use of z-scores for the classification of malnutrition
TRANSCRIPT
Use of Z-Scores for the classification of Malnutrition.
Dr. N. Seetharaman, M.D., Assistant Professor,
Department of Community Medicine
PSG Institute of Medical Sciences & Research
Coimbatore.
Presented at the XXII ISMS Conference, JIPMER
1. Objectives
2. Introduction
3. Methodology
5. Conclusion
6. Recommendations
7. References
4. Results & Discussion
To assess the nutritional status of under-five children in the urban
slums of Coimbatore, coming under the field practice area of the
Urban Health Centre of PSG Institute of Medical Sciences &
Research, and to express the results in terms of the Z-Score system
of classification.
Objectives
0
10
20
30
40
50
60
India Sub-saharanAfrica
World
UnderweightStuntedWasted
Prevalence of Malnutrition, among our children
0
10
20
30
40
50
60
Kerala Tamilnadu India Bihar
SOWC, 1998
NFHS II, 1999
Introduction
Underweight – Low Weight for age
Stunting – Low Height for age
Wasting – Low Weight for height
“Classification”s of Malnutrition.
Cut-off points Reference population
IAP’s, Gomez, Waterlow’s
Wt-for-age classifications most common
By using the Z score system, we are able to express undernutrition in terms of all the three indices, with the same cut-off values.
Z Score system
Widely Recommended, Scarcely Used.
If we use the usual systems of classification, we usually express undernutrition in terms of only one index – weight-for-age. (Underweight).
Malnourished ~~ below – 2 SD (of the median value of the reference pop).
Severely Malnourished ~~ below – 3 SD.
Comparable Across sex and ages and Across indicators.
Distinct Statistical advantages in using SD classification based upon Z-Scores.
The mean and SD of all the Z-Scores reflect the quality of the data collected.
Methodology
Study area : Ten slums coming under the field-practice area of the Urban Health Centre, PSG IMS & R, Coimbatore.
Study Population : Children less than five years of age residing in these slums. The total number of under-five children in these 10 slums is 625.
Inclusion criteria : All children up to 59 months of age Living in the selected slums.
Exclusion criteria :1. Children who are not resident of the slum, but visiting.2. Children of families who have moved into the slum within the past 1 month.
Prevalence (p) of malnutrition in slums = 50 % (based on the previous studies)allowable error (d) = 10% (of the prevalence)
Design of the study : Cross-sectional study (Prevalence study)
Sample size ( n ) = 4PQ / d2
Sampling :
To arrive at this sample size,
a) From the ten slum areas coming under the field practice area of the UHC, six slums were selected using a random number table .
b) All the under-five children in these six slum areas were taken as study subjects. (n = 405)
the estimated Sample size is 400.
Data collection was done over a period of 3 months.
Children were weighed and measured as per the WHO guidelines1 on Anthropometry.
Statistical Analysis :
Data Analysis done with EPI-INFO 2002 software package – CDC*.
Chi-square test was used to verify the statistical significance of the associations.
P value < 0.05 was considered statistically significant. The strength of the association is expressed using Odds Ratio
The prevalence of underweight, stunting and wasting were calculated in reference to the WHO recommended NCHS** standard population by using the EPI-NUT component of the EPI-INFO program.
The Cut-off levels of less than -2SD [Z score <2] for “malnourished” and less than -3SD [Z score <3] for “severely malnourished” were used.
* Center for Disease Control, Atlanta, USA ** National Center for Health Statistics, USA
More than two-thirds of the children studied are malnourished.
No significant gender difference in the prevalence.
