STDs: Research aims at hidden epidemic’

You suspect that your 17-year-old patient may have a chlamydia infection. Thanks to a nucleic acid amplification screen on a urine specimen, you are able to detect the sexually transmitted disease (STD) and report the results the next day.

Nucleic acid amplification tests (NAATs) that allow screening and diagnosis of such STDs as chlamydia and gonorrhea rank as top advances in the fight against these and other infections, say reproductive health experts.

"The introduction of nucleic acid amplification tests, specifically for chlamydia and gonorrhea, has provided incredible improvement in our ability to accurately diagnose these infections in a whole variety of populations, whether symptomatic or not," observes Julius Schachter, PhD, professor in the department of laboratory medicine at the University of California San Francisco (UCSF) and director of the UCSF Chlamydia Research Laboratory at San Francisco General Hospital Medical Center.

NAATs offer the ease of urine collection in men and women, with the added benefit of sensitivities and specificities similar to tests performed on urethral or endocervical samples.1

The impact of NAATs on test sensitivity and ease of sampling has been one of the most important advances in the past 25 years, says Edward Hook III, MD, professor of medicine and epidemiology at the University of Alabama at Birmingham and director of the STD control program for the Jefferson County (AL) Department of Health.

Similar diagnostic advances are needed if U.S. clinicians are to stem the spread of what has been termed "the hidden epidemic" of STDs.2 An estimated 15 million cases of STDs occur in the United States each year.3 On a global scale, the Geneva-based World Health Organization estimates there were 340 million new cases of chlamydia, gonorrhea, syphilis, and trichomoniasis in 1999, a sharp rise from the 250 million new cases in 1990.4

More than half of all new cases of STDs occur in young men and women younger the age of 25.5 Reliable rapid-based tests need to be developed so clinicians can detect and treat such infections, says Schachter. Research indicates that as many as one-fourth of patients diagnosed with chlamydia never return for care,6 he notes.

New test available

HIV detection has moved forward with the availability of an oral fluid-based test. The Food and Drug Administration (FDA) approved the use of oral fluid samples with the OraQuick Rapid HIV-1/2 Antibody Test (OraSure Technologies, Bethlehem, PA) in March 2004. The rapid HIV diagnostic test kit provides accurate screening in as little as 20 minutes.

Look for the development of inexpensive, rapid, noninvasive, STD tests, such as chromatographic strip tests, that can be performed on site and that can identify a variety of STDs at the same time, says Stuart Berman, MD, chief of the epidemiology and surveillance branch in the Atlanta-based Centers for Disease Control and Prevention’s (CDC) division of STD prevention.

Clinicians will have to stay a step ahead when it comes to stemming the spread of STDs. The CDC is alerting clinicians to be on the lookout for instances of lymphogranuloma venereum (LGV), an STD that occurs rarely in the United States, yet has recorded an uptick in the Netherlands, as well as Belgium, France, and Sweden.7

The infection is caused by a variant of the bacterium that causes chlamydia. Administering doxycycline 100 mg orally twice a day for 21 days may treat infection.8

According to the CDC, the most common clinical sign of LGV infection in heterosexual men is tender inguinal and/or femoral lymphadenopathy that is most commonly unilateral. Women and men who have sex with men may have proctocolitis or inflammatory involvement of perirectal or perianal lymphatic tissues.8

What’s on tap?

Clinicians may see the commercial availability of a human papillomavirus (HPV) vaccine in the future, predicts Ward Cates Jr., MD, MPH, president/chief executive officer of the Institute for Family Health at Family Health International, a Research Triangle Park, NC-based nonprofit research organization. Just-published research indicates a bivalent HPV vaccine is effective in prevention of incident and persistent cervical infections with HPV-16 and HPV-18.9 The vaccine is under development by GlaxoSmithKline Biologicals in Rixensart, Belgium, as Cervarix.

Promising results also have been reported from trials of a vaccine developed by Merck & Co. of Whitehouse Station, NJ. Research presented at the November 2004 meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy in Washington, DC, indicates that Merck’s investigational monovalent vaccine against 16 (HPV 16) has 100% vaccine efficiency against cervical intraepithelial neoplasia at stages 2 to 3, confirming earlier published research.10 The vaccine is a component of Merck’s investigational quadrivalent HPV (types 6, 11, 16, 18) L1 VLP vaccine.

Look for public health officials to combine genetic techniques and molecular biology to provide enhanced delineation of which individuals will be at risk for STDs, predicts Berman.

"We will be seeing a lot of work in the introduction of more effective intervention strategies, developing controlled efforts to reach and educate people" about STDs, agrees Schachter.

References

1. Campos-Outcalt D. Sexually transmitted disease: Easier screening tests, single-dose therapies. J Fam Pract 2003; 52:965-999.

2. Eng TR, Butler WT, eds. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: Institute of Medicine, National Academy Press; 1997.

3. Cates Jr. W. Estimates of the incidence and prevalence of sexually transmitted diseases in the United States. American Social Health Association Panel. Sex Transm Dis 1999; 26(4 Suppl):S2-S7.

4. World Health Organization. Global prevalence and incidence of selected curable sexually transmitted infections: Overview and estimates. Geneva; 2001.

5. Flynn E, Beith M. When the mood strikes. Newsweek 2004; accessed at msnbc.msn.com/id/5709145/site/newsweek.

6. Hook EW III, Spitters C, Reichart CA, et al. Use of cell culture and a rapid diagnostic assay for Chlamydia trachomatis screening. JAMA 1994; 272:867-870.

7. Lymphogranuloma venereum among men who have sex with men — Netherlands, 2003-2004. MMWR 2004; 53:985-988.

8. Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines 2002. MMWR 2002:51(No. RR-6). Accessed at: www.cdc.gov/STD/treatment/2-2002TG.htm#LymphogranulomaVenereum.

9. Harper DM, Franco EL, Wheeler C, et al. Efficacy of a bivalent L1 virus-like particle vaccine in prevention of infection with human papillomavirus types 16 and 18 in young women: A randomised controlled trial. Lancet 2004; 364:1,757-1,765.

10. Koutsky LA, Ault KA, Wheeler CM, et al. A controlled trial of a human papillomavirus type 16 vaccine. N Engl J Med 2002; 347:1,645-1,651.