Table 1 Most common problems in micro-structural assessment of the lung

Reference space

Lung volume not measured

Avoid “reference trap” by measuring lung volume and reporting data related to the whole lung

Sampling

Biased by taking tissue samples and fields of view either preferentially (e.g. “most interesting” areas) or always at the same site (e.g. “mid-sagittal section along the main bronchus”)

Use appropriate unbiased sampling protocols (e.g. SURS in combination with fractionator sampling) which gives each part of the lung an equal chance for being analyzed

Orientation

Not taken into consideration

Surface area and length estimation of anisotropic structures require randomization of orientation in space (IUR samples)

Embedding

Shrinkage in paraffin

Avoid shrinkage by using appropriate embedding protocols (e.g. glycol methacrylate after osmication)

Number estimation

Particles counted as profiles on single thin sections

Avoid “dimension trap” by using the disector for unbiased estimation of particle number