Time to DNA-PCR Positivity in Non-Breastfed HIV-Infected Infants Primarily Non-B HIV Subtype

1. A Collaborative Analysis of Data from Cohorts in Thailand, South Africa, Botswana, and the United Kingdom International Collaborative Study of Pediatric Diagnostic Tests JuLy 19, 2011 Time to DNA-PCR Positivity in Non-Breastfed HIV-Infected Infants (Primarily Non-B HIV Subtype)

2. Background Accurate diagnostic tests to detect HIV infection in infants are critical to ensure early treatment HIV DNA-PCR has imperfect sensitivity in the first two weeks of life Previous studies found that time to HIV DNA-PCR positivity increase by about 15% with ZDV prophylaxis compared with no antiretrovirals (ARV) Impact of combination ARV prophylaxis is not well characterized; no single cohort can adequately address this question CHER study 2008: Early therapy reduces mortality and HIV disease progression by more than 70% Dunn 1995: in the absence of ARVs, the proportion of HIV-infected infants who test positive is estimated to be 38% within one day after birth and it rises to 93% by 14 days after birth. Dunn 2000: ZDV monoprophylaxis delays time to positivity by about 15% compared with no ARV CHER study 2008: Early therapy reduces mortality and HIV disease progression by more than 70% Dunn 1995: in the absence of ARVs, the proportion of HIV-infected infants who test positive is estimated to be 38% within one day after birth and it rises to 93% by 14 days after birth. Dunn 2000: ZDV monoprophylaxis delays time to positivity by about 15% compared with no ARV

3. Goals Combine data from several cohorts of non-breastfeeding HIV-infected mother-infant pairs Initial phase: cohorts with primarily non-B HIV subtype Estimate the time to DNA-PCR positivity in non-breastfed HIV-infected infants Assess differences in time to DNA-PCR positivity according to maternal/infant ARV regimen A solid understanding of time to positivity in non-breastfed infants, who do not have HIV exposure after birth, will provide a foundation for studying time to positivity in breastfed infants A solid understanding of time to positivity in non-breastfed infants, who do not have HIV exposure after birth, will provide a foundation for studying time to positivity in breastfed infants

4. Inclusion/Exclusion Criteria Inclusion criteria: Infant HIV-infected and has at least one DNA-PCR result before age 3 months Maternal HIV diagnosis before or within 1 month after birth Excluded diagnostic tests with missing result or missing age at time of blood draw Excluded one infant whose mother�s ARV exposure was unknown

5. Statistical Methods Used methods for interval-censored data Timing of HIV infection uncertain; in interval between last negative and first positive DNA-PCR test Estimated the cumulative probability of DNA-PCR positivity according to age and ARV Non-parametric methods; Turnbull algorithm, Wilcoxon test Exploratory regression modeling to adjust for potential confounders Parametric methods; assumed Weibull distributions with proportional hazards; likelihood ratio test

6. Participating Cohorts

7. Infants Grouped by Most Complex Maternal/Infant ARV

8. Demographics As one would expect, more complex ARV use increased over time. No ARV and single NRTI predominantly from Thailand, sdNVP split between Thailand and Africa, and >3 ARVs mainly from Africa.As one would expect, more complex ARV use increased over time. No ARV and single NRTI predominantly from Thailand, sdNVP split between Thailand and Africa, and >3 ARVs mainly from Africa.

9. Characteristics (median [25th-75th percentile]) Maternal CD4 and viral load both highest among infants with No ARV. Gestational age at delivery was earlier and proportion of cesarean sections was greater among infants who received >=3 ARVs, reflecting management in the UK.Maternal CD4 and viral load both highest among infants with No ARV. Gestational age at delivery was earlier and proportion of cesarean sections was greater among infants who received >=3 ARVs, reflecting management in the UK.

