[1482] Flow-Cytometric Detection of Aberrant T-Cell Immunophenotype Accurately Predicts the Presence of Clonal TCR Gene Rearrangements

Karan Paisooksantivatana, Iwona Auer-Grzesiak, Joanne M Luider, Adnan Mansoor, Meer-Taher Shabani-Rad. University of Calgary, Calgary, AB, Canada

Background: Flow-Cytometric detection of aberrant T-Cells is not uncommon within blood samples of patients with lymphocytosis. PCR based analysis of T-Cell receptor gene rearrangements (TCR) for clonal expansion is usually triggered by Flow-Cytometric findings. Introducing an appropriate Flow-Cytometric criteria may promote efficient utilization of PCR-Based TCR analysis.
Design: Retrospective (1999-2011)immunophenotypic results of blood specimens with partial/complete loss of T-Cell markers (CD2, CD3, CD5 and CD7), enhanced expression of CD16+56 and inverted/increased CD4/CD8 ratio were reviewed {n=569 of 6988 (8.1%)}. TCR analysis was performed utilizing beta and gamma gene consensus primers by PCR. Monoclonality was defined as either beta and/or gamma gene rearrangements. Sensitivity, specificity, positive/negative predictive values (PPV/NPV) of immunophenotypic parameters were calculated in correlation with TCR status wherever applicable.
Results: The rate for loss of CD7, CD5 and CD5/CD7 were 89.5%, 78.9% and 71.2% respectively. Increased expression of NK-Cell associated molecules (CD16/56) and inverted CD4:CD8 ratio were reported in 59.6% and 57.5% of cases respectively. Increased CD4/CD8 ratio of >4 was seen in only 3.3% of cases. TCR results were available in 421 case with 376/569 (89.3%) being clonal. CBC data revealed lymphocytosis in 289/569 cases (48.0%), all of those being clonal for TCR (PPV; 100%). Although loss of CD2 or CD3 and CD4/CD8 ratio of >4 were seen in <3.3% of cases, they showed the highest specificity for clonal TCR (98% to 100%). Abnormal T-Cell immunophenotypes were detected in 17/27 (63%) of cases with tissue diagnosis of T-cell lymphoma.
Conclusions: Flow-Cytometric detection of two aberrant T-Cell marker (CD5 or CD7 or enhanced CD16/56) predicts clonal TCR among patients with T-Cell lymphocytosis (PPV>95%). TCR may be performed only for cases with relevant clinical manifestation of T-Cell lymphoproliferative disorders. Aberrancy of CD2 or CD4/CD8 ratio of >4 may prompt investigation for T-Cell lymphoma even in the absence of lymphocytosis.
Category: Hematopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 275, Tuesday Afternoon

 

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