Syphilis Serology

Observe safety precautions in collection and handling of specimens (see Submission of Specimens under Quick Reference Section), to prevent transmission of bloodborne infections:

1. For blood and serum specimens see Guidelines for Submitting Serologic Specimens under Quick Reference Section. A minimum of 1 ml of serum is necessary for testing.

a. Indicate time and temperature of serum inactivation on the bottom edge of the form, if applicable.

b. Indicate added preservatives on the bottom of the form, if applicable.

2. Cerebrospinal Fluid (CSF): the VDRL slide test is performed weekly.

a. Aseptically collect 1-5 ml of CSF (a minimum of 1 ml).

b. Transfer to clean, dry, sterile tube.

c. Stopper specimen tube tightly. Use of parafilm alone is not satisfactory as it usually leaks in transit.

d. Label with patient's name and date of collection.

e. Indicate "spinal fluid" or "CSF" on form.

f. When submitting CSF supernatant fluid, note original appearance of the spinal fluid on the form.

g. See general instructions for submission of serologic specimens to OSPHL (Miscellaneous Serology Section).

Precautions

CSF visibly contaminated with blood or bacteria is unsatisfactory for testing. Merthiolate may be used as a bacteriostatic agent for CSF.

Test Selection

1. RPR Test
The qualitative RPR is routinely performed on all bloods and sera submitted for syphilis serology within one working day of receipt, Monday through Friday. Specimens received after 8 AM may be tested the following work day. A quantitative RPR is performed on specimens with any degree of reactivity.

2. VDRL Test
The VDRL on serum or CSF is performed once a week on Fridays.

3. FTA-ABS (DS) Test
The FTA-ABS (DS) test is usually performed once a week on Tuesdays in the following circumstances:

A. When the FTA is requested by the submitter:

1. On a Reactive, Weakly Reactive, or Negative rough RPR/VDRL result.
2. On a Nonreactive RPR/VDRL when the clinician or laboratory clearly indicates in writing, the FTA-ABS (DS) test is necessary for the following reasons:

1. Patient has lesions or is a suspected early primary case or,
2. Patient has symptoms indicating possible latent or tertiary stages, i.e., neurological or cardiovascular manifestations.

B. When the FTA is not requested by the submitter:

1. On a RPR test which is reactive on a person who is less than 50 years old.
2. On a RPR test which is reactive on a premarital or prenatal specimen.

Reporting

For all syphilis tests, a computer-generated report is sent to the submitting provider or facility; a duplicate copy of all positive reports is sent to the Oregon State Public Health Division, Sexually Transmitted Disease Control Program (STD) for follow-up.

Interpretation of Syphilis Results

Serologic tests provide only indirect evidence of syphilis and may be reactive in the absence of clinical, historical, or epidemiologic evidence of syphilis. Therefore, careful clinical interpretation of test results and other evidence is necessary for proper diagnosis.

Disease states and chemicals known to cause biological false positive (BFP) reactions in syphilis serology follow:

1. Diseases which produce acute biologic false-positive VDRL and RPR results (positive during the course of illness, usually becoming negative within two weeks following illness):

Febrile illnesses in general such as:

atypical pneumonia	chancroid
chicken pox	filariasis
hyperproteinemia	subacute bacterial endocarditis
infectious hepatitis	infectious mononucleosis
leishmaniasis	leptospirosis
yaws	lymphogranuloma venereum
malaria	measles
rat bite fever	pneumococcal pneumonia
relapsing fever	scarlet fever
tuberculosis	typhus fever
vaccinia

Immunizations, drug addiction, pregnancy and aging may also cause acute BFPs.

2. Diseases which produce chronic biologic false-positive VDRL and RPR results(positive indefinitely:

• collagen diseases, especially lupus erythematosus and rheumatoid arthritis
• leprosy
• treponematoses, especially yaws and pinta.

3. Possible causes of biological false-positive FTA-ABS (DS) results:

• collagen diseases
• heroin use
• lupus erythematosus
• rheumatoid arthritis
• treponematoses, especially yaws and pinta.

 

TEST RESULTS		INTERPRETATION
RPR & VDRL	FTA-ABS (DS)
Reactive or weakly reactive	Reactive	These results usually indicate syphilis. Tests should always be repeated on a specimen if doubt exists
	Nonreactive	In absence of historical or clinical evidence of treponemal infection, this test should be considered equivocal.
Reactive or weakly reactive	Nonreactive	"Biologic False Positive" (BFP) reaction. Evaluate for known causes of BFP. Repeat test on a new specimen at 10 days to 2 weeks to confirm the BFP.
Nonreactive	Not done	Treponemal tests are not indicated unless very early or late syphilis is suspected on clinical grounds. A reactive FTA-ABS (DS) test would add weight to the diagnosis of syphilis.

 

Patients with primary syphilis may have a nonreactive result for one or both of the serologic tests when first seen. However, both tests will usually become reactive shortly thereafter. Most patients treated for early syphilis will have reversion of RPR and/or VDRL tests to nonreactive within two years. The FTA-ABS (DS) test will remain reactive after treatment of all stages of syphilis except early primary, including congenital. Nonreactive serologic tests and normal clinical evaluation cannot exclude incubating syphilis.

Reactive minimal reaction in the FTA-ABS (DS) test provides evidence for or against syphilis. Beaded reaction in the FTA-ABS (DS) is most often associated with chronic inflammatory diseases. Repeat testing is indicated in both instances. If test results are still equivocal, a microhemagglutination (MHA) test may be requested from CDC.

 

Treatment Follow-Up

After treatment, patients with early syphilis should be retested at 3-month intervals for one year or until little or no reaction is detected by quantitive RPR or VDRL. For those individuals whose titers remain positive at the end of one year, a nontreponemal test on a yearly basis is recommended. The FTA-ABS (DS) is not recommended for treatment follow-up.

 

References

1. U.S. Department of Health, Education, and Welfare/Public Health Service/Centers for Disease Control and Prevention/Bureau of State Services/Venereal Disease Control Division/Atlanta, Georgia; Criteria and Techniques for the Diagnosis of Early Syphilis, HEW Publication No. (CDC) 98-376.3252A.

2. U.S. Department of Health, Education, and Welfare/Public Health Service/Centers for Disease Control and Prevention, Manual of Tests for Syphilis, 1969; HEW Publication No. 411 Rev.

3. Hynson, Westcott & Dunning, RPR Card Test Procedure Manual.

4. Difco Laboratories, HATTS (Hemagglutination-Treponemal test for Syphilis) Technical Information Sheet.

5. Wentworth, Bertina B. and Franklyn N. Judson, Laboratory Methods for Diagnosis of Sexually Transmitted Diseases. APHA, pp. 19-30, 1984.