CPT® Code 87166

A dark field examination, also known as dark field microscopy, is a specialized laboratory procedure used to analyze specimens obtained from various sources, including penile, vaginal, oral, skin, or lymph nodes. This examination is particularly valuable for identifying certain microorganisms that are best visualized against a dark background, such as the Treponema pallidum spirochetes, which are the causative agents of syphilis. The procedure is designed to enhance the visibility of these microorganisms, allowing for accurate detection and diagnosis. In cases where the specimen is derived from a lymph node, a lymph node aspiration biopsy is typically performed prior to the dark field examination. For specimens collected from ulcerative lesions on the skin or mucous membranes, the lesion is first cleaned and abraded with gauze to prepare it for sampling. Subsequently, the lesion is gently squeezed to obtain a drop of serous transudate, which is then placed on a glass slide and covered with a cover slip. The prepared slide is examined under a microscope equipped with a dark-field condenser or a phase contrast microscope to assess the presence or absence of motile spirochetes. It is important to note that CPT® Code 87166 is specifically used when the laboratory conducting the examination is not responsible for the collection of the specimen, whereas CPT® Code 87164 should be utilized when the examination includes specimen collection.