I work in a small hospital lab and a positive and negative swab (quality control) is performed on each new lot and shipment of tests. This applies to all tests in the lab; pregnancy, Strep, Flu, RSV, Clostridium difficile, Mono, HIV, drug screens, and the list could go on. This has always been a requirement to meet CLIA requirements. it is to ensure the quality of the test before any tests are run on patients. Quality control is a big part of providing quality care to patients. Hope this clears it up a bit for you.