Age assessment practices: a literature review & annotated ... - Unicef

4. Age assessment methodologies
This section reviews the available literature on the most common methods of
carrying out assessments of chronological age. The methods include a range of
medical, physical, and psycho-social assessments, as well as approaches to assess
age that make use of existing local knowledge. Evidence shows that most experts
agree that age assessment is not a determination of chronological age but an
educated guess, and can only ever provide an indication of skeletal or
developmental maturity from which conclusions about chronological age may be
inferred (Crawley, 2007:36).
4.1 Medical age assessment
4.1.1 Bone age assessment
The assessment of bone age is most commonly based on x-rays of the hand and wrist,
which are compared to one of two different but similar reference atlases by Greulich and
Pyle (GP) and Tanner and Whitehouse (TW2). The GP method was established as a result
of a 1935 study which aimed to assess skeletal maturity rather than evaluate age, and it did
not taken into account inter-racial or socio-economic differences. The authors themselves
recognised that there was not necessarily a relationship between the chronological age of a
child and the amount of progress which the child had made towards attaining skeletal
adulthood (Physicians for Human Rights et al, 2003:131).
There have been many studies of the GP methods and standards, and most of these
identify significant discrepancies and variations. For example;
Ontell et al (1997) conclude that using the GP standards to determine bone age must be
done with reservations, particularly in black and Hispanic girls and in Asian and Hispanic
boys in late childhood and adolescence.
Mora et al (2001) conclude that new standards are needed to make clinical decisions that
require reliable bone ages and accurately represent a multiethnic paediatric population.
The Tanner and Whitehouse method (TW2) of bone age assessment is based on the
assessment of skeletal maturity and a prediction of adult height. Each of the 20 bones in
the hand is individually compared with a series of pictures of the development of that
particular bone. However, the reference standards that are used were established in the
1950s and 1960s, and there is evidence that bone maturity is reached sooner now than four
or five decades ago. It is also thought to be a particularly unreliable method for older groups
(those aged 15-18 years) and for those from different ethnic and racial backgrounds
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