Effect on lipid, complete blood count and blood proteins of a standardized preparation for drawing blood: a randomized controlled trial.

OBJECTIVE To compare a standardized recommended procedure for drawing blood to measure blood lipid and lipoprotein levels with the procedure commonly used in clinical practice. The aim was to see if hemoconcentration and spuriously elevated lipid levels could be avoided. DESIGN An open randomized crossover clinical trial. SETTING The University of Calgary. PATIENTS Twenty-five patients with dyslipidemia. INTERVENTIONS Blood drawing using a standardized procedure in which the patient remained seated for 5 minutes before blood collection and tourniquet use was minimized or avoided. MAIN OUTCOME MEASURES Differences in lipid levels between the usual clinical procedure and the recommended procedure for drawing blood. RESULTS Prior to drawing blood, laboratories have sat patients for an average of 1.4 minutes (95% CI, 0.9 to 1.9) and used a tourniquet in every patient. In the standardized procedure, patients rested for an average of 5.6 minutes (95% CI 5.0 to 6.2), and a tourniquet was used briefly in only 3 of 23 patients. There were no differences in lipid and lipoprotein values and no clinically significant difference in hemoglobin or albumin levels or in the calculation of hemoconcentration. CONCLUSIONS Efforts to rest patients and avoid tourniquet use when drawing blood for assessment of lipid levels are unlikely to be useful.