Handheld spirometers for home use by patients allow longitudinal spirometry data to be collected daily and may overcome some of the limitations of in-clinic spirometry (long intervals between measurements, results can be affected by site-based coaching and patient's asthma status during a given visit).

To determine the relationship between spirometry values measured by clinic-based and handheld spirometers during a clinical trial.

A post hoc correlation analysis of data from a 6-week phase 3 study of beclomethasone dipropionate (BDP; delivered by breath-actuated inhaler: BAI) versus placebo in patients aged ≥12 years with persistent asthma. During the study, forced expiratory volume in 1 s (FEV₁) was assessed by both office-based spirometry at Weeks 2, 4 and 6, and daily by handheld spirometer as a secondary study endpoint.

There was a high correlation between FEV₁ values measured at home and in-clinic (overall correlation coefficient = 0.8393, R = 0.81921, 0.85927, 0.85369 and 0.83734 for BAI 320 μg/day, BAI 640 μg/day, BDP metered dose inhaler 320 μg/day and placebo treatment groups, respectively), with the scatterplot showing an upward trend for all treatment groups. Nearly all patients achieved home FEV₁ values close to clinic FEV₁ values, with very few outliers.

Clinic-based and handheld spirometry demonstrated comparable treatment effects relative to placebo, suggesting that home spirometry could be used to help patients monitor their asthma severity. Daily measurement of FEV₁ provides more comprehensive data than can be achieved through clinic visits, and may lead to a new approach to clinical trial design.