Respiratory Research in the Department of Medicine, Alfred Hospital

Abstract Accepted for Publication December 1998

A Critical Evaluation of the Mefar Dosimeter. R.J Ward, P. Liakakos, R.F Leonard*, D.W Reid, D.P. Johns, E.H Walters.

Department of Respiratory Medicine and *Department of Clinical Biochemistry, Alfred Hospital and Monash Medical School, Melbourne, Victoria, 3181, Australia.

Correspondence to: Professor E.H Walters. Telephone: + (613) 927632405. Fax: + (613) 92763434. e.mail: haydn.walters@med.monash.edu.au

Abstract

Multicentre studies of airway responsiveness (AR) are increasingly important tools in asthma epidemiology. Because comparisons of AR are made between centres it is essential that measurement techniques are accurate and standard.

We studied the Mefar dosimeter which is currently used in the 35 centre European Community Respiratory Health Survey (ECRHS) with the next phase currently being planned. We found significant differences in driving pressures and aerosol outputs between the 3 Mefar dosimeters in our laboratory. We also found a linear relationship between driving pressure and aerosol output (R2 = 0.96).

These differences are important as they may lead to variations of up to 35% in the drug dose delivered in AR measurement between centres, which could potentially diminish the power of individual study centres to accurately detect national differences in AR.

Dosimeter driving pressure and nebuliser output should be standardised in future studies of AR. With relatively simple quality control measures in place we believe the Mefar dosimeter can produce reliable between-centre longitudinal data with an increase in the accuracy of these important studies.