<prompt> A patient presents with painful blister along the chest wall. All of the following tests are useful for diagnosis except?Direct Fluorescent antibodyPolymerase chain reactionTzansk smearLDH levels  <response>: Ans. d LDH levels.Note vesicles along the dermatome of a thoracic nerve caused by varicella-zoster virus. Laboratory studies for VZV include the following: Direct fluorescent antibody DFA testing of vesicular fluid or a corneal lesion Polymerase chain reaction PCR testing of vesicular fluid, a corneal lesion, or blood Tzanck smear of vesicular fluid lower sensitivity and specificity than DFA or PCR.Image source- stylefont-family: Times New Roman, Times, serif 