CDC draft guidelines call for a major cutback on annual TB testing

Risk assessment gives hospitals flexibility

How hospitals test health care workers for tuberculosis infection would change fundamentally for the first time in 10 years under draft guidelines from the Centers for Disease Control and Prevention (CDC).

Hospitals that treat few TB patients could eliminate annual tuberculin testing. Hospitals that see many such patients would no longer be high risk and could reduce the testing for many employees. And hospitals could begin using a less labor-intensive, more specific blood test.

"We’ve had 11 years of declining transmission of TB," says Michael Iademarco, MD, MPH, associate director for science in CDC’s Division of TB Elimination. "There was a need for revision to address the changes in the epidemiology of transmission."

The current guidelines, issued in 1994, came amid a resurgence of TB in the 1980s and early 1990s. Infection control interventions led to a decline in hospital-based TB outbreaks and overall TB rates, although the rate of TB varies greatly around the country.

New guidelines are needed to give hospitals greater flexibility in designing their infection control response to TB, Iademarco explains. "It’s a more strategic approach, more comprehensive, that takes into account the changing epidemiology."

The draft guidelines streamline the TB risk assessment. Instead of five risk categories, there now are just three: low, medium, and potential ongoing transmission.

"Today, there’s no reason for anyone to be anything more than medium risk," Iademarco notes. "If you are, then you need to take more intensive steps until you get back to medium risk."

Low-risk inpatient settings are defined as those with fewer than three TB patients in the past year (if there are fewer than 200 beds overall) or fewer than six TB patients in the past year (if there are more than 200 beds overall). A hospital may have different risk levels for different settings, such as the intensive care unit, the pulmonary ward, or the urgent care center.

CDC provides a risk-assessment worksheet, several examples of risk-assessment decisions, and step-by-step guidance. The draft guidelines are available at www.cdc.gov/nchstp/tb/Federal_Register/default.htm.

Hospitals may need to elevate their risk classification if they have a "relatively high level of immunosuppression," such as patients with HIV or organ-transplant recipients. Hospitals would also consider the level of TB in the community, an increasing incidence of TB diagnoses, or patients with drug-resistant strains of M. tuberculosis.

"In general, if uncertain about whether to classify a setting as low risk or medium risk, classify the setting as medium risk," the draft guidelines advise.

Save resources for other IC measures

The draft guidelines could be liberating for hospitals that treat few TB patients. "They’ll still have to do a thoughtful comprehensive risk assessment," Iademarco explains. "If, in that careful work, they determine their risk is low, then they should have the flexibility to take their infection control resources and, in a preventive way, continue to keep it low and not be saddled with doing lower priority screenings."

In other words, those resources used to track employees and administer the skin tests now can be used for other TB infection control measures. All hospitals should provide baseline screening of all health care workers upon hire with a two-step tuberculin skin test or QuantiFERON test, the draft guidelines advise.

The reduction in TB testing also reflects another reality: "If you test low-risk people, you’re going to end up with a lot of false positives," explains Henry Blumberg, MD, hospital epidemiologist at Grady Memorial Hospital in Atlanta. "The idea is not to do repeated tests in low-risk situations."

For facilities that treat larger numbers of TB patients, annual or even semiannual testing makes better sense, he says. "The test works really well when you’re dealing with a high-risk population," adds Blumberg.

Hospitals that currently are considered high risk would be allowed to reduce testing from every six months to annually. "If they’re a medium-risk institution, it’s possible they can justify annual screening as long as they can be sure they don’t have ongoing transmission," Iademarco adds.

Increased rates or a cluster of conversions on the QuantiFERON or tuberculin skin tests would classify the hospital as a facility of "potential ongoing transmission," requiring testing as frequently as every eight to 10 weeks "until lapses in infection control have been corrected and no further evidence of ongoing transmission is apparent," the draft guidelines state.

Currently, the risk assessment ranges from minimal and very low risk to high risk. Minimal risk facilities do not admit TB patients and are in communities without a reported TB case in the past year. Very-low-risk facilities do not admit TB patients but may evaluate cases in the outpatient setting. Those facilities do not need to conduct routine annual TB screening tests, although if TB patients have been evaluated in the past year, health care workers in the area where they were seen would need the screening.

Consider patterns of transmission

In conducting the risk assessment, the CDC also expects hospitals to consider the realities of today’s TB transmission.

TB is more prevalent among foreign-born Americans and is more transmissible among people with HIV infection. Hospitals in a rural area may not admit TB patients, but may hire foreign nurses due to the nursing shortage. That could be a factor in considering the TB risk assessment, Iademarco points out.

"What they’re worried about is the health care worker who brings TB into the hospital," he says. "Unlike the ’90s, our attention is more focused on community risk factors.

"It’s a different era," says Iademarco. "I think we have to recognize the success of the previous guidelines, but they needed significant updating."

The draft guidelines incorporate current trends in both TB transmission and new approaches to testing and treatment.

They add information about how to perform and interpret the QuantiFERON test. In December, the Food and Drug Administration approved the new version of the blood test, called QuantiFERON-TB GOLD. CDC promised to release guidelines within months on using this improved blood test, explains Mark Boyle, senior vice president for sales and marketing at Cellestis Inc., the Valencia, CA-based division of the Australian company.

The new version tests for specific proteins of M. tuberculosis. Results are available in 24 hours. "With the new QuantiFERON-TB GOLD test, anyone who had BCG will come out negative on our test," he continues. "Now we have a better picture of what’s going on. We can focus on the people who are really positive."

QuantiFERON-TB GOLD has a cost of about $25 per person tested, including $15 for the agent and $10 for the lab time, Boyle notes.

While that is significantly higher than the cost of the skin test reagents, the blood test eliminates much of the administrative burden and labor involved in the skin test.

"We’re removing it from a clinic-based system to a lab-based system where it’s more controlled," he adds.