Platelet satellitosis with spurious thrombocytopenia and neutropenia

Spurious counts and spurious results on haematology analysers: a review. Part I: platelets

The widespread use of haematology analysers (HA) has led to a major improvement of cellular haematology, because of quick and accurate results found in most instances. However, in several situations, spurious results are observed. Inadequate blood samples, situations induced by the anticoagulant(s) used, peculiar changes related to the pathology in the patient, and technical considerations about performances of the various HA must be considered. Spurious thrombocytopenia occurs in several circumstances related to the presence of ethylenediamine tetra-acetic acid (EDTA) used as the anticoagulant. Mechanism of EDTA-dependent platelet (PLT) agglutination is related to circulating (auto)antibodies directed against normally hidden epitope(s) in the glycoprotein alpha IIb/beta IIIa complex from PLT membrane exposed only in the presence of EDTA. Other spuriously low PLT counts may be related to EDTA, including PLT rosetting around white blood cells (WBC; satellitism) and PLT-WBC aggregates, but mechanisms responsible for those latter phenomena are less well known. Spurious increase of PLT count may be related to several situations, including fragmented red blood cells, cytoplasmic fragments of nucleated cells, cryoglobulins, bacteria or fungi, and lipids. Flags generated in several of these situations alert the operator on possible abnormal findings and may identify the problem. Analysing only PLT parameters is not sufficient: in many situations the WBC differential scattergram is of crucial help for flagging. Flags generated depend on the software version on the HA used, the performance in detecting the same anomalies may differ according to which analyser is used, even those from the same manufacturer. Operators must be aware of the characteristics of their analyser and be able to recognize and circumvent anomalous results.

EDTA-induced pseudo-neutropenia resolved with kanamycin

This report describes a case of spurious neutropenia caused by EDTA-dependent in vitro agglutination of neutrophils. After raising the temperature of the sample to 37 degrees C the agglutination was irreversible, but it resolved completely after addition of kanamycin. Previously this method has been shown to be effective in EDTA-dependent pseudo-thrombocytopenia, but this is the first report demonstrating successful application in EDTA-dependent pseudo-neutropenia.

Case report: immunoglobulin M-mediated, temperature-dependent neutrophil agglutination as a cause of pseudoneutropenia

The authors report the case of a 77-year-old man in whom intermittent neutropenia developed during a prolonged hospitalization. Laboratory records revealed wide variations in the patient's routine leukocyte counts. Examination of the peripheral smear revealed clumps of 2-3 polymorphonuclear leukocytes throughout the slide and large aggregates (> 50 cells) along the smear edges. Neutrophil clumping also was observed in blood anticoagulated with citrate or heparin. Replacement of patient plasma with saline prevented agglutination. Addition of patient plasma or serum to normal cells induced neutrophil agglutination. Holding the patients blood at 37 degrees C prevented agglutination, which occurred spontaneously and more exuberantly as the temperature was reduced to 22 degrees C. Flow cytometry revealed immunoglobulin M on neutrophil surfaces. Spontaneous agglutination resolved 6 months after resection of the patient's subsequently diagnosed colon cancer. This is the first report of immunoglobulin M-induced neutrophil clumping occurring in the setting of malignancy, and the first reported immunoglobulin M not to require ethylenediaminetetraacetic acid as a cofactor for agglutination.

Association of pseudothrombocytopenia and pseudoleukopenia: evidence for different pathogenic mechanisms

A case of spurious automated leukocyte and platelet counts due to EDTA-dependent platelet-neutrophil agglutination is described. Whole blood anticoagulated with K3EDTA, sodium citrate and lithium heparin was analysed at short time intervals up to 6 h from sampling at 37 degrees C and at room temperature (RT = 27 degrees C). A phenomenon of platelet clumping occurred at both temperatures with all the anticoagulants (pseudothrombocytopenia), while platelet-granulocyte agglutination was present only with EDTA at RT. Aggregates consisting of up to 80 neutrophils were seen on the blood smear. The contemporary presence of platelet clumping caused a reduction of WBC count of only 25% the initial, while leukocyte differential was markedly altered (pseudolymphocytosis). Further experiments were performed mixing plasma and serum of the patient with packed cells (PC) from a normal donor in the presence of different anticoagulants and at various dilutions and temperatures. Platelet-neutrophil agglutination occurred only in the presence of EDTA at temperatures lower than 37 degrees C, and was abolished by plasma dilutions from 1:8 onwards. Similarly, it was inhibited by incubation with dithiothreitol (DTT), in contrast with platelet clumping. The latter phenomenon was triggered by an EDTA concentration lower than that necessary to cause platelet-neutrophil agglutination (0.5 mg ml-1 vs. 0.77 mg ml-1). Obtained results suggest the causal association of 2 different phenomena, both transferable to normal cells by means of patient plasma and serum. In the article the pathogenetic implications of the case are discussed.