Most abnormal Pap tests are caused by human papillomavirus (HPV) infections. Other types of infection%u2014such as those caused by bacteria, fungi (yeast), or protozoa (Trichomonas) %u2014 sometimes lead to minor changes on a Pap test called atypical squamous cells of undetermined significance (ASC-US). The most common cause is HPV infection. Natural cervical cell changes (atrophic vaginitis) related to menopause can also cause an abnormal Pap test.
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