Molecular Testing Reduces Isolation Time in Possible TB

Veronica Hackethal, MD

August 29, 2018

Using a clinical algorithm to implement rapid molecular testing can decrease isolation time in patients with suspected active tuberculosis (TB), a study found. The study also confirmed the accuracy of the molecular TB test.

Results were published online August 28 in JAMA Internal Medicine.

The study represents the first published data on the real-world effect of molecular testing to guide discontinuation of respiratory isolation for TB.

"Routine use of molecular assay testing should be strongly considered to provide faster, more patient-centered care to hospitalized patients undergoing evaluation for TB in the United States and other low TB-burden settings," Lelia H Chaisson, MSc, from Yale School of Public Health, New Haven, Connecticut, and colleagues write.

"Together, these measures of impact place rapid molecular testing for TB among a select group of interventions that have been shown to advance the "quadruple aim": improved population health, a better patient experience, a better clinician experience, and lower costs," they add.

Since the 1980s, when several hospital outbreaks of TB occurred, the Centers for Disease Control and Prevention has issued guidelines to prevent this from happening again. The guidelines include screening, personal protective equipment, and airborne infection isolation in a private negative pressure room until active TB has been ruled out.

However, stays in isolation rooms are often prolonged because conventional testing requires negative cultures of sputum samples collected over 2 or more days. That can delay care and place a burden on healthcare resources and costs.

A faster testing approach uses semiautomated molecular testing such as GeneXpert MTB/RIF (Cepheid), which can provide results in fewer than 2 hours. Several professional societies have endorsed this test, and the Centers for Disease Control and Prevention recommends its universal adoption. However, hospitals have been slow on the uptake, and the test has yet to be widely adopted.

To test methods to encourage the adoption of molecular testing, the researchers devised a clinical risk-assessment algorithm and conducted a cohort study among patients evaluated for active TB at a large academic hospital between January 2014 and January 2016.

The algorithm was developed using input from an interdisciplinary group of experts in infection control. Researchers distributed it to clinical staff through information sessions, handouts, wall posters, a website link, and the electronic order entry system.

The algorithm used clinical assessments to guide how many sputum samples to collect. It allowed discontinuation of isolation after two negative molecular test results in individuals with low risk for active TB, and after three negative molecular tests in individuals with high risk for active TB, as determined by bedside exam.

The study included 621 adults with a median age of 54 years; 26% were women.

Compared with preimplementation of the algorithm, postimplementation results suggested that using the molecular test provided substantial clinical and financial benefits. Discontinuation of isolation was significantly faster with the molecular testing (2.9 vs 2.5 days; P = .001), as was time to discharge (6.0 vs 4.9 days; P = .003).

Using the molecular testing algorithm accurately diagnosed seven patients with active TB confirmed on sputum culture. It accurately excluded 251 patients with negative cultures, with no false positives. Only one false negative resulted from using the molecular assay, and the error was caught on a second molecular testing sample sent as a result of the risk stratification algorithm. Molecular testing also detected one patient with a negative culture who would have otherwise gone undetected.

Follow-up found that approximately 70% of clinicians adopted molecular testing, with sustained use up to 2 years after implementation.

The molecular testing algorithm saved an average of $13,347 per isolated TB-negative patient.

Assuming the hospital evaluates 250 patients for active TB annually, estimated cost savings would be $3.3 million.

The authors mention several limitations: The study took place at a single academic medical center with substantial experience with TB evaluation, so results may not apply to other settings.

Despite these limitations, Max Salfinger, MD, from the National Jewish Health Center, Denver, Colorado, writes in an invited commentary: "The results of this novel study are very encouraging."

"Although these differences [in reduction of time in isolation and decrease in time to hospital discharge] do not seem dramatic, the savings they produce are meaningful," he adds.

He suggests clinicians and hospital administrators work to identify barriers to wider adoption of rapid molecular testing for TB. They should also assess whether this new algorithm can increase adoption in other settings.

Referring to Everett Rogers, whose work about adoption of new technology identified innovators, early adopters, early majority, late majority, and laggards, Salfinger urges: "Be that early adopter and order [molecular testing] more often for patients with possible TB to decrease airborne infection isolation cost and provide better health care."

The study was funded by grants from the University of California San Francisco/San Francisco Department of Public Health Caring Wisely Program; the San Francisco Hearts Foundation; and the Johns Hopkins HIV Epidemiology and Prevention Sciences Training Program. The GeneXpert MTB/RIF test kits were donated by GeneXpert. The authors and Salfinger have disclosed no relevant financial relationships.

JAMA Intern Med. Published online August 27, 2018. Article abstract, Commentary extract

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