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NAAT cuts waste in treatment of TB, comorbidities
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Nucleic acid amplification testing reduces clinical waste in addition to differentiating tuberculosis from similar pathogens, researchers found.
The method (NAAT) did so among patients with TB–positive acid-fast bacilli (AFB) smear tests.
“Through this 10-year longitudinal study, we highlight multiple advantages NAAT has introduced in the routine management of AFB smear-positive patients, especially in the immunocompromised patient populations,” the study researchers wrote in Open Forum Infectious Diseases.
Their analysis included 130 patients who were treated at Henry Ford Hospital in Detroit, Michigan, between Jan. 1, 2001, and Dec. 31, 2011. All those patients had AFB smear-positive results for TB.
The researchers cited studies showing that NAAT, unlike the AFB smear, is highly accurate in distinguishing TB from other nontuberculosis mycobacteria (NTM). In their own study, they sought to find how it also might reduce time patients spend on unnecessary TB treatment, among other factors.
They found that 80 (61.5%) patients had NAATs that specified TB. Two of the 50 patients who yielded negative NAAT results produced TB on culture. Four different NTMs grew in cultures from the remaining 48 patients.
NAAT had 97.6% sensitivity and 100% specificity in differentiating TB from NTMs. In addition, the mean turnaround time for NAAT was 1.43 days, compared with 12.7 days for mycobacterial culture.
The researchers also examined the effect of NAAT on the time patients would spend in airborne isolation to prevent the spread of potential TB. They did so by comparing the data from their study with the expected isolation time for patients with positive AFB results before NAAT was introduced to the hospital in 2001.
They found that NAAT resulted in a mean of 6.1 less days in isolation than would have been expected before 2001. The method also reduced the time of unneeded TB therapy by a mean of 9.5 days compared with pre-NAAT years.
Patients with a positive AFB and negative NAAT had a mean hospital stay of 12 days vs. 25.4 days for those who tested positive with both methods. Likewise, those with a negative NAAT spent a mean time of 6 days in airborne isolation, compared with 23.1 days for those who tested positive with both methods (P < .001).
The researchers noted that NAAT will have a particular impact on patients with certain comorbidities beside TB.
“It is notable that the positive predictive value of a positive AFB smear was much lower in our immunocompromised HIV–infected, cancer and transplant subpopulations who have a high likelihood of NTM infection,” they wrote. “NAAT will be most useful and have a greater impact in clinical and infection control decision-making in these populations.” – by Joe Green
Disclosure: The researchers report no relevant financial disclosures.
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