AnotherLook :: Correspondence
Breastfeeding in HIV-1-positive Mothers
(Published in Lancet – September 29, 2001)
Note: This is a corrected copy of the letter from the Lancet website. The error was introduced by the Lancet and, even though it was pointed out in our review of the proof, was not corrected before publication. The official copy of the letter is available from their website. At the time of publication this required an online, no-charge, account with the Lancet.
Sir -- Ruth Nduati and colleagues (May 26, p 1651)1 claim to show that breastfeeding strikingly increases mortality among HIV-1-positive mothers. In her May 26 commentary, Marie-Louise Newell2 discusses some of the study's limitations and compares it with research by Coutsoudis and co-workers3 that draws very different conclusions. We have concerns about some additional issues. Balanced randomisation is essential in clinical trials. We believe Nduati and colleagues' randomisation was not successful. In a more detailed description of the trial,4 at birth only two of the babies in the formula-fed group were believed to be HIV-1 positive, compared with nine assigned breastfeeding. Obviously, method of feeding cannot have any impact on HIV-1 status at the time of birth, and these results suggest important differences between the mothers in the treatment groups that were not detected by the researchers nor balanced by randomisation.
The inability to mask feeding methods introduces a potential source of bias. In addition, the formula-feeding mothers might have had more extensive contact with researchers for education about the correct way to prepare formula4. These women might have, if only indirectly, received more health-care interventions than those in the breastfeeding group.
Unlike Coutsoudis, Nduati and colleagues do not distinguish between partial and exclusive breastfeeding, and do not precisely define exclusive breastfeeding. 9% of mothers were exclusively breastfeeding by 6 months, which is a much higher proportion than the 3·5% at 4-5 months in the general population in Kenya5. This difference might be due partly to the WHO definition of exclusive breastfeeding not being used by Nduati and colleagues. Adherence to exclusive formula feeding was only 71%, meaning that 29% of the mothers practised partial breastfeeding. Given that adherence was based on self-reporting, this proportion is probably an overestimate.
Because the analysis was done by intention to treat, differences between the two groups in actual feeding practices are unclear, since they both contained substantial proportions of mixed feeders. Some mothers in the formula-feeding group might have breastfed more than some mothers in the breastfeeding group.
Nduati and colleagues claim they have no reason to believe that dropouts (which were greater in number than deaths) differed between groups, but there is no reason to believe that they are the same. For example, a seriously ill woman might find formula preparation too great an effort and drop out. Conversely, some of the healthiest mothers with highest socioeconomic status in the breastfeeding group might have believed that their babies were at a disadvantage and left the trial to change to formula feeding.
We are concerned that policy may be based on this work, ignoring research by Coutsoudis and colleagues that claimed no risk to the health of mother (or child) from exclusive breastfeeding. An additional concern is the lack of written witnessed consent for participation. Surely, even if verbal information was given, women could still sign their names.
Policy decisions based on this information may seriously impact the lives of millions of mothers and children. We believe the raw data need reanalysis. Phyll Buchanan, David Crowe, Ted Greiner, George Kent, Tessa Martyn, Valerie McClain, Pamela Morrison, Denise Parker, Magda Sachs, and Karen Zeretzke contributed to the writing of the letter.
Marian Tompson, AnotherLook
1. Nduati R, Richardson BA, John G, et al. Effect of breastfeeding on mortality among HIV-1 infected women: a randomised trial. Lancet 2001; 357: 1651-55.
2. Newell ML. Does breastfeeding really affect mortality among HIV-1 infected women? Lancet 2001; 357: 1634-35.
3. Coutsoudis A, Coovadia H, Pillay K, Kuhn L. Are HIV-infected women who breastfeed at increased risk of mortality? AIDS 2001; 15: 653-55. [PubMed]
4. Nduati R, Richardson BA, John G, et al. Effect of breastfeeding and formula feeding on transmission of HIV-1: a randomized clinical trial. JAMA 2000; 283: 1167-74.
5. Kenya Central Statistical Bureau and Macro International. Demographic and health survey. Calverton MD: Macro International, 1998.
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