Automated latex photometric immunoassay for total plasminogen activator inhibitor-1 in plasma.

The highest bilirubin concentration (15 mg/L) was quantified with the Hitachi 747. Because of the inability of the Hitachi 747 to measure amniotic fluid bilirubin at low concentrations, subsequent concentrations are reported as " calculated " based on the serial dilutions. A mixed-model ANOVA using the percentage change from baseline as the dependent variable was performed. Baseline was calculated as the average of the two repli-cates for a given pool before bilirubin was added. The percentage change from baseline as a function of pool (six pools), the baseline FLM concentration (treated as a continuous variable), replicates within pools (two repli-cates), and bilirubin concentrations (treated as a categorical variable, not a continuous variable) were used in this model. The baseline FLM concentration and bilirubin concentration were modeled as fixed effects, and pool and replicates were modeled as random effects. The effect of baseline FLM concentration on FLM concentration after the addition of bilirubin was not significant (P ϭ 0.91), so the analysis was conducted excluding baseline FLM as a factor. Our results indicate that bilirubin does not produce a clinically important or consistent effect on TDx FLM II results (Fig. 1). The results of a mixed-model ANOVA statistical analysis indicated that only at a bilirubin concentration of 7.5 mg/L did the mean difference in TDx FLM II concentration from baseline (Ϫ3.3%) achieve statistical significance (P ϭ 0.04). However, despite the statistical significance, the 95% confidence interval indicated that samples would, at most, be 6% different from baseline. We do not consider 6% to be clinically significant. Furthermore, a higher concentration of bilirubin (15 mg/L) did not produce a statistically significant difference in TDx FLM II from baseline. The highest concentration of bilirubin tested in our experiments was 15 mg/L, which is ϳ50% greater than the highest concentration likely to occur in the amniotic fluid of abnormal pregnancies, including erythroblastosis fetalis (4). This study did not find a clinically significant interference at this concentration or below it. For this reason, we conclude that bilirubin does not affect the assessment of FLM by the TDx FLM II assay of amniotic fluid. Plasminogen activator inhibitor-1 (PAI-1) is a key regulator of the fibrinolytic system (1). The continuously high PAI-1 concentrations make fibrins resistant to dissolution by tissue-type plasminogen activator (tPA), which leads to multiorgan dysfunction and a bad prognosis in patients (2). Several methods have been developed for measuring the functional activity of PAI-1 …