24-OR

Abstract

Aim A 41 year-old male presented with AML/MDS in blast crisis for HLA typing. At the time his original sample was collected, his absolute WBC was 70.1 × 10 9 /L with 23% blasts. A discrepancy was present between the serologic typing and some of the molecular results. A sample was sent for confirmatory testing, with an absolute WBC count of 3.1 × 10 9 /L and no blasts present. Methods HLA typing was performed by serology (Bio Rad, GTI Diagnostics), reverse SSO by AutoReli (Life Technologies) and Luminex (One Lambda), allele-specific and generic SSP trays (Olerup, One Lambda), and SBT (Life Technologies, Abbott Molecular). Results Results obtained by serology, generic and allele-specific SSP typing trays, and AutoReli SSO gave an A ∗ 02:01, ∗ 25:01 typing. However, Luminex SSO and SBT testing methods demonstrated a homozygous A ∗ 25:01 result. SBT results using both methods showed absolutely no evidence of a second antigen. All testing methodologies gave an A ∗ 02:01, ∗ 25:01 result on the confirmatory sample. All testing was performed on DNA isolated from peripheral blood lymphocytes, as the patient passed away before a buccal swab sample could be obtained. Conclusions The likely cause of the discrepancy between all of the available typing methods is due to an allele drop out of the A ∗ 02:01 in the malignant myeloid cell line. Since the patient still had a substantial population of unaffected lymphocytes (15%), a correct heterozygous result was obtained by the molecular typing methods with a wider range of acceptable DNA concentration, as well as by serologic testing. Since the malignant cell line was probably obliterated in the confirmatory sample, all testing methods were able to obtain the correct result. Therefore, it is of utmost importance to confirm homozygous sequence based typing results by more robust molecular methods.