Item response theory methods can improve the measurement of physical function by combining the modified health assessment questionnaire and the SF-36 physical function scale.
Martin M, Kosinski M, Bjorner JB, Ware JE, Maclean R, Li T. Item response theory methods can improve the measurement of physical function by combining the modified health assessment questionnaire and the SF-36 physical function scale. Qual Life Res. 2007 May; 16(4):647-60.