Is there AIDS clue in "negative" tests that come back positive?
Ontario health officials have made a shocking discovery that threatens to blow the roof off conventional thinking about a dangerous sexually-transmitted infection — syphilis — and how to test for it among people at risk for AIDS.
In a presentation at this year’s meeting of the American Society of Microbiology, Neal denHollander, who directs research at the Public Health Laboratory of Ontario, showed how a new type of syphilis test found otherwise undetected cases in nearly five per cent of samples from STP clinics including the Hassle Free Clinic on Church.
These were positive results in samples that showed up negative in the regular screening test.
The significance of this might well be that there are many people walking around today who are carrying the STD and don’t know it. But more than that, the finding may inch us much closer to answering the question that has preoccupied me for several years now — does syphilis play an important and possibly necessary role in the development of AIDS itself?
The new technology that allows us to find the formerly unfindable STD is called the Trep-Chek. To see how well the new test performed against the regular ones, denHollander and colleagues took 557 recent blood specimens mostly from Hassle Free’s routine syphilis submissions — all had come back negative in the standard screening test (called the VDRL).
To their surprise, they found 27 registered positive.
The study, which has taken the local AIDS community by surprise, revives concerns first sounded over 10 years ago by then-chief provincial serologist Bob Notenboom. With the help of Douglas MacFadden, director of the HIV Clinic at Toronto Hospital’s Western Division, and local bookstore owner and AIDS expert John Scythes, Notenboom and his officials documented unexplainable irregularities in syphilis testing among people with HIV.
With the aid of this more sophisticated biotechnology, denHollander now has taken up the issue again. He stresses that the standard methods used to screen for syphilis are “clearly under-sensitive.”
How much of a concern is this diagnostic gap? That all depends on how dangerous one considers untreated syphilis to be.
AIDS experts readily acknowledge the high correlation between being HIV-positive and having had syphilis, but only insofar as the sores produced by syphilis allow HIV to enter the body more easily. However, some theorists argue that untreated or inadequately treated syphilis may be a factor in the development of AIDS — especially as new evidence suggests bacterial infections can “wake up” an otherwise latent, inactive HIV infection.
Indeed, emerging research into the immune response in the later stages of syphilis suggests there may be much more going on between syphilis and HIV than was previously thought. Recent findings from veteran Polish syphilis researcher Jadwiga Podwinska point to pronounced immune irregularities once the disease has reached the latent (hidden) stage.
Among HIV primary-care physicians, the surprising new findings only confirm their own doubts about syphilis tests. “Compared to other tests, they tend to be less reliable,” says John Goodhew. “I compensate for that by doing syphilis tests on everybody every year.”
But no one knows how well the syphilis tests Goodhew is using really work. Indeed, Notenboom found AIDS patients with a past history of syphilis who seemed to lose their normally lifelong specific antibodies against syphilis, while antibodies against other infections remain. “It is possible,” he says, “to have syphilis, and yet all the tests are negative.”
Could untreated chronic syphilis be making a lot of people sick, especially those with HIV? It’s a concern I voice to Bill Cameron from the University of Ottawa, one of Canada’s leading AIDS authorities.
“I agree with you,” he admits from Oxford University in England where he is a visiting research scientist. “I would be happy to see a large-scale evaluation of these newer and better tests.”