Harvey et al developed an equation for predicting the upper limit of the normal reference range for serum intact parathyroid hormone. This can help to identify patients with primary hyperparathyroidism having an atypical presentation. The authors are from the University of Calgary in Canada.


Atypical presentations for primary hyperparathyroidism include:

(1) normocalcemic

(2) “normal” serum PTH


Assay for serum intact PTH: ADVIA Centaur (Siemens)



(1) age of the patient in years

(2) serum calcium in mg/dL (Roche Diagnostics)

(3) serum 25(OH)vitamin D in ng/mL (DiaSorin 2-step assay)


patient-specific upper limit of the normal range for serum intact PTH in pg/mL =

= 119.73 – (6.07 * (serum calcium)) + (0.26 * (age)) – (0.52 * (25(OH) vitamin D))



• The equation is dependent on the various assays used.


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