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Performance characteristics of an immunoturbidimetric assay for lipoprotein-associated phospholipase A2
Mindy L Rawlins1, Sonia L La'ulu, Natalie Moon
1ARUP Institute for Clinical & Experimental Pathology, Salt Lake City, UT 84108, United States.
Background:
Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is an inflammatory biomarker for coronary heart disease and ischemic stroke risk assessment.
Methods:
The Plac turbidimetric immunoassay (TIA) for measurement of Lp-PLA(2) was evaluated for limit of blank, functional sensitivity, dilution linearity, imprecision, interferences, and comparison to an ELISA assay for Lp-PLA(2).
Results:
The assay was linear from 100 to 500 microg/l. Total inter-assay CVs were <3% for both control levels. Interference studies showed recoveries of 90-110% of expected values at interferent concentrations up to 15 g/l hemoglobin, 450 mg/l bilirubin, and 41 g/l triglycerides. Comparison of 3 sample sets collected using different protocols gave the following regression statistics for the Plac TIA compared to the Plac ELISA: sample set 1 (n=99) slope=1.5, intercept=-122.4, S(y/x)=71.3 microg/l, and r=0.61; sample set 2 (n=100) slope=2.1, intercept=-173 microg/l, S(y/x)=55 microg/l, and r=0.82; sample set 3 after 1 freeze-thaw cycle (n=30) slope=1.2, intercept=-68.6 microg/l, S(y/x)=28.6 microg/l, and r=0.82; sample set 3 after a second freeze-thaw cycle slope=1.4, intercept=-68.2 microg/l, S(y/x)=33.1 microg/l, and r=0.83.
Conclusions:
The Plac TIA reagents perform acceptably on the Roche Modular P analyzer. However, only a fair correlation was observed between the Plac ELISA and Plac TIA assays.
