How representative are clinical study patients with allergic rhinitis in primary care?

Guidelines are the cornerstone of health care decision making and are based on the best available evidence, ideally large randomized controlled trials (RCTs). Although guidelines target typical patients, RCTs are often based on narrow inclusion and exclusion criteria.

We explored to what extent typical patients, such as those consulting general practitioners for allergic rhinitis, differ from patients enrolled in RCTs.

We conducted a prospective cohort study including all the consecutive patients with allergic rhinitis cared for by general practitioners in the Languedoc-Roussillon region of France within 2 weeks during the grass pollen season. We evaluated how the characteristics of these patients differed from those of patients included in the 4 largest placebo-controlled RCTs of persistent and intermittent allergic rhinitis.

Three hundred eleven patients seen by 48 general practitioners were enrolled in this study. Only 7.4% (95% CI, 4.5% to 10.3%) of the patients would have been enrolled in the RCTs. The primary reasons for this difference were as follows: diagnosis of allergy based on skin test results, serum specific IgE levels, or both (20.4%); severity of allergic rhinitis (11.5%); other chronic diseases (11.4%); history of sinusitis (10.4%); and asthma comorbidity (10.1%). A sensitivity analysis excluding contraception and the diagnosis of allergy showed that the percentage of representative patients increased to 20.2% (95% CI, 15.8% to 24.7%).

Only a small proportion of patients with allergic rhinitis seen in the primary care setting for allergic rhinitis would be eligible for RCTs. Thus guideline developers and health decision makers need to make careful judgments about the directness of the evidence from RCTs conducted in highly controlled settings.