10. Cumulative Probability of Positive DNA-PCR by Age (Non-Parametric) Nonparametric analyses do not assume a particular shape for the probability curve Proportion positive at birth to one day is lower in the No ARV group than in the ARV groups, and it increases more rapidly from day 2 to 14. Consistent with ARV reducing intrapartum transmission (fewer intrapartum infections, so greater proportion are positive at birth and fewer positive shortly after birth). Probability of positive test reaches 90% later with more complex ARVNonparametric analyses do not assume a particular shape for the probability curve Proportion positive at birth to one day is lower in the No ARV group than in the ARV groups, and it increases more rapidly from day 2 to 14. Consistent with ARV reducing intrapartum transmission (fewer intrapartum infections, so greater proportion are positive at birth and fewer positive shortly after birth). Probability of positive test reaches 90% later with more complex ARV

11. Cumulative Probability of Positive DNA-PCR by Age (Subset: 143 infants negative at birth or day 1) After removing infants who are positive at birth-1 day or have no test result at birth-1day, the probability of a positive DNA-PCR still appears to reach high levels later with more complex ARV.After removing infants who are positive at birth-1 day or have no test result at birth-1day, the probability of a positive DNA-PCR still appears to reach high levels later with more complex ARV.

12. Cumulative Probability of Positive DNA-PCR by Age (Parametric - separate Weibull models, unadjusted) To adjust for potential confounders such as CD4 and viral load, need to make assumptions about the shape of the probability curve. One model that is commonly used is the Weibull model, with the shape assumed to be the same for all groups and the height allowed to vary (proportional hazards assumption). Plot of separate Weibull models suggests that No ARV group has different shape, so restricted modeling to the ARV groups. To adjust for potential confounders such as CD4 and viral load, need to make assumptions about the shape of the probability curve. One model that is commonly used is the Weibull model, with the shape assumed to be the same for all groups and the height allowed to vary (proportional hazards assumption). Plot of separate Weibull models suggests that No ARV group has different shape, so restricted modeling to the ARV groups.

13. Adjustment for Confounders: Infants who Received ARV(Parametric, Proportional Hazards; HR >1 Means Earlier Positivity) In the unadjusted model, which only included the ARV group, the p-value for ARV was not quite statistically significant (0.06), though the confidence intervals lay almost entirely above 1.0. In the adjusted model, which also included CD4, viral load, gestational age, and mode of delivery, the p-value rose to 0.11, but the hazard ratios and confidence intervals didn�t change substantially. In the unadjusted model, which only included the ARV group, the p-value for ARV was not quite statistically significant (0.06), though the confidence intervals lay almost entirely above 1.0. In the adjusted model, which also included CD4, viral load, gestational age, and mode of delivery, the p-value rose to 0.11, but the hazard ratios and confidence intervals didn�t change substantially.

14. Summary and Conclusions Lower DNA-PCR positivity at birth and greater increase in positivity by 14 days of age in HIV-infected, non-breastfed infants who had no ARV vs. those who had maternal or infant ARV Suggests ARV prevents a large proportion of intrapartum transmission Nonparametric estimates of the probability of DNA-PCR positivity by age differed significantly according to ARV group Time to DNA-PCR positivity was later with receipt of >3 ARVs than with single NRTI or sd-NVP (+/- ZDV)

15. Summary and Conclusions (2) In preliminary parametric regression modeling, the association between ARV group and time to positivity did not remain statistically significant However, adjustment did not change the hazard ratios and the confidence intervals were mostly above 1.0 The small number of infants exposed to > 3 ARVs limited the statistical power to detect a difference; further study is needed Our results may have implications for scheduling final HIV PCR diagnostic testing, particularly when resources are limited.

16. International Collaborative Study of Pediatric Diagnostic Tests � Collaborators R. Balasubramanian D.E. Shapiro M.G. Fowler K. Dominguez P. Tookey J. Masters J. Tosswill M. Lallemant N. Ngo-Giang Huang M. McConnell P. Mock G. Sherman S. Lockman V. Novitsky P. Palumbo S. Nesheim B. Bohannon K. Rich M. Hughes We gratefully acknowledge the study participants