Serial peak expiratory flow rate monitoring--a useful tool in epidemiological studies on occupational asthma.

Occupational asthma is the leading occupational respiratory disease. Epidemiological studies of occupational asthma have made use of the serial peak expiratory flow rate (PEFR) monitoring as a tool to identify cases, describe prevalence and to compare the mean diurnal variation (DV) in PEFR with an unexposed control group. Various indices of PEF variability can be used. The serial PEFR is a useful additional tool to the respiratory questionnaire and spirometry as it measures airway variability. It is also a practical alternative to histamine or methacholine inhalation testing. It has the advantage of providing multiple sequential readings of PEF and simple indices are available to express the airway variability of almost every subject studied. The validity of the serial PEFR recording should be further evaluated considering both the technical and human aspects. The monitoring protocol should be standardised and some criteria for validity should be pre-set. Factors that may affect DV in PEFR such as age, sex, smoking, race and the mean or maximum PEFR should be taken into account when comparing with controls.