Purpose: To test the hypothesis that articles published as "preliminary" or "pilot" reports are followed by more definitive publications in only a minority of cases.
Method: A survey of Medline was performed for reports published in 1992 in journals listed in the Abridged Index Medicus that had the word "preliminary" or "pilot" in the title. For identified reports, a Medline search of publications in 1992 through 1999 was performed, using lead author's name, second author's name, and senior (last) author's name, and at least one keyword based on the publication title. Preliminary and pilot publications were subdivided by type of study (controlled clinical study, case series, laboratory or nonclinical) and by the report of either positive or negative results. Rates of publication based on study design and publication bias were compared using the chi-square test for statistical significance.
Results: The rate of publication of follow-up reports within seven years of the initial publication was 27%. Follow-up studies of controlled clinical studies (40%) were published more frequently than were those of laboratory or nonclinical studies (31%) or case series (22%), but these differences were not significant (p >.10). There was no statistically significant difference in follow-up publication rates based on publication bias.
Conclusion: Only 27% of studies published as preliminary or pilot reports were subsequently followed by a more definitive publication. While the words preliminary and pilot suggest that publication of further, refined work is pending, this is often not the case.