Effects of anticoagulants in amino acid analysis: comparisons of heparin, EDTA, and sodium citrate in vacutainer tubes for plasma preparation.

in a single run for HDL-C using these three homogeneous HDL-C reagents. Mean concentrations of HDL-C in group 1 were 508 mg/L for the direct HDL-C assay, 517 mg/L for the N-geneous TM HDL-C assay, and 531 mg/L for the EZ-HDL TM-C assay. However, mean concentrations of HDL-C in group 2 were 253 mg/L for the direct HDL-C assay, 352 mg/L for the N-geneous TM HDL-C assay, and 253 mg/L for the EZ-HDL TM-C assay. Marked differences were noted between assays in individual patients. Sugiuchi et al. (6) and Harris et al. (12) reported precisions slightly better (CV Ͻ4%) than the results we obtained for direct HDL-C assay and N-geneous TM HDL assay. This may be due to use of different analyzers or differences in the methods of calibration. The data in our study agree with Okamoto et al. (7), who reported that higher HDL-C concentrations were obtained by the direct method than by the precipitation method. Our finding of no statistically significant interference from bilirubin in any of the three homogeneous HDL-C assays agrees with the findings of Sugiuchi et al. (6) and Harris et al. (12). We found that hemoglobin produced a negative interference (Ͼ10%) with the N-geneous TM HDL-C assay but had little effect on direct HDL-C assay and EZ-HDL TM-C assay. Nauck et al. (5) reported that hemoglobin produced a positive interference (Ͼ10%) and bilirubin produced a negative interference (Ͼ10%) with a different homogeneous HDL-C assay, which uses PEG and antibodies against apo B and apo C-III (5). We found that there was a negative interference (Ͼ10%) by Intralipid ® at triglycer-ide concentrations Ͼ20 000 mg/L for the N-geneous TM HDL-C and EZ-HDL TM-C assays but not for the direct HDL-C assay. However, we found inconsistent HDL-C bias among high triglyceride concentration serum samples , suggesting that interference measurements using Intralipid may not truly represent the clinical situation. The negative bias of HDL-C concentration observed in serum of high triglyceride concentration (10 000 mg/L to 29 000 mg/L) using EZ-HDL TM-C assay was much more apparent than with the other two homogeneous HDL-C assays. Harris et al. (12) reported a positive bias for N-geneous TM assay with high triglyceride concentration (4000 mg/L to 10 000 mg/L) serum samples. We are unable to explain this discrepancy. We conclude that these three homogeneous HDL-C assays are acceptable (total error Ͻ22%) for clinical laboratory use according to NCEP performance …