Final answer:
The most sensitive test to diagnose HSV is the Polymerase Chain Reaction (PCR), which offers rapid and reliable results.
Step-by-step explanation:
The most sensitive laboratory test to diagnose Herpes Simplex Virus (HSV) is Polymerase Chain Reaction (PCR). PCR testing is highly preferred because it provides rapid and reliable results without the need to wait for culture amplification, which makes it especially useful for detecting systemic infections. While immunostaining methods and culture from lesions are alternative options, they generally require more time and are less sensitive compared to PCR. Moreover, if symptoms continue and PCR results are negative, serologic techniques to detect antibodies against HSV can also be employed to assist in diagnosis.