Overcounting of black Africans in the UK: the problem of undetected record duplication.

Difficulties in recording unfamiliar African names, leading to inconsistent reporting of 'surname' code of the same individual, has raised concern that there is overcounting of newly diagnosed HIV-positive black Africans in the UK. Date of birth was used as a proxy indicator for duplication of entries of black Africans in the national HIV/AIDS patient database. Significantly more black Africans (59%) than whites (56%) share the same date of birth (p = 0.0023), and among black Africans certain birthdays occur at a very high frequency. Those born in Africa may not know their exact date of birth and so may be choosing, or have chosen for them, memorable or auspicious dates instead. After removal of individuals with birthdays consisting of the same number day and month, the evidence of disproportionate duplication of black Africans' dates of birth was weaker (p = 0.0129). Although this investigation provided evidence of selective failure to detect duplicated reports of the same individual among reports of HIV-positive black Africans, in practical terms, the relatively small proportion (2.4%) of remaining excess duplicates is equivalent to 141 black African individuals on the database, and would not impact on the overall picture of the HIV epidemic in the UK.