Background: Investigators of clinical trials in which the list of outcomes include patient-reported outcomes (PROs) - usually labeled quality of life (QoL) - have a large number of instruments from which to choose. The extent and manner in which PRO instruments are used in clinical trials can be assessed using data from clinical trial registries. Most medical journals now require a clinical trial be registered before its results are considered for publication. This requirement is intended to discourage publication bias, such as the reporting of tests of hypotheses different from those stipulated at the start of the trial and selective reporting of partial results.
Purpose: To assess the usage of PRO instruments in registered trials by various trial characteristics and to determine if the instruments are adequately identified in the registry.
Methods: A local copy of the ClinicalTrials.gov database was made in September 2007. The outcomes of all interventional trials registered since September 2004 were assessed for usage of a PRO instrument. Odds ratios of PRO usage were estimated by a logistic regression model.
Results: Of 17,704 interventional trials, 2481 (14.0%) used at least one PRO instrument. However, less than half of those trials (41.0%) identified the instrument to be used. PRO usage is positively associated with phase (III), randomization type (randomized), intervention type (behavior) and sponsorship type (university/research organization).
Conclusions: PRO instruments are used in a significant percentage but minority of clinical trials. Trial registries should require that all PRO instruments be identified, including the concepts or outcomes they are intended to measure.