Evaluation of Different Mixing Procedures for K2 EDTA Primary Samples on Hematological Testing

Giuseppe Lippi, MD; 1 Gian Luca Salvagno, MD; 1 Martina Montagnana, MD; 1 Giuseppe Banfi, MD; 2 Gian Cesare Guidi, MD1


Lab Med. 2007;38(12):723-725. 

In This Article

Materials and Methods

Three primary 3.0-mL siliconized vacuum tubes containing 5.4 mg K2 EDTA (Terumo Europe, Haasrode, Belgium) were sequentially collected from 20 healthy volunteers who gave informed consent for being tested. During venipuncture, the patients were seated with the arm oriented transversely to determine a 45B0 angle with the floor. Blood was always collected from an antecubital vein of the left arm by a skilled phlebotomist.

Regardless of the available recommendations, the first primary tube was collected, was not inverted, and was left standing in a vertical position for 30 to 60 minutes at room temperature and then analyzed. The second and third primary tubes were respectively inverted 6 and 12 times immediately after collection and analyzed 30 to 60 minutes after venipuncture.

Each specimen was assayed only once for hemoglobin, hematocrit, red blood cell count (RBC), mean cell hemoglobin (MHC), mean cell volume (MCV), platelet count (PLT), mean platelet volume (MPV), and white blood cell count (WBC) on the Advia 120 automated hematology analyzer (Bayer Diagnostics, Newbury, Berkshire, UK), which is provided with an autosampler that inverts the primary tubes several times before analysis. Calculated indexes were hematocrit and mean hemoglobin content (MHC).

The instrument was calibrated against appropriate proprietary reference standards material and controlled daily with the use of proprietary controls. A recent multicenter evaluation of the within-run precision of the Advia 2120 system, which employs technology identical to that of the Advia 120 analyzer, yielded coefficients of variation ranging from 1.6% to 2.3% for WBC, from 2.1% to 2.8% for PLT, from 0.6% to 0.9% for RBC, and always lower than 0.7% for hemoglobin, MCV, and MCH.[4] Results are given as mean B1 standard deviation. The significance of differences between samples was assessed by Wilkoxon's paired test, and statistical significance was set at P<0.05. Bland-Altman plots were used to evaluate the mean percentage bias between results obtained by the independent analyses on the samples. The study was revised by the Institutional Review Board and approved by the local ethics committee.


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