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Guest Editorial

Child Growth Monitoring: Is there a consensus?

Normal growth in a child, in terms of both height and weight, is a well-established measure of the health of the individual, and, from the population perspective, a marker of healthcare in the country. It therefore follows that a good growth-monitoring programme may be considered an effective tool for early identification of silent pathology, both in terms of disorders of stature (height) and nutrition (weight). A major challenge of monitoring growth in children is that there are no standard ‘‘cut-offs’’ used for defining pathology: for example, tall or short stature, and malnutrition or obesity. In most countries, weight and length, rather than BMI, are preferred parameters in young children, and monitoring is done using age- and sex-specific population-based growth charts.

Until recently, the effectiveness and efficiency of growth-monitoring programmes has remained unclear. In the UK, for example, the 1998 Coventry Consensus on growth monitoring of children recommended only a single height measurement at school entry, with a cut-off point at the 0.4th centile using the 1990 UK growth reference charts as a good screening tool.[1] Routine linear growth monitoring to detect centile crossing was found to have low sensitivity and specificity. For children aged less than 2 years, the Consensus found no justification for the routine monitoring of length, and recommended weighing less often with more emphasis on accuracy.[2]

However, a recent paper by Floor Grote and colleagues provides evidence-based data that support growth-monitoring programmes.[3] This is clearly important as linear growth failure as early as during infancy may point towards the diagnosis of congenital growth hormone deficiency (GHD).[4] [5] By contrast, recent evidence also suggests that a greater weight gain and a rapid linear growth rate in infancy are associated with an increased risk of later childhood obesity (weight gain: RR or OR 1.35 to 9.38; linear growth: RR or OR 1.06 to 5.7; no meta-analytical data; included studies reported either RR or OR).[6] [7] Early weight acceleration may also lead to later insulin resistance, independent of birth weight.[8]

Grote and colleagues have proposed stringent auxological referral criteria for early identification of “short” children based on height standard deviation scores (SDS), target height or genetic potential, and growth velocity. These criteria were applied to 1140 people with one of four conditions associated with poor growth (Turner's syndrome; cystic fibrosis; celiac disease; and mixed pathology of GHD, celiac disease, and Turner's syndrome) and to three previously published reference samples of children from the Netherlands (3521 people). The criteria used included:

1. “Short for target height” ([height SDS minus target height SDS less than –2] PLUS [a height SDS less than –2])
2. “Very short” (height SDS less than –2.5)
3. “Height deflection” ([change in height SDS greater than 1.0] PLUS [a height SDS less than –2]).

Applying these criteria individually would have resulted in a vast number of false-positive results, creating an increased number of unnecessary referrals, as a large number of short children grow normally without any pathology. A normal-statured child who subsequently grew poorly may also fail to trigger a height centile cut-off point for referral for a long period of time, which would lead to false-negative results. “Short for target height” had the best individual predictive value: 76.9% with Turner's syndrome and 58.8% with mixed pathology were identified accurately. The paper found that using all three criteria in combination led to detection of 85.7% of children with Turner's syndrome and 76.5% of children with mixed pathology, with a low false-positive referral rate (1.5–1.9%) in children aged 3–10 years from the reference populations.

To keep a low false-positive rate (0.3–0.9%) in children aged less than 3 years, more stringent combination criteria allowed detection of 14.7% of children with Turner's syndrome and 26.1% of children with mixed pathology:

1. “Extremely short” (height SDS less than 3.0)
2. “Repeatedly very short” (height SDS less than 2.5 at least twice within 1 year).

A benefit of linear growth monitoring was also reported in the systematic review published by Debra Fayter and colleagues, which assessed the efficiency of height screening in children from Europe, North America, and Australia/New Zealand. The review found a yield of 0.05–0.62, 0.02–0.07, and 0.22–1.84 per 1000 children screened for GHD, Turner's syndrome, and other potentially treatable conditions, respectively. The optimum age for growth monitoring could not be concluded by the review owing to the wide age range among studies at which screening took place. However, a yield of 0.54–0.56 of potentially treatable conditions was found by a single school-entry measurement.[9]

