Table 2 Definitions, main findings and authors’ conclusions of inconsistency between abstracts and full reports in the included studies

Bhandari 2002 [2]

Inconsistencies including minor differences (in study title, number of authors, presentation of all outcomes, and authors’ data interpretations) and major differences (in study objective and/or hypothesis, study design, primary or any secondary outcome measure, sample size, analyses, results, and precision measures.

Major inconsistency found in designating a primary outcome measure (14%), and results for primary outcome measure (19%)

The overall abstract-reporting quality was inadequate. The use of abstracts as a routine guide to orthopedic practice requires to be reconsidered.

Boutron 2010 [4]

In trials with primary outcome showing statistically non-significant results, the spin of reporting were (1) with a focus on statistically significant result; (2) with interpretation of non-significant results as showing equivalent or comparable treatment effectiveness; and (3) with an emphasis or claim of beneficial effect.

Spin identified in the abstracts of Results (38%) and Conclusions (58%) sections. Among the Conclusions section of abstracts, 24% focusing only on treatment effectiveness

Result reporting and interpretation in abstracts was frequently inconsistent with full reports in RCTs with non-significant findings.

Davies 2002 [22]

Abstracts were considered discordant with full reports if abstracts reported different sample size, or different primary aims and/or conclusions.

Discordance found in primary aims (25%), conclusions (35%) and sample sizes (39%).

Considerable differences found between abstracts and full reports in perinatology

Dyson 2006 [27]

Major differences defined as inconsistency on major results and conclusions; minor differences defined as inconsistency that would not change the overall clinical approach

Major differences existed in 7%, among which half of these inconsistencies could affect clinical action by changing the emphases of the conclusions.

Caution must be exercised in using information from conference abstracts in veterinary science

Harris 2002 [18]

Abstract rated as deficient: 1) if it contained information or a claim that was inconsistent with the body of the article (labeled discrepancy), 2) or if information or claim was reported in the abstract but not in the article (labeled omission)

Proportion of deficient abstracts ranged from 8% to 18% across journals, with an average of 13% over the entire sample

Readers should be aware that abstract-full-report inconsistencies are not uncommon in psychology.

Hopewell 2006 [7]

Inconsistencies defined as any differences in objectives, study designs, study quality, participants, interventions, outcomes, results, and conclusions.

16% of abstracts differed in primary outcomes, 54% in number of participants randomized and 78% in number of participants analyzed.

Information given in oncology conference abstracts is unstable and needed to be improved.

Klassen 2002 [23]

Differences in abstract-full-report pairs included conclusions, outcomes, effect sizes, and sample sizes.

5% of abstracts changed the conclusions regarding treatment efficacy, 13% had different effect sizes for outcomes, 59% had different sample sizes.

Significant differences between conference abstracts and subsequent full reports were found in pediatrics research.

Kottachchi 2010 [19]

Inconsistencies including minor (changes in number of authors and study title) and major (changes in study hypothesis/design, measurements in primary/ secondary outcomes, changes in sample size, statistical analysis, or different study results or measures of precision) inconsistency.

Minor change in number of authors (55%) and study title (70%).

Major change in study design (5%), sample size (37%), primary outcome (28%), secondary outcome (31%), and conclusion (6%).

A substantial inconsistency was found when comparing abstracts with full reports in digestive diseases.

Lehmen 2014 [12]

Abstracts considered to have a deficiency if they had data that were inconsistent with or not found in full reports, or if they did not report pertinent negative results

75% of the abstracts had at least one 1 deficiency

A surprisingly high percentage of inconsistency between abstracts and full reports was reported in spinal RCTs.

Ochodo 2013 [3]

Abstracts defined as overly optimistic if they chose to report the best results only, or if they reported stronger recommendations or conclusions than in the full reports

23% of the abstracts were overly optimistic

Abstracts were frequently found to be misreported and overly optimistic in diagnostic accuracy studies.

Pitkin 1999 [10]

Abstracts considered deficient if they reported different data from full reports, or they provided data that could not be found in full reports

Deficient abstracts varied from 18% to 68%

Even in large-circulation general medical journals, data in abstracts were commonly inconsistency with full reports.

Preston 2006 [24]

Inconsistencies were discrepancies in study objective and/or hypothesis, study design, primary outcome measure, sample size, statistical analysis, results of primary/secondary outcomes, and conclusions.

29% abstract-full-report pairs had at least one inconsistency.

Inconsistencies found in conclusions (7%), primary outcome measures (4%), sample size (18%), results for primary (8%) and secondary (29%) outcomes.

Inconsistencies were frequently observed. Most conclusions remained unchanged.

Rosmarakis 2005 [20]

Difference between abstracts and full reports categorized into minor or major; difference in any number by 10%, or statistically non-significant results changed to be significant (or vice versa) was considered major

Difference found in 59% pairs of abstracts and full reports, among which 77% was major difference

Significant inconsistencies were found between abstracts and full reports in infectious diseases and microbiology.

Snedeker 2010 [21]

Difference in abstract-paper(s) match including number of authors, study objectives, pathogen(s), intervention(s), species, sample size, housing, number of bacterial outcome measures, intervention effect, and overall conclusion

One-third (32%) of matches had different results; 14% differed in the direction of intervention effect; 26% significantly differed in outcome results; 11% differed in overall conclusion on efficacy of the intervention

Abstracts may not always accurately report the same information as in full reports in the field of pre-harvest and harvest-level food safety.

Toma 2006 [25]

Inconsistencies included differences in the study designs, purpose of trials, sources of funding, allocation concealment, sample size, results, and conclusions.

24% of abstracts had different sample size, 41% had different treatment effect estimates.

Inconsistencies between meeting abstracts and subsequent full reports were not uncommon in cardiology.

Turpen 2010 [26]

Inconsistencies included any differences in study design and results

29% abstract-full-report pairs had different numbers of participants randomized, 70% had unidentifiable primary outcome.

Abstract provided inconsistent results that could not allow urologists to critically appraise study validity.

Ward 2004 [11]

Abstracts considered deficient if they had data but not in full reports (omission), inaccurate factual information that differed from full reports, inconsistency in following the “Instructions for Authors” for respective journals, or difference in the information placement between abstracts and full reports

61% of the abstracts had at least one deficiency. 25% had an omission; 19% had qualitative inaccuracies; 25% had quantitative inaccuracies; 5% were inconsistent with the “Instructions for Authors”; 14% had information placement difference

Improvement is needed to rectify the inconsistency of abstract reporting in pharmacy-specific journals.