Obesity predictors in people with chronic spinal cord injury: Common mistake.

Sir,

I was interested to read the paper by Sabour. H and colleagues published in J Res Med Sci in March 2011.[1] The purpose of the authors was to assess obesity predictors of people with spinal cord injury (SCI) using a cross-sectional study. Why did the authors use a cross-sectional design! For prediction studies, we need two different sets of cohort data or at least one cohort dataset splitting that to develop our prediction model and then to validate it. Therefore, by using a cross-sectional design, we cannot say anything about prediction.[234]

As the authors pointed out, waist circumference (WC) is classified based on Standard Classification (men >102 cm, women >85 cm). Standard classification for WC is not applicable for the Iranian population as there is no difference between men and women regarding mean WC.[5]

Therefore, applying such a classification will actually lead to overestimation of the obesity in women as well as underestimation of the outcome in men.

Because self-reported height and weight were used in this study, validity (accuracy) and reliability (precision) of the data cannot be guaranteed. Moreover, these variables have been used to calculate another variable such as body mass index (BMI)! Thus, any interpretation based on these variables cannot be clinically correct. Most of the times, misleading results can easily affect the main results and conclusions of such researches.

Moreover, for prediction purposes, using the Pearson Correlation Test is one of the common mistakes in reliability analysis as well as prediction researches.[234]