Journal Scan: Studying the studies: A review of evidence from trials evaluating atopic dermatitis therapies

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What they did

The authors reviewed 21 randomized controlled trials published or completed between 2008 and 2011 that evaluated the prevention or treatment of atopic dermatitis in dogs. Dogs of any age or disease severity were included, and atopic dermatitis was diagnosed based on "the presence of characteristic clinical signs and the exclusion of pruritic dermatoses of similar appearance." Studies that enrolled dogs with other diseases in addition to atopic dermatitis were excluded. All studies reported measures of efficacy and safety that primarily involved the mitigation of pruritus, skin lesions scores, or both.

What they found

Researchers evaluated the quality of the evidence in these studies based on a quality rating scale1 as outlined below in the context of treating patients in clinical practice:

• High quality of evidence: Further research is very unlikely to change our confidence in the estimate of effect.

• Moderate quality of evidence: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.

• Low quality of evidence: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
• Very low quality of evidence: Any estimate of effect is very uncertain.

No therapy was designated as high quality. Evidence of the efficacy of topical and oral glucocorticoids (0.5 mg/kg once to twice daily and tapered to effect) and oral microemulsified cyclosporine (Atopica-Novartis Animal Health; 5 mg/kg once daily and tapered to effect) was graded as moderate quality.

Data from randomized controlled trials evaluating the efficacy of generic microemulsified cyclosporine, a nano-emulsion cyclosporine formulation, injectable recombinant feline interferon and canine interferon, oral fexofenadine, and oral masitinib for the treatment of atopic dermatitis were determined to be of low quality.

Only very low quality evidence was found for the use of synthetic T-cell receptor V-beta peptides, tepoxalin, Trichuris vulpis eggs, single mite allergen immunotherapy, pentoxifylline, and black currant seed oil. A randomized controlled trial of a diet rich in essential fatty acids (Atopic Care-Affinity Petcare) provided low-quality evidence of a glucocorticoid-sparing effect when used in dogs with atopic dermatitis.

The authors acknowledge that many of the randomized controlled trials had very low numbers of subjects, which may make it difficult to detect smaller treatment effects. In addition, use of modified or unpublished severity scales as well as the variable outcome measures used made standardization difficult.

Take-home message

Topical or oral glucocorticoids and cyclosporine remain the cornerstone of therapy for dogs with atopic dermatitis in terms of safety and efficacy. New therapies have shown some promise but will require further research to ensure positive outcomes.

REFERENCE

1. Guyatt GH, Oxman AD, Vist GE, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ 2008;336:924-926.

Olivry T, Bizikova P. A systematic review of randomized controlled trials for prevention or treatment of atopic dermatitis in dogs: 2008-2011 update. Vet Dermatol 2013;24(1):97-117.

Link to abstract: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3164.2012.01088.x/abstract