Hi, I'm new to using CHAT but am also unclear whether the BMI z score change (bmiz_change) variable is accurately calculated or not. A simple subtraction of the two bmiz variables from baseline to followup is not equal to the bmiz_change column. Am I missing something here?
Thanks for raising this on the forum. Yes, at my own glance, bmiz_change appears to be wrong. It looks like the data owners had another variable, chg_bmiz, which is more correct but was removed for redundancy with bmiz_change. I will swap the variables in a future release.
For the time being, I suggest using a calculation of your own for the BMI Z-score change between baseline and follow-up.