1. ¹Department of Cellular and Molecular Biology, Princess Margaret Hospital, Toronto, Ontario, Canada
2. ²Department of Pathology and Laboratory Medicine, Vancouver Hospital and Health Sciences Center, BC, Canada
3. ³Leukemia/BMT Program of British Columbia, BC, Canada
4. ⁴Department of Pathology and Laboratory Medicine, British Columbia Cancer Agency, BC, Canada

Correspondence: Dr H Khoury, MD, Princess Margaret Hospital, Department of Cellular and Molecular Biology, Room 9-111, 610 University Ave., Toronto, Ontario, Canada M5G 2M9. E-mail: khaytham@uhnres.utoronto.ca

Received 3 December 2003; Revised 22 March 2004; Accepted 23 March 2004; Published online 4 June 2004.

Abstract

Acute myelogenous leukemia with t(8;21) is a distinct clinicopathologic entity in which the malignant myeloblasts display a characteristic pattern of surface antigen expression. Quantitative analysis of surface marker expression in patients with this chromosomal abnormality compared to acute myelogenous leukemia patients with a different karyotype has not been reported. From 305 consecutive newly diagnosed acute myelogenous leukemia patients underwent immunophenotyping and cytogenetic analysis at our center; 16 patients (5.2%) had a t(8;21). Fluorescence intensity values were obtained, using a set of reference microbeads, by conversion of mean channel fluorescence to molecular equivalent of soluble fluorochrome. Patients with t(8;21) displayed higher levels of CD34, HLA-DR and MPO expression (P<0.001 for each) and lower levels of CD13 (P=0.03) and CD33 (P=0.02) expression. In order to study the sensitivity, specificity and predictive value of these markers, molecular equivalent of soluble fluorochrome thresholds were statistically determined. The statistically established threshold for each of the individual markers (CD34>60.5 10³, HLA-DR>176.1 10³, MPO>735.1 10³, CD13<24.3 10³ and CD33<17.3 10³) had a sensitivity of 100%, a specificity of 62–92% and a positive predictive value of 7–45%. In multivariate analysis, two quantitative patterns (CD34>60.5 10³ and MPO>176.1 10³; CD33<17.3 10³ and MPO>176.1 10³) had a sensitivity, specificity and positive predictive value of 100%. These aberrant phenotypic patterns might help identify patients with t(8;21) at diagnosis and could be useful in minimal residual disease monitoring.