Syphilis rates in the United States have been increasing in recent years, with almost 20,000 cases occurring in 2014 -- the highest number of cases in more than 10 years.
In light of this upward trend, the U.S. Preventive Services Task Force (USPSTF) published its final recommendation statement(www.uspreventiveservicestaskforce.org) and evidence summary(www.uspreventiveservicestaskforce.org) on June 7, recommending that asymptomatic, nonpregnant adults and adolescents who are at increased risk for syphilis be screened for the disease -- an "A" recommendation.
"Clinicians play an important role in helping to control the rising rates of syphilis infection and should focus on screening those at increased risk," said USPSTF member Ann Kurth, Ph.D., R.N., M.P.H., in a news release.(www.uspreventiveservicestaskforce.org)
The AAFP issued its own parallel recommendation on syphilis screening on June 8.
The USPSTF said patients at highest risk for syphilis infection include men who have sex with men (MSM) and people who are living with HIV infection. Based on 2014 surveillance data, 61 percent of cases of primary and secondary syphilis occurred among MSM, and almost half of MSM who were diagnosed as having syphilis also were infected with HIV.
- On June 7, the U.S. Preventive Services Task Force published its final statement recommending that nonpregnant adults and adolescents who are at increased risk for syphilis be screened for the disease.
- This final recommendation is consistent with and updates the USPSTF's 2004 recommendation.
- After posting the draft recommendation statement for public comment in December, the USPSTF responded to a variety of comments, including one calling for clarification of which populations were considered to be at increased risk.
This final recommendation is consistent with and updates the USPSTF's 2004 recommendation on screening for syphilis in the at-risk population.
The recommendation also complements a 2009 recommendation statement(www.uspreventiveservicestaskforce.org) in which the task force recommended screening for syphilis infection in all pregnant women -- also an "A" recommendation -- which, again, the AAFP mirrored in its own recommendation.
Response to Public Comment
After posting the draft recommendation statement for public comment in December, the USPSTF received a number of requests to clarify which populations were considered to be at increased risk. In response, the task force added language to the Clinical Considerations section explaining that men and women living with HIV (including men who are not MSM) are considered to be at increased risk for syphilis.
In addition, men (not just young males) and women who have identified sociodemographic risk factors associated with increased prevalence rates of syphilis may be considered at increased risk. Risk factors include male gender combined with age younger than 29, certain racial/ethnic groups, a history of incarceration and a history of working in the sex industry. Regional variations in prevalence have also been documented.
Also in response to public comments, the USPSTF provided updated surveillance data from 2014. In addition, some commenters requested additional information on various screening tests, but the task force determined that the tests are outside the scope of this recommendation for a variety of reasons (e.g., diagnostic tests performed in symptomatic patients or newer technologies not yet evaluated for screening in a primary care setting).
Additional Risk Factors
The recommendation statement said men accounted for 91 percent of all cases of primary and secondary syphilis in 2013, with those ages 20-29 having the highest disease prevalence -- nearly three times higher than that of the U.S. male population overall.
Syphilis prevalence rates also are higher among specific racial/ethnic groups. In 2014, for example, rates of primary and secondary syphilis were highest among blacks (18.9 cases per 100,000), followed by Hispanics (7.6 cases per 100,000), American Indians/Alaska Natives (7.6 cases per 100,000), native Hawaiians/Pacific Islanders (6.5 cases per 100,000), whites (3.5 cases per 100,000) and Asians (2.8 cases per 100,000).
The USPSTF noted that the risk for syphilis infection can be reduced by consistent and correct use of condoms, limiting sexual activity to a mutually monogamous relationship with a partner who does not have syphilis, or abstaining from sex.
Accuracy of Screening Tests
Screening for syphilis usually requires a two-step process, with a nontreponemal test such as a rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test performed first, followed by a confirmatory treponemal antibody detection test such as a Treponema pallidum particle agglutination (TP-PA) or fluorescent treponemal antibody absorption (FTA-ABS) test. Positive results on both types of tests indicate past or present syphilis infection.
Sensitivity of the RPR and VDRL tests is estimated to be 86 percent and 78 percent, respectively, for detecting primary syphilis infection, 100 percent for detecting secondary syphilis infection, and 98 percent and 96 percent, respectively, for detecting latent syphilis infection.
Specificity ranges from 85 percent to 99 percent for each test but may be reduced in people who have pre-existing conditions (i.e., collagen vascular disease, pregnancy, IV drug use, advanced malignancy, tuberculosis, malaria, and viral or rickettsial disease) that produce false-positive results.
The TP-PA and FTA-ABS tests have a sensitivity of 88 percent and 84 percent, respectively, for detecting primary syphilis infection and a sensitivity of almost 100 percent for detecting syphilis infection in other stages, as well as a specificity of 96 percent to 97 percent.
When the USPSTF released its draft recommendation back in December, Jennifer Frost, M.D., medical director for the AAFP Health of the Public and Science Division, told AAFP News that 15 years ago, syphilis was an uncommon diagnosis in the United States.
"The rate has more than doubled since then, particularly in gay and bisexual men," she said. "And although the USPSTF's recommendation mirrors its 2004 recommendation, we need to have heightened awareness about whether our patients are at risk so that they can be informed about the importance of prevention, screened if at increased risk and treated if their tests are positive."
More From AAFP
American Family Physician: Syphilis: A Re-emerging Infection
(Sept. 1, 2012)