4 ms·

That’s why you’re supposed to submit an unused swab with the samples, so that they can make sure the swab itself isn’t the source.

• giantg2 6mo ago
  That only works if both swabs suffered the same contamination. If the contamination is sporadic, then it won't show.
  • etyhhgfff 6mo ago
    And the method to analyze the swabs could also contain contaminations that screw the results.