EFFECTS OF SAMPLE AGING ON TOTAL CHOLESTEROL VALUES DETERMINED BY THE AUTOMATED FERRIC-CHLORIDE SULFURIC-ACID AND LIEBERMANN-BURCHARD PROCEDURES

  • 1 January 1980
    • journal article
    • research article
    • Vol. 26  (5) , 592-597
Abstract
To investigate the comparability of 3 commonly used methods for determination of total cholesterol in plasma in several studies, fresh [human] plasma samples and plasmas and reference sera that had been stored frozen at -15.degree. C for as long as several years were used. Duplicate determinations by the manual method of Abell et al. were compared with estimates from 1 to 5 continuous-flow analyzers by the ferric chloride-sulfuric acid procedure and also with estimates from 5 to 13 continuous-flow analyzers by the Liebermann-Burchard procedure with calibrator, as part of the laboratory standardization activities of the Lipid Research Clinics. The agreement among all 3 procedures was generally within acceptable limits (within 5% of the manual method) when plasmas or sera were fresh or had been frozen for less than 1 mo. Results by the manual method of Abell et al. agreed well with those by the automated Liebermann-Burchard method for samples that had been stored at -15.degree. C for as long as 2 yr. The automated ferric chloride-sulfuric acid procedure often showed unacceptably high values (as compared with those from the manual method) for samples that had been stored frozen for 1 yr or more. With the ferric chloride-sulfuric acid method, measured cholesterol concentration increased about 2.5%/yr of storage for at least 2 yr. Reference sera of plasmas that were kept in long-term frozen storage (-15.degree. C) are unsuitable for ongoing standardization of the automated ferric chloride-sulfuric acid assay for cholesterol.