TB tracking prevents HCW exposures

'Good — but see where prevention didn't work.'

Closely tracking infections among health care workers helps Vanderbilt University Medical Center in Nashville, TN, detect clusters and prevent further infections.

Tuberculosis remains the primary infectious disease threat to health care workers, with exposures occurring from delays in diagnosis, according to a Vanderbilt analysis. From 2006 to 2011, 1,844 employees were exposed in 62 events, resulting in nine new latent TB infections, the analysis showed. The tracking of specific exposures was possible because of Vanderbilt's homegrown occupational health surveillance system.

The occupational health software links with the human resources database, so employee health professionals can determine who was working in a particular unit. If there is a conversion on a TB skin test, they can check to see if any other conversions occurred on the same unit.

Twice, Vanderbilt has detected increased conversions and provided additional training and personal protective equipment, says Mary Yarbrough, MD, MPH, FACOEM, associate professor of clinical medicine and executive director of Vanderbilt's health and wellness program.

On a quarterly basis, employee health works with infection control to review cases of TB conversions and other exposure events, Yarbrough says.

"We're so focused on prevention, which is good, but we've also got to look and see where the prevention didn't work," she says. "Where did we have our exposures? What diseases resulted from that and what can we do [to prevent the exposures]?"

Connections with conversions

The surveillance software makes it easy to look for connections. "If someone comes in and converts on a TB test, we can go back and see if they had any exposures. Were there any other people on that unit that had conversions or exposures?"

For example, when an increase in conversions was detected in the emergency department, occupational health investigated and found that employees were not always closing the door of isolation rooms and some employees were not wearing the respirators. After re-training and a switch to bi-annual TB testing, no conversions occurred the following year, says Yarbrough, who presented her results at the annual stakeholder meeting of the National Personal Protective Technology Laboratory of the National Institute for Occupational Safety and Health (NIOSH) in Pittsburgh.

Another cluster of TB conversions was detected among environmental services workers. It turned out that respirator use had waned with the switch to new management of the contracted service. "We were able to quickly educate [workers] and get their masks issued," Yarbrough says.

Yarbrough also was able to establish the effectiveness of the respiratory protection program. Employees who work with TB patients and wear N95 respirators do not have a greater risk of conversion than employees who don't work with TB patients, she says.

Early identification is key

The surveillance program also allowed Yarbrough to look at other airborne diseases. In that six-year period, there were two measles exposure events that resulted in the exposure of 17 employees. They were all vaccinated and there were no secondary cases.

Similarly, the vaccination effectiveness also was demonstrated in the 45 varicella exposures. While 1,434 employees were exposed, none developed varicella disease. The lower rate of pertussis vaccination (34.5%) put employees at greater risk. In 89 exposure events, 818 employees were exposed, leading to two cases of occupationally-acquired pertussis.

The electronic health record helps occupational health improve vaccination rates, says Yarbrough.

TB exposures were most likely to be associated with unidentified cases, she says. Most often, those are cases that do not present with "classic" symptoms, such as night sweats, cough and weight loss, she says. The patient may have been transferred to another facility with a diagnosis other than TB, or may have TB in addition to another medical condition or even a surgical need, she says.

Vanderbilt is constantly looking for ways to improve the detection of TB, Yarbrough says. Fortunately, most cases are detected swiftly. "We have lots of cases that don't result in exposures. People use precautions and everything works like it should," she says.