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Open in new tab WHO
child growth
standards
and the
identification
of severe
acute
malnutrition
in infants
and children
A Joint Statement
by the World Health
Organization
and the United Nations
Children’s Fund
This statement presents the recommended cut-offs, summarizes the rationale
identification of 6–60 month old infants and children for the management of
for their adoption and advocates for their harmonized application in the
severe acute malnutrition (SAM). It also reviews the implications on patient load, on
discharge criteria and on programme planning and monitoring.
Using weight-for-height: WHO and UNICEF
recommend the use of a cut-off for weight-for-
height of below -3 standard deviations (SD)
of the WHO standards to identify infants and
children as having SAM. The commonly used
cut-off is the same cut-off for both the new 2006
WHO child growth standards (WHO standards)
as with the earlier National Center for Health
Statistics (NCHS reference). The reasons for the
choice of this cut-off are as follows:
1) Children below this cut-off have a highly
elevated risk of death compared to those
who are above;
2) These children have a higher weight gain
when receiving a therapeutic diet compared
to other diets, which results in faster
recovery;
3) In a well-nourished population there are
virtually no children below -3 SD (<1%).
4) There are no known risks or negative effects
associated with therapeutic feeding of these
children applying recommended protocols
and appropriate therapeutic foods.
Using MUAC: WHO standards for mid-upper
arm circumference (MUAC)-for-age show that in
a well nourished population there are very few
children aged 6–60 months with a MUAC less
than 115 mm. Children with a MUAC less than
115 mm have a highly elevated risk of death
compared to those who are above. Thus it is
recommended to increase the cut-off point from
110 to 115 mm to define SAM with MUAC.
When using the WHO child growth standards to
identify the severely malnourished among 6–60
month old children, the below -3SD cut-off for
weight-for-height classifies two to four times
as many children compared with the NCHS
reference. The prevalence of SAM, i.e. numbers
of children with SAM, based on weight-for-
height below -3 SD of the WHO standards and
those based on a MUAC cut-off of 115 mm, are
very similar. The shift from NCHS to WHO child
growth standards or the adoption of the new
cut-off for MUAC will therefore sharply increase
case loads. This has programmatic implications.
Recommendation
BOx 1. DiagnOstic cRiteRia fOR saM in cHilDRen ageD 6–60 MOntHs
indicator
Measure
Severe wasting (2)
Weight-for-height (1)
Severe wasting (2)
MUAC
Bilateral oedema (3)
Clinical sign
1 Based on WHO Standards (www.who.int/childgrowth/standards)
2,3 Independent indicators of SAM that require urgent action
cut-off
< -3 SD
< 115 mm
2
BOx 2. saM ManageMent
independent
additional criteria
• No appetite
• Medical
complications
type of therapeutic
feeding
facility-based
intervention
Discharge criteria
(transition criteria
from facility to
community-based
care)
F75→
F100/RUTF
And 24 hour medical
care
Reduced oedema
Good appetite
(with acceptablea intake
of RUTF)
a Child eats at least 75% of their calculated RUTF ration for the day
• Appetite
• No medical
complications
community-based
RUTF, basic
medical care
15 to 20%
weight gain
Rationale
The WHO Child Growth Standards
In 2006, WHO published child growth standards
for attained weight and height to replace the
previously recommended 1977 NCHS/WHO
child growth reference. These new standards
are based on breastfed infants and appropriately
fed children of different ethnic origins raised
in optimal conditions and measured in a
standardized way (1). The same cohort was
used to produce standards of mid-upper arm
circumference (MUAC) in relation to age (2).
The new WHO growth standards confirm earlier
observations that the effect of ethnic differences
on the growth of infants and young children in
populations is small compared with the effects of
the environment. Studies have shown that there
may be some ethnic differences among groups,
just as there are genetic differences among
individuals, but for practical purposes they
are not considered large enough to invalidate
the general use of the WHO growth standards
population as a standard in all populations.
These new standards have been endorsed
by international bodies such as the United
Nations Standing Committee on Nutrition (3),
the International Union of Nutritional Sciences
(4) and International Pediatric Association and
adopted in more than 90 countries (5).
