Negative Control Reference Standard

What is a negative control?

A negative control is a fundamental quality control measure in scientific experiments. Its purpose is to ensure the accuracy and specificity of experimental results and to eliminate the possibility of false positives.

Core Definition:

In an experiment, a negative control is a sample or group known not to produce a positive reaction. It contains all experimental components except the target substance.

Function and Purpose:

*Verify Specificity: If a negative control shows a positive result (i.e., a negative control that should be negative shows a positive result), it indicates a problem with the entire experimental system, such as:Reagent Contamination: Contamination of reagents or equipment with the target substance.

*Nonspecific Binding: Binding of detection tools such as antibodies or probes to non-target molecules.

*Operational Error: Improper operation introduces extraneous contaminants.

*Baseline Setting: Helps determine the cut-off value for determining a positive result. The signal from any test sample must be significantly greater than that from the negative control to be considered positive.

Application

PCR testing (e.g., COVID-19 nucleic acid testing):

*Negative control: Pure water or buffer solution that does not contain any viral nucleic acid.

*If the negative control result is positive, all sample results from this test are unreliable, potentially due to contamination, and must be retested.

Immunohistochemistry/ELISA (protein testing):

*Negative control: Tissue or sample treated with an unrelated antibody or a buffer solution without the primary antibody.

*If staining or signal is observed in this control, the staining is nonspecific and the experimental results are invalid.

Drug trials:

*Negative control: An experimental group given a placebo (e.g., a sugar pill) to compare and evaluate the actual effects of a drug.