Convergence criterion not satisfied in logistic regression

[Aline1610]

Hello,

I am performing an univariate conditional logistic regression for my nested case-control study. My dependent variable is the lymphoma status and my indepedent variable is the energy intake with 3 classes including a "missing values" category.

When i generated the PROC LOGISTIC model with the STRATA function, this warning appeared :

"ERROR: NRRIDG Optimization cannot be completed.
ERROR: Optimization routine cannot improve the function value. You may want to change the convergence criteria (ABSFCONV=,
FCONV=, GCONV=, XCONV= options) in the MODEL statement" 

When i removed the "missing values" category the warning disappeared. I dont understand why with this variable only i have this problem. I already tested many other variables with a "missing values" category and the proc logistic models worked well. What should i do ? It asks me to change the convergence criteria but i have no clue what does this mean...

Thanks in advance for your help !

Aline.

[PaigeMiller · Accepted solution]

It is possible that when the value of energy intake is MISSING then it only appears with one value of lymphoma status, and so this could cause problems. You should check this.