Sputum, skin tests cut TB transmission in shelters
February 1, 1999 7 minutes read
Sputum, skin tests cut TB transmission in shelters
Programs help homeless in Birmingham, Denver
(Editor’s note: This is the second of a two-part series on targeting special populations for TB screening.)
Public health departments shouldn’t stop at providing directly observed therapy (DOT), some TB experts say. Instead, they should add location-based screening for special populations. The experts point to recent studies lending support to the idea that DOT alone isn’t enough to stop the spread of disease among certain populations. One reason is that among those populations — the homeless, for example — efforts to implement DOT are hampered by the exceptional challenges of contact investigations.
In Los Angeles, TB controllers have begun using mobile chest radiography to screen the county’s large and widespread population of homeless people. (See TB Monitor, Jan. 1998, p. 1.) There, that method has yielded enough active cases to convince county officials that time and money required for mobile chest X-rays have been well spent.
Other jurisdictions have been experimenting with different solutions. In Denver, for example, all homeless shelters in the city now require clients to show proof they’ve been skin-tested on a regular basis. In Birmingham, AL, with the endorsement of the city’s shelters, TB controllers regularly collect sputum samples on site at selected night shelters.
TB controllers in both places say their choice of screening methods seems to be working well and fits their particular needs. "You have to find out where you have transmission in the community and then design the right program to deal with it," says William J. Burman, MD, infectious disease specialist at Denver Medical Health Center. "You never want to do something that dilutes the efforts of the TB control program, like screening in a low- incidence group — screening at a suburban school, for instance."
In Denver, he adds, there was no question where transmission was taking place: among the homeless population. The remainder of the TB cases result from transmission to household contacts, and controlling them requires no special programs, he says.
The number of hardcore homeless in Denver is estimated at about 3,000; a larger group consisting of the transient homeless boosts the total as high 8,000 to 9,000. Of the 87 cases of TB the city averages each year, 10 to 12 occur among the homeless population. Over the last eight to nine years, about 30 cases have been attributed to shelter transmission.
TB controllers chose skin testing as their method of screening for several reasons, Burman says. Screening with chest X-rays would have been too expensive, he explains, because "we don’t have the incidence to justify that." Taking sputum samples didn’t seem to be a feasible way to go, either.
Now in its third year, the skin-testing program’s coverage has increased steadily; last year, outreach workers screened 5,000 people on site at shelters. "We figure we’ll screen about 75% of the homeless population this year," he adds.
The percentage of cases located through on-site screening (as opposed to identifying patients who decide on their own to seek care) also has risen steadily each year the skin-test program has been in place. By last count, TB controllers were finding 75% of TB cases occurring among the homeless population through shelter screening. One more measure of the program’s success is that even though numbers of homeless have increased, the number of TB cases among the homeless has stayed steady, Burman says.
Shelter clients are screened either in the evening at night shelters or during daylight hours when they show up at the day shelter for clean clothing and a shower. They receive cards, which are now a prerequisite for admission to all of the city’s shelters, that document they have received the skin test. Nurses go to shelters twice a week, placing skin tests the first day and reading them the next. Most cards can be issued on the spot, as soon as the skin test has been read.
The decision by city shelters to buy into the screening, which evolved over a period of time, is key to the program’s success, says Burman. The screening program began in the early 1990s, but at that point, having a card was voluntary, "which meant no one did it," he notes. Then, several cases of TB were linked to shelters, and some shelter staff were found to have converted their skin tests.
Because of those incidents and with input and encouragement from the health department, the shelters eventually decided to make having a card mandatory, he says. The move toward mandating the cards started 1995; now, all require guests to carry a card.
The system has some drawbacks
The card system isn’t foolproof, he adds. The cards have become a saleable commodity on city streets. "We even know what the market value of a card is," Burman says wryly. Clients sometimes lose their cards, as well. TB controllers finally decreed that individuals must wait for a period of time before they can be re-tested, to cut down on "lost cards" that actually had been sold.
"Some shelter clients feel [the system] is a hassle," says Jan Tapy, an adult nurse practitioner who serves as a primary care provider at the health department. "We’ve had people who’d lost too many cards [and were denied a bed] leave angry." (No one, she adds, is denied a bed in really cold weather.)
