Hi Statalist,

I am new to the forum and to multiple imputations. I plan to run a cox regression model, but three covariates (World Health Organization Clinical stage, CD4 T-cell count and HIV viral load) have missing values. I have used the mi command to impute missing values for the three variables.
I have the following questions:
1. When I ran the sum command for CD4 T-cell count and HIV viral load after imputation of missing variables, I noted that Ithe newly computed variables include negative numbers which is odd. can this be prevented?

sum baseline_cd4

Variable Obs Mean Std. Dev. Min Max

baseline_cd4 100,777 267.6011 226.9528 -498.9758 1580

2. For the cox regression, I plan to transform both CD4 T-cell count and HIV viral load. I plan to analyze CD4 T-cell count in increments of 100 cell ( gen b_cd4_100 = baseline_cd4/100) and categorize HIV Viral load ( egen viralload0_cat = cut( rnavload_0 ), at( 0 , 1000,10000, 100000,9914937 )
With these transformations, will the integrity of the multiple imputations be maintained? or do I need to carry out the transformation before the multiple imputations?

Thank you.


Max