Which type of control ensures the test system can produce a positive result when a target is present?

• A. Positive control.
• B. Negative control.
• C. Blank control.
• D. Procedural control.

Answer: (A)

A positive control demonstrates that the assay can actually detect the target when it is present. It uses a sample known to contain the target at a detectable level, and running it through the same steps as test samples should produce a positive result. This confirms that the reagents, detection method, and procedure are functioning properly, so a positive result for real samples can be trusted. If the positive control fails to yield a positive result, you don’t know whether a negative sample means the target isn’t there or the assay isn’t working at all. That’s why the positive control is the best way to verify the system’s ability to produce a positive result when the target is present. For contrast, a negative control should remain negative to show there’s no unintended signal, and blanks or procedural controls help check for contamination and proper protocol execution, but they don’t confirm that the assay can detect the target.