Although the SF-36 is the most widely used generic measure of HRQoL in clinical trials, with validity established in numerous conditions, it cannot be assumed that the SF-36 is a valid measure in this rare disease population.
Like all other papal bulls, the 1567 bull has been endowed with perpetual validity in accordance with the formula "ad perpetuam rei memoriam" ("for a permanent record of the matter"), which is stated in its very beginning.
Therefore, monitoring depressive symptoms requires reliable instruments with tested validity in patients with schizophrenia.
Although the LupusPRO and LIT may have been developed in alignment with best measurement science, with content validity in the target population of interest and adequate measurement properties as required by the FDA, to the best of our knowledge, at the time of this study there was not comprehensive, publicly available, documented evidence that demonstrated this.
First, the small sample size and restriction of patients to those with severe asthma may have produced problems with external validity in the selection of subjects.
In trials with valid symbolic cues, the ball colour predicted the duration of the occlusion interval with 100% validity; in neutral trials the colour provided no information about the duration of the occlusion period.
Because there is little consensus concerning the optimal way of dealing with study validity in meta-analysis, the impact of excluding/including outcomes of studies with (possible) high risk of bias was investigated [22], [23].
Finally, the primary concern with internal validity in research trials of IBIs is poor follow-up rates, with many trials following-up less than 40% of participants [ 29].
However, the GPRD has been used numerous times for studying cancer, and previous validation studies provided convincing evidence that most cancer diagnoses are recorded with high validity in the GPRD (>90%) (20).
