What is the Difference Between LoD and LoQ?

The key difference between Limit of Detection (LoD) and Limit of Quantification (LoQ) lies in their sensitivity and precision. LoD is the lowest concentration of an analyte that can be detected, while LoQ is the lowest concentration at which the analyte can not only be detected but also measured with acceptable precision and accuracy.

• Limit of Detection (LoD): LoD is the smallest amount of an analyte that can be distinguished from the absence of the substance. It is determined by utilizing both the measured Limit of Blank (LoB) and test replicates of a sample known to have a low concentration. Typically, the confidence level for LoD is 99%.
• Limit of Quantification (LoQ): LoQ is the lowest concentration at which the analyte can be reliably detected and measured with predefined goals for bias and imprecision. It is determined by assay's precision at low analyte levels and is a measure of functional sensitivity. LoQ may be equivalent to LoD or it could be at a much higher concentration.

In summary, LoD represents the lowest concentration of an analyte that can be detected, while LoQ represents the lowest concentration at which the analyte can be detected and measured with acceptable precision and accuracy. LoQ is usually higher than LoD.

Comparative Table: LoD vs LoQ

The following table highlights the differences between the Limit of Detection (LoD) and the Limit of Quantitation (LoQ):

In summary, LoD refers to the smallest concentration of an analyte that can be detected, while LoQ refers to the lowest concentration at which the analyte can be both detected and quantified reliably. LoQ is typically higher than LoD, as it reflects not only the ability to detect the analyte but also the accuracy and precision of the quantification process.