Interference of blast cell fragments with automated platelet counting.

INTRODUCTION: Automated haematology analysers may inaccurately determine platelet counts in several circumstances. Spuriously elevated automated platelet counts have been reported in some acute leukaemia (AL) cases because of fragmentation of circulating blast cells (pseudoplatelets). Haemorrhagic diathesis is a common manifestation of AL, which is often caused by severe thrombocytopenia. Therefore, overestimation of the actual platelet count in patients with AL can affect its clinical management. We aimed to detect the frequency of pseudoplatelets in patients with AL. METHODS: Complete blood cell counts were performed on 86 AL patients with three automated analysers (ADVIA 2120, Coulter LH 750 and Sysmex XE-2100D). Platelet counts were also performed by quantitative flow cytometry (QFC). The platelet counts of the automatic analysers were compared to the platelet counts by QFC. Blood smears were checked for the presence of pseudoplatelets. RESULTS: The automated analysers overestimated the platelet count due to the presence of pseudoplatelets in patients with AL. Pseudoplatelets were observed in the blood smears of 11 patients (13%). Three of these patients were near the prophylactic platelet transfusion threshold. CONCLUSION: Spurious increases in automated platelet counts by blast cell fragments are little known but frequent artefacts that should be ruled out by careful examination of peripheral blood smears.

Mean platelet volume: comparison of three analysers towards standardization of platelet morphological phenotype.

INTRODUCTION: The aim of this study was to show variability in the measurement of the mean platelet volume (MPV) depending on the instrument used. METHODS: This prospective analysis was carried out to measure MPV with three instruments, in 30 healthy controls and 113 hospital patients. RESULTS: Firstly, for values in the normal range, the values obtained with the Siemens Advia(®) 2120 are lower than those given by the Beckman Coulter LH750(®) (-0.89), which are in turn lower than those obtained with the Sysmex XE-2100D(®) (-1.11), which represents a 20-25% variation in the measurement. These results emphasize the lack of universal external calibration for MPV analysis and thus make any intercentre comparison of MPV impossible unless the automated haematology analyser used is indicated. Secondly, we stress the differences in behaviour of the instruments in the presence of abnormally large platelets, i.e. an underestimate of the platelet count and the MPV may be provided because instruments using impedance technology may fail to take into account these platelets, but they rightly flag them. CONCLUSION: To harmonize our procedures, we propose definitions of platelet size (normal size, macroplatelets and giant platelets) based on the coordinated interpretation of the MPV, the distribution of platelet volume and the morphological appearance.

Evaluation of schistocyte monitoring after haematopoietic stem cell transplantation.

INTRODUCTION: Observation of schistocytes on the peripheral blood following haematopoietic stem cell transplantation (SCT) is a common finding. As their presence is not specific to the onset of SCT-related thrombotic microangiopathy, we evaluated the interest of schistocyte measurement twice a week during the entire follow-up of 195 patients undergoing SCT, particularly focussing on the 125 allogeneic SCT. METHODS: Schistocytes were strickly defined as triangular-, crescent- or helmet-shaped red blood cells according to consensus standards and were checked blindly under the microscope and with computer image analysis. RESULTS: Mean schistocyte percentage was 0.7% (±0.5%, reference value ≤0.5). High schistocyte percentage was observed after allografts (0.79%) when compared to autologous SCT (0.47, P < 0.001). All but one patients undergoing allogenic SCT had schistocytes ≥0.6%. Conversely, significant schistocytosis was observed in 20% of the autologous SCT. Initial diagnosis [chronic myelocytic leukaemia, acute lymphoblastic leukaemia (ALL)], high-risk status, unrelated transplant and conditioning regimen including total body irradiation influenced higher schistocyte percentage (≈0.9%). Significant rise in the schistocyte percentage was observed during acute/chronic graft-versus-host disease, veno-occlusive disease (VOD), cholestatic hepatitis, haemorrhagic cystitis (HC) and pulmonary complications. Multivariate analysis showed a significant association between thrombotic microangiopathy (TM), renal impairment and delayed thrombopaenia after day 50, and schistocyte >1.2%. SCT-TM grade ≥2 occurred in nine patients. A marked rise in schistocyte >4.5% was observed, which was not reached during the other SCT-related complications. Children with ALL, undergoing unrelated allogeneic SCT, with early acute graft-versus-host disease refractory to steroids were prone to present SCT-TM, associated with VOD, interstitial pneumopathy and HC, resulting in a high mortality rate (six of seven patients). Our data confirmed that schistocytosis was common after SCT. Mild percentages were likely concomitant with extensive endothelial damage but higher percentage should have prompted to a close monitoring with SCT-TM investigation. CONCLUSION: In our experience, systematic schistocyte count after HSCT proved to be useful: the occurrence of an increased percentage was a surrogate marker for complications even if unspecific for TM.

[Neutropenia and/or thrombocytopenia due to acute parvovirus B19 infection]. / Neutropénie et/ou thrombopénie associée(s) à une infection aiguë par le parvovirus B19.

