What does CVI stand for in the context of RCV?

• A. Intra-individual biological variation
• B. Inter-individual variation
• C. Coefficient of Variation Index
• D. Clinical Variation Index

Answer: (A)

CVI stands for intra-individual biological variation—the natural fluctuation of a biomarker within the same person over time. In the RCV framework, this is the biological component of total variation, paired with analytical variation (CV_A) to determine whether a change between successive results is clinically meaningful. The RCV is calculated from the combined variability: it uses the square root of the sum of the squares of CV_A and CV_I, multiplied by a critical value (often 1.96 for 95% confidence). So, a change exceeding the RCV suggests a true, biologically meaningful difference beyond expected variability. Inter-individual variation refers to differences between different people, not within the same person; the other terms aren’t standard descriptors in this context.