Undiagnosed patient spreads TB to HCW

Case highlights need to isolate

The spread of active tuberculosis to health care workers and patients at a Washington, DC, hospital has highlighted the risk posed by the undiagnosed patient.

A phlebotomist developed active TB and 56 employees tested positive for latent TB infection after a highly infectious patient spent three weeks on general medical wards before being placed in a negative pressure room.

"Although the incidence of TB continues to decline, heightened awareness and vigilance is required by hospital staff to identify and treat persons with suspected TB promptly," says Kashes Ijaz, MD, MPH, chief of the Outbreak Investigations Team for the Division of TB Elimination at the Centers for Disease Control and Prevention (CDC). "Patients with suspected TB should be placed in respiratory isolation until infectious TB is ruled out."

Clinicians should be especially cautious when evaluating patients with HIV or AIDS because the signs of TB may be more difficult to discern. That was one of the complicating factors in the Washington, DC, case, Ijaz says.

The patient, who had AIDS and was schizo-phrenic, was first admitted to a different hospital with a fever and nonproductive cough. He had a normal chest X-ray and sputum specimen. "One sputum [test] may not be adequate to totally come to the conclusion that he was noninfectious. Usually we require three sputums," says Ijaz. "But there was some evidence that he was not infectious while he was at that hospital."

A few weeks later, the patient was admitted to the DC hospital with similar symptoms. The staff suspected that he had a central-line infection, treated him with intravenous vancomycin, and released him after six days. Three days later, he returned with these findings, according to the CDC’s Mortality and Morbidity Weekly Report: "His CD4 T-lymphocyte count was 30 cells/µL. A chest radiograph revealed hilar adenopathy, and a computerized tomography scan of the chest revealed a questionable left upper lobe infiltrate thought to represent pneumonia." He received ceftriaxone to treat suspected pneumonia.

Finally, the hospital staff learned that a stool culture obtained during the patient’s first admission had grown M. tuberculosis. "The patient was placed in isolation that day. Three subsequent sputum specimens were 4+ AFB smear-positive, indicative of a high degree of infectiousness, and a contact investigation was initiated," according to the MMWR report.

The patient, who was ambulatory, had contact with 261 patients and 784 staff. Four patients who were hospitalized in different rooms and the phlebotomist developed TB. Thirty-nine patients and 56 staff members had positive TB skin tests.

TB outbreaks persist around country

Although TB has declined continuously in the United States in the past decade, the risk of hospital-based outbreaks remains significant in many parts of the country. With 14,871 cases in 2003 (5.1 per 100,000 population), the rate of decline in TB was the lowest since 1992. Nineteen states reported increases in 2003, and 12 states and the District of Columbia had rates higher than the national average.

California, New York, and Texas had the most cases, but even less populated states can experience outbreaks. For example, Virginia reported a 5.4% increase in TB in 2003, the third consecutive increase. Although nationally TB is more prevalent among foreign-born people, the Virginia Department of Health noted that "TB affected people of all ages and races, and living in all geographic areas [of the state]."

Outbreaks also have occurred in Maine, Oregon, and Washington state homeless shelters.

"The real danger is the undiagnosed case," says Al DeMaria, MD, Massachusetts state epidemiologist. "Very rarely do you get TB from a diagnosed case."

Or, as Ijaz says, "The health care providers should think TB."

Respiratory etiquette, which was developed in the wake of severe acute respiratory syndrome, could help prevent the spread of TB from undiagnosed patients. A majority of hospitals are asking coughing and febrile patients to cover their mouths with tissues, wear surgical masks, and use alcohol-based hand gels. At many hospitals, health care workers in close contact with coughing and febrile patients, such as triage nurses, also wear surgical masks.

The decline in TB after CDC issued guidelines in 1994 led the Occupational Safety and Health Administration (OSHA) to withdraw its proposed TB rule Dec. 31, 2003. The agency noted that the occupational risk of TB was also lower. "[A]n OSHA standard is unlikely to result in a meaningful reduction of disease transmission caused by contact with the most significant remaining source of occupational risk: exposure to individuals with undiagnosed and unsuspected TB," the agency said in the Federal Register.1

Yet to Bill Borwegen, MPH, occupational safety and health director for the Service Employees International Union (SEIU), the recent outbreaks are evidence of the continued need for a standard.

"If [the Washington, DC, health care] workers had been trained as required under the proposed TB rule, they would have been more sensitive to the signs of a patient walking through the hospital, coughing," he says.

Strong infection control practices can reduce the risk from the undiagnosed patient, says Henry Blumberg, MD, program director of the Division of Infectious Diseases at Emory University School of Medicine in Atlanta and hospital epidemiologist at Grady Memorial Hospital. Grady still sees a significant number of TB patients. "TB is still on our radar screen and we put a lot of emphasis on TB infection control," he says.

Grady uses a screening tool to determine which patients should be isolated while TB is ruled out. (See sample tool, p. 76.)

"If TB is in the physician’s differential diagnosis, or if the sputum specimen for AFB is ordered, the patient has to be in respiratory isolation," says Blumberg. "If the patient is HIV infected and has an abnormal chest X-ray, he is isolated."

In 2003, the tuberculin skin test conversion rate among health care workers at Grady was four out of 5,306 administered, or 0.8%. Some employees may test positive due to community exposures or even false positives, he notes.

"Administrative controls are the most important [aspect of] a TB infection control program," Blumberg says. "I think almost all the risk is from undiagnosed patients. If you have someone who is undiagnosed and infectious, you can see what happens."

Screening may be challenging especially when evaluating HIV-infected patients, Ijaz adds. "Hosp-ital infection control programs are encouraged to develop protocols and implement administrative procedures for HIV-infected patients with pulmonary symptoms suggestive of TB," he says. That would include cough, fever, night sweats, and weight loss.

Some patients may be isolated unnecessarily until TB is ruled out, but the extra vigilance pays off, Blumberg says.

Reference

1. 68 Fed Reg 75,767-75,775 (Dec. 31, 2003).