Missed diagnosis, outdated PPDs lead to chaos
As tuberculosis rates decline nationwide, employee health professionals are facing a new challenge of complacency. Low-risk hospitals are vulnerable for sudden outbreaks and should make sure they remain prepared for the occasional case of TB, tuberculosis experts say.
"The lack of experience means that there’s probably more of a chance that the diagnosis of tuberculosis could be missed at first," says John Jereb, MD, medical epidemiologist in the field services branch of the Division of Tuberculosis Elimination at the Centers for Disease Control and Prevention (CDC) in Atlanta. "The sicker the patient gets, the more contagious the patient gets. There’s a compounding of bad events when the diagnosis is delayed."
That describes a recent scenario at The Ottawa Hospital, in which a tuberculosis patient exposed numerous other patients and health care workers before he was diagnosed properly. TB rarely is seen at the hospital; the incidence of TB in the Ottawa region is five cases per 100,000 population.
The patient, who had previously lived in Venezuela, first went to a walk-in clinic, where the doctor gave him a referral to a specialist. The day before his appointment, he developed bloody sputum and spent two hours in the emergency department (ED). He was discharged — still without a diagnosis of TB. Health care workers in the ED did not use respirators or take any precautions. The next day, a respiratory specialist diagnosed TB and began treatment.
About six weeks later, the patient suffered a heart attack. He still had active TB infection, but he was mistakenly put into a positive-pressure room in the coronary care unit. He needed an urgent cardiac catheterization, but there were no N95 respirators in that unit. Health care workers used procedures masks, instead, although those do not prevent the transmission of TB.
"Remarkably, we had very little known transmission as a result of all these things," says Eileen Bailey, RN, CIC, infection control practitioner, who presented her lessons learned at a recent conference of the Association of Professionals in Infection Control and Epidemiology. Two health care workers had positive skin tests, but because their screening had not been conducted annually, the hospital can’t be sure that the infection occurred from this case.
The incident led to a review of the hospital’s TB precautions and inservice training on the symptoms of TB and protective measures. All the designated negative-pressure rooms have been checked, in light of recent renovations, to see if they still function.
Employee health is attempting to improve compliance with annual skin testing. "Education is so important," Bailey says, "so people understand the reason for having their PPD [purified protein derivative tests] done annually."
Ottawa Hospital is not alone. Undiagnosed TB has led to transmission in other areas, such as the 66 cases of latent TB infection uncovered at a food-processing plant in Maine, which has a statewide incidence of TB of 1.9 cases per 100,000. Usually, there are about 24 TB cases a year statewide in Maine.1
"The diagnosis is missed everywhere in the world," Jereb says. "Even in countries where tuberculosis is very common, the diagnosis is missed. It’s not an easy thing to diagnose."
But there are steps hospitals can take to maintain their vigilance and protect employees. Here are some recommendations from Jereb and his colleagues at the CDC:
• Use a two-step process for baseline testing.
One inherent problem with the TB skin test involves false positives. The issue becomes even more pronounced when it’s used in an area of very low incidence of TB. (The CDC defines very low risk as a facility that hasn’t treated a TB patient in an outpatient area in the past year and would transfer any TB patients to other facilities for inpatient care. Hospitals that see five or fewer TB patients a year are considered low risk.)
"Once a condition becomes very rare, if you find a positive, then your result is more likely to be a false positive than a true positive," Jereb says. "It sets up a scenario in which we’re going to be very suspicious that positive results may be false positives."
The two-step TB test involves administering the skin test twice within a one week to three week period. That allows employee health professionals to identify employees who have a "boosting" effect from the skin test — in other words, the initial test sensitizes their immune system, leading to a positive result on subsequent tests.
"You have a useful bit of information that my tuberculin skin test is reactive because of boosting," Jereb explains. "You don’t have any way to test me or screen me for latent TB infection from now on out."
By detecting employees with this "boosting" effect, you may be ensuring that they don’t receive unnecessary treatment for latent TB infection after future tests turn out positive.
