Identifying the concepts contained in outcome measures of clinical trials on four internal disorders using the International Classification of Functioning, Disability and Health as a reference.

OBJECTIVES To systematically identify and compare the concepts contained in outcome measures of clinical trials on chronic ischaemic heart disease, diabetes mellitus, obesity, and obstructive pulmonary disease, including asthma using the International Classification of Functioning, Disability and Health (ICF) as a reference. METHODS Randomized controlled trials between 1993 and 2003 were located in MEDLINE and selected according predefined criteria. The outcome measures were extracted and the concepts contained in the outcome measures were linked to the ICF. RESULTS 166 trials on chronic ischaemic heart disease, 227 trials on diabetes mellitus, 428 trials on obesity, and 253 trials on obstructive pulmonary disease were included. Ten different health status questionnaires (fulfilling the inclusion criteria) were extracted in chronic ischaemic heart disease, 19 in diabetes mellitus, 47 in obesity, and 39 in obstructive pulmonary disease. Across conditions at least 75% (range 75-92%) of the extracted concepts could be linked to the ICF. In diabetes mellitus and obesity the most used ICF categories were general metabolic functions (b540), in obstructive pulmonary disease respiration functions (b440) and in chronic ischaemic heart disease heart functions (b410). CONCLUSION In all 4 health conditions the majority of studies were drug trials focusing on clinically relevant parameters and not on functioning. The ICF provides a useful reference to identify and quantify the concepts contained in outcome assessment used in clinical trials.