Erythema infectiosum (fifth disease) is the most common clinical presentation of acute parvovirus B19 infection in infancy. In healthy adults, most cases of infection are asymptomatic or accompanied by a flu-like syndrome like headaches and myalgia. Haematological manifestations are dominated by transient aplasia of erythroid progenitor cells which remains asymptomatic in most of non immunocompromised patients. Patients with sickle cell disease, thalassemia or other disorders associated with shortened red blood cell survival are at particular risk for marked anemia or red blood cell aplasia. In immunosuppressed patients, anemia may be chronic because of persistent viral load. Neutropenia, lymphopenia or thrombocytopenia have also been reported in acute parvovirus B19 infection. Mechanisms of these cytopenias are not yet elucidated. We present two patients with thrombopenia and/or neutropenia but without anemia due to acute parvovirus B19 infection.

[Persistent thrombocytopenia in a child: morphological examination of blood platelets established the diagnosis of Wiskott-Aldrich syndrome]. / Thrombopénie persistante chez un enfant: l'examen morphologique des plaquettes a conduit au diagnostic de syndrome de Wiskott-Aldrich.

Thrombocytopenia frequently occurs in laboratory practice. The present work illustrates, through the presentation of a case report of Wiskott-Aldrich syndrome, the difficulties encountered to identify and characterize thrombocytopenia. The clinicobiological validation of a low platelet count involves both the biologist, who must assume the validation of numeration while mentioning the morphological characteristics of the platelets and other blood cells, as well as the physician who has to interpret these data according to the clinical context.

[Thrombocytopenia: clinicobiologic validation and classification]. / Validation et classification clinicobiologique d'une thrombopénie.

Thrombocytopenia occurs frequently. We will illustrate, through the presentation of a clinical case, the difficulties encountered to identify and characterize thrombocytopenia. The clinicobiological validation of a low platelet count implies, at the same time, the biologist, who must assume the validation of numeration while mentioning the morphological characteristics of the platelets and other blood cells, as well as the clinician who must interpret these data according to the clinical context. Firstly, we will detail the basic rules to correctly ensure this validation. Secondly, we will see which are the arguments which that make it possible to direct the diagnosis towards an acquired or inherited thrombocytopenia. Lastly, we will approach the classification of inherited thrombocytopenias.

Automated measurement of schistocytes after bone marrow transplantation.

Bone marrow transplantation-related thrombotic microangiopathy (BMT-TMA) is a severe complication partly suspected on the evidence of a microangiopathic haemolysis. Microscopic schistocyte observation confirms the mechanical origin of the haemolysis, but remains a tedious procedure that lacks standardization. Direct measurement of abnormal red blood cell (RBC) fragments is now available on some automated haematology systems. We compared in 131 patients (69 BMT with five BMT-TMA, 38 thrombotic thrombocytopenic syndromes, 11 macroangiopathies, 13 dyserythropoiesis) percentages of microscopic schistocytes and automated RBC fragments (Bayer ADVIA 120) to evaluate the clinical relevance of the automated measurements for BMT-TMA detection. The analyser correlated well with the microscope (intraclass correlation coefficient: 0.82) and quantified RBC fragments with a moderate overestimation (+0.4%) as compared to microscopic counts. BMT patients had higher RBC fragments when they had TMA (1.1 vs 0.4% without TMA). Automated counting was useful to flag BMT-related TMA, particularly when RBC fragments were above 1%. As RBC fragments were frequently detected in BMT patients even without TMA, a threshold of less 1% that ruled out TMA was determined with a 98% negative predictive value. The new RBC fragment automated parameter proved its clinical value to assess BMT-TMA, which might be useful for day-to-day monitoring of the post BMT period.

[Contribution of the complete blood cell count to the efficiency of fragmentation haemolytic anaemia diagnosis]. / Diagnostic des anémies hémolytiques mécaniques: contribution de l'hémogramme.

Schistocytes result from red cell fragmentation. The identification of the schistocytes is critical for decisions on appropriate management of the patients. Detection of schistocytes on a peripheral blood smear is an abnormal finding, which raises the occurrence of a microangiopathy. The avaibility of effective treatment prompted the urgency to establish this crucial diagnosis. Nevertheless, schistocytes can be observed in a broader spectrum of disorders than thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, or might be delayed even absent.

[Is detection of schizocytes by computerised image analysis accurate?]. / Est-il possible de compter les schizocytes au moyen d'un logiciel d'analyse d'image?

Schistocytes result from red cell fragmentation. The identification of the schistocytes is critical for decisions on appropriate management of the patients. Currently, a systematic approach to the counting method remains rewarded. We programmed a computer image analysis device (Q-Win, Leica) in order to detect fragmented red cells. A good correlation between the computer and a well-trained biologist was found after minor modifications of the computer's results. Image analysis should reduced the biologist-to-biologist variation and improve the identification and enumeration of the schistocytes.

[Schistocytes: which definition should be taken and which method should be used to identify and count them?]. / Schizocytes: quelle définition retenir et quelle méthodologie utiliser pour les identifier et les compter? Résultats d'une enquête auprés de 24 biologistes.

Schistocytes result from red cell fragmentation. The identification of the schistocytes is critical for appropriate management of the patients. We report the results of a survey about the determination of schistocytes. The analysis of the answers of 24 well-trained biologists points out the different approaches used to count these cells, and the urgent need for guidelines to identify and enumerate them.