Health MOTs: consider reference change values

In their article Buss and colleagues state: “Furthermore, many common tests, such as serum lipids, have substantial measurement variation, making repeated measurements (as might occur in a yearly ‘MOT’) challenging to interpret.”1Although true, the term “measurement variation” implies that the expected maximum difference between two results from the same healthy patient over a period of time is only caused by variation in the laboratory method (analytical variation) (CVa). Natural variation (biological variation) (CVb) is also a significant contributor, however, and is important to consider.For example, the total cholesterol in a single person can naturally vary by 6.0%2 (CVb) independently of the CVa. Therefore, if a patient has a total cholesterol of 5.1 mmol/L on their first yearly health MOT—which borders the upper “healthy” limit of 5.2 mmol/L—and if the CVa is an additional 2.1%, then a result of 5.8 mmol/L one year later is not a significant increase,2 despite appearing…
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