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ecommended to monitor asthma at home (Seaton 1978). This became part of an international
consensus document in 1992 (Irnfant rgg2). The pEF technique was standardised in an
American Thoracic society paper in 1994 (American Thoracic Society and Association.
lgg4).By 1998 all the published asthma guidelines included PEF monitoring as part of an
individualised management strategy (woolcock, Rubinfeld et al' 1989; National Heart Blood
and Lung Institute 1991; British Thoracic Society 1993; GINA 1995; Jain, Kavuru et al'
1998). The concept was to provide an objective measurement of airflow obstruction'
particularly for the significant proportion of patients who otherwise had difficulty in
recognising their asthma severity (Rubinfeld and Pain L976;Burdon, Juniper et al' 1982; Sly'
Landau et al. 1985; Kendrick, Higgs et al. 1993; Fishwick and Beasley 1996)'
However, there are issues with using pEF as this predominately reflects alteration in large
airway calibre which is different to FEVr that reflects changes in calibre of both large and
medium sized airways (Osmanliev, Bowley et al' t982; Robinson' Chaudhary et al' 1984;
Dolyniuk and Fahey 1986; Gregg 2000). PEF is effort dependant so is susceptible to both
respiratory muscle strength and patient motivation (Tzelepis, pavleas et al. 2005). while the
reproducibility of pEF has been reported to be good with a coefficient of variation in well
trained subjects of between 5 to I4Vo, still more than Sovo of asthmatic patients show a 107o
difference and 33vo of patients show more than a 20vo difference between the percent
predicted value of FEVr and PEF (Kelly and Gibson 1988; Paggiaro' Moscato et al' 1997)' In
addition, the standard deviation for PEF readings is consistently greater than that of FEVr' In
another study, the coefficient of pEF repeatability was 107o for healthy adults but rTvo for
healthy children, LTVo inasthmatic adults and2SVo in asthmatic children @nright, shenill et
al. 1995). This poorer repeatability in asthmatic subjects has been confirmed by other studies
(Meijer, Postma et al. 1996; Timonen, Nielsen et al' IggT; Holcroft' Eisen et al' 2003)' In
addition, significant differences in variability were also described between encouraged PEF
readings done in a laboratory and those done at home (Reddel' Ware et al' 1998; Gannon'
Belcher et al. 1999).
The two methods of using pEF to detect or monitor asthma was either by determining daily
PEF variability or by using the comparison of the current PEF to a subject's best PEF (Jain'
Kavuru et al. l99g). pEF variability is associated with acute asthma exacerbations @ellia,
Cibella et al. 1985; Beasley, Cushley et al. 1989; Jindal, Aggarwal et al' 2002)' Cross
sectional studies have demonstrated significant (albeit weak) correlations between PEF
variability and overall severity of inflammation, symptoms scores, FEVr and bronchial hyper-
responsiveness (Higgins, Britton et al. lgg2;Brand, Duiverman et al' 1997; Douma' Kerstjens
L4