Detección de un error sistemático constante en un procedimiento directo de medida del colesterol de las lipoproteínas de baja densidad

In our primary care laboratory, we routinely perform the direct low density lipoprotein (LDL) cholesterol test, supplied by Olympus España and created by WAKO, in patients with triglyceride levels of >400 mg/dl. Studies in the literature have reported systematic error when this method is used. Because an ultracentrifuge was not available to study the possible lack of specificity reported in the literature, we used this test to measure LDL cholesterol in patients with triglyceride levels of ≤200 mg/dl in whom, on applying the Friedewald formula, the results for LDL cholesterol would be more concordant with those obtained by ultracentrifugation. We detected a constant systematic error in the direct LDL cholesterol test versus Freidewald calculation and, using statistical methods, we concluded that this constant systematic error is due to the fact that the Olympus reagent measures, nonspecifically, VLDL cholesterol. We believe that users of this reagent should be aware of these data and that a rapid response should be given to the two questions posed at the end of the study.