Assessing patient report of function: content validity of the Functional Performance Inventory-Short Form (FPI-SF) in patients with chronic obstructive pulmonary disease (COPD)

Purpose The performance of daily activities is a major challenge for people with chronic obstructive pulmonary disease (COPD). The Functional Performance Inventory (FPI) was developed based on an analytical framework of functional status and qualitative interviews with COPD patients describing these difficulties. The 65-item FPI was reduced to a 32-item short form (SF) through a systematic process of qualitative and quantitative item reduction and formatted for greater clarity and ease of use. This study examined the content validity of the reduced, reformatted form of the instrument, the FPI-SF.