Affiliations : *Division of Clinical Chemistry, Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand
** Department of Clinical Chemistry, Faculty of Associated Medical Science, Khonkaen University, Khonkaen 40002, Thailand
*** Department of Biotechnology, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand
****National Institute of Health, Department of Medical Sciences, Nonthaburi 11000, Thailand
*****Department of Pathology and Laboratory Medicine, Dallas Veterans Affairs Medical Center and University of Texas Southwestern Medical School, Dallas, TX 75216, USA
Source: Clinica Chimica Acta 2004; 339: 135-145
Background: Cholesterol oxidase is used for the determination of serum cholesterol. It can be derived from Streptomyces, Pseudomonas fluorescens, Cellulomonas, and Brevibacterium. This study compared the performance characteristics of four enzymes in the endpoint cholesterol determination. Methods: Using the Mega analyzer, we studied assay optimization, linearity, precision, recovery, interference, stability, and compared 110 patient samples. Results: The linearity for the four enzymes was up to 13.0 mmol/l at the optimal enzyme activity. The average within-run CVs ranged from 1.6% to 1.9% and between-day ranged from 2.8% to 3.0%, within the NCEP analytical criteria. The analytical recoveries obtained from four reagents ( 96.5%) were excellent. The assays using these enzyme sources compared favorably with the commercial method and appeared accurate near the clinical decision cut-points. Hemoglobin concentration at 1.9 g/l interfered with the P. fluorescens cholesterol oxidase. Bilirubin caused a negative interference while lipemia generated a positive interference with all enzyme sources. Reagents were stable up to 6 weeks. Conclusions: Streptomyces, Cellulomonas, and Brevibacteriumwere essentially analytically equivalent. Streptomyces and Cellulomonas cholesterol oxidase are one-quarter as expensive Brevibacterium. Cellulomonas is a new source of cholesterol oxidase for determining serum cholesterol by the endpoint method.