Improving the quality of peak flow measurements for the diagnosis of occupational asthma.

INTRODUCTION Serial measurements of peak expiratory flow (PEF) are recommended in the evidence-based review list as the first stage in objective confirmation of occupational asthma. Different centres have reported widely different success in obtaining records of sufficient data quantity for diagnosis. We investigated different methods of instruction and determined the return rate and quality of the resulting record for the diagnosis of occupational asthma. METHODS Consecutive new referrals were recruited from a specialized occupational lung disease clinic and requested to carry out serial PEFs for the assessment of suspected occupational asthma. Requests to carry out the records were either from written postal instructions or personal instruction from a PEF specialist. Record quality received from other clinicians was also analysed separating those using dedicated occupational forms, and those submitting on graph type forms. RESULTS The postal return rate was 56% and the personal rate 85%. The number of records fulfilling all the data quality criteria were similar in the postal and personal groups (55 and 59%, respectively). Pre-existing records from other clinics plotted from graph charts (fulfilling all criteria) were only adequate in 23%, compared with 61% adequate for pre-existing records plotted from occupational forms. Failure of the record to contain consecutive work periods of > or =3 workdays was the most common failure. CONCLUSION The return rate of PEFs for diagnosing occupational asthma is better when patients have been given specific instructions from a PEF specialist and the data quantity better when recorded on a dedicated form.