• Consider other causes of false positive skin tests.
"For employees who have good baseline testing with two steps, if they have a positive later on, you know it’s not a boosting response. But you still can’t be sure it’s not a false positive. It’s just not a perfect test," Jereb says. "If we get calls about positive tests from a facility that never sees TB patients, our first guess is that they are false positive results — just based on the law of averages. The more positive results you find — the more of a pattern you find in the positive results — the greater the suspicion that it might be transmission," he says.
Latex allergy from residue from a vial stopper might lead to a react, although Jereb notes there aren’t any scientific data to support this. Also, the mycobacterium genus contains dozens of species. All of them may be able to make someone sensitive to the skin test.
Anyone who has received the bacille Calmette-Guerin (BCG) vaccine, which is common in many countries, is more likely to have a positive skin test result. And some foreign workers from countries with endemic TB, such as nurses hired from the Philippines, are likely to have been exposed to TB and may actually have latent TB infection. That’s true even if they had BCG because the vaccine is notoriously ineffective in preventing tuberculosis.
Experts in the local or state health department may help determine whether a skin test is reaction is likely to be a true positive.
• Don’t rely on annual chest X-rays.
"Annual chest X-rays should not be done on individuals with a positive skin test result," Jereb says. "The only reason to get a chest X-ray is if they have symptoms of tuberculosis."
Jereb cites a 1983 joint bulletin from the Food and Drug Administration and the World Health Organization for this long-standing advice.2
"The first time the skin test is discovered to be positive, the initial chest X-ray establishes a baseline and determines whether there could be some early tuberculosis at that moment," he says.
"There’s a world of literature that shows it doesn’t do a bit of good to get these chest X-rays annually. People don’t get tuberculosis on an annual schedule," Jereb says.
• Update your tuberculosis control plan.
The greatest challenge to TB control is the sense that TB isn’t likely to ever appear in your community or hospital.
Even if you’re in a rural community, individuals with TB may pass through for various reasons. They could be migrant farm workers, foreign students, or travelers on the nearest interstate. The first and more important control involves "keeping a high degree of suspicion at first contact," Jereb says.
Make sure you maintain your engineering controls — negative-pressure rooms that are available and have been checked periodically. Employees who are most likely to have contact with TB patients should receive training and fit-testing with N95 respirators.
The current CDC guidelines, released in 1994,3 advise hospitals to conduct a risk assessment and determine their needs for a PPD testing schedule and for maintenance of engineering controls.
Those guidelines now are under revision. The Occupational Safety and Health Administration (OSHA) rules on those issues may be delayed indefinitely. This fall, speculation rose that OSHA was preparing to halt action on its proposed TB standard, essentially killing it.
As you develop your facility’s TB control plan, bring in a variety of participants, including risk managers, union officials, and physicians, Jereb advises. Consider the particular population patterns of your community and the likelihood that TB patients may pass through the community.
Mostly importantly, Jereb says, you should consult your local health department for assistance — not just when you have a problem, but when you conduct your planning and review.
While federal agencies may be in flux regarding TB guidance, your state may have its own laws and regulations on skin testing and other worker protections.
"It’s very, very important that [employee health professionals] understand the influence and importance of their state health departments," he says. "They all have someone experienced in TB. They understand the laws; they know the policies; and they know how to get you help at the local level.
"When you want someone to back you up and to be there as your ally, that’s your health department," he says.
- Centers for Disease Control and Prevention. Progressing toward tuberculosis elimination in low-incidence areas of the United States: Recommendations of the Advisory Council for the Elimination of Tuberculosis. MMWR May 3, 2002; 51(RR05):1-16.
- Food and Drug Administration. Chest X-ray Screening Examinations. Rockville, MD: Department of Health and Human Services Publication (FDA) 83-8204.
- Centers for Disease Control and Prevention. Guidelines for preventing the transmission of mycobacterium tuberculosis in health care facilities, 1994. MMWR 1994; 43(RR13):1-132.