Yes. This is one of the most important things parents need to understand about PANDAS testing. Rapid strep tests miss a meaningful proportion of actual strep infections when used as the only test. Overnight throat cultures are more reliable but still not perfect. Strep can also reside in areas a routine office swab doesn't reach — tonsillar crypts, the perianal area, or the sinuses. The antibody tests used to detect a recent strep infection also have documented limitations. A negative rapid strep test or a single set of normal antibody titers does not close the door on a PANDAS diagnosis if the clinical picture fits. A provider experienced in PANS and PANDAS will know how to look further when standard tests don't tell the whole story.