Stature prediction equations for elderly Hispanics in Latin American countries by sex and ethnic background.

BACKGROUND: We estimate prediction equations of stature from knee height for elderly Hispanic Blacks, Mulattos, Mestizos, Mexicans, and Whites. We test the predictive power of estimated equations, assess the magnitude of relative errors in measures of body mass index (BMI), quantify errors committed when using predicted rather that observed height, and evaluate the differences in the strength of the relation between BMI and diabetes.
METHODS: Using data collected in 1999-2000, we split each sex and/or ethnic group into validation and cross-validation groups, estimate equations from the validation groups, then test them on the cross-validation groups. We use robust linear regression to assess the sex- and/or ethnic-specific relation between knee height and stature. We evaluate the accuracy of classifications by obesity and of estimates of risk of diabetes when using estimated versus observed height.
RESULTS: Our equations are slightly less accurate than those obtained from U.S. data ( 4), although ethnic-specific parameters are comparable. Classification of subpopulations by obesity has high sensitivity and specificity. The estimated measure of BMI strongly attenuates estimated effects of obesity on diabetes. Thus, although the predicted heights fall within acceptable error bounds, their utilization in modeling relations to other health outcomes may give misleading inferences.
CONCLUSIONS: Knee height is a good surrogate for current height for elderly populations. It is always preferable to use ethnic-specific predictions, because the relation differs by ethnicity. Great care has to be exercised when classifying populations using surrogate measures of height, or in estimating relations between measures that are functions of surrogate height and health outcomes.