What does the current “intact” PTH test measure?
Biochemically, the “intact” PTH test measures PTH and its inhibitor as a combined value. This is like measuring the sum of insulin and glucagon and trying to use the value to predict carbohydrate metabolism. The term “intact” is a misnomer since the “intact” PTH assay is not measuring “intact” 1-84 PTH exclusively Functionally, the “intact” PTH test is a poor predictor of bone status in the renal dialysis patient. Bone biopsy studies have demonstrated that if a patient has an “intact” PTH assay value of greater than 100 pgm/mL, the “intact” PTH assay value is a very poor predictor of renal bone status of high, normal and low bone turnover (overall predictability is only 73%).