As Grote and colleagues' data suggest that we can refine referral criteria, at least for linear growth, a further question arises about which growth charts we should use for the process. The recently published international WHO growth charts for infants and children up to the age of 5 years seem to be the best candidate. These charts provide data on “how children should grow” based on recommended practices associated with healthy outcomes with an aim to achieve full genetic potential.[10] [11] The data were obtained from children in six countries with different ethnic backgrounds and cultures who were exclusively or predominantly breast-fed in early infancy. Breast-fed infants demonstrate an optimum growth pattern associated with healthier outcomes of lipid profile, blood pressure, and insulin resistance.[8] Currently, most population-specific growth charts used both in surveillance and in clinical practice (e.g. 1990 charts, UK; Centers for Disease Control and Prevention [CDC] charts, US) describe “how children are growing” and do not include exclusively breast-fed infants.

Recently, however, concerns have been voiced regarding the application of WHO standards to individual countries. In the UK, for example, birth weight and length z-scores of full-term children from two population-based UK birth cohorts were greater (mean z-scores 0.17 and 0.34) than the WHO standard, which included children from resource-poor countries.[12] From the age of 4–12 months and at age 4–5 years, the UK cohort was heavier than WHO standards. Consequently, the risk of being identified underweight (less than 2nd centile) at 12 months was considerably lower according to the WHO standards (RR 0.15, 95% CI 0.07 to 0.32), and the risk of being classified as obese at 4–5 years (using a BMI greater than the 98th centile) was slightly increased (RR 1.35, 95% CI 1.02 to 1.78), compared with the UK 1990 charts. However, no differences in length were noted. By contrast, Lai Ling Hui and colleagues reported a lower birthweight in Hong Kong Chinese children compared with WHO standards.[13] However, when measured at up to 36 months of age, weights exceeded the WHO standards (in boys but not girls), but children were shorter. Differences were attributed to the genetic background and to rapid environmental transitions. Mercedes de Onis and co-workers have highlighted that, using the WHO Growth Standards, rather than the CDC charts, for weight, fewer infants in the US would be below the 5th centile and more would be above the 95th centile, primarily owing to differences in infancy feeding patterns.[14]

To remove any confusion, in the UK, the Department of Health Scientific Advisory Committee on Nutrition and the Royal College of Paediatrics and Child Health have jointly recommended that the WHO growth standards should be used in preference to the UK 1990 charts in full-term infants from the age of 2 weeks until 24 months, for both weight and height, reasoning that the WHO growth standards depict a pattern of slower weight gain, which is associated with a better long-term outcome.[15]

Does Grote and colleagues' new evidence and the introduction of WHO charts warrant a global re-visit of growth-monitoring recommendations? Using a single height cut-off point at school entry is clearly not sufficient, both to avoid unnecessary referrals and to detect early pathology. A cut-off of 0.4th centile on the 1990 UK height charts (–2.67 SDS), for example, would result in a slightly greater specificity but a lower sensitivity in detecting treatable pathology, compared with Grote and colleagues’ auxological criteria of –2.5 SDS as an auxological “rule”. This would result in a lower false-positive rate, but would miss a small number of children with treatable pathology. Correction for parental heights was not recommended as part of screening by the Coventry Consensus, although the data presented by Grote and co-workers make the introduction of this — and their algorithm — essential to practice. In view of the global epidemic in obesity, with its concomitant economic challenges, one would agree that the WHO standard would be more appropriate — at least in the earlier years — as it sets a lower weight standard that could potentially reduce the risk of later obesity.

Continuing research to identify the overall benefits, harms, and diagnostic accuracy of growth monitoring is needed.[15] Changes in growth charts and in growth-monitoring programmes are likely to alter trends and prevalence of diseases, such as overweight, obesity, malnutrition, and possibly long-term morbidity. It is, however, important to implement effective interventions to justify growth-monitoring programmes.[16]

Dr Ameeta Mehta DCh, MRCP, MSc, MD*
Clinical Editor
BMJ Knowledge
amehta@bmjgroup.com

Professor Peter Hindmarsh BSc, MD, FRCP, FRCPCH
Developmental Endocrinology Research Unit
Institute of Child Health
University College London
p.hindmarsh@ucl.ac.uk

* Dr Mehta is also a qualified Paediatric Endocrinologist.

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