Genotyping and serotyping profiles showed weak Jk^a presentation for previously typed as Jk_null donors

Kidd blood group system consists of two major antigens: Jk^a and Jk^b . Both the antigens are absent in individuals typed as Jk_null and may develop clinically significant anti-Jk3 antibody. Screening donors for provision of Jk_null blood is an ongoing task for blood centres with Jk_null blood units kept frozen for specific requirements. In 2016, we discovered a previously typed Jk_null donor to be Jk^a weak positive. Therefore, a study was conducted for our donors to verify Jk_null status and to reinforce our typing protocol.

In this experiment, donors previously typed and screened as Jk_null were tested with four antisera of Jk^a and Jk^b , and each with gel card for serology testing. Sequence analysis was performed for SLC14A1 gene for the detection of JK^null and weak alleles for genetic testing.

Among the 30 samples, four were serologically identified as Jk(a+^w ) and genotypically identified as heterozygous for the JK*01W.01 allele. The other 26 were confirmed to be Jk_null with JK*02N.01 as the most frequent allele. None of JK*B weak alleles were detected, but three were identified as false positives in the tube method. Gel card gave great accuracy for Jk^b detection, but failed to give consistent results for weak Jk^a .

By combining the tube method and gel card method in serology, along with complementary genetic testing, the possibility of misinterpreting weak Jk^a expression was eliminated, and we were able to provide Jk_null blood for safe clinical transfusion.