Determining Reference Change Values
This article is part of the NiaHealth Research Process series.
When tests of an analyte are repeated, there are a number of reasons why serial results may differ. A changing result may reflect true progression or improvement of a disease (or risk factor), or it could reflect random analytical variation (e.g. analytical imprecision) or intra-individual biologic variation (e.g. around an individual’s own biological setpoint).
Calculation of a reference change value (RCV) can determine if a change in an analyte concentration (absolute delta or % delta) on serial measurement is likely to be due to random variation within the patient or the measurement (Jones et al., 2024). The RCV calculation (available here) takes into account both analytical variation (CVa) and intraindividual variation (CVi) for a given analyte. If the difference between two serial results exceeds the RCV, it is likely to be clinically relevant. If the difference is less than the RCV, then the variation is likely to be related to biological and analytical variations and not considered clinically significant (Timbrell, 2024).
RCVs are only available for biochemical tests. For some other tests (e.g. DXA), least significant change (LSC) values and minimal clinically important differences (MCIDs) are reported.
NiaHealth Approach to RCVs
Where available, NiaHealth will include RCVs on implementation guides for new tests, with the decision of whether to include a comparison of the change in results to the RCV within the dashboard to be made on a test-by-test basis.
Our editorial standards & process
At NiaHealth, our mission is to make proactive health possible for all Canadians—by combining science with humanity. We believe that rigorous, evidence-informed health information should never feel out of reach. Every word we publish is intentional. We choose language that empowers rather than overwhelms, clarifies rather than complicates, and respects the lived experiences behind every health question. Learn more here.
