Cole et al developed curves to describe the change in body mass index (BMI) with age and gender in pediatric patients in the United Kingdom based on 1990 reference data. The SD Score describes the number of standard deviations from the mean (50%) curve for a given BMI result.
body mass index (BMI) for patient =
= (body weight in kilograms) / ((body height in meters)^2) in kilograms per square meter
Age range for patients: from 1 to 22 (although data from 0 to 1 year was available, it changes rapidly and so was excluded to simplify the analysis)
Parameters to determine SD score:
(1) 50% curve for BMI relative to age and gender
(2) L curve (degree of skewness) relative to age and gender
(3) S curve (coefficient of variation) relative to age and gender
Data for mean (50%) BMI curve for age and gender
|
age in years |
boys |
girls |
|---|---|---|
|
1 |
17.3 |
17.4 |
|
2 |
16.1 |
16.4 |
|
3 |
15.7 |
15.8 |
|
4 |
15.5 |
15.5 |
|
5 |
15.4 |
15.4 |
|
6 |
15.5 |
15.5 |
|
7 |
15.5 |
15.6 |
|
8 |
15.7 |
15.9 |
|
9 |
15.9 |
16.4 |
|
10 |
16.3 |
16.9 |
|
11 |
16.8 |
17.4 |
|
12 |
17.4 |
18.1 |
|
13 |
18.0 |
18.8 |
|
14 |
18.6 |
19.4 |
|
15 |
19.3 |
19.9 |
|
16 |
19.9 |
20.4 |
|
17 |
20.5 |
20.7 |
|
18 |
21.1 |
21.1 |
|
19 |
21.5 |
21.3 |
|
20 |
22.0 |
21.5 |
|
21 |
22.4 |
21.8 |
|
22 |
22.9 |
21.9 |
based on Figures 1 and 2, page 27
This data was analyzed in JMP and the following equations were calculated:
|
Gender |
Age Range |
Equation |
|---|---|---|
|
male |
1 to 6 |
(-0.030556 * ((age)^3)) + (0.458333 * ((age)^2)) - (2.253968 * (age)) + 19.1 |
|
|
6 to 22 |
(0.0001275 * ((age)^4)) - (0.009871 * ((age)^3)) + (0.2651489 * ((age)^2)) - (2.387667 * (age)) + 22.284276 |
|
female |
1 to 6 |
(-0.012037 * ((age)^3)) + (0.2603175 * ((age)^2)) - (1.684788 * (age)) + 18.83333 |
|
|
6 to 22 |
(0.0002778 * ((age)^4)) - (0.018113 * ((age)^3)) + (0.4062743 * ((age)^2)) - (3.211087 * (age)) + 23.7107 |
L curve data
|
age in years |
boys |
girls |
|---|---|---|
|
1 |
-1.27 |
-1.18 |
|
2 |
-1.39 |
-1.22 |
|
3 |
-1.51 |
-1.26 |
|
4 |
-1.62 |
-1.30 |
|
5 |
-1.72 |
-1.34 |
|
6 |
-1.80 |
-1.38 |
|
7 |
-1.86 |
-1.39 |
|
8 |
-1.90 |
-1.39 |
|
9 |
-1.90 |
-1.38 |
|
10 |
-1.90 |
-1.36 |
|
11 |
-1.86 |
-1.34 |
|
12 |
-1.81 |
-1.32 |
|
13 |
-1.75 |
-1.28 |
|
14 |
-1.68 |
-1.26 |
|
15 |
-1.62 |
-1.24 |
|
16 |
-1.56 |
-1.22 |
|
17 |
-1.50 |
-1.19 |
|
18 |
-1.45 |
-1.17 |
|
19 |
-1.40 |
-1.16 |
|
20 |
-1.35 |
-1.15 |
|
21 |
-1.31 |
-1.14 |
|
22 |
-1.27 |
-1.13 |
based on Figure 3, page 27
This data was analyzed in JMP and the following equations were calculated:
|
Gender |
Age Range |
Equation |
|---|---|---|
|
male |
1 to 8 |
(0.0007744 * ((age)^3)) - (0.003272 * ((age)^2)) - (0.116665 * (age)) - 1.150635 |
|
|
8 to 22 |
(-0.00033 * ((age)^3)) + (0.0153639 * ((age)^2)) - (0.175489 * (age)) - 1.339173 |
|
female |
1 to 7 |
(0.0008333 * ((age)^3)) - (0.008214 * ((age)^2)) - (0.016905 * (age)) - 1.157143 |
|
|
7 to 22 |
(-0.000142 * ((age)^3)) + (0.0059323 * ((age)^2)) - (0.057339 * (age)) - 1.236155 |
S curve data (as percent from 0 to 100)
|
age in years |
boys |
girls |
|---|---|---|
|
1 |
7.4 |
7.5 |
|
1.5 |
7.2 |
7.4 |
|
2 |
7.1 |
7.5 |
|
3 |
7.1 |
7.8 |
|
4 |
7.2 |
8.4 |
|
5 |
7.5 |
9.1 |
|
6 |
8.2 |
9.9 |
|
7 |
9.0 |
10.8 |
|
8 |
9.8 |
11.6 |
|
9 |
10.4 |
12.2 |
|
10 |
10.9 |
12.6 |
|
11 |
11.3 |
12.8 |
|
12 |
11.6 |
13.0 |
|
13 |
11.7 |
12.9 |
|
14 |
11.8 |
12.9 |
|
15 |
11.8 |
12.8 |
|
16 |
11.7 |
12.8 |
|
17 |
11.7 |
12.7 |
|
18 |
11.6 |
12.6 |
|
19 |
11.6 |
12.5 |
|
20 |
11.5 |
12.4 |
|
21 |
11.5 |
12.4 |
|
22 |
11.4 |
12.3 |
based on Figure 4, page 27
This data was analyzed in JMP and the following equations were calculated:
|
Gender |
Age Range |
Equation |
|---|---|---|
|
male |
1 to 3 |
(-0.03333 * ((age)^3)) + (0.35 * ((age)^2)) - (1.116667 * (age)) + 8.2 |
|
|
3 to 8 |
(0.0982143 * ((age)^3)) - (0.520357 * ((age)^2)) + ( * (age)) + 7.7378571 |
|
|
8 to 22 |
(0.0026018 * ((age)^3)) - (0.141185 * ((age)^2)) + (2.4706286 * (age)) - 2.270756 |
|
female |
1 to 3 |
(-0.16667 * ((age)^3)) + (1.15 * ((age)^2)) - (2.28333 * (age)) + 8.8 |
|
|
3 to 9 |
(0.008333 * ((age)^2)) + (0.6607 * (age)) + 5.6738 |
|
|
9 to 22 |
(0.0022179 * ((age)^3)) - (0.115906 * ((age)^2)) + (1.907926 * (age)) + 2.857789 |
SD score for patient BMI relative to mean value for age and gender =
= ((((BMI value for patient) / (mean value for age and gender)^(L curve value))) - 1) / ((L curve value) * (S curve value) / 100)
where:
• The 100 in the denominator converts S value from a percent to a decimal fraction.
Purpose: To evaluate the body mass index (BMI) of a pediatric patient from 1 to 21 years using the United Kingdom (UK) population data from 1990.
Objective: other testing, severity, prognosis, stage
ICD-10: E40-E46, E66, F50,
