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. 2016 Jan 28;4:e1649.
doi: 10.7717/peerj.1649. eCollection 2016.

Deficiencies of Effectiveness of Intervention Studies in Veterinary Medicine: A Cross-Sectional Survey of Ten Leading Veterinary and Medical Journals

Free PMC article

Deficiencies of Effectiveness of Intervention Studies in Veterinary Medicine: A Cross-Sectional Survey of Ten Leading Veterinary and Medical Journals

Nicola Di Girolamo et al. PeerJ. .
Free PMC article


The validity of studies that assess the effectiveness of an intervention (EoI) depends on variables such as the type of study design, the quality of their methodology, and the participants enrolled. Five leading veterinary journals and 5 leading human medical journals were hand-searched for EoI studies for the year 2013. We assessed (1) the prevalence of randomized controlled trials (RCTs) among EoI studies, (2) the type of participants enrolled, and (3) the methodological quality of the selected studies. Of 1707 eligible articles, 590 were EoI articles and 435 RCTs. Random allocation to the intervention was performed in 52% (114/219; 95%CI:45.2-58.8%) of veterinary EoI articles, against 87% (321/371; 82.5-89.7%) of human EoI articles (adjusted OR:9.2; 3.4-24.8). Veterinary RCTs were smaller (median: 26 animals versus 465 humans) and less likely to enroll real patients, compared with human RCTs (OR:331; 45-2441). Only 2% of the veterinary RCTs, versus 77% of the human RCTs, reported power calculations, primary outcomes, random sequence generation, allocation concealment and estimation methods. Currently, internal and external validity of veterinary EoI studies is limited compared to human medical ones. To address these issues, veterinary interventional research needs to improve its methodology, increase the number of published RCTs and enroll real clinical patients.

Keywords: Clinical epidemiology; Evidence-based medicine; Meta-research; Randomized controlled trials; Research methodology; Study design; Veterinary research.

Conflict of interest statement

The authors declare that they have no competing interests. Nicola Di Girolamo is a private practitioner and Reint Meursinge Reynders is self-employed in his private practice of orthodontics.


Figure 1
Figure 1. Study flow.
Figure 2
Figure 2. Association (odds ratio and 95% confidence intervals) between randomization, discipline and type of intervention (surgical/non-surgical).
Notice that the overall prevalence of randomized controlled trials (RCTs) and prevalence of surgical RCTs were lower in veterinary medicine (ORs: 4.2 and 3.7, respectively). However, surgical interventions were more likely to be non-randomized in both disciplines (ORs: 14.3 and 2.3).
Figure 3
Figure 3. Number of patients randomized in RCTs and methodological quality.
(A) Difference in number of patients randomized in veterinary and general medicine. (B) Difference in number of patients randomized in cross-over and other study designs. (C) Correlation between the number of methodological issues (primary outcome, power calculation, random sequence generation, allocation concealment, estimation methods, intention-to-treat) reported and number of patients enrolled in each RCT. Notice that the y-axis was plotted on a logarithmic function.
Figure 4
Figure 4. Association between type of patients enrolled (real clinical patients vs non-patients) and adequacy of reporting of key methodological issues in RCTs published in leading veterinary journals (n = 114).
M-H, Mantel-Haenszel; CI, Confidence interval.
Figure 5
Figure 5. Sensitivity and subgroup analysis of the association between discipline and reporting of key methodological items.
Primary analysis. Inclusion of explicit RCTs. Exclusion of surgical RCTs. Inclusion of parallel explicit RCTs. Exclusion of non-patient RCTs. M-H, Mantel-Haenszel; CI, Confidence interval.

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The authors received no funding for this work.

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