Blood cholesterol concentration: fingerstick plasma vs venous serum sampling

To assess whether venous and fingerstick blood samples yield similar cholesterol concentrations, we obtained both types of samples simultaneously in 108 volunteers participating in a cholesterol screening program. All samples were analyzed by the same enzymatic method in a standardized laboratory, and pairs of simultaneous samples were measured in the same laboratory run. Cholesterol concentrations in fingerstick-derived plasma were consistently higher than in the venous serum (P less than 0.0001), by a positive bias averaging 3.6%. Cholesterol values in fingerstick plasma also were higher than cholesterol results for venous serum placed in a capillary collection tube (average bias +2.4%). The positive bias of fingerstick plasma vs venous serum results appears to be at least partly due to specimen handling, although a true physiological difference between venous and fingerstick cholesterol concentrations is probably also involved. If a positive bias of this magnitude from fingerstick blood sampling is left unadjusted, substantial numbers of people will be labeled "at risk" and referred to physicians when their true values were actually within the acceptable range.