Effect of laboratory error on the identification of persons with hypercholesterolemia in an employee health service
Lichtenstein, M.J.; Dewey, M.J.
American Journal of the Medical Sciences 295(1): 11-14
1988
ISSN/ISBN: 0002-9629 PMID: 3337135 Document Number: 306246
Of 117 employees seen consecutively in the Tennessee (USA) State Employee Health Service voluntary screening programme 86 had cholesterol concentrations above the reference range reported by a commercial clinical laboratory. This was 3 times greater than the calculated expected number of 29 (17 at moderate risk, 12 at high risk for coronary disease). Age and sex adjustment using Lipid Research Clinics guidelines reduced the number with high cholesterol to 55 (24 at moderate risk, 31 at high risk). Split-sample cholesterol estimations run independently by the commercial laboratory and a university laboratory showed excellent correlation but a systematic difference of 12.4 mg/100 ml between the 2 laboratories. Further adjustment for that difference reduced the number with increased cholesterol to 41 (26 at moderate risk, 15 at high risk). This illustrates how small systematic laboratory errors in cholesterol estimation can greatly exaggerate the number of persons reported to have clinically important cholesterol increases. Clinical laboratories should report age- and sex-adjusted cholesterol reference ranges and provide clients periodic quality assurance reports that their estimations of cholesterol concentrations are accurate.