[Detection of weak D antigen by flow cytometry].

Flow cytometry was previously applied for analysis of Rh(D) antigen density, therefore it was suggested that the flow cytometry may be used for routine detection of weak D positive phenotypes. This study was purposed to evaluate its practicability. Six weak D positive and 7 DEL individuals were detected by using saline, IAT and absorption/elution test from 2010 to 2011 years. By RHD genotyping, zygosity analysis and sequencing, 3 cases of weak D type 15, 3 cases of partial D type DVI-III and 7 cases of DEL carrying RHD1227A alleles were identified. Taking 2 normal Rh(D)-positive and 2 D-negative samples as controls, all the samples were tested by using flow cytometry, and the median fluorescence intensities were observed as well. The results indicated that all weak D type 15 and partial D type DVI samples were detected to be positive by flow cytometry, as compared with 2 Rh(D)-negative samples (P < 0.05). Seven 7 DEL samples were tested to be negative (P > 0.05), although one of 7 DEL was tested as "±" in IAT and strong positive in absorption/elution. The RHD zygosity analysis showed this DEL individual as RHD(+)/RHD(+) homozygote. It is concluded that the sensitivity of detecting D antigen by flow cytometry is similar to that of IAT, but lower than absorption/elution test. As for detecting weak D or partial D antigens, IAT is easier than flow cytometry; as for identifying DEL, the flow cytometry is not sensitive enough.