Negative Control
Definition
A sample known not to contain the target antigen. Run alongside case samples to detect contamination or non-specific background reactivity. A reactive negative control means the assay cannot distinguish true signal from artefact and the run is invalid.
- Purpose
- Confirms the assay is not producing false positives
- Composition
- Sample confirmed free of the target antigen
- Run alongside
- Case samples and a positive control in the same batch
- Failure meaning
- A reactive result invalidates the entire run
Common questions
What causes a negative control to react unexpectedly?+
Reagent cross-contamination, carryover between wells, non-specific binding, or a degraded reagent lot are the usual causes. Whatever the cause, the analyst must discard the batch's results and rerun the assay with fresh materials before reporting anything.
How is a negative control different from a blank?+
A blank typically contains no biological material at all, testing the reagents and equipment alone, while a negative control is a real sample known to lack the target antigen. The negative control checks for false positives arising specifically from the biological matrix, not just the reagents.
Related terms
- Positive Control
- A sample of known composition containing the target antigen at a concentration that should produce a defined signal. Run alongside case samples...
- Accreditation
- Formal recognition by a standards body (such as UKAS in the UK, A2LA in the US, or NABL in India) that a...
- 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...
- ISO/IEC 17025
- The international standard for testing and calibration laboratories, published jointly by the International Organization for Standardization and the International Electrotechnical Commission. It...
- 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...
- Limit of Quantitation (LOQ)
- The lowest concentration at which the assay can produce a quantitative measurement with acceptable precision and accuracy, typically defined as the concentration...
- OSAC
- Organization of Scientific Area Committees for Forensic Science: established by NIST and DOJ in 2014, it develops consensus forensic standards through structured...
- Proficiency Test
- A blind or semi-blind comparison exercise in which an examiner or laboratory analyses a set of test prints of known ground truth;...
Explained in these topics
- Quality Assurance in Serology LaboratoriesA blank or known-negative sample run to check for false-positive signals from reagent contamination or cross-reaction. A failing negative control indicates con...
- Sensitivity, Specificity, and Quality Controls in Forensic Immunoassays