POTENTIAL EFFECTS OF CORRECTION OF INACCURACIES OF THE MINI-WRIGHT PEAK EXPIRATORY FLOW METER ON THE USE OF AN ASTHMA SELF-MANAGEMENT PLAN

Background - Patient self-management plans for asthma use peak expirat ory flow (PEF) meter readings for decisions on adjusting asthma treatm ent. PEF meters have been shown to be inaccurate and the effect of thi s inaccuracy on such treatment plans has been determined. Methods - PE F measurements were made by 127 severe asthmatic patients at least twi ce a day for at least two weeks using a mini-Wright meter. The daily v ariation from ''best'' PEF and the within day PEF variability were cal culated before and after correction for the meter's known inaccuracy. The effect of this data correction on the number of days when trigger points were reached for changing asthma therapy was then determined. R esults - Continuous PEF readings were available from 114 subjects with a median of 157.5 days of data per subject (range 15-489 days). Corre ction of the PEF data led to the number of days of satisfactory asthma control being reduced in 72% of subjects with just one subject showin g an increase in satisfactory control. Data correction reduced the per centage of total days of satisfactory control from 46% to 36% of days, and increased the days requiring more inhaled steroids from 33% to 36 %. The days on which a course of oral corticosteroids was required inc reased from 16% to 23%. Conclusions - The accuracy of PEF meters signi ficantly influences the interpretation of currently used asthma self-m anagement plans. Managing asthma with the corrected PEF data would hav e increased the amount of treatment received by these patients since t he severity of the asthma was underestimated by the raw data.