ObjectivesInfection is associated with impaired nutritional status especially of infants under 5 years old. We assessed the impact of infection indicated by both the acute phase proteins (APP), C-reactive protein (CRP) and α-1-acid glycoprotein (AGP), and as reported by maternal recall on the nutritional status of infants. Methods505 pregnant women were enrolled into a nested longitudinal cohort study of vitamin A. Data analysis was restricted to infant data at 9-months (n = 385 mother-infant dyads) postpartum. Incidence and severity of respiratory infection and diarrhea over the previous 14 days were assessed by maternal recall; information on infant/child feeding practices were also collected. Infant weight, recumbent length and heel-prick capillary blood collection were taken at 9-months postpartum. Indicators of VA status [(retinol binding protein (RBP)], iron status (Hb, ferritin) and subclinical inflammation APP, CRP and AGP, were determined. Subclinical inflammation was defined as CRP >5 mg/L and/or AGP >1 g/L. Impacts of infection on infant nutritional status were estimated with multivariable logistic regression models adjusted for clustering and differences at enrollment. ResultsInfection prevalence, based on elevated CRP and AGP levels, was 36.7%. For diarrhea reported symptoms, 42.4% of infants at 9-months had no indication of infection as indicated by CRP and AGP; whilst for acute respiratory reported symptoms, 42.6% had no indication of infection. There was a weak but significant positive association with infection among VA deficient (RBP <0.83 μmol/L) infants based on maternal reported symptoms but not with iron deficiency (ferritin <12 μg/L). The odds of having infection, based on raised CRP and AGP, in underweight infants was 3.7 times higher (OR: 3.7; P = 0.019). Infants with iron deficiency were less likely (OR: 0.40; P = 0.001) to have infection based on CRP and AGP, whilst infants with VA deficiency were 5 times more likely (OR: 5.06; P = 0.0001) to have infection. ConclusionsAcute phase proteins are more useful in defining infection in a population compared to reported symptoms of illness. Not controlling for inflammation in a population while assessing nutritional status might result in inaccurate prevalence estimation. Funding SourcesSupported by the Bill &Melinda Gates Foundation (OPP53344).