TUESDAY, Feb. 26, 2002 (HealthDayNews) -- Management of tuberculosis, an infectious disease that usually affects the lungs and is spread easily through coughing, involves much more than simply treating the disease.
Whenever a new case is diagnosed, U.S. health departments engage in an epidemiological version of "Six Degrees of Separation," conducting ever-widening "contact investigations" to find people the infected individual came in contact with, have them tested for TB and, if necessary, get them treated.
"Every TB case is a former contact, so tracing the contacts and finding who is infected is the only way we are going to prevent TB from developing," says Dr. Mary Reichler, a medical epidemiologist in the division of tuberculosis elimination at the Centers for Disease Control and Prevention (CDC).
The process is time-consuming, labor-intensive, and, far too often, not as efficient as it needs to be.
Two new studies appearing in tomorrow's issue of the Journal of the American Medical Association looked at ways to streamline the process.
The first study, led by Reichler, analyzed investigations that had already been carried out by health departments in parts of Massachusetts, New Jersey, Mississippi, Maryland and Colorado. These programs were considered to be among the best.
Researchers looked at 349 active TB patients, involving 3,824 contacts, and found 13 percent of the infected individuals had no contacts at all identified while an additional 11 percent had no close contacts identified. Fifty percent of individuals residing at homeless shelters (considered a high-risk group) cited no contacts at all.
"One would presume that nearly every person has at least one close contact," Reichler says. These unidentified contacts could be walking around with tuberculosis and spreading the disease to yet more people.
This is not just idle chatter: Overall, about one-third of contacts tested are found to be infected with the Mycobacterium tuberculosis bacteria.
The study also revealed only 55 percent of the contacts completed screening, a complicated process that can take up to 10 weeks, and only three-quarters of children under the age of 15 (also considered high risk) were screened.
What to do about these gaps and omissions?
"We need a standard set of data that are routinely collected during contact investigations," Reichler says. "We also need to develop standard definitions for what is a contact and what is a close contact, based on exposure, and also define how long one needs to be around a case in order to be at high risk of infection."
Those at high risk of developing TB after exposure also need to be identified. In this study, only 10 percent of the contact records included an HIV status and only 1 percent recorded how many hours the contact had spent with the infected person.
It really comes down to using resources most efficiently and effectively -- something the authors of the second study tried to do.
Using data from 292 cases of TB and their 2,941 contacts, these researchers constructed a model to predict which contacts would have positive skin tests for tuberculosis.
Three factors appeared to be the best predictors: a positive sputum smear (the organisms were present in sputum analyzed under a microscope); the presence of cavities on the chest X-ray; and time spent with the infected person. Those who spent more than 120 hours with the patient seemed at the highest risk of having a positive result, although, in general, more time increased the odds of a positive test.
This model is intended for use by health departments.
"They could take it right now sort of off-the-shelf and begin to use it," says Dr. William Bailey, the study's lead author and a professor of medicine and director of the Lung Health Center at the University of Alabama at Birmingham. Bailey and his colleagues are devising a simplified flow-chart approach so public health workers could enter certain factors and be advised what course to take.
"The tradition is to examine those most closely associated with the patient and only extend the contact investigation if a high percentage are infected, but that's hard to operationalize without some practical tips like we were able to come up with," Bailey says.
What To Do: For more information on preventing, detecting and treating TB, visit the CDC's Division of Tuberculosis Elimination. The American Lung Association also has answers to your questions about TB.