Results & Discussion
22.7 %
48.4 % 49.6 %
Malnourished67.9 %
Normal32.1 %
0
10
20
30
40
50
60
70
80
90
100
Wasted Stunted Underweight TOTAL
49.6
48.4
22.7
47
45.5
15.5
36.7
29.419.9
49.6
48.8
9.1
50.3
60
17
0
10
20
30
40
50
60
70
Current Study,Coimbatore slums
India NFHS II Tamilnadu NFHS II Rajeshkumar Haryana Laxmiah, Punjab
Malnourished
Comparative Prevalence of Malnutrition
Underweight Stunting Wasting
21.2
20.39.4
18
23
2.8
10.6 12
3.8
11.5
18.1
0.6
1922.3
12
0
10
20
30
40
50
60
70
Severely malnourished
Significantly lower prevalence of malnutrition among infants (0-11 months) compared to other age-groups. (P < 0.05)
010203040506070
0-11 12 _ 23 24-35 36-47 48-59
Age group
% s
tunt
ed
0
5
10
15
20
25
30
0-11 12 _ 23 24-35 36-47 48-59
Age group
% w
aste
d0
20
40
60
80
0 - 11 12 _ 23 24-35 36 - 47 48 - 59
Age - group
% u
nder
wei
ght
Stunting Wasting
Underweight
Conclusions
WHO guidelines for assessing the severity of malnutrition in a community.
Wasting
Underweight
Stunting
Indicator
Wasting
Underweight
Stunting
Indicator
22.7 %
48.4 %
49.6 %
Prevalence in Current study
22.7 %
48.4 %
49.6 %
Prevalence in Current study
22.7 %
48.4 %
49.6 %
Prevalence in Current study
> 1510-145-9< 5Wasting
> 3020-2910-19<10Underweight
> 4030-3920-29<20Stunting
Very highHighMediumLow
Severity of malnutrition by prevalence ranges (%)
Indicator
22.7 %
48.4 %
49.6 %
Prevalence in Current study
> 1510-145-9< 5Wasting
> 3020-2910-19<10Underweight
> 4030-3920-29<20Stunting
Very highHighMediumLow
Severity of malnutrition by prevalence ranges (%)
Indicator
The prevalence of malnutrition is a Significantly lower among infants (0-11 months) compared to other age-groups. (P < 0.05)
There is no significant gender difference in the prevalence of malnutrition.
The prevalence of malnutrition peaks in the 24-36 months age-group.
Recommendations
Need for more studies that report prevalence in terms of the Standard Deviation (or) Z-Score system of classification of malnutrition, for meaningful comparisons.
Make use of the statistical software “Epi-Info 2002” available for free download from www.cdc.org for calculating the Z-Scores.
For nutritional interventions, ‘Catch’ the children young – before 3 years – before malnutrition sets in and before the child gets stunted for life.
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3. WHO. Physical status: the use and interpretation of anthropometry. Report of a WHO Expert Committee. WHO Technical Report Series No. 854. World Health Organization, Geneva. 1995.
1. UNICEF. The state of the world’s children 1998. United Nations Children’s Fund, Geneva. 1998 : 1-41.
2. International Institute of Population Science. National Family Health Survey India. (NFHS II). I.I.P.S, Mumbai. 1999.
4. H.P.S. Sachdev. Assessing Child Malnutrition - Some Basic Issues, NFI archives 156. Nutritional Foundation of India, New Delhi. 1996.
8. Rajesh Kumar, Arun K.Agarwal, Sharad D.Iyengar. Nutritional Status of Children: Validity of Mid-Upper Arm Circumference for Screening Undernutrition. Indian Pediatrics 1996 march; 33: 189-196.
7. A. Laxmaiah, K.Mallikharjuna Rao, GNV Brahmam, Sharad Kumar, M.Ravindrenath, K.Kasinah et al. Diet and Nutritional Status of Rural Preschool Children in Punjab. Indian Pediatrics 2002 April; 39: 331-338.
5. C.Gopalan. Combating Malnutrition – Basic Issues and Practical Approaches. Nutrition Foundation of India Special publication series 3. Nutrition Foundation of India , New Delhi. 1994
References
6. A.K.Nigam. Determining Grades of Malnutrition in Children: Standard Deviation Classification and the Alternative. Demography India 2003 January; 32:1:137-155.