Comparison of four methods to assess fungal alpha-amylase in flour dust

The aim of the study was to compare four different immunological methods to analyse fungal alpha-amylase in flour dust samples. Three European researc h groups have independently developed four immune assay based methods to me asure alpha-amylase in air samples. Three of the methods use polyclonal ant ibodies and one method uses monoclonal antibodies, Eighty personal samples have been collected during two to three work-shifts in four bakeries. Sampl ing was performed with PAS-6 inhalable dust samplers and aliquots from each sample were analysed by the three laboratories. The agreement between the four methods was high compared with agreement between immunological methods to measure other allergens in the air, e.g. for rat allergens. For the thr ee methods with polyclonal antibodies the mean differences for individual s amples was less than a factor of two. The arithmetic means (AM) of the esti mated alpha-amylase exposure mere 12.5, 11.3, 8.6 and 25.9 ng/m(3) for the respective methods with values ranging from below the detection limit to 19 2, 215, 207 and 615 ng/m(3) The AM for all samples analysed by the methods with polyclonal antibodies varied by about a factor of 1.5. About one-third of the values were below or at the detection Limit for all methods. In a r egression analysis the squared correlation coefficients (R-2) between the m ethods varied between 0.91 and 0.95 for the log transformed values. For wor kplace monitoring, results from the methods using polyclonal antibodies wil l be relatively comparable. High levels of alpha-amylase might differ in ab solute numbers,vith a factor of two or more between the different methods b ut will anyway be considered as high and should result in preventive action s. On the other hand, this study also shows that despite the relative agree ment between methods, there is a clear need for standardization. (C) 2000 B ritish Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.