Which diagnostic evaluation is most reliable for postmenopausal bleeding?

The most reliable diagnostic evaluation for postmenopausal bleeding is the endometrial biopsy. This procedure involves obtaining a tissue sample from the endometrium, which allows for direct examination of the lining of the uterus. Identifying abnormalities, such as endometrial hyperplasia or malignancy, is crucial in evaluating the cause of postmenopausal bleeding.

Given that postmenopausal bleeding can be associated with serious conditions, including endometrial cancer, an endometrial biopsy provides not only a definitive diagnosis but also important information on the underlying pathology. Other tests, like the Pap smear, are not designed to assess the endometrium and are more focused on cervical screening. Serum prolactin levels may help evaluate certain endocrine disorders but do not directly address the causes of postmenopausal bleeding. Lastly, serum FSH and LH levels can indicate ovarian function or decline but are not specific for diagnosing the causes of bleeding in postmenopausal individuals. Therefore, the endometrial biopsy stands out as the most reliable and informative option in this clinical scenario.