Levels of evidence in otolaryngology journals.

Objective: To identify trends in clinical research and levels of evidence in otolaryngology journals.

Study Design And Setting: We reviewed all original research articles from 1993, 1998, and 2003, in 4 major otolaryngology journals. Levels of evidence were graded 1 (strongest) through 5 (weakest).

Results: Of 2584 total articles, 1924 (75%) were clinical research. During the study period, there was increased median sample size (from 22 to 30, P=0.06), more planned research (from 30% to 37%, P=0.023), more internal control groups (from 36% to 43%, P=0.011), and more articles with P values (from 26% to 45%, P<0.001) or confidence intervals (from 1.2% to 7.6%, P<0.001). Most evidence was level 4 (57%), but median levels increased slightly over time (P=0.027). Therapy articles had the weakest evidence (80% levels 3 to 5) and diagnostic test assessments had the strongest (75% levels 1 and 2).

Conclusion: Although clinical research increased in quantity and quality, sample sizes were modest, most articles lacked controls, and confidence intervals were rare. Therapy articles would benefit from higher evidence levels.

Significance: By defining the current levels of evidence in otolaryngology journals, this overview should help guide future efforts.