Vaginal discharge is a poor way of diagnosing STIs, with asymptomatic infections associated with an increased risk of HIV

Michael Carter
Published: 26 June 2012

Symptoms are a poor way of detecting discharge-causing sexually transmitted infections (STIs) in women, investigators report in the 1 July edition of the Journal of Infectious Diseases. The research was conducted in South Africa, where diagnosis of STIs relies on the presence of symptoms. The women recruited to the study had multiple partners and many were sex workers, meaning that they had a high risk of HIV infection.

Symptoms were present in only 12% of women with laboratory-confirmed infections. The study also showed that laboratory-diagnosed STIs were associated with a threefold increase in the risk of infection with HIV. There was no such association for symptoms. 

“These data create a compelling argument for readdressing the STI management strategy in high-risk populations,” comment the authors. “Healthcare systems should include regular screening for STIs by means of laboratory testing in these groups rather than relying on symptoms only.”

The diagnosis and treatment of STIs is a major public health priority. If left untreated, infections such as gonorrhoea can cause long-term complications and can also increase the risk of HIV transmission and acquisition.

In resource-limited countries, such as South Africa, the diagnosis of STIs is reliant upon the detection of symptoms. Genital discharge is the most obvious symptom of infections such as chlamydia and gonorrhoea.

However, it is well known that STIs can be asymptomatic. Investigators from South Africa therefore designed a prospective study involving 242 women at high risk of HIV to assess the prevalence of asymptomatic infections.

Enrolled in the CAPRISA 002 study, the women were screened for STIs at baseline and again at six-monthly intervals.

Symptoms of STIs were recorded and laboratory testing for common STIs was conducted at each follow-up appointment. The investigators also conducted tests to see if symptomatic and asymptomatic STIs were associated with levels of inflammatory cytokines. Elevated levels could increase susceptibility to HIV. The researchers also performed analysis to see if symptomatic and asymptomatic infections were associated with an increased risk of HIV.

Almost all the women (95%) reported one or more casual sex partner in the three months before enrolment and 79% identified as sex workers.

There was a high prevalence of laboratory-confirmed STIs at enrolment. Overall, a fifth of women were diagnosed with having any sort of infection. During the study, the incidence of any STI was 27 cases per 100 person-years.

Vaginal discharge was present in 15% of women at baseline. The prevalence of discharge at the six- and twelve-month follow-up visits was 2 and 5% respectively.

However, laboratory monitoring showed that 28% of woman had a discharge-causing STI at baseline, with 19 and 24% testing positive for such infections at their six- and twelve-month visits.

Many of the women presenting with discharge did not have a STI. Only 34% of discharge incidents were accompanied by a positive laboratory test confirming the presence of an infection. In contrast, 77% of laboratory-confirmed STIs had no accompanying symptoms.

Using laboratory tests as the “gold standard”, the investigators calculated that symptoms for screening had a sensitivity of just 12% and a specificity of 94%.

“Therefore, only 12.3% of women with a confirmed laboratory-diagnosed STI would have been appropriately treated using vaginal discharge as an indicator for syndromic treatment,” write the authors.

Both symptomatic and asymptomatic infections were associated with elevated concentrations of inflammatory cytokines in the genital tract. “Women who had asymptomatic STIs had subclinical inflammation that may increase their susceptibility to HIV infection.”

A total of 28 women became infected with HIV (incidence, 7.2 cases per 100 person-years).

The presence of laboratory-confirmed discharge-causing STIs was associated with a threefold increase in the risk of infection with HIV (HR = 3.3; 95% CI, 1.5-7.2).

Gonorrhoea was associated with an especially high risk of infection with HIV. The unadjusted analysis showed that this infection increased the risk almost eightfold (HR = 7.74; 95% CI, 2.82-21.24; p < 0.001). The association remained highly significant after controlling for potential confounders (HR = 4.62; 95% CI, 1.34-15.93; p = 0.154).

There was no association between the presence of vaginal discharge and risk of infection with HIV.

“The current symptom-driven syndromic management system is untenable for high-risk populations and underscores the need for a paradigm shift in diagnosing STIs,” conclude the authors. “Only when more effective STI treatment is achieved are we likely to see STI management playing a role in HIV prevention.”

This conclusion is echoed by Dr Myron Cohen in an editorial that accompanies the study: “We must redouble our efforts to think of every possible way to recognize and treat classical STDs. Surely this problem is no more impossible to attack or less important than any other part of the HIV-1 pandemic.”

Reference

Mlisana K et al. Symptomatic vaginal discharge is a poor predictor of sexually transmitted infections and genital tract inflammation in high-risk women in South Africa. J Infect Dis 206: 6-14, 2012 (click here for the free abstract).

Cohen MS Classical sexually transmitted diseases drive the spread of HIV-1: back to the future. J Infect Dis 206: 1-2, 2012 (click here for a free extract).