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Test characteristics: Difference between revisions
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== Biological variation == | == Biological variation == | ||
The human body is tightly regulated by homeostasis, but no compound in the blood stays at the exact same level over time. The concentration of compounds in the blood change with age, time of day, food intake, | The human body is tightly regulated by homeostasis, but no compound in the blood stays at the exact same level over time as the body follows a biological rhythm, causing the concentration of compounds to fluctuate over time. The concentration of compounds in the blood change with age, time of day, food intake, any inflammation in the body, etc. This is called biological variation. | ||
For example, measuring HbA1c over time is important in the follow-up and management of diabetes mellitus. However, as with any biomarker, HbA1c has biological variation, which is approximately 3.2%, meaning that a 3.2% change in HbA1c over time may reflect a normal biological variation in the biomarker rather than an actual increase or decrease in long-term average blood glucose. | |||
== Total variation == | |||
Analytical and biological variation occur simultaneously and increase the ''total variation.'' For example, the analytical variation of HbA1c is 3.0% and the biological variation is 3.2%, yielding a total variation of 4.4%. This means that a change in HbA1c of less than 4.4% may not reflect a change in long-term average blood glucose but rather a result of analytical and biological variation. | |||
== Reference range == | == Reference range == | ||