For example, for increasing target concentrations up to 2.5 g/L, the Roche and
Abbott methods exhibited the smallest increase of variability.
The mean recovery of the spiked unconjugated bilirubin (expressed as a percentage of the target set by the reference laboratory for the high bilirubin concentration, excluding in-house results of manufacturers) was 86% for the Ortho VITROS method, 102% for the Siemens/Dade Behring method, 106% for the Roche method, 108% for the Beckman Coulter method, 110% for the
Abbott method, and 111% for the Siemens/Bayer method.
We conclude that with the
Abbott method, measured tHcy concentrations within the reference interval are lower for blood collected into NaF (P <0.001) and ACD-B tubes than for blood collected into EDTA, lithium heparin, and sodium citrate tubes.
In summary, Hcy concentrations measured by the
Abbott method in EDTA- and citrate-anticoagulated plasma agree well after a plasma-volume correction factor is taken into consideration.
Any Hb [A.sub.1c] method can in principle be used for this calibration, but we chose the
Abbott method, also utilizing the boronic acid affinity principle, because this made it possible to calibrate the present method to read both %GHb values and "standardized" %Hb [A.sub.1c] values.