K2- or K3-EDTA: the anticoagulant of choice in routine haematology?

Abstract

Summary The choice of K2‐ or K3‐EDTA as the preferred anticoagulant for blood count remains controversial. We compared the effect of different concentrations of both anticoagulants on normal blood. In optimal conditions (appropriate anticoagulant concentration and measurements done between 1 and 4 h after phlebotomy), no marked differences are seen between either EDTA salt. Important discrepancies appear, however, in less optimal conditions, as often happens in day to day practice. The packed cell volume, when measured on centrifuged blood, decreases with increasing anticoagulant concentrations and this is most pronounced with the K3 salt. This phenomenon has been reported by different authors and is ascribed to shrinking of erythrocytes in an hypertonic medium. Automated instruments react in a different way, their MCV is not influenced by K3‐EDTA concentrations up to ten times normal, while K2‐EDTA, at high concentrations, results in a slight increase in MCV, as measured with three of the instruments. With most instruments, the accuracy of the white cell count is not markedly influenced. However, when measured with the Unipath CD 3000 all tested blood samples, taken in high K3 (but not in K2) concentrations, showed an appreciable decrease in the leucocyte count (to less than 50% of the original value, at a concentration of 15g/l, 24 h after blood collection). Measurement of RDW and automated differentials is also influenced by the choice of anticoagulant when determinations are done in less than optimal conditions. We conclude that the choice of anticoagulant, its use at an appropriate concentration and the age of the blood sample are important matters and should be given due consideration. However, generally it is only in less than optimal conditions (too small blood samples for the amount of anticoagulant and delayed measurement) that marked divergencies between results obtained with different systems are observed.

Effects of preanalytical variables on peptide and protein measurements in human serum and plasma: implications for clinical proteomics

“…Dipotassium, tripotassium and disodium are applied as cations [49,102]. Of note, there have been reports on the impact of different EDTA salts in hematology [49].…”

Evaluation and Comparison of Stability and Reliability of CBC Parameters Determined by Using Automatic Celltac G MEK-9100 Hematology Analyzer during Extended Storage at 4°C

“…K2-EDTA having a less diluents effect and slighter influence on MCV, haematocrit, and effects on red blood cell size to increase the concentration, had been selected in our study over K3-EDTA [7,[9][10][11][12][13].…”

Platelet analysis in laboratory hematology

“…There are two forms, K2-EDTA and K3-EDTA. The two different salts actually lead to slightly different reference ranges for the blood count, but the changes are not without controversy [42,43]. One of the reasons is that EDTA requires a certain reaction time, as far as the hydration of the cells is concerned, which is why one should wait for at least 15 min before analyzing a freshly drawn blood sample.…”