Analytical performance and diagnostic accuracy of immunometric assays for the measurement of circulating oxidized LDL.
BACKGROUND
Oxidized LDL (ox-LDL) plays an important role in the pathogenesis of coronary heart disease (CHD). Several tests for circulating ox-LDL have been published. We believe it is critical to carefully evaluate these assays because small differences in performance may have profound effects when results are compared; we therefore compared the analytical and clinical performances of 2 assays: one developed in our laboratory and a commercial assay (Mercodia) that uses the same monoclonal antibody (4E6).


METHODS
We determined the variance of ox-LDL in both tests, including its longitudinal stability (n = 225; 3 time points per person) and its diagnostic accuracy, by ROC analysis of 95 consecutive CHD patients and 20 controls.


RESULTS
The between-person variability was 77% for the in-house assay (with the remaining 23% being within-person and analytical variance) and 74% for the commercial assay. For comparison, previously reported values were 66% for high-sensitivity C-reactive protein and 82% for total cholesterol. The areas under the curves for CHD in the 2 assays were identical (0.85). The odds ratios (logistic regression) for CHD among persons with high ox-LDL (>or=15 mg/L) compared with persons with low ox-LDL were not different: 4.3 (95% confidence interval, 1.4-12) for the in-house assay and 3.3 (1.1-10) for the commercial assay.


CONCLUSIONS
The longitudinal stability of ox-LDL, as assessed by multiple measures in people over time, is similar to that of total cholesterol and high-sensitivity C-reactive protein. Both assays tested similarly distinguish between healthy controls and CHD patients.
Holvoet
Paul
P
Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium. paul.holvoet@med.kuleuven.be
Macy
Elizabeth
E
Landeloos
Michele
M
Jones
Dan
D
Jenny
Nancy S
NS
Nancy
Jenny S
JS
Van de Werf
Frans
F
Tracy
Russell P
RP
D000328:Adult; D000911:Antibodies, Monoclonal; D003327:Coronary Disease / Q000175:diagnosis*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood*; D012372:ROC Curve; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies
D000911:Antibodies, Monoclonal; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein