Verification of equipment for measuring the diffusion capacity of the lung for carbon monoxide.

The JENSEN et al. [1] study represents a tremendous and successful effort on quality assurance and quality control as part of a large clinical study. The study or probably more likely the presentation of the study by JENSEN et al. [1] has a few limitations seen from a metrological point of view to which I want to draw attention. Traceability is the key stone of quality control of measurements and must be addressed in all metrological studies. Metrological traceability is a property of a measurement result relating the result to a stated metrological reference through an unbroken chain of calibrations of a measuring system or comparisons, each contributing to the stated measurement uncertainty [3]. Thus, traceability refers to the completeness of the information about every step in a process chain.