Meta-analysis has been performed on 11 studies on the effect of levocabastine nasal spray in allergic rhinitis in comparison to placebo. Meta-analysis allows us to estimate the size of the combined effect in addition to its statistical significance. The combined effect of levocabastine nasal spray was found to be significantly larger than that of placebo (odds ratio 2.3, P < .001). No significant heterogeneity of effect of treatment has been found across the 11 individual studies. The procedure of meta-analysis is explained in a didactical way using the fixed effects model, with special reference to randomized clinical studies in the field of allergy. The rationale for selection of an appropriate response parameter is also discussed.
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