CPT® Code 87166

1. Indications

The dark field examination is indicated for the following conditions and scenarios:

• Syphilis Diagnosis This procedure is primarily performed to identify Treponema pallidum spirochetes, which are responsible for syphilis, particularly in patients presenting with symptoms suggestive of this sexually transmitted infection.
• Microorganism Identification It is utilized for the detection of other microorganisms that can be visualized against a dark background, aiding in the diagnosis of various infections.
• Specimen Analysis from Various Sources The examination can be conducted on specimens obtained from different anatomical sites, including penile, vaginal, oral, skin, or lymph nodes, depending on the clinical presentation.

2. Procedure

The dark field examination involves several procedural steps to ensure accurate results:

• Specimen Collection If the specimen is from a lymph node, a lymph node aspiration biopsy is performed first to obtain the necessary sample. For specimens from ulcerative lesions on the skin or mucous membranes, the area is cleaned and abraded with gauze to prepare it for sampling.
• Sample Preparation After cleaning the lesion, it is gently squeezed to extract a drop of serous transudate. This drop is then placed on a glass slide, which is subsequently covered with a cover slip to create a suitable environment for microscopic examination.
• Microscopic Examination The prepared slide is examined using a microscope equipped with a dark-field condenser or a phase contrast microscope. This specialized equipment enhances the visibility of motile spirochetes, allowing for their identification and assessment.

3. Post-Procedure

After the dark field examination, the laboratory will analyze the slide for the presence of motile spirochetes. The results will be documented and reported to the requesting physician. Depending on the findings, further diagnostic steps or treatments may be recommended. It is essential for healthcare providers to follow up with patients regarding the results and any necessary interventions based on the examination outcomes.