[1417] Utility of CD11a and CD18 in the Diagnosis of Acute Promyelocytic Leukemia by Flow Cytometric Immunophenotyping.
Yi Zhou, Jeffrey L Jorgensen, Sa A Wang, L Jeffrey Medeiros, Sergej N Konoplev. University of Texas MD Anderson Cancer Center, Houston
Background: Acute promyelocytic leukemia (APL) is a curable disease, but it can be rapidly fatal if the patient is not diagnosed and treated in a timely fashion. Flow cytometric immunophenotyping (FCI) has a rapid turn around time, and may serve as a screening test for confirmatory molecular/cytogenetic tests for t(15;17)(q22;q21/PML-RARA). CD34-/HLA-DR-/CD117+ is a well recognized phenotype for APL, but is known to lack specificity. The leukocyte integrin αL β2 (CD11a/CD18) is expressed in most cases of acute myeloid leukemia (AML). In a small number of published studies, CD11a/CD18 was often dim or negative in APL. The goal of this study was to examine CD11a/CD18 expression in a group of APL cases and in a group of AML cases in which APL was considered in the differential diagnosis.
Design: We retrospectively examined 83 cases of AML with a clinical, morphologic, or immunophenotypic suspicion for APL, for which CD11a and CD18 were added to our routine AML FCI panel (which also included CD34 and HLA-DR). A marker was scored as positive if 30% or more of the blasts were brighter than isotype controls. All cases of APL were confirmed by molecular/cytogenetic testing.
Results: There were 43 cases of APL and 40 cases of non-APL, which were mostly AML with or without maturation (WHO criteria). The results for CD11a, CD18, CD34 and HLA-DR were as follows. Considering these markers singly, HLA-DR (absence) was the most sensitive for APL, but all single markers had low specificity in this study group. The classic CD34-/HLA-DR- pattern showed moderate sensitivity and specificity for APL. A pattern of negativity for CD11a and/or CD18 showed high sensitivity but lower specificity. Negativity for all four antigens had the highest specificity but lacked sensitivity.
| APL N (%) | Non-APL N (%) | Specificity | |
| HLA-DR- | 42 (98) | 14 (35) | 65% |
| CD34- | 36 (84) | 16 (40) | 60% |
| CD11a- | 37(86) | 16 (40) | 60% |
| CD18- | 38 (88) | 20 (50) | 50% |
| CD11a- or CD18 - | 42 (98) | 26 (65) | 35% |
| CD34-/DR - | 35 (81) | 11 (28) | 72% |
| CD11a-/CD18 - | 33 (77) | 10 (25) | 75% |
| DR-/CD11a-/CD18- | 32 (74) | 6 (15) | 85% |
| CD34-/DR-/CD11a-/CD18- | 27 (63) | 4 (10) | 90% |