Equation of Harvey et al for Predicting the Upper Limit of Normal for Serum Intact Parathyroid Hormone (PTH)

Atypical presentations for primary hyperparathyroidism include:

(1) normocalcemic

(2) “normal” serum PTH

Assay for serum intact PTH: ADVIA Centaur (Siemens)

Parameters:

(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))

Limitations:

• The equation is dependent on the various assays used.