What is a smear test (wipe test) and when is it performed in a radiological setting?

• A. A wipe test measures airborne contamination levels.
• B. A wipe test checks for removable surface contamination; performed after spills, cleanup, or periodically to verify surface cleanliness.
• C. A wipe test determines patient contamination.
• D. A wipe test validates calibration of a radiation detector.

Answer: (B)

In radiological protection, a smear test (wipe test) is used to assess what contamination can be removed from a surface. A wipe is used to sample a defined area, and the wipe is then analyzed for radioactivity. This tells you how much contamination is removable, which is important because removable contamination can be transferred by touch or cleaning personnel and recontaminate other areas.

This test is typically performed after spills and cleanup to verify that decontamination was effective, and it can also be done periodically as part of routine surface surveys to confirm surfaces remain clean. It focuses on removable contamination, not the total or fixed contamination that might remain on a surface after proper cleaning. It’s different from airborne monitoring (which measures contamination in the air) and it doesn’t assess patient contamination or calibrate detectors.