Maturation Index: a Contribution to Quantification in the FAB Cla.ssification of Acute Leukaemia

Abstract

The French--American--British co-operative study group (FAB) criteria were used to classify acute leukaemia in 194 adult patients. The dividing lines between FAB subgroups M1--M2 and M5A--M5B appeared to be less well defined. In an effort to improve subtyping we introduce the maturation index (MI). (formula: see text). Clearly distinct subgroups emerged after arrangement of cases according to MI values. Immature and rather mature cases in both myeloblastic and monoblastic leukaemia were divided at a MI of 4%. Assignment to M3, which is based essentially on morphological grounds, could be made on numerical grounds too, MI being at least 85% in all of our cases. A few cases showing M2 morphology and a positive alpha-naphthylacetate esterase (ANE) staining should probably be categorized as M4. Application of the original FAB criteria resulted in disagreement of 14% between three investigators, while with our additional criteria the discrepancy was only 2%.

Bone biopsy in haematological disorders.

“…[66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] Only rarely have studies of bone marrow biopsies been reported,7' 72 except after chemotherapy. 73 With deepening understanding of the role of the marrow microenvironment in haematopoiesis, bone marrow biopsies in acute leukaemia will be reported more frequently.…”

Maturation changes in relapsing acute myeloid leukaemia

“…In several cases the changes were high enough to make assignment to another FAB-group mandatory. When the FAB-classification was quantified according to van Rhenen et a1 (2), this occurred in 5 out of 17 patients (29%). There appeared to be a tendency of lower MI's (<20) to rise and of higher MI's (>20) to decrease, both in myeloid and monocytoid groups.…”

“…Differential counting of 100 cells in the peripheral blood and 500 bone-marrow cells was carried out on coded smears, by two of us, on May-Griinwald-Giemsa stained smears made at presentation and at first or second relapse. The original FAB-criteria were used (l), as further quantified by van Rhenen et al (2).…”

Motility of Leukaemic Cells in Acute Leukaemia Related to Tumour Mass, Maturation and FAB Classification

“…Classification was done according to the FAB criteria, using cytochemical stains (Sudan black and a-naphtyl-acetate esterase) [13,14]. The degree of maturation was expressed as the maturation index (MI) [14].…”