New ATS/CDC guidelines will insist on nine months of preventive therapy
Controllers ask that six-month regimen remain an acceptable option
By next fall, new recommendations for preventive therapy — make that "treatment of latent TB infection" as the preferred phrasing now goes — are expected to state firmly that nine months of isoniazid prophylaxis are preferable to six. What’s not yet certain is whether the six-month regimen will be relegated to a humble footnote or manage to hang on to some of its former status by making the list of acceptable options.
The new recommendations are the product of joint deliberations between the American Thoracic Society (ATS) and the Centers for Disease Control and Prevention (CDC).
At a meeting in Atlanta last month of the Advisory Council for Elimination of Tuberculosis (ACET), the reaction to the news — first announced at the ATS conference in Chicago in February — consisted mostly of grumbling and dismay.
Are the new recommendations a ploy to force programs to swallow the new two-month, short-course regimen of rifampin and pyrazinamide, side effects and all? How are programs already having a tough time getting six months of isoniazid into their patients supposed to convince them to take nine? In a year of level funding, where will the extra money come from?
Nancy Dunlap, MD, PhD, medical director of Alabama’s TB control program, drew appreciative laughter from the ACET audience when she proposed innocently: "Why don’t we just make nine months the footnote, and put six months back into the table?"
ATS and CDC point men for the new guidelines argue that what looks like a new and harder line is really just a reality check; plus, they say, one way or another, six months will still be available as an option.
"This statement really makes it clearer where the bar has been all along," says Larry Geiter, PhD, MPH, a consultant for Sequela Research Foundation in Rockville, MD, and the researcher who had been given the job of corralling existing evidence on preventive therapy for HIV-positive patients. "This will also give people the chance to go back to their legislators and cite this statement as a clear, unambiguous point for advocacy."
As for the two-month course of preventive therapy, Geiter says he and the other guideline authors, far from wanting to push RIF/PZA onto programs, share their peers’ reservations about the new regimen. "We have concerns about toxicity, and we honestly don’t know what will happen when we give this to thousands of people," Geiter says.
Nine months for all, for clarity’s sake
The decision to settle on nine months as an optimum duration of prophylaxis for both HIV-negative and -positive patients was intended partly to dispel potential confusion, adds David Cohn, MD, associate director of Denver Public Health, and the person given the job of reviewing data for HIV-positive patients.
The data clearly argue that nine months is better than six among HIV-negative patients, Cohn explains. Among the immune-compromised, however, no study has ever directly compared the efficacy of 12 months to that of six; hence the decision was made to split the difference for the sake of clarity.
But from a programmatic point of view, the troubles with urging nine months onto programs are manifold, says Eric Brenner, MD, medical epidemiologist at the state of South Carolina’s Department of Public Health. "Six months is already a hard sell for someone who isn’t feeling sick," says Brenner (who took the floor at the ATS conference in Chicago to make his points). "The longer you tell someone they have to take pills, the harder the sell." Drop-off rates, already a problem at six months, can be expected to increase with nine, he adds. So may toxicity, at least to some small extent.
Finally, it stands to reason that a regimen that’s 50% longer will demand half again as much in the way of resources, whether that amounts to clinic visits, telephone calls, or direct observation of therapy.
The guidelines will run simultaneously in the CDC’s Morbidity and Mortality Weekly Report as well as the ATS’s Journal of Respiratory and Critical Care Medicine.
The recommendations also will take a new look at targeted screening for latent TB infection, says Cohn. They will urge programs to screen only high-risk populations, and not to screen frivolously, but rather to test only with the intention to treat.
Along with nine months of INH, the table of acceptable options for preventive therapy also was expected to include nine months of treatment on a twice-weekly basis (with directly observed preventive therapy); the new two-month, short-course regimen of rifampin/pyrazinamide; and rifampin daily for four months.
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