Biochemical Ratios for Predicting Primary Hyperparathyroidism: Revisiting Simple yet Powerful Diagnostic Tools.

Area of Science:

• Endocrinology
• Clinical Biochemistry

Background:

• Differentiating primary hyperparathyroidism (PHPT), normocalcemic PHPT (NPHPT), and vitamin D deficiency-related secondary hyperparathyroidism (VDSHPT) presents a diagnostic challenge.
• Biochemical markers are crucial for diagnosing and differentiating these conditions.

Purpose of the Study:

• To evaluate the diagnostic utility of various biochemical markers in distinguishing PHPT, NPHPT, and VDSHPT.
• To assess the accuracy of serum calcium, phosphate, chloride, PTH, and derived indices in these patient groups.

Main Methods:

• A cross-sectional study involving 437 participants categorized into PHPT (n=161), NPHPT (n=97), VDSHPT (n=89), and control (n=90) groups.
• Analysis of serum calcium, phosphate, chloride, PTH, and vitamin D levels.
• Calculation of indices including Ca/P, Cl/P, Ca×Cl/P, and the PF Index (Ca×PTH/P).

Main Results:

• Calcium levels were highest in PHPT, while phosphate levels were lowest (p<0.001).
• Ca/P and Ca×Cl/P ratios were significantly higher in PHPT (p<0.001).
• Ca×Cl/P ratio showed high diagnostic accuracy for PHPT (specificity 89.2%), while Ca/P ratio had high sensitivity (77.6%). No significant difference in Ca/P and Ca×Cl/P ratios was observed between NPHPT and VDSHPT groups. Markers had high sensitivity but poor specificity in NPHPT.

Conclusions:

• The Ca×Cl/P and Ca/P ratios are valuable biochemical markers for diagnosing PHPT.
• Biochemical markers demonstrate limited specificity in differentiating NPHPT, underscoring the need for additional diagnostic approaches.
• These markers are useful for screening but require complementary diagnostic strategies for definitive diagnosis.