Preanalytical variability in laboratory testing: influence of the blood drawing technique.

The predominant technique used to draw blood for laboratory testing is a conventional straight needle attached to an evacuated tube system. However, alternative tools might be advantageous in exceptional circumstances. The use of butterfly devices has been traditionally discouraged for reasons of costs and due to the high risk of obtaining unsuitable samples, but there is no convincing evidence to support the latter indication. The purpose of this study was to compare results of hematological and clinical chemistry testing, after drawing blood into evacuated tubes, employing either a traditional 21-gauge straight needle or a 21-gauge butterfly device with 300-mm-grade polyvinyl chloride tubing. Blood samples and complete sets of data were successfully obtained for 30 consecutive outpatients. Of the 43 hematological and clinical chemistry parameters measured, means for paired samples collected by the two alternative drawing techniques did not differ significantly, except for serum sodiu...