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Increased screening for syphilis boosts detection of early latent infections among Australian gay men
Michael Carter, 2017-05-03 07:10:00
testing among gay men increased detection of early latent infections and was
accompanied by a fall in the proportion of cases involving secondary syphilis,
investigators report in the online edition of Clinical Infectious Diseases.
“We believe this
is the first study to demonstrate that increased serological screening of MSM [men who have sex with men]
for syphilis is associated with greater detection of early syphilis with a
measurable impact on secondary syphilis on a country level, providing evidence
that screening is likely to have interrupted the progression of syphilis,”
comment the authors. “This may have potentially reduced the infectiousness of
syphilis, as it is believed that secondary stage of syphilis infection is
particularly infectious, and prevented sequelae such as ocular and
accompanying editorial, Dr Jeffrey Klausner of the University of California
states that the research provides “very compelling evidence of the benefits of
increased targeted screening for syphilis.”
Since the late
1990s, rates of syphilis have been increasing among gay and other MSM in major
cities around the world. Many of these infections involve MSM living with HIV.
There are several
stages of syphilis infection: primary syphilis; secondary syphilis; early
latent syphilis and tertiary syphilis. Early syphilis can be cured with a
single dose of penicillin. Prompt detection of the infection is especially important
as its latter stages can lead to organ damage. Even secondary syphilis can
affect the brain and eyes.
National Syphilis in Gay Men Action Plan released in 2009 recommends frequent
syphilis testing for HIV-negative MSM and opt-out syphilis screening as part of
the routine care provided to HIV-positive MSM. The guidelines recommend that
all MSM be tested for syphilis at least once a year with more frequent testing
for those at high risk of the infection.
A team of
investigators examined rates of syphilis testing and diagnoses among
HIV-negative and HIV-positive MSM. They especially wanted to see if increased
testing was accompanied by an increase in the proportion of syphilis infections detected in
the early latent stage.
Data from 46
sexual health clinics across Australia were analysed. There were approximately
359,000 clinic visits during the study period. A third of these visits involved
men with HIV.
The proportion of
HIV-negative men tested for syphilis increased from 48% in 2007 to 91% in 2014
(p < 0.001). The mean number of annual tests per HIV-negative patient increased
from 1.3 to 1.6 (p < 0.001).
was accompanied by a significant increase in the proportion of cases of
syphilis diagnosed in the early latent stage of infection (27 to 44%), p <
0.001), while the proportion of cases involving secondary infection decreased
from 24 to 19% (p = 0.03). There was also a fall in the number of cases of
primary syphilis detected (49 to 38%, p = 0.017).
An increase was
also observed in the proportion of HIV-positive MSM tested for syphilis as part
of their routine care, from 42 to 77% (p < 0.001). The mean number of tests
per patient per year increased from 1.6 to 2.3 tests (p < 0.001). Although
encouraged by these increases, the authors nevertheless comment, “as
HIV-positive MSM account for a disproportionate number of syphilis infections
and repeat infections in many countries, further efforts and strategies to
boost syphilis screening of HIV-positive MSM in health services where testing
is suboptimal are warranted.”
The proportion of
early syphilis cases among HIV-positive men that were early latent infections
increased from 23 to 45% (p < 0.001). At the same time, the proportion of
secondary infections decreased from 45 to 26% (p = 0.0003). The proportion of
cases involving primary infection remained stable.
Among men with
HIV, there was a correlation between the decreasing proportion of cases of
secondary syphilis and increased testing coverage (p = 0.005) and increased
frequency of testing (p = 0.001).
infection can precede primary infection, occur between the primary and secondary
stages, or follow secondary syphilis. One of the largest clinics involved in
the research gathered data on titres. These generally increase at the beginning
of the infection and fall over time, even without therapy. Median titre for
early latent syphilis was 1:32, between that for primary (1:4) and secondary
(1.12) syphilis. The authors believe this observation supports their hypothesis
that a substantial proportion of the early latent cases they detected were likely
to have been latent infections that preceded secondary syphilis.
“This study has
shown that substantial increases in screening for syphilis were achieved among
both HIV-positive and HIV-negative MSM across Australia and these were
associated with an increase in the detection of early latent syphilis together
with a relative decrease in secondary syphilis,” write the authors. “With
reported rates of syphilis at historical highs in many countries other
potential measures aimed at syphilis control such as vaccine development,
chemoprophylaxis and community-based screening require further investigation.”
In his editorial Jeffrey
Klausner notes the current political indifference to the communities most
affected by syphilis. He therefore calls for infectious disease specialists and
public health advocates to lobby for more public health resources to be devoted
to the prevention of the infection. “A renewed syphilis response has to start
somewhere,” he writes. “It has to start with us.”