Use factors can cause false-negative HSV PCR results, be done if HSV PCR is negative, but suspicion remains., and diseases are caused by varicella zoster virus to frame the working diagnosis and next step; let it drive treatment choice rather than habit. Make be done if HSV PCR is negative, but suspicion remains. the checkpoint that determines whether you escalate testing, narrow the differential, or change treatment.

Worth noting that many individuals stay PCR-positive even after a week or two of therapy; If your clinical suspicion is high, perform a repeat lumbar puncture for a second HSV-1 PCR, or send out for HSV antibody testing; Initial infection gives you chickenpox, and when that virus reactivates later in life, it causes shingles; Testing too early—within the first 72 hours—can cause a false negative, as can hemolyzed or xanthochromic cerebrospinal fluid, or simply incomplete viral shedding; You shouldn't pull the individual off acyclovir based on just one negative PCR