Reactive arthritis that is due to chlamydia transmission is infection responds to antibiotic therapy. Other infectious causes of the condition do not.

So it is worth checking the synovial fluid of affected joints for evidence of chlamydia polymerase chain reaction (PCR), according to Dr. Atul Deodhar, professor of medicine at Oregon Health and Science University in Portland.

In a recent randomized trial, 6 months of rifampin plus either azithromycin or doxycycline significantly improved outcomes versus placebo in patients with chlamydia-induced reactive arthritis. Synovial fluid PCRs were positive for chlamydia in all 42 patients (Arthritis Rheum. 2010;62:1298-307).

The study "has changed my practice. I now send synovial fluid for PCR. I have found several patients" positive for chlamydia, "and we are treating them with antibiotics," Dr. Deodhar said; he also sends urine samples for chlamydia testing.

The primary end point in the study – an improvement of 20% or more in at least four of six variables such as swollen joint count – was achieved by 17 of 27 antibiotic patients (63%) but only 3 of 15 placebo patients (20%). Six patients treated with antibiotics but none of the patients in the placebo group went into complete remission during the trial. Patients on antibiotic were also more likely to clear chlamydia from their joints.

It’s a different story when reactive arthritis is triggered by gastrointestinal pathogens such as salmonella, shigella, campylobacter, and yersinia. In those cases, "avoid antibiotics," Dr. Deodhar said.

He and his colleagues found antibiotic therapy just didn’t help in a population study of 575 likely reactive arthritis cases among 6,379 people with culture-confirmed GI infections. His team confirmed reactive arthritis in 54 of the 82 (66%) subjects they were able to exam. Enthesitis was the most frequent finding; arthritis was less common (Ann. Rheum. Dis. 2008;67:1689-96).

Some patients had been given antibiotics for their GI infections, others not. It "didn’t really make any difference to patients developing or not developing reactive arthritis or the severity of it. Antibiotics are not going to prevent people with dysentery from developing reactive arthritis," Dr. Deodhar said.

They also found that the presence or absence of human leukocyte antigen B27 did not predict risk. In sporadic reactive arthritis cases, the presence of the antigen is "not actually that important in deciding if someone has or does not have reactive arthritis," he said.

Onset of reactive arthritis comes a few days to a maximum of several weeks following the inducing infection. Asymmetrical mono- or oligoarthritis of the lower extremity is the most common joint finding. Uveitis, dactylitis, and enthesitis are also possible.

Besides antibiotics for chlamydia-induced disease, sulfasalazine and tumor necrosis factor inhibitors may help with difficult cases.

Nearly two-thirds of sexually active young women don't get regular chlamydia transmission, a CDC study finds.

That means more than 9 million young American women don't know whether they've been infected, study leader Karen Hoover, MD, MPH, said in a teleconference from this week's National STD Prevention Conference in Minneapolis.

And the odds of being infected are pretty high: Chlamydia is the most common STD, as well as the most common reportable infection in the U.S.

"There were 1.3 million reported cases of chlamydia in 2010, but the CDC believes the actual number is more than twice that -- 2.8 million new cases each year in the U.S.," Gail Bolan, MD, director of STD prevention at the CDC, said at the teleconference.

Among women, nearly 5% of 19-year-olds and more than 1% of 15-year-olds are infected. Men are at least as likely to be infected. But it's women who suffer the most severe consequences. That's because chlamydia infection often is silent -- without symptoms -- until the infection becomes more serious.

Left untreated, 10% to 15% of women will get pelvic inflammatory disease (PID). And up to 15% of those women will be left infertile. And some will die from chlamydia-related ectopic pregnancy.

The CDC recommends an annual chlamydia test for any sexually active woman age 25 and younger. Women over age 25 should get annual tests if they have a new sex partner or have multiple sex partners. Routine screening isn't recommended for men.

When diagnosed, chlamydia is easily treated. But treatment isn't permanent, as Kelly Morrison Opdyke, MPH, and colleagues found in another conference presentation.

Opdyke's Cicatelli Associates Inc. team studied 63,774 people who tested positive for chlamydia from 2007 to 2009. They found that 25% of men and 16% of women have a new chlamydia infection when retested within six months.

And those are just the people who get another test. People who show up for screening tests tend to be healthier than those who don't. Yet only 11% of men and 21% of women got that chlamydia retest in the Opdyke study.

Those who test positive for chlamydia are supposed to get a repeat test three months after treatment. Sex partners should be evaluated and treated as well. Women are at increased risk for reinfection if their sex partners have not been treated appropriately.

Unfortunately, you might not be able to rely on your health care provider to offer you that test.

California Department of Health researcher Holly Howard, MPH, and colleagues studied six of their state's large family planning clinics. They found that only 70% of patients were retested for chlamydia or for gonorrhea, the second most common STD.

When the clinics installed pop-up reminders on patients' computer records -- using existing billing software -- the retesting rate went up to 86%.

To remind patients to ask for chlamydia retests, SUNY Buffalo researcher Gale Burstein, MD, MPH, and colleagues used a simple email system. Four to five weeks after testing positive for chlamydia or gonorrhea, students got an automated email reminder. That was followed by a personal email and, if needed, a telephone call.

What happened? Retest rates for chlamydia went from 16% to 89%.

"We must not only increase chlamydia screening rates but ensure re-testing," Bolan said. "And we must encourage and support individuals' efforts to protect themselves. This may mean abstaining from sex, reducing the number of sex partners, or proper condom use."