TB Monitor International-Leave foreign screening alone, CDC advises
TB Monitor International-Leave foreign screening alone, CDC advises
Cultures eyed in Vietnam
A child from the Marshall Islands infects 56 people with TB in a town in North Dakota.1 A study in California finds that overseas screening procedures often fail to iden tify active cases that turn up among children, Latin Americans, and smear- positive cases.2
Is the solution to change the overseas screening procedures?
Probably not, says Nancy Binkin, MD, MPH, associate director for international activities at the Centers for Disease Control and Preven tion's Division of Tubercu -losis Elimination. One reason is because casting a wide net overseas ultimately brings more immigrants and refu -gees under the purview of American-style diagnosis and treatment.
"I think it's best to stick with our current system," says Binkin. "Keep those who are smear-positive and a threat to public health off of airplanes, but bring the rest here to the United States, where we have a good means of diagnosis. And if they need to get treated, it's much more likely they'll get the therapy they need here."
Ironically, Binkin is involved in a project in Vietnam that involves gearing up screening capabilities to include not just chest X-rays and sputum smears, but culture capability as well. Part of the rationale is "just to see what we might be missing," she explains; that doesn't mean she thinks the procedure ought to become standard fare.
For one thing, what's possible to pull off in Vietnam — a country blessed with skilled lab technicians and a therapeutic party line that amounts to, "If you don't show up for therapy, you don't go to America" — might not work as well someplace else. "We have people coming from over 200 countries, some of which don't even have electricity," notes Binkin. "But it's hard to do things on a country-by-country basis. You have to get to the lowest common denominator."
Maybe more important, the issue illustrates how fixing something that's not actually broken might wind up making things worse, she adds.
Unforeseen consequences
Suppose, for example, you begin requiring foreign countries to perform cultures on the sputum specimens taken from anyone with a suspicious chest X-ray. By narrowing the field of focus to just those with culture-confirmed TB, "you'd miss a superb opportunity for catching folks who are candidates for preventive therapy," says Binkin.
Placing a tuberculin skin-test on every would-be immigrant in the Philippines or Vietnam isn't really practical, either: "You'd have 60% to 80% of people testing positive."
Plus, trying to gear up a lab unaccustomed to doing cultures generates its own set of potential problems. A few years ago, when just such an upgrade was attempted in the Philippines, the first thing to go was the help: As soon as lab techs got properly trained, they'd emigrate to the United States, where the payscale was better. About the time a full quota of workers was finally produced, a typhoon struck, contaminating all the cultures.
Barring such difficulties, making cultures part of the screening requirement brings up the problem of what to do about susceptibility testing and the related issue of making sure patients with resistant disease get treated properly.
Deferring such issues until immigrants and refugees get to the United States makes follow-up stateside all the more important, agree Binkin and other experts.
"With the next cycle of cooperative agreement funding, follow-up of B notifications is now an outcome measure," Binkin says. "States will be expected to be measuring follow-up, and they'll be expected to do well."
Even without any budget-related prodding, a CDC study found that follow-up for Class B1s and B2s stands at 90% or better in most places. Surprisingly, perhaps, "most people just come in," says Binkin. "They might need a letter reminding them where to go for evaluation, but that's about all it takes." That's been the case, at least, with Asian immigrants; one-time residents from the former Soviet Union are proving to be another matter. (One striking exception, New York state, since has mended its ways; there, conscientious employees now fill out and return forms for 95% of immigrants arriving with B notifications.)
Linking an evaluation to some penalty or reward for the immigrant or refugee has been proposed, Binkin adds. "Some people are proposing that you make citizenship contingent on coming in and completing your therapy," she notes. "But a lot of people who come in don't go on to become permanent citizens; they just sort of melt into the woodwork."
Electronic notification
A more feasible way to boost follow-up may be to make it easier for states to return B notification paperwork. With that goal in mind, the Division of Quarantine (DQ) is in the process of setting up a secure data network so states can receive and send Class B notif ication data electronically. "We're moving very swiftly to make this available," says DQ's data manager Frank Seawright.
The division will issue digital certificates to certain locations. "For example, we would issue a certificate to a machine in Ohio," Seawright says. When a user sitting at that computer asks for B notification data, the digital certificate will be verified. Then the user will be asked to supply a "pass phrase," a sort of code word consisting of certain letters and numbers. Data will be encrypted at one end and decrypted at the other.
The whole process shouldn't take longer than, say, buying something from an Internet shopping site. Along with being used to send and receive Class B notification data, the system also could be used as a real-time monitor of outbreaks. "We could, for example, issue digital certificates to all the emergency rooms in New York City and ask them to notify us whenever they had a suspect case of West Nile virus," he says.
Most state TB programs already know the most important thing about immigrants and refugees with B notifications: At about a 3.5% return, they're a great place to look for active TB, says Binkin. "For active case-finding, B notifications are a lot more fruitful than contact investigations," she says. After all, with active cases of TB turning up at the rate of about 3% among B1s and B2s, the case rate translates to over 3,000/100,000 — and that's "way up there," Binkin says.
References
1. Curtis AB, Ridzon R, Vogel R, et al. Extensive transmission of Myco bacterium tuberculosis from a child. NEJM 1999; 341:1,491-1,495.
2. Sciortino S, Mohle-Boetani J, Royce SE, et al. B notification and the detection of tuberculosis among foreign-born recent arrivals in California. Int J Tuberc and Lung Dis 1999; 3:778-785.
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