Diagnosing severe acute malnutrition
(severe wasting or kwashiorkor or
marasmic kwashiorkor)
In 1999, WHO defined severe malnutrition in
children as a weight-for-height1 below -3 SD2
(based on NCHS reference) and/or the presence
of oedema (6). Experts in a meeting in 2005, (7,8)
recommended to add MUAC less than 110 mm
(in 6 to 60 month old children) as an independent
diagnostic criterion. Since the 2005 meeting, the
WHO standards have been published and there
is therefore a need to reassess diagnostic criteria
including MUAC. The rationale for keeping the
same cut-off for weight-for-height when defining
severe acute malnutrition and for adjusting the
MUAC cut-off up to 115 mm, based on the WHO
standards is given below.
Risk of death and severe acute malnutrition
Following the release of the WHO child growth
standards, the relationship between weight-for-
1 When assessing weight-for-height, infants and children
under 24 months of age should have their lengths
measured lying down (supine). Children over 24 months
of age should have their heights measured while
standing. For simplicity, however, infants and children
under 87 cm can be measured lying down (or supine) and
those above 87 cm standing.
2 A z-score is the number of standard deviations (SD)
below or above the reference median value.
3
FIGURe 1
Odds ratio for mortality by weight-for-height.
adapted from reference 9
o
i
t
a
r
s
d
d
O
10
8
6
4
2
0
More than -1
-2 to < -1
-3 to < -2
< -3
Weight-for-height
Note: reference category: children with a weight-for-height
> -1 SD.
height and the risk of dying was reassessed in
existing epidemiological studies.1 This analysis
showed that children with a weight-for-height
below -3 sD based on the WHO standards have
a high risk of death exceeding 9-fold that of
children with a weight-for-height above -1 SD
(figure 1) (9). similar studies using MUac as
diagnostic criteria showed that the risk of dying
is increased below 115 mm (10). The elevated
risk of death below these cut-offs requires the
implementation of intensive nutritional and
medical support.
Specificity of recommended cut-offs for
diagnosing severe acute malnutrition
Weight-for-height below -3 sD is a highly
specific criterion to identify severely acutely
malnourished infants and children. Statistical
theory shows that in a well-nourished
population, only 0.13% of children will have
a weight-for-height less than -3 SD, giving a
specificity of more than 99%2 for this cut-off.
With the release of the WHO standards for
MUAC-for-age, the revision of the earlier
1 The assessment of the risk of death associated with
different degrees of wasting can be carried out only by
community based longitudinal studies with a follow up
of untreated malnourished children. This can be analysed
only from a limited number of existing studies. For
ethical reasons, these observational studies cannot be
repeated, as an effective community-based treatment of
severe acute malnutrition is now possible.
2 Specificity is defined as the percentage of healthy
individuals correctly diagnosed as healthy by the
diagnostic test.
4
recommended MUAC cut-off of 110 mm as an
independent diagnostic criterion for severe
acute malnutrition was necessary. a higher
cut-off of 115 mm is recommended as it will
identify more infants and children as having
severe acute malnutrition and still have a high
specificity of more than 99% over the age range
6–60 months.
Children below -3 SD of the WHO
child growth standards benefit from
therapeutic feeding
Currently, children with severe acute
malnutrition are treated with special therapeutic
foods, most commonly Ready-to-Use-
Therapeutic Foods or F75 and F100 milk-based
diets.
Data from Malawi suggests that infants and
children 6–60 months of age with a weight-
for-height above -3 SD of the NCHS reference
also benefit from these therapeutic diets
(11). The children who are above -3 SD of the
NCHS reference but are below -3 SD of the
WHO standards are most likely to benefit from
therapeutic feeding.
