variables used to define households with worst case rental housing needs

Does anyone know which variables in the AHS are used to calculate "worst case rental housing needs" according to the HUD defintion (especially the last criterion):

- have incomes below 50 percent of AMI
- spent more than 50 percent of income on rent, or live in severely inadequate housing,
- are not assisted by Federal, state, or local housing assistance programs.

Thanks much.

Jason Schmidt
Senior Quantitative Analyst
Research and Policy Analysis
Federal Reserve Bank of Minneapolis
612.204.5496
jason.schmidt@mpls.frb.org