Warning:

This document is being maintained for historical purposes, but is now out of date. To view current guidelines please visit:

• STD Treatment Guidelines   at http://www.cdc.gov/STD/treatment

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1993 Sexually Transmitted Diseases Treatment Guidelines

09/24/1993

SUGGESTED CITATION
Centers for Disease Control and Prevention. 1993 Sexually
transmitted diseases treatment guidelines. MMWR 1993;42(No. RR-14):
{inclusive page numbers}.

CIO Responsible for this publication:
National Center for Prevention Services,
Division of Sexually Transmitted Diseases and HIV Prevention

Diagnostic Considerations and Use of Serologic Tests -
     
     Darkfield examinations and direct fluorescent antibody tests
of lesion exudate or tissue are the definitive methods for
diagnosing early syphilis. Presumptive diagnosis is possible with
the use of two types of serologic tests for syphilis: a)
nontreponemal (e.g., Venereal Disease Research Laboratory {VDRL}
and RPR, and b) treponemal (e.g., fluorescent treponemal antibody
absorbed {FTA-ABS} and microhemagglutination assay for antibody to
T. pallidum {MHA-TP}). The use of one type of test alone is not
sufficient for diagnosis. Nontreponemal test antibody titers
usually correlate with disease activity, and results should be
reported quantitatively. A fourfold change in titer, equivalent to
a change of two dilutions (e.g., from 1:16 to 1:4, or from 1:8 to
1:32), is necessary to demonstrate a substantial difference between
two nontreponemal test results that were obtained using the same
serologic test. A patient who has a reactive treponemal test
usually will have a reactive test for a lifetime, regardless of
treatment or disease activity (15%-25% of patients treated during
the primary stage may revert to being serologically nonreactive
after 2-3 years). Treponemal test antibody titers correlate poorly
with disease activity and should not be used to assess response to
treatment.

     Sequential serologic tests should be performed using the same
testing method (e.g., VDRL or RPR) by the same laboratory. The VDRL
and RPR are equally valid, but quantitative results from the two
tests cannot be directly compared because RPR titers are often
slightly higher than VDRL titers.

     Abnormal results of serologic testing (unusually high,
unusually low, and fluctuating titers) have been observed among
HIV-infected patients. For such patients, use of other tests (e.g.,
biopsy and direct microscopy) should be considered. However,
serologic tests appear to be accurate and reliable for the
diagnosis of syphilis and for evaluation of treatment response for
the vast majority of HIV-infected patients.

     No single test can be used to diagnose neurosyphilis among all
patients. The diagnosis of neurosyphilis can be made based on
various combinations of reactive serologic test results,
abnormalities of cerebrospinal fluid (CSF) cell count or protein,
or a reactive VDRL-CSF (RPR is not performed on CSF) with or
without clinical manifestations. The CSF leukocyte count is usually
elevated ( greater than 5 WBC/mm3) when active neurosyphilis is
present, and it is also a sensitive measure of the effectiveness of
therapy. The VDRL-CSF is the standard serologic test for CSF; when
reactive in the absence of substantial contamination of the CSF
with blood, it is considered diagnostic of neurosyphilis. However,
the VDRL-CSF may be nonreactive when neurosyphilis is present. Some
experts recommend performing an FTA-ABS test on CSF. The CSF
FTA-ABS is less specific (i.e., yields more false positives) for
neurosyphilis than the VDRL-CSF; however, the test is believed to
be highly sensitive.

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