Pseudothrombocytopenia

Abstract

In a prospective 9 month study at a medical department with special interest in immunology and rheumatology, 10 patients with spuriously low thrombocyte counts ‐ pseudothrombocytopenia ‐ were registered. The phenomenon was observed when the counting of platelets was performed on a Thrombocounter C apparatus or by manual counting using K2EDTA stabilized blood since platelet agglutination was considerably less pronounced when solutio citratis glucosi fortis (ACD) was used as the anticoagulant. Results of our in vitro studies indicate that the mechanisms contributing to pseudothrombocytopenia involve the interacton of circulating immune complexes with platelet membrane Fc receptors causing agglutination. Fab'2‐fragments of isolated patient IgG did not react with normal donor thrombocytes. This finding argues against agglutination due to true antiplatelet antibody activity.

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

“…Prevalence was 0.2% in plateletpheresis donors (Sweeney et al, 1995). For hospitalized patients, 0.1-2.0%, incidence was reported (Manthorpe et al, 1981;Payne & Pierre, 1984;Savage, 1984;Bragnani et al, 2001). Up to 17% of patients referred to the outpatient clinic for isolated thrombocytopenia were in fact found to have EDP (Silvestri et al, 1995;Cohen et al, 2000).…”

“…In several instances it was shown that EDP appeared during hospitalization, and particularly after an infection, and that antibodies frequently bind to PLT from the relevant patient but also to PLT from all patients, with the exception of PLT from Glanzmann type I patients (van der Lelie, van der Plas-Van Dalen & von dem Borne, 1984;Berkman et al, 1991;Edelman & Kickler, 1993). However, it is not possible to exclude non-Ig proteins as inducing EDP in some instances (Mant et al, 1975;Onder, Weisntein & Hoyer, 1980;Bizzaro & Brandalise, 1995), or other mechanisms, as the interaction of circulating immune complexes with PLT membrane Fc receptors causing agglutination in presence of EDTA (Manthorpe et al, 1981).…”

Pseudothrombocytopenia—A Review on Causes, Occurrence and Clinical Implications

“…Manthorpe et al in 1981 first reported anti-platelet antibody activity based on immunofluorescence experiments using Fab'2-fragments of isolated IgG [31]. Then, Pegels et al confirmed the existence of an immunologically-mediated phenomenon caused by presence of IgG, IgM, or IgA directed against platelet antigens, manifesting mostly at 0-4 • C in EDTA samples [32].…”

“…Before being replaced by EDTA, the ACD was the most widely used additive for routine platelet enumeration [31].…”