From Lee B. Reichman, M.D., professor of medicine and the founding executive director of the New Jersey Medical School's National Tuberculosis Center.
Dr Reichman has also worked as a consultant to the medical industry on developing blood tests for TB (CST).
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Wednesday, March 24, 2004
Today is World TB Day, but why would there be a day commemorating a disease that has been eradicated?
Because, contrary to popular belief, tuberculosis is not a disease of the past. In fact, TB kills more people than any other microbial disease -- an estimated 2 million to 3 million per year worldwide.
Even more disheartening, this disease is the No. 1 killer of people infected with HIV.
In the United States, the Centers for Disease Control and Prevention estimates that 15 million residents are infected with TB in its latent -- or dormant -- phase.
Ten percent of those individuals with latent infection will go on to develop active TB in their lifetime, which is even more likely for individuals with diabetes, kidney disease, HIV infection (10 percent annually) or those taking immunosuppressive therapies for arthritis, an organ transplant or cancer.
Left untreated, active TB will cause serious illness and eventually death.
The San Francisco metropolitan area has one of the highest TB rates in the United States, with 225 active TB cases reported to the CDC in 2002 (13.1 per 100,000).
Yet attention has focused for the last couple of years on anthrax, SARS, West Nile virus, monkey pox and mad cow disease -- all of which have had little effect on the Bay Area's population.
As an international city with large immigrant and migrant populations, as well as individuals with immunosuppressive diseases, San Francisco is especially at risk.
People with active TB are highly infectious and are the source of continual transmission of TB.
Preventing progression from latent infection to active disease is crucial to the goal of TB elimination.
Unfortunately, old TB detection practices that have become ingrained make it extremely difficult to accurately identify those with latent TB.
Still in widespread use today, the tuberculin skin test (TST or Mantoux) was developed in 1890 -- the decade that saw the invention of the gas-powered automobile - - and has a high rate of false-positive and false-negative results.
In addition, interpretation of the TST is highly subjective, not reproducible and requires two patient visits -- one to take the test and another to have the results interpreted.
On average, more than 30 percent of those tested do not return for the results.
The U.S. Institute of Medicine has regarded the failings of the TST for TB infection as the single largest problem for TB control in the United States.
With one-third of the world's population infected with latent TB and multi-drug-resistant TB rising at alarming rates (300,000 new cases estimated by the World Health Organization for last year alone), it is in the interest of every country to support rapid scale-up of TB control. It is time to put the TST to bed and begin using accurate TB tests, such as a simple blood test under review with the FDA that is more accurate and reliable for detecting TB.
In addition to its integral role in the control and spread of TB, a simple, one-step blood test should yield dramatic cost savings in terms of medical staff time and the elimination of common false-positive results, the latter involving costly follow-up testing and unnecessary TB therapy. For hospitals and health departments, such a test would relieve the huge administrative and cost burden associated with maintaining TB testing compliance.
Old habits may die hard, but allowing people to die is even harder. There is no good reason not to relinquish the TST to history.
