Functional Sensitivity
The lowest analyte concentration that can be measured with acceptable imprecision, typically defined as 20% coefficient of variation.
Full Definition
Functional sensitivity represents the practical lower limit of detection for hormone assays, defined as the lowest concentration at which the assay maintains acceptable analytical performance with a coefficient of variation of 20% or less. Unlike analytical sensitivity (limit of detection), functional sensitivity provides a clinically meaningful measure of assay reliability at low concentrations. This parameter is particularly important for hormone tests where low levels have clinical significance, such as thyroid-stimulating hormone in hyperthyroidism or testosterone in hypogonadal patients. Functional sensitivity specifications help clinicians understand the reliability of results near the lower reference range and guide interpretation of suppressed or low-normal values.
Usage
Usage note: Distinguish from analytical sensitivity, which may be lower but less clinically relevant.
In Context
- "The assay's functional sensitivity of 0.02 mIU/L allows reliable detection of suppressed TSH levels." — Laboratory method validation report
- "Results below the functional sensitivity threshold should be interpreted with caution due to increased imprecision." — Clinical interpretation guidelines