A 23-year-old woman presents with a 5-day history of vaginal…

A 23-year-old woman presents with a 5-day history of vaginal itching, burning vulvar discomfort after urination, and a new vaginal discharge. A pelvic examination reveals a thick, white vaginal discharge and an examination of the external genitalia reveals significant vulvar edema and erythema. She has no other medical problems, takes no medications, and reports one prior episode of vulvovaginal candidiasis about three years prior. Which one of the following is the preferred initial step in attempting to make a diagnosis of vulvovaginal candidiasis in a woman with suspected uncomplicated vulvovaginal candidiasis?