ABSTRACT
BACKGROUND: Ethylenediaminetetraacetic acid (EDTA) contamination of serum samples is common but under-recognized unless EDTA is measured. Incorrect order of draw with closed phlebotomy (vacutainer) does not cause EDTA contamination. EDTA contamination occurs largely or solely during open phlebotomy due to syringe tip or needle-tip contamination when delivering blood into EDTA sample tubes before other sample tubes or direct transfer of blood from EDTA containing tubes to other tubes. Therefore, preference for closed phlebotomy or following the order of tube fill when open phlebotomy is used may reduce EDTA contamination. METHODS: The laboratory's comments for EDTA-contaminated serum samples were amended to encourage closed phlebotomy and with open phlebotomy filling of serum tubes before EDTA and fluoride-EDTA tubes. The weekly frequency of EDTA sample contamination, normalized for weekly urea and electrolyte (U&E) requests, was studied 52 weeks before and 43 weeks after amending the comments. RESULTS: Median (IQR) frequency of EDTA-contaminated samples per week per 10,000 U&Es decreased by 58% [5.6 (3.1-9.2) versus 2.3 (1.1-4.4); P < 0.001] after the introduction of the new comment. CONCLUSION: Explicit automated laboratory feedback comments promoting closed phlebotomy and order of tube fill with open phlebotomy were associated with a 58% reduction in EDTA-contaminated samples and thus may play a role in improving phlebotomy practise.