The aim of the study was to investigate the difference between encouraged self-recorded peak expiratory flow (PEF) with unobserved readings and to investigate any long-term changes in PEF self-recording.
Patients were trained in the PEF technique and asked to keep 2-hourly PEF records until the next clinic visit. The patients PEF were then rechecked at the second clinic visit by a series of two unobserved, an observed and an encouraged PEF measurement. A subgroup of patients were reassessed at a third clinic visit.
Forty-one patients produced serial PEF readings. Significant differences between unobserved and encouraged PEF readings were detected; there was a mean decrement of 21 L·min-1 and limits of agreements suggested that the decrement could be as high as 60 L·min-1. Visual and statistical analysis of the serial PEF provided showed a consistent deterioration in PEF over the record in 54% and 39% of cases, respectively. No significant differences were found in the subgroup who attended a third clinic visit.
The results suggest that significant inaccuracies in unobserved peak expiratory flow readings can occur between clinic visits and this can be reflected as a consistent deterioration in some. This should be kept in mind when interpreting self-recorded peak expiratory flow measurements. Re-evaluation at the third visit following the retraining effect of the second visit on peak expiratory flow technique appears to reduce inaccuracies. It is believed that peak expiratory flow technique should be re-evaluated at each clinic visit.