If a test result is detected but not quantified, what does this indicate about the concentration relative to LOD and LOQ?

If a test result is detected but not quantified, what does this indicate about the concentration relative to LOD and LOQ?

• A. It is below LOD.
• B. It is above LOQ.
• C. It is invalid data.
• D. It is above LOD but below LOQ.

Answer: (D)

When a result is detected but not quantified, the concentration sits between the detection and quantification limits. It is high enough to be distinguished from background noise (above the limit of detection), but not high enough to be measured with acceptable accuracy and precision (below the limit of quantification). The limit of detection marks the smallest amount that can be confidently detected, while the limit of quantification is the smallest amount that can be measured reliably. So this scenario means the substance is present, but a numeric concentration cannot be reported.

When a result is detected but not quantified, the concentration sits between the detection and quantification limits. It is high enough to be distinguished from background noise (above the limit of detection), but not high enough to be measured with acceptable accuracy and precision (below the limit of quantification). The limit of detection marks the smallest amount that can be confidently detected, while the limit of quantification is the smallest amount that can be measured reliably. So this scenario means the substance is present, but a numeric concentration cannot be reported.