The admission samples and samples taken 6 h after admission were immediately assayed
by the Access AccuTnI (Beckman Coulter), and then were frozen within 8 h and stored at -20/-70 [degrees]C until analysis by the new cTnI assay.
We measured the absorbance at 420 nm and determined the [Beta]-galactosidase activity by the formula [optical density [(OD).sub.420]/[OD.sub.600] of assayed
culture x volume (milliliters) assayed
x time (min)] (37).
To study the correlation between the PTH concentrations measured by the Bio-PTH and I-PTH assays, we assayed
62 serum samples at the same time in the Bio-PTH and I-PTH assays.
The whole blood samples were analyzed fresh, whereas the plasma samples were stored deep-frozen for 1 week at -70 [degrees]C before being assayed
in the Dade Behring BN II nephelometer with the Dade Behring N High Sensitivity CRP assay.
Samples were fractionated once, and aliquots were kept frozen until assayed
, up to 3 years.
Because it is usual for rather small series to be assayed
for ACTH in a clinical setting and because nonisotopic methods with stable calibration are of great practical interest, we compared these assays.
In subsequent studies, UC 1 was assayed
at 20, 50, 100, 150, and 200 [micro]L, and UC 2 was assayed
at 20, 40, 50, 60, 80, and 100 [micro]L; protein concentrations were derived by extrapolation of the absorbance values from a calibration curve.