What is the difference between the detection limit and the quantitation limit?

• A. They are the same.
• B. Detection limit is the smallest amount that can be quantified with acceptable accuracy and precision.
• C. Detection limit is the smallest amount detectable.
• D. Detection limit is the smallest amount detectable; quantitation limit is the lowest amount that can be quantified with acceptable accuracy and precision.

Answer: (D)

The key idea is that there are two thresholds: one for merely seeing a signal above background, and a higher one for measuring it reliably. The detection limit is the smallest amount of analyte that can be distinguished from the blank or background noise; it does not require an accurate or precise quantity to be reported. The quantitation limit is higher and represents the smallest amount that can be quantified with acceptable accuracy and precision, meaning you can report a numerical value with a defined confidence. In practice, LOD is about detectability (presence/absence with some confidence), while LOQ is about reliable measurement.

That’s why the correct statement says the detection limit is the smallest detectable amount, and the quantitation limit is the lowest amount that can be quantified with acceptable accuracy and precision. The other options are incomplete or incorrect because they either claim they’re the same, or they equate detection with quantification, or they omit the requirement for accuracy and precision.