Is it possible to correctly assess the pre-analytical characteristics of faecal tests?

ISO 15189 (Medical laboratories—Requirements for quality and competence) requires the sources of variation to be assessed in all phases of the examination process. “Section 5.5.1.4. Measurement uncertainty of measured quantity values” requires the laboratory to “determine measurement uncertainty for each measurement procedure in the examination phase used to report measured quantity values on patients’ samples” (1). The laboratory shall define the performance requirements for the measurement uncertainty of each measurement procedure and regularly review estimates of uncertainty measurement.