VDI 4256 BLATT 1
Bioaerosols and biological agents - Determination of performance characteristics - Culture-based counting methods
|Publication Date:||1 October 2010|
|ICS Code (Other standards related to microbiology):||07.100.99|
|ICS Code (Ambient atmospheres):||13.040.20|
The guideline VDI 4256 Part 1 specifies which statistical characteristics have to be identified for the characterization of the methods for determination of microbial air pollutants based on counting.
Under counting methods are summarized here the methods for quantitative determination of units that are capable of reproduction, i.e. colony-forming units (CFU) from a defined sampling volume on a suitable culture medium.
A difference is made thereby between direct methods where counting takes place directly from the sample (e.g. filters, impaction plates applied on culture media) and indirect methods where counting does not take place before an advanced preparation of the sample (e.g. removal of the bioaerosols from the filter, suspension and dilution).
The differentiation and identification of individual genera and species and their numerical determination as well as the characteristics related to the methods of identification are not subject of this guideline.
This guideline primarily describes such characteristics that shall be determined in the course of a method development. At present there are still no legal regulations and limit values for the limitation of microbial air pollutants. While numerous measurement methods have already been standardized in the meantime thus increasing the comparability of measurement results, these methods have not yet been validated to the global extent as described herein. This guideline provides the instrument for a complete validation as required in the future.
In addition thereto, Section 7 gives guidance to the user of the method when applying the relevant standardized and validated method. This guideline is thus also an aid to the internal quality assurance of a laboratory.
An illustrative computational example where the results of a round robin test have been evaluated with the aid of this guideline is given in Annex A. To facilitate validation and verification, an MSExcel ® evaluation programme is added to this guideline, by means of which the characteristics as herein described can be computed.