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02-06-2013 | Respiratory | Article

Pediatric BDR cutoff shunned

Abstract

Free abstract

medwireNews: Researchers say that the definition of a significant bronchodilator response (BDR) as a change in forced expiratory volume in 1 second (FEV1) of at least 12% is inappropriate for use in children.

And, despite finding that an alternative cutoff of 8% improved the sensitivity and specificity of the test for diagnosing asthma, the study authors suggest that it may be better not to use any form of cutoff in pediatric patients.

"Because most children with asthma have baseline FEV1 within the normal reference range, the increase in FEV1 after bronchodilator administration is limited," say Sze Man Tse (Harvard Medical School, Boston, Massachusetts, USA) and colleagues.

They add: "The widely accepted BDR cutoff of 12% is based on general population and asthmatic patient studies consisting of mostly adults, who might have a higher interindividual variability in baseline FEV1."

The study, published in the Journal of Allergy and Clinical Immunology, included 1041 children with mild-to-moderate asthma and 250 controls. At baseline, mean FEV1 % predicted values were similar between the two groups, and within the normal range, at 93.7% and 98.4%, respectively. However, BDR was greater among asthma patients at a mean of 10.7% versus 2.7%.

The authors found that the BDR could differentiate between children with and without asthma with modest accuracy, with an area under the curve of 74.5%.

Using a cutoff value of 12% of initial FEV1 resulted in good specificity, 89.5%, but poor sensitivity, 35.6%, Tse and colleagues report. A cutoff of 8% performed significantly better with specificity and sensitivity of 76.5% and 54.4%, respectively, while 5% was the optimum cutoff, leading to corresponding values of 63.5% and 73.6%.

However, both of these values are generally considered to be within measurement variability, which may be even greater in children given their imperfect technique, say the authors.

"Thus, we advise against choosing a specific BDR cutoff for the diagnosis of asthma but rather to use the BDR test as a guide in the treatment and diagnosis of asthma because the persistence of a positive response might be associated with worse clinical outcomes in asthmatic patients over time," they write.

Tse and colleagues also caution against the use of the 12% cutoff in pediatric study populations.

"In children this criterion will lead to a subset of patients selected for a higher degree of airway airflow obstruction, which might limit generalizability of the results…. On the other hand, in intervention studies a higher cutoff could select for children who have a higher chance of showing an intervention effect," they warn.

medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Kirsty Oswald, medwireNews Reporter