When Laboratory Results Make No Sense

Use of tapelift sampling is a perfect method to determine the type of mould growing on a substrate, say on a wall, ceiling and other flat surfaces. Since the mould sticks on the tape with it’s structures intact, identification of most moulds is possible to genus if not species. Results from a tape sample are generally a listing of the identified moulds in a ranking order.

Due to lack of standardized methods labs tend to report analytical results of tape samples in different ways. Below are a few examples:

Laboratory 1:

• Cladosporium sp- Heavy growth
• Penicillium sp- Moderate growth
• Ulocladium sp- Slight growth
• Stachybotrys sp (a few spores)

Laboratory 2:

• Cladosporium sp- Major
• Penicillium sp- Minor
• Ulocladium sp- Trace
• Stachybotrys sp- trace

Laboratory 3:

• Spores, conidiophores and hyphae of Cladosporium detected
• Spores, conidiophores and hyphae of Penicillium detected
• Spores, conidiohores, and hyphae of Ulocladium detected
• Spores of Stachybotrys detected

Which of these lab results would be useful to a mould investigator? The only common factor in these results is that the 3 labs have identified the same types of mould. The additional information they have provided is rather subjective and/or confusing and hence of little if any practical use to a mould investigator.

One great disadvantage of tape sample is that the area analysed is very small. Unless one has taken hundreds of tape samples, trying to apply results of one or two tape samples to the whole building is a big mistake. For example if a lab reports that the growth on the tape was heavy, it’s a big mistake to say there was heavy growth of mould in the building. Visual assessment of the extent and density of mould growth in a building is more reliable and of practical use than the assessment of tape or bulk samples in the laboratory. 

In conclusion, use of tape lift samples as a tool for mould investigation should be limited to determining the type of mould present on a specific surface.