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Fig. 3 | Particle and Fibre Toxicology

Fig. 3

From: Assessing particle and fiber toxicology in the respiratory system: the stereology toolbox

Fig. 3

Sampling strategies for homogeneously and heterogeneously distributed lung lesions. Systematic random sampling such as SURS and fractionator sampling are well recommended for homogeneously distributed lung lesions where small sample sizes are sufficient to reach a high precision of the estimate. However, site-specific lesions might not be adequately represented in systematic uniform random sampled tissue or fields of view. Different sampling strategies are therefore recommended for heterogeneous lesions in dependence on lung lesion distribution: Focal lesions which are randomly distributed over the whole lung are best addressed with an initial random tissue sampling followed by the proportionator approach for image acquisition. This enhances the efficiency greatly. If no proportionator is available, a more rigorous image sampling is required to obtain sufficient information as explained in Example IV for the airways. Site-specific lesions as for example in the bronchioles are best approached with stratified sampling in a two-step procedure within randomly sampled histological sections. First, the volume of the compartment of interest is estimated (for example bronchioles) and second, the lesion in the compartment of choice. An example of such a two-step sampling is presented in the Examples II and III for the parenchyma (protocol paragraphs). Note that this approach is still random, though site-specific. SURS and whole lung estimates could still be applied, but are likely to “dilute” the effect; hence subtle pathological changes might be missed. Region-specific lesions such as centrilobular emphysema might be more challenging to assess. If the region-specific lesion can be defined in both control and treated subjects, stratified sampling is recommended. If not, but the lesion is very prominent, SURS is still a valid alternative in combination with pathological description of the region of the lesion. However, certain limitations of the random sampling approach need to be recognized, particularly if the lesions are only very mild and their region not strictly defined

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