I started SSDI in 2004 and had a review in 2012 or so. I think it was a long questionnaire, maybe 5-7 pages (multiple choice and comment section). Maybe it differs from area to area when reviews get sent out. I'm not sure how it works but I bet they use statistics for reviews. Govn't is big on using statisticians because it's a very reliable form of math (prediction, probability, etc.).