Limit of quantitation (LOQ)
Definition
The lowest concentration at which the assay can produce a quantitative measurement with acceptable precision and accuracy, typically defined as the concentration where the coefficient of variation falls below 20%. The LOQ is always higher than the LOD. Between the LOD and LOQ the analyte can be detected but not reliably measured.
Related terms
- Limit of detection (LOD)
- The lowest concentration of analyte that produces a signal reliably distinguishable from the instrument noise, conventionally three times the standard deviation of...
- Cross-reactivity
- The capacity of an antibody raised against one analyte to bind structurally related compounds. In RIA, cross-reactivity is the main driver of...
- Epitope degradation
- The destruction or alteration of the molecular site on an antigen that an antibody recognises, caused by hydrolysis, oxidation, UV radiation, or...
- Negative control
- A sample known not to contain the target antigen. Run alongside case samples to detect contamination or non-specific background reactivity. A reactive...
- Positive control
- A sample of known composition containing the target antigen at a concentration that should produce a defined signal. Run alongside case samples...
- Repeatability
- The agreement between successive measurements of the same specimen made by the same analyst, on the same instrument, in the same laboratory,...
- Reproducibility
- The closeness of agreement between measurements obtained under changed conditions: different analysts, different instruments, different laboratories, or different times. A wider measure...
- Robustness
- The capacity of a method to remain unaffected by small, deliberate variations in its operating parameters, such as slight changes in temperature,...
- Selectivity
- The ability of a method to measure the target analyte specifically, even when other substances that might plausibly appear in a real...
Explained in these topics
- Method Validation and Fitness for PurposeThe smallest quantity at which a measurement can be reported with acceptable precision and accuracy, typically the blank mean plus ten standard deviations. Abo...
- Sensitivity, Specificity, and Quality Controls in Forensic ImmunoassaysThe lowest concentration at which the assay can produce a quantitative measurement with acceptable precision and accuracy, typically defined as the concentrati...