Impact of incomplete coverage of neonatal dried blood spot screening on estimating HIV-1 seroprevalence
Hutchinson, E.J.; Streetly, A.; Grant, C.; Pollitt, R.; Eldridge, P.; Nicoll, A.
Epidemiology and Infection 117(1): 173-177
1996
ISSN/ISBN: 0950-2688 PMID: 8760966 DOI: 10.2307/3864647Document Number: 301050
Census data, local fertility statistics, maternity data, and data from the HIV-1 prevalence monitoring program were used to develop a model to predict the effects of under-coverage of neonatal dried spot screening, which has been observed in infants with mothers of the Black African ethnic group. The data and statistics were limited to South London, England, which included the boroughs of Lambeth, West Lambeth, Southwark, and Camberwell. The model assumed HIV-1 prevalence values for African mothers to be 0-20% and 0-0.5% for all other mothers. It assumed a general fertility rate of 160/1000 for African mothers and 64/1000 for all other mothers. Coverage for neonatal dried spot screening was assumed to be 95.6% for African mothers and 98.15% for all other mothers. The relative inclusion ratio (RIR) (the probability that samples from a group at different risk of HIV infection were included in the survey divided by the probability of inclusion for samples from all other infants) was used as the adjustment factor allowing for under-coverage. The RIR was close to unity (0.975) (i.e., 95.6% actual coverage for African mothers in South London divided by 98.15% for all other mothers in South London), suggesting minimal bias. Under usual conditions, substantial bias would not occur unless RIR fell to values of 0.87 (i.e., coverage of 86% divided by 98.15%) or below. When HIV-1 prevalence was assumed to be 0.3% in all others, there was no difference between true and observed HIV-1 prevalence until it reached 3% in African mothers. At 3% HIV-1 prevalence for African mothers and 0.3% for all others, the difference was only 0.01% (i.e., observed prevalence of 0.34% compared to a true prevalence of 0.35%). These findings suggest that the Unlinked Anonymous HIV Monitoring Programme Dried Blood Spot Survey appears to identify accurately levels of HIV prevalence in the population of reproductive age women. It is still a useful tool for resource allocation, planning of services, provision of care, and counseling.