Absence of risk and of negative
consequences of therapeutic feeding
The current treatment protocols for managing
severe acute malnutrition have no known risk,
and minimise negative social consequences.
less stringent admission criteria for
therapeutic feeding should be promoted
as earlier criteria did not identify all infants
and children at high risk of mortality. The
below -3 SD cut-off based on the WHO growth
standards for weight-for-height and the MUAC
cut-off of 115 mm seem well adapted to current
protocols.
implications of using the
WHO standards
Programmatic implications of the
adoption of the WHO standards and
changing the MUAC cut-off for identification
of children with SAM
Using the new WHO standards in developing
country situations results in a 2–4 times
increase in the number of infants and children
falling below -3 SD compared to using the
former NCHS reference (12,13).
n
i
a
g
t
h
g
i
e
w
%
25
20
15
10
5
0
To better estimate the increase in patient load
resulting from the adoption of the WHO growth
standards, an analysis was performed on a
data base comprising 560 different nutritional
surveys conducted in 31 countries (14). The data
set contained anthropometric measurements for
more than 450 000 children aged 6–60 months.
the prevalence of saM defined by weight-
for-height below -3 sD of the WHO standards
and by a MUac cut-off of 115 mm were very
similar: 3.22% and 3.27% respectively. When
using the NCHS reference, the prevalence of
severe acute malnutrition was very similar when
defined using weight-for-height below -3 SD and
with MUAC below 110 mm: 1.48% and 1.49%,
respectively.
it is important to note that using either the
WHO standards or the ncHs reference, the
cases selected using weight-for-height and
MUac were not the same. Only about 40%
selected by the one criterion were also selected
by the other. Part of the explanation is that
children with a low MUAC tend to be younger
than those with a weight-for-height less than
-3 SD. The implications of these differences
in terms of associated risk and response to
treatment deserves further investigation and in
the meantime both should continue to be used
as independent criteria for admission.
Selection of patients according to the WHO
standards is greatly facilitated by the use of
look-up tables as shown in annex 1.1
Redefining discharge criteria
Previously recommended discharge criteria
based on a minimum weight-for-height are
not applicable to programmes using MUAC as
admission criteria, as some children selected
using MUAC already fulfil these weight-for-
height discharge criteria on admission into the
programme. This is a concern especially with
large scale community-based programmes
relying extensively on MUAC as the criterion for
admission.
It is recommended that the discharge criterion
be based on percentage weight gain. Using
a discharge criterion based on percentage
weight gain has the advantage of being easy
1 More detailed tables are available on: http://www.who.
int/childgrowth/standards/weight_for_length/en/index.
html and http://www.who.int/childgrowth/standards/
weight_for_height/en/index.html
FIGURe 2
Percentage of weight gain needed to move
from -3 to -2 or -1 sD with the WHO growth
standards in relation to length or height
40
50
60
70
80
90
100 110
120
130
Length/height (cm)
Data are shown for girls only. The top curve corresponds to a
change up to -1 SD, the lower curve to a change up to -2.
to apply to children admitted based on MUAC
as well to those admitted on weight-for-height.
This approach has the added advantage as
it eliminates the need for repeated height
measurements during treatment.
Children with weight-for-height above -2 and
below -1 SD, have a lower mortality risk than
those below -3 SD. Those with a weight-for-
height above -1 SD have an even lower risk of
death (figure 1). Reaching a weight-for-height
above -2 or above – 1 SD can be used as a
yardstick for defining discharge criteria. For
children admitted at -3 SD weight-for-height
defined by the WHO standards, a discharge at
-2 SD and at -1 SD corresponds on average to
a weight gain of 9% and 19% respectively. This
percentage varies little for different lengths or
heights (figure 2). for simplicity, it is possible
to use 15 % weight gain as discharge criterion
for all infants and children admitted to
therapeutic feeding programmes (see table 2
in annex). When weight-for-height is used as an
admission criterion, it is advisable to continue to
discharge children at weight-for-height -1 SD.
For children with oedema, the same discharge
criterion should be applied using the weight
after oedema has disappeared as the baseline.
However, for children who have a weight-for-
height above -3 SD or a MUAC above 115 mm
once they are free from oedema, a discharge
two weeks after the disappearance of oedema is
usually sufficient to prevent relapse.
5