Assessment of Diurnal Variability of Peak Expiratory Flow in Stable Asthmatics

Abstract

Five daily readings of peak expiratory flow (PEF) were obtained for three days on 100 patients with chronic stable asthma. The variability of PEF was calculated as the amplitude percent mean (A%M) from the readings obtained on the third day, and compared to previously reported data from 152 healthy Indian adults. Patients with severe asthma exhibited significantly higher A%M than patients with both mild and moderate asthma (p < 0.05), but there was considerable overlap across disease categories. The area under the receiver operating characteristic curve plotted to assess the performance of PEF variability as a discriminator in diagnosing asthma was 0.826, with best discrimination at a value of 12.5 (sensitivity 0.640, specificity 0.941). Using a cut-off value of 16.5 (as proposed earlier by us) improved specificity to 0.987 but reduced sensitivity to 0.510. Using a traditional cut-off of 20, specificity remained almost unchanged (0.993), but sensitivity dropped further to 0.440. Thus A%M>16.5 is a useful marker of bronchial asthma in epidemiological studies in India. However, its use in population screening, clinical diagnosis, or in the assessment of the severity of asthma in individual patients has serious limitations because of poor sensitivity.

Domiciliary diurnal variation of exhaled nitric oxide fraction for asthma control

“…There are reports indicating good relationships between diurnal PEF variations, asthma control and asthma exacerbation [6,34,35], while others report only limited usefulness as a measure of asthma control [36][37][38]. However, there are reports of significant diurnal variation in FeNO measurements in the mornings compared with evenings, as we have found [18,39].…”

Variations in PEFR among Males and Females With Respect To Anthropometric Parameters

“…The subjects were asked to inspire deeply, and then blow into the instrument's mouthpiece with nostrils closed. Each subject made three PEFR measurement manoeuvres since this requires practice and maximum effort, and the highest value was considered [3,11].…”

Guidelines for diagnosis and management of bronchial asthma: Joint ICS/NCCP (I) recommendations

“…A diurnal variation in PEF more than 20% is suggestive of poor control of bronchial asthma. [ 115 116 117 ] The optimum number of daily measurements required to document PEF variability is also not clear. [ 118 ] Alternatively, PEF can be monitored once daily by taking this measurement first thing in the morning (before taking any drugs) and comparing the reading to a known personal best.…”