Enigmatic Weak D antigen: An Experience in a Tertiary Care Hospital of East Delhi.

INTRODUCTION

The Rh blood group system is one of the most polymorphic and immunogenic blood group systems in humans. The expression of Rh blood group antigen is complex, among that Rh-D antigen is the most important antigen because of its immunogenicity. It is easy to detect D antigen in most of the cases. Sometimes, variable expression of Rh-D antigen leads to presence of weak forms. Weak D reacts variably with anti D sera and poses a problem in blood banking. Molecular genetics of Rh-D revealed that weak D antigen is a Rh-D phenotype that possesses less numbers of complete D antigens on the surface of red blood cells.

AIM

Present study was carried out to study weak D positivity in a tertiary neuropsychiatry hospital of East Delhi for compatibility testing in blood transfusion, to assess the implications and need of weak D testing and for population genetics study. This study tried to observe pattern of weak D antigen in four broadly classified religious communities also (Hindus, Muslims, Sikhs and Christians).

MATERIALS AND METHODS

This was a two years prospective hospital based study including patients as well as donors. All patients were tested for Rh-D factor by commercially available monoclonal anti-D sera. The individuals who were found negative with anti-D were further investigated for weak D antigen by using indirect antiglobulin test (IAT) by tube as well as gel card technique.

RESULTS

The results were compiled by using SPSS software version 21.0 and Microsoft excel. Among 3619 cases, 3502 (96.7%) were Rh-D factor positive while 117(3.2%) were Rh D factor negative. Among these 117 Rh-D negative cases, 9 (7.6% out of total Rh-D negatives and 0.25% out of total samples) were weak D positive and 108(2.98%) were actually D negative individuals after IAT. Weak D positivity showed a slight predominance in females (55.5%). As per broad religious communities, weak D antigen was found in Hindus only and not observed in Muslims, Sikhs and Christians. In weak D positive individuals, B phenotype (0.43%) was found to be most common followed by A (0.26%) and O (0.2%).

CONCLUSION

Considerably high frequency of weak D antigen was noticed in study samples of this hospital. With this data based information, it is felt worthwhile to perform weak D testing routinely of those individuals who are negative with saline anti-D to prevent possibility of haemolysis and for efficient blood transfusion practices by making compatible blood available.