But other shelter clients, newly awakened to the dangers of TB transmission, like the system, she adds. "I’ve had people at a shelter come up to me and say something like, All the people here are coughing! I don’t want to be around them.’"
The number of people with positive skin tests runs as high as 30%. Once they’ve been screened for active disease, about a third of those who test positive and are judged to be at high risk for reactivation are offered isoniazid prophylaxis. In one case, about 63% of close contacts to a case completed prophylactic therapy, Tapy adds.
Skin testing isn’t completely accurate, of course, Burman points out. "We know that up to 20% of patients with active pulmonary TB are skin-test negative." Still, anyone who is symptomatic is referred by outreach workers doing the skin testing for a full evaluation, including a chest X-ray. "Hopefully, that means people who are sick enough to test negative are [identified]," he explains.
Those found to have active TB are hospitalized and then housed at no charge in a motel for several months until they’re deemed noninfectious. "If they break their quarantine, we have a lock-up ward where they can go for a couple of days," Tapy says. "They usually get religion after that and keep the rest of their appointments."
In Birmingham, a different route
In Birmingham, TB controllers have opted instead to collect sputum samples. Over a recent nine-month period, working from cultures and smears from the samples, the process has netted seven cases — four of them smear-positive — out of 438 people screened. That represents only a portion of the city’s homeless population (which, according to 1995 estimates, numbers almost 2,700); but already, DNA fingerprinting suggests there may have been a decline in recent transmission, says Nancy Brook, disease intervention specialist and acting director of TB control for the state of Alabama.
One reason for the program’s apparent success may be indirect, she says: Having representatives from the health department show up on a regular basis at shelters probably has given TB controllers a heightened profile within the homeless community, and it may have encouraged many homeless people to seek care who might not otherwise have done so.
The Birmingham program depends partly on volunteer labor, which has been key to making it work, Brook says. Volunteers are recruited from the schools of medicine and of public health at the University of Alabama at Birmingham. Working alongside paid outreach workers from TB control, the volunteers visit four men’s night shelters in the city four times a year. Plans call for expanding the visits to include two women’s shelters, she says.
"Visiting four shelters four times each a year may not sound like a lot of work, but it is," she adds. Visits have to be scheduled late in the day, when outreach workers ordinarily would be ending a long day on the streets; and the worse the weather, the better the yield because homeless people are most likely to turn out in search of shelter when it’s wet and cold.
Why sputum and not skin testing
The decision to begin screening the city’s homeless population (and to use sputum collection as the means for doing it) was based on a number of factors, says Brook. "We had several cases [among homeless people]. When we tried to do contact investigation, we found it was almost impossible."
Once the decision to begin targeted screening was made, there was the matter of how to go about it. Offering chest X-rays wasn’t feasible, not least because the county doesn’t own a portable X-ray machine. Skin testing didn’t seem to be a good choice, either. "We tried skin testing, but there was the problem of having to go back and read the tests," Brook says. "[Skin testing] takes a lot of time; plus, without documentation, what were we to do with people who’d test positive but who told us their skin test had looked the same way last time?"
Workers and volunteers began collecting sputum samples in 1996, with the program starting rather slowly due to personnel turnover and assorted funding problems.
Controllers rotate shelter visits
A citywide shelter policy prohibits guests from staying more than five days in a row at the same facility, so in theory, everyone should pass through each shelter sooner or later. But some people patronize one shelter exclusively, even if that means going without a bed some nights; plus, clients enrolled in substance abuse programs stay in the same place until they finish treatment. So TB controllers decided to visit at least four of the city’s six major shelters four times a year.
Outreach workers and volunteers work from 5:30 p.m. to 7 p.m., screening between 30 and 60 people. The procedure includes some history- taking — what shelters the men have stayed at recently, for how long, and how long they’ve been in the shelter system.
Once the survey is completed, shelter clients go back outside, usually to a station set up at the rear entrance of the shelter, for sputum collection. Hardly anyone has a problem producing a sample, Brook says. Turnaround time for lab results is quick, usually no more than two days. "It’s a time-consuming process," she says. "But we are getting yields, so it’s worth it."
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