Abstract
BackgroundThe aim of this study is to analyze possible random and systematic measurement errors and to detect methodological limits of the previously established method.FindingsTo examine the distribution of random errors (repeatability standard deviation) of the detection procedure, collective samples were taken from two uncontaminated rooms using a sampling vacuum cleaner, and 10 sub-samples each were examined with 3 parallel cultivation plates (DG18). In this two collective samples of new dust, the total counts of Aspergillus spp. varied moderately by 25 and 29% (both 9 cfu per plate). At an average of 28 cfu/plate, the total number varied only by 13%.For the evaluation of the influence of old dust, old and fresh dust samples were examined. In both cases with old dust, the old dust influenced the results indicating false positive results, where hidden moist was indicated but was not present. To quantify the influence of sand and sieving, 13 sites were sampled in parallel using the 63-μm- and total dust collection approaches. Sieving to 63-μm resulted in a more then 10-fold enrichment, due to the different quantity of inert sand in each total dust sample.ConclusionThe major errors during the quantitative evaluation from house dust samples for mould fungi as reference values for assessment resulted from missing filtration, contamination with old dust and the massive influence of soil. If the assessment is guided by indicator genera, the percentage standard deviation lies in a moderate range.
Highlights
The aim of this study is to analyze possible random and systematic measurement errors and to detect methodological limits of the previously established method
The aim of the present study was to analyze possible random and systematic measurement errors and to detect methodological limits of the previously established method caused by statistical broad standard deviations, influence of old dust, sand and sieving, contamination with soil, stability of samples, mass or surface relation, assessment by indicator genera, sampling with filter holder or with vacuum-cleaner
To evaluate the distribution of random errors of the measurement, a collective sample was taken from a non-colonized room using a sampling vacuum-cleaner (Vampirette, Siemens, Germany), and 10 sub-samples each were examined with 3 parallel plates (DG18) from the filtered 63-μm dust fraction
Summary
The aim of this study is to analyze possible random and systematic measurement errors and to detect methodological limits of the previously established method. As there always will be an influence by the outdoor air, we assessed methodological possibilities to control this influence at the level of interpretation of the measurements. The further development of the assessment model was based on two facts influenced by the outdoor air: first, the background load of all species increases in summer. This is compensated through a percent evaluation of moulds relative to the total number. The increased amounts of these genera indicate moisture damage. The percent evaluation of (page number not for citation purposes) http://www.biomedcentral.com/1756-0500/2/218 indicator genera is intended - above a base load in winter
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