Perception of Pulmonary Function in Children with Asthma and Cystic Fibrosis.

Background: Under-perception of pulmonary dysfunction may delay appropriate treatment, while over-perception may result in unnecessary treatments. Objectives: To evaluate the ability of patients with asthma or cystic fibrosis and their subspecialty caregivers to assess changes in lung function based on their subjective clinical impressions. Methods: Patients were asked to qualitatively describe how they felt compared to their prior visit (same/better/worse) and to quantitatively estimate their forced expiratory volume in 1s (FEV1) after being reminded of their FEV1 at the prior visit. Providers made similar estimates based on history and physical examination and knowledge of prior FEV1. After adjusting for relevant clinical covariates, lung function estimates were categorized as accurate (5% of measured FEV1), overestimated (>5% above measured), and underestimated (>5% below measured). Results: One hundred nine patients estimated FEV1 on 179 occasions. Concordance between patient qualitative assessment and FEV1-based categories was low (=0.08); 44% of patients reported feeling better than the FEV1-based category showed. Quantitatively, 56% of patient estimates were accurate, 18% were underestimated, and 26% overestimated; accuracy improved with age (odds ratio=1.16, P=0.01). Concordance between provider qualitative assessments and FEV1-based category was moderate (=0.35); about 19% said their patient looked better than the FEV1-based category showed. Quantitatively, 65% of provider estimates were accurate, 16% were underestimated, and 19% were overestimated; accuracy improved with years of experience. Conclusions: Patients' and providers' perceptions of lung function were low to moderately accurate. Relying on subjective impression may place patients at risk for unnecessary treatments or increased morbidity. These findings highlight the importance of objective lung function assessment.