A double-blind comparative immunotypic study between two institutions phenotyping non-Hodgkin's lymphomas

To establish the feasibility of immunotyping specimens transported over great distance, the University of Arizona and the Cleveland Clinic exchanged 39 lymphoma cases (26 B-cell, 13 T-cell cases) via air express for phenotyping. They were exchanged with the use of glass slides with adherent snap-frozen sections. The method involved immunohistochemistry using a common battery of 20 antibodies directed at B- and T-cell antigens. Using similar, but not identical, methods and reagents, cases were assayed before and after transport. Results were generated as paired determinations in a double-blind fashion (1,338 total determinations, 669 paired determinations/669 antigens). Using "pretransport" values as the baseline, there was subsequent agreement with baseline in 624 of 669 antigenic determinations (93.3%) and disagreement in 45 (6.7%). Interinstitutional agreement was 94% for T-antigens (Leu-1-7,9) and 93% for B-antigens (K, lambda; IgM, G, A, D; B1, B2, B4, L14; J5, common acute lymphocyte leukemia antigen [CALLA]; Ia). In spite of 6.7% disagreement, there was agreement of overall phenotypic profile (e.g., B vs. T and subset stage) in all 39 cases. This is because discrepancies were isolated and the battery offset undue reliance on a single antigen. The disagreements relate mainly to certain B-antigens: CALLA/J5 (eight disagreements) and B1 and B2 (six and five disagreements, respectively). T-antigen disagreements were more sporadic (e.g., Leu-5 [three disagreements]). These discrepancies may relate to antigen loss with transport, variable antigen density or antibody avidity, methodologic differences, quality of reagents, or differences of phenotype interpretation. A further exchange of the 45 disagreement slides indicated that difference of observer interpretation was a minor factor (3 of 45). In conclusion, the authors' study demonstrates a high degree of immunotype reproducibility (approximately 93%), suggesting promise for institutions doing collaborative lymphoma studies.