Table 2.

Interference of PTH (7–84) in the Bio-PTH and I-PTH assays.1

Final concentration of PTH (7–84), ng/LBio-PTH assayI-PTH assay
Bio-PTH, ng/LCross-reactivity, %I-PTH, ng/LCross-reactivity, %
06.912.3
756.1−1.183.995.5
7006.70.0717100.7
20008.50.1>1800
75008.80.0>1800
  • 1 PTH was measured in duplicate with each assay. Serum with I-PTH of 23.4 ng/L was measured simultaneously with the Bio-PTH and I-PTH assays with and without the addition of an equal volume of PTH (7–84) at the final concentrations of 0–7500 ng/L.