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improvement to 70Vo PEF would have occurred (Diner, Brenner et al. 2001). Predicted PEF
values has also been shown to be alter with age, sex, race, height and smoking making advice
based on "predicted values" difficult (Gregg and Nunn 1973; Nunn and Gregg 1989; Higgins,
Britton et al. 1992; Higgins, Britton et al. 1993; Boezen, Schouten et al. 1994; Boezen,
Schouten et al. 1995; Bellia, Cuttitta et al. 1997; Jain, Kavuru et al. 1998; Bellia, Catalano et
al. 2004).In addition, significant variation in predicted PEF values has been demonstrated
even within the same populations (Jindal, Aggarwal et al.2002).
The number of PEF measurements also contributes to accuracy and studies have used between
two and twelve readings (Gannon, Newton et al. 1998; Jindal, Aggarwal et al.2N2). Taking
twelve measurements daily as the gold standard, using four of these detected only 60-807o of
the variability and using two measurements detected only 20-45Vo of the variability
@'Alonzo, Steinijans et al. 1995). Another study showed that four, three and two daily
measurements explained 90-95Vo,70-82Vo and 55Vo of the diurnal variability respectively
(Gupta, Aggarwal et al. 2000). Patients also need to repeat the measurements several times on
each occasion as, on review of 5,809 test sessions, it was the third manoeuvre that most
frequently (40Vo of the time) gave the highest reading (Gannon, Belcher et al. 1999).
Practically, it would be difficult to request patients to do anything beyond two readings per
day over several days, let alone weeks or months. With a circadian rhythm playing a part,
ideally but also difficult would be to request the PEFs be done regularly at specific times of
the day. Finally, the age at which the child becomes able to use a peak flow effectively is also
variable (Clough 1996).
Overall the recommendation is not to use PEF for diagnosis, but international guidelines
continue to recommend PEF monitoring in the assessment of asthma, although more recently
for selected groups; those with severe asthma, poor perceivers, as a short term monitoring
procedure for exacerbation or to assess the adjustment of the medication dose (Reddel 2006).
PEF monitoring did reduce symptoms and improve other parameters such as days lost from
work, physician consultations and hospital visits in some studies (Ignacio-Garcia and
Gonzalez-Santos 1995; Cowie, Revitt et al. 1997). However, others showed no major changes
in outcomes in adults (Jones, Mullee et al. 1995; Turner, Taylor et al. 1998; Adams, Boath et
al.200l; Tierney, Roesner et aL.2004) or children with asthma (Mortimer, Fallot et al. 2003).
In children, it was difficult to perform (Gorelick, Stevens et al.2004) and was not useful in
dictating management during acute asthma (Wensley and Silverman 2OM). A Cochrane
review in 2004 concluded there was not enough data even combining seven trials (921 adults
and 46 children) to show that personalised self management plans with or without PEF
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