The 6 minute walk test looks at distance, amount of O2 needed, and oxygen desaturation during the walk. I ended up doing my 6 minute test 4 times before I got listed. The first three times I ended up walking a fairly long distance without O2, the forth time was after I had been hospitalized for 3 weeks with cdif and could barely function. That was the score they used.
Good luck in your transplant journey. Feel free to ask me any questions about the process or the transplant itself.