New TB test proving much more accurate

A new tuberculosis test offered in Washington state only by the Spokane Regional Health District has been saving health care costs and putting minds at ease since February.

Recently the district used its new blood test, called QuantiFERON-TB Gold, to diagnose 30 people who had come in contact with someone in the region who had active TB. Of these, 19 people had tested positive by the commonly used tuberculin skin test, or TST. The medical technology for this test, previously known as a PPD for purified protein derivative, is about 114 years old.

The new blood test found that of the 19 people whose skin test yielded a positive result, only one was actually positive for TB.

“If we only had the skin test to go by, all 19 would have had to undergo treatment,” said Karie Brouillard, a health district microbiologist.

Treatment involves an X-ray, an assessment and as long as nine months on isoniazid, a drug that can cause liver damage for which a patient should be monitored, among other side effects.

Cost of the treatment could range from $739 to $1,311, said Cindy Jobb, the health district’s clinic manager.

“If we can prevent putting someone on this medication, it certainly makes sense,” Jobb said.

Someone who tests positive for the tuberculosis bacteria may not actually have the active disease. In these latent cases, the bacteria remain dormant unless the body becomes unable to fight off infection.

TB, an airborne disease that typically attacks the lungs, is responsible for more than 2 million deaths a year. Symptoms include a persistent cough, blood in sputum, fatigue, chills fever and night sweats.

While the incidence of TB is declining in the United States, it continues to surface in metropolitan “hot spots,” and it is particularly dangerous to people with immunosuppressive diseases such as AIDS.

The Food and Drug Administration approved the QuantiFERON-TB Gold test as a diagnostic tool in December 2004. It detects the body’s immune responses to specific proteins associated with tuberculosis infection.

Before the new QuantiFERON test was made available to the general public, the health district tested it on 142 clients and employees. This verification process showed the old skin test had a 50 percent failure rate, health district officials said.

Since introducing this test to Washington in February, the health district has conducted 181 tests, showing 50 positive results.

The district is taking appointments for the test, which is given Tuesdays, Wednesdays and Thursdays at its clinic in the Public Health Center, 101 W. College Ave., by calling (509) 324-1500. Test results are made available once a week.

Cost is $53 for patients whose blood is drawn at the clinic and $33 for samples drawn elsewhere. One limitation of the test is that it must be started within 12 hours of the blood draw.

“People have been willing to drive across the state to be drawn,” Brouillard said.