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Indian Pediatr 2019;56: 19-20 |
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Height Velocity Percentile Curves in Indian
Children: Time to Move Beyond Standard Growth Charts
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Alpesh Goyal 1
and Rajesh Khadgawat2
From the Departments of 1,2Endocrinology
and 1Metabolism, All India Institute of Medical Scienecs
(AIIMS), New Delhi, India.
Email:
[email protected]
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G
rowth assessment forms an important component of
holistic evaluation of a child, as it provides information on his/her
overall well-being. Growth may be assessed using single-point height
estimates (cross-sectional data) or serial measurements of height
(longitudinal data). Rate of change in height measured over a period of
6-12 months (height velocity) is a far more sensitive measure of growth
than single time-specific height measures. For this reason, abnormal
height velocity alone (<–2 SDS for 1 year or <–1.5 SDS for 2 years) even
in absence of short stature (current height <–2 SDS) is considered as a
criterion for evaluation of growth disorders, including acquired growth
hormone deficiency [1]. Tracking an individual using height velocity
percentile curves may help differentiate those with normal variant of
growth and pubertal development such as constitutional delay of growth
and puberty (who are expected to grow at a normal height velocity) from
those with pathological short stature. Additionally, height velocity may
be extremely helpful in showing early effectiveness of a medical
intervention and predicting final stature (using height velocity and
peak height velocity) [2].
Population-specific reference curves are needed for
growth interpretation, due to variations in genetic and environmental
factors affecting growth in different populations. Currently, the growth
charts available for Indian children aged >5 years are based on
cross-sectional data [3-5]. Height velocity charts are already available
for few countries [6-8]; there is an urgent need to generate good
quality height velocity data for our country. This demands longitudinal
follow-up of years – involving a healthy, sufficiently large population,
which is geographically and ethnically diverse – in order to capture the
normal variability in height.
We have previously studied height velocity over 12
months period in apparently healthy school children aged 3-17 years from
Delhi [9]. The data were derived from 5635 participants belonging to
seven fee-paying schools in five zones of Delhi. Pubertal assessment was
also performed for a subset of participants (n=1553) and data
from study participants at pubertal onset (boys: testicular volume
³4 mL, and
girls: thelarche) were used to determine the 3rd,
50th and 97th
percentiles for age at onset of puberty. The peak height velocity was
attained in boys and girls at age of 12-12.9 years and 10-10.9 years,
respectively; and was significantly higher in boys compared to girls. On
studying the distribution of height velocity according to pubertal
staging, we noted that maximum height velocity was attained in Tanner
stage 3 in boys and in stage 2 among girls. The boys achieving late
puberty (>97th centile) had
higher height velocity compared to those with normal puberty (3rd–97th
centile) or early puberty (<3rd
centile), but no such relationship was observed among girls. This was
the first large study from India evaluating height velocity data over 12
months among healthy school children from Northern India, which also
looked at pubertal status at baseline in a subset of study participants,
in order to account for the relationship between puberty and height
velocity. However, this study had certain limitations. The data,
although derived from a large population, was not representative of the
population belonging to lower socioeconomic status or rural areas. This
would call for a study with database derived from a more heterogeneous
population, including children from different socioeconomic status,
ethnicity and regions. The longitudinal follow-up was limited to one
year only. Study with longer follow-up would have provided more
information about height velocity. Finally, the pubertal assessment was
only done at baseline; a longitudinal assessment could have resulted in
more accurate determination of age of pubertal onset, and the
relationship between puberty and height velocity.
In this issue of Indian Pediatrics, Khadilkar,
et al. [10] have published a study on height velocity percentiles
in healthy school children aged 5-17 years from Delhi and Pune. The
study is based on seven year longitudinal follow-up (2007-2013) of a
cohort of 2949 children belonging to affluent class, including only
individuals with a minimum of three annual measurements in the final
analysis. Annual measurements were performed at similar time of the
year, and by same set of observers, to exclude the seasonal and
inter-observer bias. Authors have reported age- and gender-specific
smoothed percentiles (3 rd,
10th, 25th,
50th, 75th,
90th and 97th)
for height velocity using the lambda-mu-sigma (LMS) method. The peak
height velocity was attained at 10.5 years in girls (median 6.6 cm/year)
and 13.5 years in boys (median 6.8 cm/year). In their peak height
velocity-centered analysis (including subset of study participants who
had data for two preceding and succeeding years around the peak), peak
velocities were higher – 9.7 cm/year (10.8 years) in girls and 10.3
cm/year (13.4 years) in boys.
The authors should be complemented for a
well-conducted study with data generated using sufficiently long
follow-up of seven years from two different cities in Northern and
Western India. The height velocity percentile curves will serve as a
useful addition to the existing growth charts. The study, a useful
complement to pre-existing height velocity data derived from our study,
recruited children from affluent class only, thereby limiting
generalizability of results to economically deprived and rural
population. It is important to remember that a significant proportion of
children catered to by pediatricians/endocrinologists in public
hospitals belong to the later group. Second, pubertal assessment was not
performed in the study participants; therefore, correlation between peak
height velocity and pubertal staging in this group of study participants
could not be derived. Because the longitudinal data was sufficiently
long, an assessment of pubertal status at baseline and on follow-up
(even in a subset of study participants) could have provided peak height
velocity for pubertal stage and enabled generation of separate
percentile curves for early-, delayed- and averagely-maturing children.
However, assessment of pubertal status is one of the most difficult
tasks to be performed in population-based studies – less acceptable to
parents as well as school authorities, and challenging to the
investigators.
To conclude, height velocity is an extremely
sensitive marker of growth, which provides information about tempo of
growth in an individual. An assessment of height velocity is extremely
important in early diagnosis of disordered growth, even before a
diagnosis based on the absolute cut-off becomes apparent. The generation
of height velocity percentile curves based on longitudinal follow-up of
healthy school children is a welcome addition to existing growth
reference curves for our population. However, it may just be a beginning
in the right direction; good quality large-scale multicenter
longitudinal data of sufficiently long duration involving ethnically and
culturally diverse study population is needed in the near future.
Inclusion of children belonging to economically weaker section of
society and rural background will aid in generalizability of the study
results. Additionally, assessment of pubertal status at baseline and
longitudinal follow-up will provide peak height velocity for pubertal
status and chronological age, making the results more creditable. A
well-conducted study meeting above requirements will also help generate
separate percentile curves for adolescents with differing timings of
sexual maturity.
Funding: None; Competing interest: None
stated.
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