Which specimen is the sample of choice to evaluate latent or tertiary syphilis?

To evaluate latent or tertiary syphilis, cerebrospinal fluid (CSF) is the specimen of choice. This is due to the ability of Treponema pallidum, the causative agent of syphilis, to invade the central nervous system, especially in the later stages of the disease, which includes latent and tertiary phases.

In cases of tertiary syphilis, there can be neurological involvement, manifesting as conditions like neurosyphilis. CSF analysis allows for the detection of specific antibodies against T. pallidum, as well as other indications of infection that may not be apparent in serum or other body fluids. This makes it a crucial specimen for accurately diagnosing and assessing the extent of the disease, particularly when neurological symptoms are present.

Serum samples are typically used for initial syphilis screening and detecting antibodies, but they may not provide sufficient information for evaluating the central nervous system's involvement. Chancre fluid is primarily relevant for primary syphilis, where it can be used to identify the organism directly, but it is not useful for latent or tertiary syphilis. Joint fluid may be examined in cases of symptomatic involvement of the joints but is not a standard specimen for diagnosing latent or tertiary syphilis