A Correction factor for underreporting was ascertained by studying attendance at the laboratory facility over two time periods defined by the cost of HIV screening.Estimates of HIV prevalence obtained from corrected data using the modified nonparametric back-calculation are comparable with UN estimates obtained by a different method.Parameter estimates obtained using 3-step and 4-step models were similar but the standard errors of these parameters were higher in the 4-step model.
Literature on ordinary back-calculation, nonparametric back-calculation, and modified back-calculation methods was reviewed in detail.
Also, an indepth review of disease mapping techniques including multilevel models and geostatistical methods was conducted.
The modified nonparametric back-calculation method makes use of HIV data instead of the AIDS incidence data that are used in parametric and ordinary nonparametric back-calculation methods.
In this approach, the hazard of undergoing HIV test is different for routine and symptom-related tests.
This thesis has two broad aims: the first is to develop statistical models which adequately describe the spatial distribution of the Nigerian HIV/AIDS epidemic and its associated ecological risk factors; the second, to develop models that could reconstruct the HIV incidence curve, obtain an estimate of the hidden HIV/AIDS population and a short term projection for AIDS incidence and a measure of precision of the estimates.
To achieve these objectives, we first examined data from various sources and selected three sets of data based on national coverage and minimal reporting delay.
The constant hazard of routine testing and the proportionality coefficient of symptom-related tests were estimated from the data and incorporated into the HIV induction distribution function.
Estimates of HIV prevalence differ widely (about three times higher) from those obtained using parametric and ordinary nonparametric back-calculation methods.
The bulk of infection was found in patients aged 15-49 years, about 86 percent of infected females and 78 percent of males were in this age group.
Attendance at the laboratory and the proportion of HIV positive tests witnessed a remarkable increase when screening became free of charge.