Failure to thrive: the prevalence and concurrence of anthropometric criteria in a general infant population

Background

Failure to thrive (FTT) in early childhood is associated with subsequent developmental delay and is recognised to reflect relative undernutrition. Although the concept of FTT is widely used, no consensus exists regarding a specific definition, and it is unclear to what extent different anthropometric definitions concur.

Objective

To compare the prevalence and concurrence of different anthropometric criteria for FTT and test the sensitivity and positive predictive values of these in detecting children with “significant undernutrition”, defined as the combination of slow conditional weight gain and low body mass index (BMI).

Methods

Seven criteria of FTT, including low weight for age, low BMI, low conditional weight gain and Waterlow''s criterion for wasting, were applied to a birth cohort of 6090 Danish infants. The criteria were compared in two age groups: 2–6 and 6–11 months of life.

Results

27% of infants met one or more criteria in at least one of the two age groups. The concurrence among the criteria was generally poor, with most children identified by only one criterion. Positive predictive values of different criteria ranged from 1% to 58%. Most single criteria identified either less than half the cases of significant undernutrition (found in 3%) or included far too many, thus having a low positive predictive value. Children with low weight for height tended to be relatively tall.

Conclusions

No single measurement on its own seems to be adequate for identifying nutritional growth delay. Further longitudinal population studies are needed to investigate the discriminating power of different criteria in detecting significant undernutrition and subsequent outcomes.Failure to thrive (FTT) is regarded as an indicator of physical or psychosocial problems in early childhood and is associated with subsequent growth delay and cognitive deficiencies.^1,2,3 Although the concept of FTT is widely used, no consensus exists regarding a specific definition.⁴ Thus, FTT has been used to cover a broad range of different anthropometric indicators, usually based on centile charts for weight or height.^5,6 Criteria involving behavioural characteristics of the child or quality of the mother–child relationship were proposed in early work, which linked the condition to emotional deprivation,^7,8 but a consensus in 1985 concluded that the diagnosis should be based solely on anthropometric parameters.⁹ Reviews further recognised that the unifying characteristic in FTT was relative undernutrition,^10,11 thus approaching the concept of “protein energy malnutrition” (PEM), a term used to describe nutritional deprivation among children in developing countries.⁴ However, FTT and PEM are described in different literatures, with FTT mainly comprising children in more affluent societies.Most early studies on FTT used criteria based on attained low weight or, sometimes, height with a cut‐off around the 3rd or 5th centile.⁵ Dynamic measures of weight gain are now increasingly being used,⁶ including fall from a normal birth weight below a given cut‐off, dropping through major centile spaces and, recently, slow conditional weight gain, taking into account the normal phenomenon of regression to the mean, with small children tending to move upwards through the centiles and large children tending to cross downwards.^12,13,14,15 Although FTT and PEM both refer to paediatric undernutrition resulting in growth deviation,⁴ different criteria are often used in developing societies. Thus, weight may be expressed as a percentage of the median weight for age, like the Gomez criterion, whereas severe undernutrition is often assessed using weight for height, which has the advantage of not requiring age to be known. Thus, Waterlow''s criterion expresses weight as a percentage of the median weight for measured height.^16,17 However, weight for height has not been used much to diagnose FTT in affluent countries, but recently published age‐specific body mass index (BMI; weight (kg)/height (m²)) standards for childhood^18,19,20 could make this method more feasible.Thus, several definitions of FTT are in use, but it is unclear to what extent these definitions concur, hampering comparison between studies. The few studies that have compared different definitions found poor concordance, but were performed in highly selected clinical cohorts.^21,22 To our knowledge, no such comparison has been carried out in a whole population of children from affluent societies.In this study, we compare the prevalence and concurrence of different anthropometric criteria of FTT when applied to a birth cohort of Danish infants.