RESUMO
BACKGROUND AND OBJECTIVE: Flow cytometry (FC) to identify platelet-associated (PA) immunoglobulin (Ig) is a potentially useful diagnostic test for idiopathic thrombocytopenic purpura (ITP). However, the restricted application of PAIg measurement to thrombocytopenic populations primarily comprised of ITP patients will artificially enhance the test's diagnostic specificity. For this reason, we performed a prospective study in which the results of a sensitive technique for detecting PAIg, as is FC, were correlated to the cause of the thrombocytopenia. DESIGN AND METHODS: A total of 118 patients with platelet counts <100 x 10(9)/L and 30 normal donors with a platelet count >200 x 10(9)/L were studied for PAIg employing a flow cytometer. Forty-two children and 20 adults were diagnosed as having immune thrombocytopenia and 27 children and 29 adults had nonimmune thrombocytopenia of different etiology. RESULTS: Raised levels of PAIg were found in 56/62 patients with immune thrombocytopenia and in 34/56 patients with non-immune thrombocytopenia. Diagnostic values of PAIg for the detection of immune thrombocytopenia were: sensitivity 90.3% and specificity 39. 3%. An enzyme-linked immunoabsorbant assay (ELISA) for the detection of autoantibodies to platelet glycoprotein (GP) complexes was used in adults, 9 with immune-related thrombocytopenia and 16 with non-immune thrombocytopenia, in order to determine the true non-specific nature of the positive PAIg test. By ELISA, 8/9 patients with immune thrombocytopenia and 7/16 with non-immune thrombocytopenic disorders showed autoantibodies to platelet GP complexes. INTERPRETATION AND CONCLUSIONS: PAIg detection by FC constitutes a sensitive but non-specific assay thus making it unnecessary and inappropriate for establishing the diagnosis of ITP.
Assuntos
Plaquetas/imunologia , Citometria de Fluxo/normas , Imunoglobulina G/sangue , Púrpura Trombocitopênica Idiopática/diagnóstico , Adolescente , Adulto , Idoso , Autoanticorpos/sangue , Criança , Pré-Escolar , Humanos , Imunoglobulina M/sangue , Pessoa de Meia-Idade , Estudos Prospectivos , Púrpura Trombocitopênica Idiopática/sangue , Púrpura Trombocitopênica Idiopática/imunologia , Padrões de Referência , Sensibilidade e Especificidade , Trombocitopenia/sangue , Trombocitopenia/diagnóstico , Trombocitopenia/imunologiaRESUMO
OBJECTIVE: To evaluate the recommendations of the First Latinamerican Consensus Conference for the Immunophenotyping of Acute Leukemia in untreated patients with de novo disease immunologically classified employing flow cytometry and an extended panel of monoclonal antibodies. MATERIAL AND METHODS: In that conference it was recommended the use of the following antibodies: cytoplasmic CD79a (cCD79a) and CD19 to define B-progenitor acute lymphoblastic leukemia (B-ALL); cCD3 and CD7 for T-cell ALL (T-ALL), and CD13, CD33 and myeloperoxidase (cMPO) for acute myeloblastic leukemia (AML). We analyzed the expression of these cellular antigens in 91 non-consecutive patients classified with the extended panel as: B-ALL 28 cases; T-ALL 7; B-T-ALL 2; AML 47; and mixed-lineage acute leukemia 7 cases. RESULTS: All 28 B-ALL cases were positive with each of the two recommended antibodies cCD79a and CD19, whereas in 24 AML cases (the expression of cCD79a was not assayed in 23 cases) and in 7 T-ALL patients both antigens were absent. cCD3 and CD7 antigens were identified in 71% and 100% of T-ALL, respectively. CD7 antigen was not detected in any of the 28 patients with B-ALL but it was expressed in 6 of 47 AML cases, while none of 75 B-ALL and AML cases were positive to cCD3. Forty nine percent of AML were positive for the three recommended markers: cMPO, CD13 and CD33, and 51% of AML cases reacted with one or two of these three monoclonal antibodies. Six out of 28 cases of B-ALL had aberrant expression of myeloid antigen (CD33 in 3 cases and CD13 in 3 cases). CONCLUSIONS: There was no difference in the definition of AL lineage between employing the extended antibody panel and that recommended by the Latinamerican consensus.