Primary Hyperparathyroidism perfectly predicted with a Vitamin D-Based nomogram – Nov 2011

A New, Vitamin D- Based, Multidimensional Nomogram for the Diagnosis of Primary Hyperparathyroidism.

Endocr Pract. 2011 Nov 8:1-21.
Harvey A, Hu M, Gupta M, Butler R, Mitchell J, Berber E, Siperstein A, Milas M.
Department of Endocrine Surgery, University of Calgary, Calgary, Alberta, Canada.

Objective: The biochemical diagnosis of primary hyperparathyroidism (1?HPT) has traditionally been based on elevated calcium and PTH values.
These classic criteria fail to diagnose the subset of patients where calcium, PTH or both lie within the "normal" range.
The purpose of this study was to refine diagnostic criteria for 1?HPT to capture these atypical patients.

Methods: Total serum calcium, intact PTH, and 25-hydroxy vitamin D levels were measured in 1?HPT and healthy patient groups.
Multivariate analysis of healthy patient data first identified factors that significantly impacted PTH levels, and defined a new PTH reference range with a mathematical model.
The model was then validated for prediction of atypical 1?HPT in patients with surgically confirmed disease.

Results: Calcium (p<0.015), vitamin D (p<0.0001) and age (p<0.0002) independently impacted PTH.
With these variables, we created a 4-dimensional nomogram that distinguished normal patients from those with hyperparathyroid states.

Mathematically, this nomogram predicts 1?HPT when measured serum PTH is higher than PTH calculated by the formula:
PTH (pg/ml) = 120- (6 × calcium (mg/dL))- (0.52 × 25-hydroxy vitamin D (ng/ml)) + (0.26 × patient age (years)).

When applied to our surgical group, this nomogram successfully identified

• 100% (238/238) of patients with classical 1?HPT,
• 96% (64/67) with normocalcemic 1?HPT and
• 53% (21/40) with 1?HPT and normal PTH.

Conclusion: This study uniquely defines a patient-specific normal limit of PTH based on readily available parameters of calcium, 25-hydroxy vitamin D and age. Our nomogram may allow for more rapid definitive diagnosis and treatment of 1?HPT in patients with atypical presentations.

PMID: 22068245  Download the PDF from ResearchGate via VitaminDWiki

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