Colleges should target high-risk for skin tests
Colleges should target high-risk for skin tests
Approach saves money, gives better readings
A targeted approach to TB testing that relies on prescreening and focuses on students with high-risk factors for the disease works well to find and treat both active TB and latent TB infection (LTBI), says a recent study conducted at Virginia Commonwealth University (VCU) in Richmond.
Though most colleges and universities across the country require students to be tested for tuberculosis before they matriculate, the effectiveness of universal screening is poor, many TB experts say. Student compliance typically is low, and student health services often are too underfunded to follow up methodically. Plus, the programs don’t make economic sense because prevalence rates across an entire student body are generally low.
"We wanted to judge the effectiveness of a fairly common practice among colleges across the country," said study author Venkatarama Koppaka, MD, PhD, medical director of the Division of TB Control with the Virginia Department of Health and a field officer with the Division of Tuberculosis Elimination of the Centers for Disease Control and Prevention (CDC) in Atlanta. "What we found was not unexpected — that when you apply this kind of approach over a broad group of people, there will be difficulties in compliance with those policies. We also found it’s hard to assess accuracy of results when you rely on multiple sources of testing to provide the information."
In addition, in the relatively small group of students who underwent testing at Student Health Services, those who turned out to have a positive tuberculin reaction had at least one of the standard risk factors for TB, Koppaka says.
Study suggests definable risk factors
That suggests that universities should target groups for testing only if they have clearly defined risk factors, he adds. Such a policy will more likely "capture" students who are most likely to carry tuberculosis; plus, it will be much more cost-effective.
Perhaps more important from a medical standpoint, the predictive value of skin testing improves tremendously when TB testing is conducted among an at-risk population rather than a broader population, Koppaka notes. "When you’re testing people that are likely to be infected, you can place greater reliance on positive test results and wind up with far fewer false positives," he adds.
A recent American College Health Association (ACHA) survey supports the notion that targeted TB screening is cheaper, more effective, and safer than broad-based screening and will result in a lower rate of false-positive results.
To define risk groups, school administrators should start with a risk assessment of everyone and use the results to determine who should get the tuberculin test, says Koppaka.
The VCU retrospective study reviewed the compliance rates of 4,677 new full-time students entering VCU at the start of the 1998-99 academic year. The school requires all new students to undergo testing for TB at student health services or by an outside source — a common requirement at colleges across the United States. (In a survey conducted on behalf of the ACHA involving 624 schools nationwide, 61% said they required skin tests from at least some students.)
At VCU, more than 2,600 (56.4%) students satisfied the testing requirement upon entry. The school mailed reminders to the students with incomplete records, resulting in another 597 students being tested. That still left 30% of students who never underwent TB testing.
Of all students screened (3,246), 149 were found to have latent LTBI by outside providers, and the remaining 18 received their diagnosis at Student Health Services. No active cases of TB were found. Asian/Pacific Islanders comprised nearly half of the 167 students who had LTBI. Six of the LTBI-positive students had worked in a health care setting. Of the cases found by Student Health Services, all had at least one risk factor (as defined by American Thoracic Society and CDC guidelines) for LTBI, with foreign birth being the most common (14 of 18).
According to Betty Anne Johnson, MD, PhD, director of VCU’s Student Health Services and co-author of the study, the investigation was initiated with a view toward altering the current testing program at the college. "One of the problems is that nobody knows what risk factors college students have for TB exposure, so we designed an approach to determine those factors," Johnson says. "We also have a lot of problems entrusting [the testing] process to anyone besides ourselves or public health departments, the military and corporate employee health services," she adds. "TB testing is complex, and private physicians don’t do as well."
The study has not yet resulted in a change in VCU’s approach to TB testing for incoming students; for now, the school will continue to enforce, to the best of its ability, its universal testing program, says Johnson. But there are plans for a follow-up study during the upcoming school year.
To standardize the testing process, the school will require all incoming students to receive their skin test results at Student Health Services. The sample size of students tested in the controlled setting of Student Health Services during the study was small, notes Johnson, and test results from outside providers were often unreliable.
"That way, in the future we should be able to tell with assurance — at our university, at least — what are the risk factors for new students. We also may be able to alter the process so that not everybody has to come in for a skin test," Johnson says.
Still lots of work to be done
For instance, if the results from Koppaka’s study — which shows being foreign-born or having worked in a health care setting are risk factors for LTBI — are mirrored in the upcoming large-scale investigation, VCU may begin relying on those prescreening criteria. That will greatly reduce the number of TB tests administered.
VCU considers the results of Koppaka’s study to be preliminary, Johnson adds, so the risk factors identified in the study may change after the larger follow-up.
"The beauty of this is that a limited testing policy will ease the strain on our limited resources," says Johnson. "It’s expensive to conduct skin tests on a large group of students, but it’s cheap to ask a couple questions on the health history form that we send out to new students. We might be able to identify only 10% to 20% of entering students that need to come in for a skin test."
Targeted screening isn’t discriminatory, Koppaka adds, because all students are initially evaluated for risk. "On the surface, it might seem discriminatory, but we’re not restricting the evaluation to one group of people — we’ll assess everyone for risk factors. Our hope is that we can develop practical means of applying those recommendations to the college population," he says.
Researchers still don’t know precisely what are the TB risk factors among college students, notes Johnson. "What about substance abuse, those students on dialysis, or those who have diabetes?" she asks. "I don’t think anyone knows the answers to these questions yet."
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