LOD and LOQ
Definition
Limit of detection is three times the SD of blank or S/N of 3:1. Limit of quantitation is ten times SD of blank or S/N of 10:1. Below LOD: 'not detected'. Between LOD and LOQ: 'detected, below LOQ' rather than a number.
- LOD definition
- 3x SD of blank, or signal-to-noise 3:1
- LOQ definition
- 10x SD of blank, or signal-to-noise 10:1
- Below LOD reporting
- Not detected
- Between LOD and LOQ reporting
- Detected, below LOQ
Common questions
Why is a result between LOD and LOQ not reported as a specific number?+
Below the LOQ the measurement is not precise enough to be quantitatively reliable, even though the method can still confidently confirm the analyte's presence at that level.
Why do labs validate both LOD and LOQ instead of just one?+
LOD sets the threshold for confidently detecting that an analyte is present, while LOQ sets the threshold for reporting a reliable quantitative value; they answer two different questions in a method's validation.
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