Target TB screening, report tells universities
Broad-based screening won’t get job done
Many colleges and universities screen at least some students for TB, but often in the wrong way or for the wrong reasons, the first comprehensive survey of such practices has found. When it comes to TB skin-testing, many institutions are simply spinning their wheels without going anywhere in particular, the report suggests.1
"That was a surprise to us — how many schools are doing broad-based screening and how often the screening is just an item on a list to check off, without much follow-up," says Karen Hennessey, PhD, MSPH, Epidemic Intelligence Service officer in the National Immunization Program at the Centers for Disease Control and Prevention.
That probably helps explain why so few TB cases reported to have occurred at colleges and universities were uncovered through screening programs. Overall, 4.7 TB cases were identified for every 100,000 students screened. Of 114 cases reported during a four-year period, only 32 were identified as a result of a required skin-test screening. Most of the rest were found when students became symptomatic or through contact investigations; in a handful of cases, the means of discovery was not recorded.
The survey, which was conducted on behalf of the American Public Health Association, gathered responses from 624 schools nationwide. Of that total, 61% of the schools replied that they required a skin test from at least some students; 26% said they required the test of all new students; 8% required it only from new international students; and 47% asked for skin-testing only among students enrolled in certain academic programs (including health care, teaching, and social work).
Of the 348,368 students screened at all the schools, an average of 3.1% had positive skin tests (with a median rate of 0.8% positivity). The schools that screened only international students had a much better yield, at 22.9%.
One clear lesson from those findings is that targeted screening is much better than broad-based screening, says Hennessey. Not only is targeted screening cheaper, it’s safer because it avoids turning up the false-positives (who’d perhaps be offered unneeded prophylaxis) that result when a low-prevalence population is screened, she says.
The problem is that some schools say targeted screening is hard to implement, she adds. "Schools feel it’s difficult to target only international students," she says. "They feel it might be [perceived as] discriminatory."
Along with problems about whom to screen, the survey turned up a second set of shortcomings in the ways screening is carried out.
For example, some schools accepted multi-puncture and Tine tests; many recorded results not in millimeters of induration but instead as simply "positive" or "negative" some schools didn’t bother to collect the data in a central bank; and others excused students from screening because of a history of a BCG vaccination.
Screening unnecessary at some schools
Screening shouldn’t be an all-or-nothing proposition, Hennessey says, even though that approach often seems the easiest way to go. In fact, not all schools should be doing TB screening, she adds. "First, you should look at your school population and see whether you need to be screening," she says. "See if you have a population at risk. Then decide what kind of screening program you should have and set goals for it. Collect the data and look at it periodically to see if those goals are being met."
A good screening problem includes efforts aimed at educating students about the benefits of prophylaxis, and the ability to provide isoniazid preventive therapy. "You must have all that in place, and then do follow-up and see what proportion of students actually do take the INH," she adds.
If a school decides to do screening, it’s important to target only students from high-risk groups — that is, students from parts of the world with high rates of TB; immunocompromised students and students working in health care settings, says Hennessey.
In addition, only the Mantoux skin test should be accepted, and students vaccinated with BCG should not be exempted. Finally, results of screenings should be collected and periodically analyzed in a data bank, says Hennessey.
Reference
1. KA Hennessey, JS Schulte, L Cook, et al. Tuberculin skin test screening practices among U.S. colleges and universities. JAMA 1998; 280:2,008-2,012.
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