Analysis of the presenting features of adult acute leukemia: the French-American-British classification.

The authors have performed a clinical and statistical analysis of the presenting features of adult acute leukemia classified according to the French-American-British (FAB) hematopathologic criteria. Observations were made on 70 variables of history, physical examination, and laboratory examination recorded for 195 patients seen during a recent six year interval. The incidence of each category as determined by consensus of three observers was L1, 9%; L2, 17%; L3, 3%; M1, 21%; M2, 22%; M3, 5%; M4, 21%; M5, 4%; and M6 1%. there were recurring features of each FAB category and for aggregated categories (myeloid, lymphoid). Some groups such as L1, M3, M4, and M5 were characterized by many distinctive characteristics. In contrast, the L2, M1, and M2 categories had few distinctive characteristics, although L3 shared many features with the other lymphoid groups. The distinctness of the categories was quantitated by stepwise discriminant analysis. Using only a few computer-selected clinical variables, the authors classified patients into the correct FAB category with an accuracy of over 65% for some groups. The accuracy in discriminating between lymphoid and myeloid groups, the important therapeutic distinction, was 82%. This study demonstrates that many of the categories defined by the FAB criteria have characteristic clinical features at presentation.