Bombay blood group: Is prevalence decreasing with urbanization and the decreasing rate of consanguineous marriage.

CONTEXT

Bombay blood group although rare is found to be more prevalent in the Western and Southern states of India, believed to be associated with consanguineous marriage.

AIMS

To estimate the prevalence of the Bombay blood group (Oh) in the urban population of Puducherry. To find the effect of urbanization on consanguineous marriage and to establish whether consanguinity plays a part in the prevalence of Oh group. To compare Oh group prevalence with that of other neighboring states, where population is not predominantly urban.

SETTINGS AND DESIGN

This is a descriptive study in a tertiary care hospital in Puducherry, over a period of 6 years.

MATERIALS AND METHODS

All blood samples showing 'O' group were tested with anti-H lectin. Specialized tests like Adsorption Elution Technique, inhibition assay for determination of secretor status were performed on Oh positive cases. Any history of consanguineous marriage was recorded.

STATISTICAL ANALYSIS USED

All variables were categorical variable and percentage and proportions were calculated manually.

RESULTS

Analysis of the results of 35,497 study subjects showed that the most common group was 'O' group constituting 14,164 (39.90%) of subjects. Only three "Oh" that is, Bombay phenotype (0.008%) were detected. Consanguinity was observed in two cases (66.66%).

CONCLUSIONS

This study shows the prevalence of Bombay blood group representing the urban population of Puducherry, to be high (0.008%) and associated with consanguineous marriage (66.66%). Thus, consanguinity is still an important risk factor present, even in an urban population in Southern India.