Subclinical mastitis among HIV-infected and uninfected Zimbabwean women participating in a multimicronutrient supplementation trial

Subclinical mastitis, defined as raised milk sodium/potassium (Na/K) ratio is common and associated with poor infant growth and increased mother-to-child HIV transmission. In 1996-97, we conducted a randomized controlled trial of multiple micronutrient supplementation, at recommended daily allowance levels, from 22 to 35 weeks gestation until 3 months post-partum, on the prevalence and severity of subclinical mastitis among 84 HIV-infected and 83 HIV-uninfected lactating Zimbabwean women and on their infants' growth. Spot milk samples collected before 4.5 months post-partum were analysed for Na/K ratio by flame photometry. There was no significant difference in prevalence of subclinical mastitis between HIV-infected and HIV-uninfected women. After controlling for infant age at time of sampling, micronutrient-supplemented HIV-infected women had non-significantly (P = 0.08) lower geometric mean Na/K ratio (0.43, 95% CI 0.35-0.51) than HIV-infected women given placebo (0.51, 95% CI 0.42-0.61). Micronutrient supplementation had no effect on the prevalence of subclinical mastitis among HIV-uninfected women (odds ratio [OR] = 1.26, 95% CI 0.45-3.51, P = 0.80) but induced a borderline decrease in prevalence (OR = 2.82, 95% CI 0.96-8.26, P = 0.07) among HIV-infected women. Infant weight between 1.5 and 4.5 months was lower in women with higher milk Na/K ratio. Thus, the importance of subclinical mastitis for infant growth suggests that further investigations to decrease the condition, perhaps using higher micronutrient doses, are warranted.