliable to differentiate these two conditions. The index (Ca/P × PTH) is excellent to specifically recognize PHP or HPT from healthy subjects.

The importance of hypophosphatemia in the clinical management of primary hyperparathyroidism

AIM

The levels of serum phosphorus (P) are low or low-normal in primary hyperparathyroidism (PHPT), and there is an inverse relationship between the levels of parathormone (PTH) and P. However, when considering the diagnostic and surgical indication criteria of PHPT, serum P levels are generally ignored. The aim of this study was to retrospectively evaluate the association of serum P levels with the clinical outcomes of PHPT.

MATERIALS AND METHODS

A retrospective evaluation was made of the data of 424 consecutive patients (370 females, 54 males) with PHPT who presented at our centre.

RESULTS

The mean age of the study population was 57 ± 11.68 years. The mean P was 2.57 ± 0.53 mg/dl. Asymptomatic disease was determined in 199 (47%) patients. Male patients had significantly lower levels of P. Symptomatic patients and patients with renal stones, vitamin D < 20 µg/l, calcium level ≥ 11.2 mg/dl, 24 h urinary calcium > 400 mg/day, or hypomagnesemia, were seen to have significantly lower levels of P (p < 0.05). Hypophosphatemia (hypoP) was found in 202 of 424 patients (47%), and these patients had a higher rate of symptomatic disease (63% to 44%, p < .0001). Of the 61 (88%) patients with moderate hypoP, 54 (88%) had at least one of the surgical criteria. A statistically significant increase in the incidence of hypoP was determined in symptomatic and male patients. In the patients with hypoP, serum PTH and urine calcium levels were found to be higher, and lumbar T-scores and serum vitamin D levels were lower. The patients with hypoP had higher rates of renal stones and osteoporosis (p < 0.05).

CONCLUSIONS

The current study results show that hypoP is associated with a higher risk of osteoporosis and renal stones in PHPT patients. Even if patients are asymptomatic, moderate hypoP may be associated with poor outcomes of PHPT. Therefore, moderate hypoP may be a new criterion for parathyroidectomy, regardless of hypercalcemia level.

Serum Calcium/Phosphorus Ratio in Biochemical Screening of Primary Hyperparathyroidism

OBJECTIVE

Primary 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.

METHODS

A 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.

RESULTS

There 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).

CONCLUSION

The calcium/phosphorus ratio is a simple and inexpensive method for primary hyperparathyroidism screening when a cutoff value of 2.59 is used.