Single Breath Count as a Diagnostic Tool for Children With Asthma

Objective: To determine the test characteristics of single breath count (SBC) in differentiating asthma from no asthma, exacerbations from no exacerbations, and to determine the ability of SBC to assess response to treatment. Methods: This prospective observational study was conducted in the pediatric department of a tertiary care teaching hospital over a 2-year period. Children (6 to 16 y age) were divided into 3 groups: asthma with nonsevere exacerbation (group 1), asthma without exacerbation (group 2), and healthy children (group 3). Baseline tests (spirometry and SBC) were done for all the groups, and posttreatment tests were done for groups 1 and 2. Pulmonary score (PS) was measured in group 1. Receiver operating characteristic (ROC) curves and correlation coefficients were derived. Results: One hundred sixty-four children (asthma=82, healthy=82) were enrolled (male, 59.8%). The median (IQR) SBC values of the 3 groups at baseline were as follows: group 1: 27 (25-31), group 2: 32 (28-36), and group 3: 35 (31-40). Posttreatment, significant change was noted in group 1 ( P <0.05). All the spirometry parameters showed a significant positive correlation with SBC. A strong negative correlation (ρ=−0.647) was seen between SBC and PS in group 1 ( P <0.001). The area under the curve (AUC) for SBC was 0.71 (95% CI: 0.62-0.84) for differentiating between “exacerbation” and “no exacerbation” ( P =0.014). The cutoff value of SBC was 28 for this differentiation. Conclusions: SBC, like spirometry and PS, can differentiate asthma exacerbation from no exacerbation (a cutoff of 28 was suggestive). SBC can be used as a simple bedside test to monitor treatment response in children with nonsevere asthma exacerbation.