Study did not prove benefit

EDITOR—Hossain et al conclude that vitamin A along with standard antibiotic reduces the severity of acute shigellosis and that vitamin A supplementation should be added to the standard treatment for acute shigellosis.1 We disagree with those conclusions.

The benefit of vitamin A as adjuvant treatment for shigellosis can be judged only in a study in which patients receive adequate antimicrobial treatment.2 In Hossain et al's study 64% of patients were infected with strains of shigella resistant to nalidixic acid, which was used to treat study patients. It is unclear how many patients were given an alternative effective antibiotic or when treatment was changed.

The inadequacy of antimicrobial treatment in this study is reflected in clinical cure rates of less than 50% in patients who did and did not receive vitamin A supplements. That is not acceptable as adequate antimicrobial treatment routinely achieves a cure rate of 65% or more. 3 4 Indeed, Hossain and colleagues calculated their sample size based on a 98% cure rate in the vitamin A group. …