4 CASES OF SPURIOUSLY LOW WBC COUNT DUE TO IN-VITRO LEUKOCYTE AGGLUTINATION - CONTRIBUTION OF THE HEMATOLOGY ANALYZER COULTER(R)-STKS IN DETECTING THIS CLINICALLY MISLEADING ARTIFACT

Four spuriously lowered WBC counts due to in vitro leukoagglutination were reported from an automated cell counter (Coulter STKS). Leukocyte aggregates (3 to 50 cells), detected in the peripheral blood smears, included different cell types, normal (neutrophils, eosinophils, monoc ytes, lymphocytes) or abnormal (lymphoma cells). The phenomenon was as sociated with either a spurious leukoneutropenia or an underestimation of hyperleucocytosis. Leukoagglutination was extensively investigated in 3 cases : as shown in several reports, leukoagglutination may occu r with various features, especially due to temperature and anticoagula nt dependence. Our four cases reflected this variability. Furthermore, one case was found both temperature-dependent and anticoagulant-indep endent, a pattern not yet described in the literature. A common STKS g raphic pattern was found in our 4 cases, suggesting that hematology an alyzers such as Coulter STKS may be useful to detect leukoagglutinatio n. In conclusion, each leukoneutropenia and/or each suggestive graphic pattern must be controlled by means of a blood smear examination in o rder to rule out the possibility of in vitro leukoagglutination.