What is the role of positive controls in molecular assays?

The role of positive controls in molecular assays is crucial for verifying that the assay system is functioning as intended. Positive controls contain a known quantity of the target nucleic acid, which allows the assay to confirm that all elements, including reagents and equipment, are operational and capable of detecting the analyte of interest. When the positive control is processed along with test samples, it should yield a predictable and consistent result, ensuring that any negative results obtained from samples are not due to a failure of the assay itself. This validation is fundamental for achieving reliable and accurate results in molecular diagnostics.

In contrast, the other choices do not accurately represent the primary role of positive controls. Detecting contamination in reagents typically involves negative controls, which are designed to show the presence of undesired substances. Monitoring the sensitivity of the assay relates more closely to the assay design and performance evaluation than to the function of positive controls. Lastly, serving as a negative control is the opposite of what a positive control does; negative controls are used to confirm that no unexpected reactions occur in the absence of the target.