Comparison of preprints and final journal publications from COVID-19 Studies: Discrepancies in results reporting and spin in interpretation

Objective: To compare results reporting and the presence of spin in COVID-19 study preprints
with their finalized journal publications

Design: Cross-sectional

Setting: International medical literature

Participants: Preprints and final journal publications of 67 interventional and observational
studies of COVID-19 treatment or prevention from the Cochrane COVID-19 Study Register
published between March 1, 2020 and October 30, 2020

Main outcome measures: Study characteristics and discrepancies in 1) Results reporting
(number of outcomes, outcome descriptor, measure (e.g., PCR test), metric (e.g., mean change
from baseline), assessment time point (e.g., 1 week post treatment), data reported (e.g., effect
estimate and measures of precision), reported statistical significance of result, type of statistical
analysis (e.g., chi-squared test), subgroup analyses (if any), whether outcome was identified as
primary or secondary and 2) Spin (reporting practices that distort the interpretation of results
so that results are viewed more favorably).

Results: Of 67 included studies, 23 (34%) had no discrepancies in results reporting between
preprints and journal publications. Fifteen (22%) studies had at least one outcome that was
included in the journal publication, but not the preprint; 8 (12%) had at least one outcome that
was reported in the preprint only. For outcomes that were reported in both preprints and
journals, common discrepancies were differences in numerical values and statistical
significance, additional statistical tests and subgroup analyses conducted in journal
publications, and longer follow-up times for outcome assessment in journal publications.
At least one instance of spin occurred in both preprints and journals in 23 / 67 (34%) studies,
the preprint only in 5 (7%) studies, and the journal publications only in 2 (3%) of studies. Spin
was removed between the preprint and journal publication in 5/67 (7%) studies; but added in
1/67 (1%) study.

Conclusions: The COVID-19 preprints and their subsequent journal publications were largely
similar in reporting of study characteristics, outcomes and spin. All COVID-19 studies published
as preprints and journal publications should be critically evaluated for discrepancies and spin.