Instrumental reports and effect of anticoagulants in a case of neutrophil agglutination in vitro.

BACKGROUND

The aim of this study was to investigate a case of EDTA-induced polymorphonuclear leukocyte (PMN) agglutination in vitro on Bayer Technicon H*1. Coulter Counter STKS and STKR analyzers.

METHODS

Venous whole blood was anticoagulated with K3.EDTA, sodium citrate, lithius heparinate, acid citrate dextrose (ACD) and with two other anticoagulant mixtures containing citric acid-theophylline-adenosine-dipyridamole (CTAD) or citrate-pyridoxal 5'-phosphate-tris (CPT).

RESULTS

PMN agglutination, EDTA--but not temperature--dependent, was found by mere chance in an asymptomatic 48-year-old Caucasian male who did not show detectable PMN antibodies. Pseudoneutropenia without pseudoleukopenia was registered on H*1 exclusively in EDTA anticoagulated blood with a characteristic higher density PMN population on the BASO cytogram. Spuriously low white blood cell (WBC) counts and pseudoneutropenia appeared on STKR and STKS in EDTA anticoagulated blood, but signals on PMN agglutination were unsatisfactory. Accurate total and differential WBC counts were obtained in CTAD or CPT anticoagulated samples on the three analyzers. Heparin was the worst choice because it induced pseudothrombocytopenia and pseudoleukocytosis on STKR and STKS.

CONCLUSIONS

Since PMN agglutination was not observed on peripheral smears and was undetected on EDTA anticoagulated samples processed immediately by H*1, the presence in vivo of PMN clumps should be excluded. Further hematological investigations will demonstrate in the long run whether the observed PMN agglutination in vitro is a transient occurrence in an apparently healthy subject not taking drugs at the time of observation.