Surveillance of mother-to-child-transmission programmes: the case for universal screening

3 July 2007. Related: Pregnancy.

Polly Clayden, HIV i-Base

A paper in June AIDS authored by Nigel Rollins and coworkers shows data first presented at World AIDS Conference in Toronto describing mother-to-child transmission in Kwazulu Natal, South Africa. [1, 2]

In the introduction, the authors write: “In spite of substantial financial and human resource investments in prevention of mother-to-child transmission of HIV (PMTCT), it remains unclear to what extent these programmes have reduced the number of children becoming infected or dying with HIV each year.”

In this study, routine, anonymous, unlinked, HIV prevalence testing was performed on infants with consenting parents or guardians, attending 6-week immunisation clinics at seven primary health care clinics offering PMTCT services. Dried blood spot (DBS) samples were collected on filter paper and tested for HIV antibodies (maternal) using a commercial ELISA. DBS samples of infants that were antibody positive were then tested for HIV RNA by PCR. The mothers also answered questions about any previous pregnancies and whether the child was alive or dead.

There were 2489 infants aged 4-8 weeks in the transmission analyses.

The investigators reported the detection of HIV antibodies, in 931 infants (37.4%; 95% CI, 35.5–39.4%). Maternal prevalence rates varied with maternal age: 20.8% (95% CI, 17.7–24.2%) in mothers aged 16–20 years, which was significantly lower than that in women aged 20–29 years (45.5%; 95% CI, 42.7–48.3%), p<0.001, or women more than 30 years (38.0%; 95% CI, 33.9–42.2%); the higher prevalence in 20–29 year old women compared with women >30 years was also statistically significant, p=0.003.

Overall, 931 infants were HIV-exposed and 188 were HIV-positive, giving a transmission rate of 20.2% (95% CI, 17.8–23.1).

Of the mothers who reported being HIV-positive, 93% also reported taking nevirapine (NVP).

Amongst mothers reporting NVP use the transmission rate was 15% (95% CI, 11.9–18.6) compared to 26.0% (95% CI, 21.9–30.3%) in mothers who did not report having taken NVP. The transmission rate among women who reported themselves HIV-positive was 15.6% (95% CI, 12.5–19.1%); among mothers who reported themselves as HIV-negative but whose infants were antibody positive the transmission rate was 30.5% (95% CI, 24.0–37.6%).

In univariate analysis, reported NVP use was significantly associated with lower transmission rates (OR, 0.50; 95% CI, 0.36–0.70, p<0.001). Home delivery was associated with twice the transmission risk compared with clinic delivery (OR, 1.97; 1.04–3.71), p=0.037, but the difference between home and hospital delivery was not significant (OR, 0.86; 95% CI, 0.57–1.29), p=0.466. HIV-positive mothers who attended antenatal clinic on more than three visits had less transmission (OR, 0.67; 95% CI, 0.43–1.02), although this did not reach statistical significance, p=0.064.

In multivariate analysis, reported non-use of NVP and home deliveries remained significantly associated with increased MTCT risk.

There were also 172 mothers (6.9% of the total) who reported themselves as HIV-negative but whose infants were found to be antibody positive.

In the discussion the authors make the case for universal screening of infants at immunisation clinics. They write: “Conventional monitoring and evaluation of PMTCT programmes usually report on process indicators such as the quality of counselling or intermediate outcomes such as the number of mothers or children receiving prophylaxis.“

However, these are no guarantee of decreased transmissions or improved survival.” And they suggest that, “Linked HIV testing of all 6-week-old infants at immunisation clinics could identify infected infants at an early stage and give maximum opportunity for protecting their health. It would also offer the mother another chance to learn her own status and gain access to care and treatment.”

References:

1. Rollins N, Mzolo S, Little K et al. HIV prevalence rates amongst 6 week old infants in South Africa: the case for universal screening at immunization clinics. XVI International AIDS Conference, Toronto, Canada. 13-18 August 2006. Oral abstract THAC0104.
2. HIV prevalence rates amongst 6 week old infants in South Africa: the case for universal screening at immunisation clinic. HTB October 2006.
3. Rollins N, Little K, Similo Mzoloa S et al. Surveillance of mother-to-child transmission prevention programmes at immunisation clinics: the case for universal screening. AIDS 2007, 21:1341–1347.