Developmental assessment is the process of mapping a child’s performance compared with children of similar age. The comparison group is obtained from a representative sample of the population that the child comes from. Several factors contribute to performance varying greatly among different population groups. In a multicultural society, it can be challenging to find appropriate benchmarks for these standards. We aim here to highlight what normal developmental parameters are, when and how to assess a child, and when to refer for specialist assessment.
Development is the process by which each child evolves from helpless infancy to independent adulthood. Growth and development of the brain and central nervous system are often termed psychomotor development and is usually divided into four main domains:
When the baby develops in the mother’s womb, brain development starts by the fourth week of gestation and progresses rapidly throughout intrauterine life and early childhood. Brain development—the target of developmental surveillance and screening—reflects neurological maturation. It consists of a complex process of cell growth, migration, connection, pruning, and myelination, and it persists through at least the second decade (20 years of age). This fundamental phenomenon, which determines brain development, is a pre-programmed process that occurs in all children.
The pattern of development is remarkably constant, within fairly broad limits, but the rate at which goals are achieved varies from child to child. Skills are acquired sequentially, with one goal acquired after another. Later goals, often, depending on the achievement of earlier goals within the same field—for example, children must learn to sit independently before they can stand and then walk. Descriptions of normal development, linked to the ability to perform a particular task at a particular age, relate to the performance of the average child. The acquisition of a key performance skill, such as walking, is referred to as a milestone. For each skill, the normal age range for the attainment of the milestone varies widely.
It is important to know which milestones are most consistent. Smiling socially by the age of 8 weeks is a consistent milestone, whereas crawling is not. Crawling occurs at a widely varying time point, and some children with normal development never learn to crawl.
Genetic factors may determine the fundamental developmental potential, but environmental factors have crucial influences on the profile achieved. Positive experiences during early childhood may enhance brain development, particularly in the area of linguistic and social skills. Unfortunately, however, the brain is also vulnerable to various insults, particularly in the early embryonic stages, but also in later life.
Studies on abandoned Romanian children provide good evidence of how an adverse environment affects brain growth. Children who were institutionalised have smaller brains than those who have adopted abroad or brought up in a family environment, including foster care in Romania. Other studies showed significant gains in cognitive and language skills after abandoned children are taken into care.
Many clinicians use the term “global developmental delay” to mean a significant delay in two or more of the four main developmental domains listed above. The significant delay is defined as performance two or more standard deviations below the mean on age appropriate standardised norm-referenced testing (usually a secondary care procedure). In the United Kingdom and the United States, the term global developmental delay is usually reserved for younger children (typically under 5 years of age).
In the UK learning disability is usually applied to older children, when IQ testing is more valid and reliable (although formal testing of IQ is rarely performed in clinical practice and the child’s assessment is based on functional abilities).
In the US, the term developmental disability or mental retardation is used in the over 5 age group.
The term developmental impairment or disorder covers a heterogeneous group of conditions that start early in life and present with the delay or an abnormal pattern of progression in one or more developmental domain. Children with autism spectrum disorder fall into this category. In this context, the use of the term developmental delay has been challenged because it conveys a message that the child may “catch up,” which is often not true. Nevertheless, it remains in common use because it is well understood by professionals and parents.
The global developmental delay affects 1-3% of children. About 1% (90-141 per 10,000) of children have an autism spectrum disorder, 1-2% a mild learning disability, 0.3-0.5% a severe learning disability, and 5-10% have a specific learning disability in a single domain.
Children develop at different rates, and it is important to distinguish those who are within the “normal” range from those who are following a pathological course. We now have good evidence that early identification and early intervention improve the outcomes of children with developmental impairments. A persuasive body of work, which reviewed evidence from neurosciences, developmental psychology, social sciences, epidemiology (including animal and human studies), longitudinal studies, case series, and case reports, describes
Given the importance of the early years, early intervention is crucial. Early intervention seems to be even more important for children with developmental disabilities than for children more generally, because learning is cumulative, and barriers to healthy development early in life impede development at each subsequent stage. Obviously, identification of abnormality must be followed by further action. Children develop relentlessly, and if they are on a deviant path the course becomes more difficult to change as time goes by. Early child health promotion, which includes support for parenting and treatment, is an effective investment that may prevent the need for more intensive, costly, and often less effective intervention later on. A series of systematic reviews of strategies for improving child development in relatively deprived countries, published in the Lancet, found good evidence that interventions at pre-school age are highly cost-effective.
Children with developmental problems may present in several ways:
Development can be assessed at several levels, depending on the circumstances. Screening is a process to identify children at increased risk of having developmental difficulties that use relatively brief and simple techniques, according to well-recognised criteria. Screening tests are inherently imperfect assessments because they have to balance the risk of missing a child with delays (sensitivity) versus erroneously identifying children without true delays (specificity). Repeating the test after an appropriate time interval, or conducting a secondary screening with a more accurate and specific test, may improve test accuracy.
Primary care practitioners can opportunistically ask flexible questions about a child’s development at every visit where possible, as part of comprehensive medical care. The questions can be like:
Children identified as at risk (often by a health visitor) may be referred for further assessment in primary or secondary care. Currently, standardised developmental screening tools are not routinely used in primary care in India, though a standardised tool (Trivandrum developmental screening chart) is available.
These indicators suggest that development is seriously disordered and that the child should be promptly referred to us:
Positive indicators (the presence of any of the following)
Negative indicators (activities that the child cannot do)
The child usually has an initial consultation to clarify the nature of the developmental difficulties. Investigations (blood and urine tests, cranial imaging) may be arranged at this stage or later.
The child may then undergo a structured developmental assessment and intervention package of care over 2 to 3 sittings, after which a diagnosis will be reached, a report issued, and recommendations for ongoing support made.
Examples of developmental instruments used in secondary care that are more accurate, sophisticated, and time-consuming (2-3 hours) than those used in primary care include the Griffiths mental development scales, Bayley scales of infant development, and the Wechsler preschool and primary scale of intelligence.
Adapted from BMJ 2013;346:e8687 doi: 10.1136/bmj.e8687