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Background: Mother to child transmission (MTCT) of HIV-1 remains an important problem in sub-Saharan Africa where most new pediatric HIV-1 infections occur. Early infant diagnosis of HIV-1 using dried blood spot (DBS) PCR among exposed infants provides an opportunity to assess current MTCT rates. Methods: We conducted a retrospective data analysis on mother-infant pairs from all PMTCT programs in three regions of northern Tanzania to determine MTCT rates from 2008-2010. Records of 3,016 mother-infant pairs were assessed to determine early transmission among HIV-exposed infants in the first 75 days of life. Results: Of 2,266 evaluable infants in our cohort, 143 had a positive DBS PCR result at ≤75 days of life, for an overall transmission rate of 6.3%. Transmission decreased substantially over the period of study as more effective regimens became available. Transmission rates were tightly correlated to maternal regimen: 14.9% (9.5, 20.3) of infants became infected when women received no therapy; 8.8% (6.9, 10.7) and 3.6% (2.4, 4.8) became infected when women received single-dose nevirapine (sdNVP) or combination prophylaxis, respectively; the lowest MTCT rates occurred when women were on HAART, with 2.1% transmission (0.3, 3.9). Treatment regimens changed dramatically over the study period, with an increase in combination prophylaxis and a decrease in the use of sdNVP. Uptake of DBS PCR more than tripled over the period of study for the three regions surveyed. Conclusions: Our study demonstrates significant reductions in MTCT of HIV-1 in three regions of Tanzania coincident with increased use of more effective PMTCT interventions. The changes we demonstrate for the period of 2008-2010 occurred prior to major changes in WHO PMTCT guidelines. © 2014 Buchanan et al.
This study is a retrospective data analysis on mother-infant pairs from PMTCT program records in three regions of Tanzania, using stored DBS samples stored as standard of care from HIV-exposed infants to determine early MTCT prevalence rates from HIV-exposed children ≤75 days of age. “Early” MTCT in this context, therefore, encompasses in-utero transmission, intrapartum transmission, and early breast milk infection. This study was conceived and designed in conjunction with members from the Tanzanian Ministry of Health and Social Welfare Laboratory Services Division. Following Tanzanian national guidelines, HIV-exposed infants undergo DBS PCR testing at their first visit to a Reproductive Child Health (RCH) clinic, usually between 4–8 weeks of age. Using a heel prick, five circles are filled with blood on a specific filter paper (Whatman) and sent to a Zonal PCR Laboratory. The Kilimanjaro Christian Medical Centre Clinical Laboratory is one of four such laboratories in Tanzania responsible for processing, testing, and storing DBS results for the three regions we studied. In the laboratory, one DBS circle is used to run a DNA-PCR test and if positive, a second circle is analyzed to confirm the first result. Only if both PCR tests are positive does the result become classified as positive and this result is then sent back to the RCH clinic. Every DBS card is labelled with the infant’s name and a unique identifier which is also recorded in the EID and PMTCT Mother-Child Follow-up Register that remains at the clinical site. Other information recorded in the registry includes: date of birth, date sample taken, PMTCT regimen used by the mother, infant regimen, infant feeding option, and initiation of co-trimoxazole prophylactic therapy. Three research assistants, each assigned to one region of northern Tanzania (Arusha, Kilimanjaro, and Tanga) visited all health facilities providing PMTCT and EID services within the regions. Using these national registries, de-identified information was collected from all mother-infant pairs where the infant received a first DBS PCR between January 1, 2008 and September 30, 2010. During this time period, possible maternal PMTCT regimens included either: 1) no medication; 2) sdNVP only; 3) combination prophylaxis (AZT, recorded as>or <4 weeks prior to delivery, and sdNVP and lamivudine (3TC) given at labor and delivery along with AZT plus 3TC for one week); or 4) HAART. The infant regimens provided during this time period included sdNVP at birth, with or without AZT (either for 1 week or 4 weeks depending on duration of maternal prophylaxis). After reviewing the registries of all facilities for the three regions as described, all positive DBS PCR results recorded at site registries were cross-checked by retrieving the original samples from the zonal laboratory (Kilimanjaro Christian Medical Centre). This enabled us to exclude any potential false positive PMTCT transcription errors from site PMTCT registries. Data were entered using the Cardiff Teleform system (Cardiff Inc., Vista, CA, USA) into an Access database (Microsoft Corp., Redmond, WA, USA). All data were manually reentered into a second Microsoft Access database and compared using Stata version 12 (StataCorp LP, College Station, TX, USA). All subsequent analyses were performed with Stata version 12, using a 5% level of significance (two-sided). Descriptive statistics were used to summarize demographic data. Categorical data were compared using the Chi-square test or Fisher’s exact test, where appropriate. The study was approved by the Duke University Institutional Review Board, the KCMC Research Ethics Committee, and the National Institute of Medical Research in Tanzania. All data collection was retrospective in nature and was collected as part of the routine delivery of PMTCT services in Tanzania. All ethical bodies approved the request for a waiver of informed consent due to the fact that all information collected was on de-identified patient information and PCR samples.
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