Reports from disease experts and a national task force underscore a recent uptick in sexually transmitted diseases (STDs) among younger populations, flagging syphilis risk as especially high among young men in same-sex relationships or those infected with HIV.
New statistics from the Centers for Disease Control and Prevention (CDC) paint a grim picture of rising STD rates. In analyzing the three most common types—chlamydia, gonorrhea and syphilis—for the year 2014, the agency reported an increase in cases for the first time in at least 10 years.
From 2013 to 2014 alone, rates for chlamydia, for primary and secondary syphilis, and for gonorrhea have risen by 2.8%, 15.1%, and 5.8%, respectively. The highest rates of gonorrhea and chlamydia were reported among younger populations aged 15 to 24. This age group also represented two-thirds of all reported STD cases.
“America’s worsening STD epidemic is a clear call for better diagnosis, treatment, and prevention,” said Jonathan Mermin, MD, director of National Center for HIV/AIDS, Viral Hepatitis, STD, and Tuberculosis Prevention, in a statement. “STDs affect people in all walks of life, particularly young women and men, but these data suggest an increasing burden among gay and bisexual men.”
Primary and secondary syphilis cases among men who have sex with men (MSM) have been on the rise for at least 15 years. “In 2014, rates of [primary and secondary] syphilis increased among MSM, who account for 83% of reported cases among men when the sex of the partner is known,” according to CDC. More than 50% of these men who received syphilis diagnoses in 2014 were also HIV-positive.
In an update of 2004 recommendations on syphilis screening, the United States Preventive Services Task Force (USPSTF) in a new draft statement gave an “A” rating to screening non-pregnant adults and adolescents at increased risk, placing an emphasis on MSM, and people with HIV. 2013 surveillance data indicate that risk for contracting syphilis is highest between these two groups, the task force indicated.
“One study found that rates of syphilis coinfection were 5 times higher in HIV-positive [men who have sex with men] compared with HIV-positive men who do not have sex with men,” according to the draft statement. Disease prevalence is especially high among those under age 29 and among certain ethnic groups such as blacks and Native Hawaiians/Pacific Islanders.
The quest for more effective syphilis screening tests is a work in progress.
Screening for syphilis currently involves a two-step process: a nontreponemal test (rapid plasma reagin or Venereal Disease Research Laboratory) followed by a treponemal test (Treponema pallidum particle agglutination or fluorescent treponemal antibody absorption) if the first test is positive. Such screening methods detect antibodies of the organism rather than conducting a direct assay. According to the USPSTF, while specificity rates are fairly high among these tests, sensitivity is more variable. As an example, sensitivity rates among the nontreponemal tests can range anywhere from 78% to 86% for detecting primary syphilis infection.
Assay-based, automated treponemal tests have recently emerged as an alternative to the more traditional, two-step process. These include: enzyme-linked immunoassays, chemiluminescence immunoassays, and multiplex flow immunoassays. Such tests “are often used in a reverse sequence screening algorithm, in which an automated treponemal test is performed first, followed by a nontreponemal test (quantitative) if the initial automated treponemal test is positive,” according to USPSTF.
Whether these tests measure up to more traditional methods is still under question. In reviewing several studies that compared the reverse sequence screening algorithm with the two-step approach, USPSTF observed that although the new approach found more cases of syphilis, it yielded more false positives. “Overall, more studies on the reverse-sequence screening algorithm are needed before definitive conclusions can be made on its effectiveness,” the task force concluded.