In assay performance, differentiate LOD and LOQ.

In assay performance, differentiate LOD and LOQ.

• A. LOD is the lowest detectable quantity; LOQ is the lowest quantifiable with acceptable precision and accuracy.
• B. LOD is the lowest quantity quantifiable; LOQ is the lowest detectable quantity.
• C. LOD is higher than LOQ; LOQ is undefined.
• D. LOD and LOQ are synonymous.

Answer: (B)

In assay performance, distinguish detection from quantification. The limit of detection is the smallest amount of analyte that can be distinguished from a blank or background noise with reasonable confidence; it means you can say something is present, but you cannot reliably measure its exact amount at that level. The limit of quantification is the smallest amount that can be measured with acceptable precision and accuracy, meaning the result is quantitative and dependable. In practice, LOD and LOQ are often derived from the calibration data using the signal’s variability and the slope of the response. A common rule is LOD ≈ 3 times the standard deviation of the blank divided by the slope (3σ/S), while LOQ ≈ 10 times the standard deviation of the blank divided by the slope (10σ/S). This reflects the idea that you need a stronger signal-to-noise ratio to quantify than to simply detect. So, the best description is that LOD is the lowest detectable quantity, whereas LOQ is the lowest quantifiable quantity with acceptable precision and accuracy (and LOQ is typically higher than LOD).

In assay performance, distinguish detection from quantification. The limit of detection is the smallest amount of analyte that can be distinguished from a blank or background noise with reasonable confidence; it means you can say something is present, but you cannot reliably measure its exact amount at that level. The limit of quantification is the smallest amount that can be measured with acceptable precision and accuracy, meaning the result is quantitative and dependable.

In practice, LOD and LOQ are often derived from the calibration data using the signal’s variability and the slope of the response. A common rule is LOD ≈ 3 times the standard deviation of the blank divided by the slope (3σ/S), while LOQ ≈ 10 times the standard deviation of the blank divided by the slope (10σ/S). This reflects the idea that you need a stronger signal-to-noise ratio to quantify than to simply detect.

So, the best description is that LOD is the lowest detectable quantity, whereas LOQ is the lowest quantifiable quantity with acceptable precision and accuracy (and LOQ is typically higher than LOD).