Screening for Syphilis

The prevalence of syphilis in the United States began to decline with the introduction of penicillin therapy in the 1940s, falling to about 7,000 cases in 1956. Since then, reported cases of syphilis have increased. In the 1970s, much of the increase was a consequence of infection in men who have sex with men (MSM). The AIDS epidemic produced changes in sexual behavior that have reduced the incidence of syphilis in MSM; however, syphilis has increased dramatically in African Americans, Hispanics, and inner-city residents. This trend peaked in 1990, when more than 50,000 cases of primary and secondary syphilis were reported, representing a 9% increase in just 1 year. Since then, the reported cases of syphilis declined to a low in 2000 but began steadily to increase again subsequently, once again fueled by cases among MSM and provoking concern that salutary changes in sexual behavior in response to the AIDS epidemic may be reversing.

If a patient is not identified and treated during the primary or secondary stages of the disease, the infection becomes latent and is identifiable only by means of laboratory tests until late, often irreversible, clinical manifestations appear. The prevention of destructive cardiovascular and neurologic lesions by means of appropriate screening for latent syphilis is an important task for the primary physician. Because false-positive results are common and are potentially traumatic for the patient, it is critical that the sensitivity and specificity of the various serologic tests be understood.

EPIDEMIOLOGY AND RISK FACTORS (1,2)

With the exception of infection in utero or, rarely, by means of blood transfusion, syphilis is transmitted exclusively by direct sexual contact with infectious lesions. It follows that risk increases with sexual activity. Because syphilis is readily treated with antibiotics, it is less common in populations with access to medical care. The reported incidence of syphilis in nonwhites in the United States is much higher than in whites. Rates are highest in urban areas. It must be remembered, however, when incidence rates in different populations are compared, that case reporting has been shown to be more complete in public clinics than among private practitioners.

The age-specific incidence rates parallel those of gonorrhea, with the peak incidence for both diseases occurring between ages 20 and 25 years. A diagnosis of gonorrhea, nongonorrheal urethritis, HIV infection, or another sexually transmitted disease should be considered a risk factor for syphilis. Drug abuse is an important risk factor. MSM are also at high risk. Coinfection with HIV is common in this population.

The importance of an accurate sexual history in determining the risk for syphilis is obvious. Patients with early syphilis report an average of three recent sexual contacts. The probability that syphilis will develop in a known contact following a single exposure is approximately 30%.

NATURAL HISTORY OF SYPHILIS AND EFFECTIVENESS OF THERAPY (3, 4, 5, 6 and 7)

Treponema pallidum enters the bloodstream within a few hours after inoculation through intact mucous membranes or abraded skin. A primary lesion occurs at the site of the inoculation between 10 and 90 days after contact. The incubation period depends on the size of the inoculum but is usually less than 3 weeks. The painless chancre usually resolves within 4 to 6 weeks, ending the primary stage. The secondary stage is usually heralded by a maculopapular rash that appears approximately 6 weeks after the primary lesion has healed. When the rash subsides, after 2 to 6 weeks, untreated syphilis enters the latent stage (arbitrarily divided into early latent for the first year and late latent thereafter). If untreated, patients with secondary syphilis may relapse clinically during early latency.

Because anorectal or vaginal chancres are not likely to be brought to medical attention, primary syphilis is often not diagnosed among MSM or among women. Whereas more than 40% of syphilis cases are detected in the primary stage among male heterosexuals, only 23% and 11%, respectively, are detected in the primary stage among MSM and among females.

Natural history studies from Oslo, Norway, and Tuskegee, Alabama, indicate that clinically manifest tertiary disease develops in approximately one third of persons with untreated syphilis and that evidence of cardiovascular syphilis can be found in more than one half at autopsy. In the retrospective Oslo study, 10% of patients had clinically evident cardiovascular syphilis, 7% had neurosyphilis, and 16% had gummatous disease. The incidence of cardiovascular syphilis was higher and that of neurosyphilis was lower in the prospective Tuskegee study.

Factors that influence the progression to clinical tertiary disease are incompletely understood. Congenital syphilis or disease contracted before age 15 years does not predispose to cardiovascular tertiary disease. In general, late complications seem more likely to occur among untreated men than among untreated women.

The antibiotic regimens recommended in Chapter 141 are highly effective in eradicating early syphilis. If the response to therapy is appropriately monitored by following the quantitative Venereal Disease Research Laboratory (VDRL) test or rapid plasma reagin (RPR) titer, the risk for late complications is virtually eliminated. Antibiotic treatment of late syphilis has less predictable results. Improvement among patients with general paresis has been reported in 40% to 80% of cases. Not surprisingly, structural cardiovascular changes caused by syphilis are not reversed by antibiotic treatment.

Only gold members can continue reading. Log In or Register to continue