Fluid therapy directly interferes with immunoassay for cardiac troponin I.

Abstract

To investigate interference in cardiac troponin I (cTNI) immunoassay induced by some widely used loading fluids. A biochemistry unit of a university hospital. Human serum with a cTNI concentration of 0.32 microg/l was diluted at 10, 20, 40, and 80% with saline serum (SS), Plasmion (P) (a modified fluid gelatin), hydroxyethyl starch (HES), and 20% human albumin (Alb). Serum with a cTNI concentration of 1.29 microg/l was diluted at 20, 40, 60, and 80%. Four samples with increasing cTNI concentrations (from 0 to 8.14 microg/l) were diluted at 80% with the four fluids. Differences (delta-C) between expected concentrations resulting from the dilutional effect and those measured with the Access cTNI immunoassay were expressed in microg/l. Statistical analysis was performed using a nonparametric test. No false positivity was observed. At a low cTNI concentration (0.32 microg/l), interference was observed with SS and HES at 40 and 80% dilution and with P and Alb at 80%. When cTNI was 1.29 microg/l, interference was observed with each fluid at a dilution of 20% and increased with the increase in dilution. The highest interference was observed with HES, the lowest with P. When the dilution was at 80% for increasing concentrations of cTNI, the higher the initial cTNI was the higher the interference appeared, mostly with SS and HES. SS, P, Alb, and HES interfere in this cTNI immunoassay. This interference is higher with SS and HES and is higher when the percentage of hemodilution or real cTNI concentration increases.