Quality of published clinical trials on asthma

The quality of 287 clinical trials on asthma treatment published between 1984 and 1997 is described in this article, using a scale adding to a maximum of 14 points. The mean quality score was 8.60 (standard deviation 1.55). Quality improved throughout time from 8.17 +/- 1.40 before 1989 until 9.55 +/- 1.66 after 1992. Several methodological issues were associated with higher quality, namely parallel design, longer length of the follow-up, complete description of the exclusion criteria, description of the initial and ending recruitment dates, higher sample size, explicit sample size calculation, blinding, full description of randomization, intention-to-treat analysis, full description of the intervention, and evaluation of bias. The higher statistical significance, however, was not associated with higher clinical trial quality.