title: Thrombocytopenia: diagnosis with flow cytometry and antiplatelet antibodies.
abstract: OBJECTIVE
  To identify antiplatelet antibodies by flow cytometry (direct method) in patients with thrombocytopenia.
  
  
  METHODS
  Between January 1997 and March 2004 a total of 15100 patients were referred to the Centro de Hematologia de São Paulo for hematological investigation of several diagnoses (anemia, leukopenia, thrombocytopenia, coagulation abnormalities, adenomegaly, leukemia and others). Of those, 1057 were referred because of thrombocytopenia and were divided into two groups: Group Idiopathic thrombocytopenic purpura, with no identifiable cause; and Group Other thrombocytopenia, which included low normal platelet counts cause to be established, hepatitis C and HIV infection, hypersplenism, EDTA-induced artifacts, laboratory error, and other causes. Flow cytometry immunophenotyping was done in 115 cases to identify platelet autoantibodies (direct method).
  
  
  RESULTS
  Of the total number of patients, 1057 (7%) presented low platelet counts, 670 were females (63.4%) and age range of one to 75 years. Of the 115 cases (9.7%) submitted to immunophenotyping, the results were positive in 40% and the test was inconclusive in 5%. Idiopathic thrombocytopenic purpura was found in 52% of patients, more often in women. Hepatitis C virus infection was found in 7% and HIV infection in 1%. Low normal platelet counts were found in 17%, laboratory errors in 6%, and laboratory artifacts in 1% of cases. Platelet autoantibodies were found in 76.9% of all idiopathic thrombocytopenic purpura cases. It was negative in 83.3% of the low normal counts.
  
  
  CONCLUSIONS
  antiplatelet autoantibodies when present help to diagnose idiopathic thrombocytopenic purpura. When absent, suggest other causes of thrombocytopenia.
authors.affiliation: Department of Clinical Pathology, Hospital Israelita Albert Einstein - HIAE, São Paulo, SP, BR.
authors.forename: João Carlos de Campos
authors.initials: JC
authors.lastname: Guerra
authors.affiliation: Division of Flow Cytometry, Department of Clinical Pathology, Hospital Israelita Albert Einstein - HIAE, São Paulo, SP, BR.
authors.forename: Ruth Hissae
authors.initials: RH
authors.lastname: Kanayama
authors.affiliation: Division of Flow Cytometry, Department of Clinical Pathology, Hospital Israelita Albert Einstein - HIAE, São Paulo, SP, BR.
authors.forename: Sonia Tsukasa
authors.initials: ST
authors.lastname: Nozawa
authors.affiliation: Clinical Laboratory, Centro de Hematologia de São Paulo - CHSP, São Paulo, SP, BR.
authors.forename: Márcia Regina
authors.initials: MR
authors.lastname: Ioshida
authors.affiliation: Clinical Laboratory, Centro de Hematologia de São Paulo - CHSP, São Paulo, SP, BR.
authors.forename: Irina Yoko
authors.initials: IY
authors.lastname: Takiri
authors.affiliation: Clinical Laboratory, Centro de Hematologia de São Paulo - CHSP, São Paulo, SP, BR.
authors.forename: Robson José
authors.initials: RJ
authors.lastname: Lazaro
authors.affiliation: Hospital Israelita Albert Einstein - HIAE, São Paulo, BR.
authors.forename: Nelson
authors.initials: N
authors.lastname: Hamerschlak
authors.affiliation: Diagnósticos da América S/A-DASA, São Paulo, SP, BR.
authors.forename: Luiz Gastão Mange
authors.initials: LG
authors.lastname: Rosenfeld
authors.forename: Celso Carlos de Campos
authors.initials: CC
authors.lastname: Guerra
authors.affiliation: Division of Flow Cytometry, Department of Clinical Pathology, Hospital Israelita Albert Einstein - HIAE, São Paulo, SP, BR.
authors.forename: Nydia Strachman
authors.initials: NS
authors.lastname: Bacal