Sputum-based molecular assay accurately identifies culture-confirmed TB
A sputum-based molecular testing strategy (GeneXpert MTB/RIF) was safe, feasible, easily adopted, and was associated with both clinical and economic benefits in guiding the discontinuation of respiratory isolation for patients undergoing evaluation for active tuberculosis (TB), according to findings from a prospective cohort study published in JAMA Internal Medicine.
“Respiratory isolation is effective for reducing
nosocomial TB transmission, but delays care and places a
considerable burden on patients, clinicians, and
hospitals,” the investigators wrote. “Molecular
testing is simpler, faster, and more accurate than conventional
microbiologic testing and has been deemed a public health
priority, although it has not been widely adopted.”
A total of 621 consecutive patients undergoing a sputum
examination for active pulmonary TB during a 2-year period at a
San Francisco hospital were included in the
prospective analysis. Study investigators only included patients who had molecular
testing ordered and completed and measured the accuracy of the
testing strategy in reference to mycobacterial culture.
Additionally, the investigators evaluated the duration of each
testing and isolation process component, the length of hospital
stay, the average days in isolation and the hospital, and the
average cost associated with the molecular testing algorithm.
In the period prior to implementation of the molecular testing,
a total of 301 patients had ≥1 sputum microscopy and culture
ordered, with 233 (77%) patients having a rapid TB testing
evaluation process completed. Comparatively, a total of 234
patients out of 320 patients after implementation had a
molecular test ordered, whereas 98% of patients received results
for ordered tests.
Approximately one-quarter of participants were women (26%), and
the median age was 54 years (interquartile range, 44 to 63
years). In the 7 patients with culture-confirmed TB, the
molecular testing algorithm was associated with an accurate
diagnosis. Additionally, the algorithm resulted in the exclusion
of TB in the patients with
Mycobacterium tuberculosis (MTB) culture-negative
results (n = 251).
The investigators observed significant reductions from pre- to
post-implementation of the algorithm in the median duration to
final rapid test results (39.1 vs 22.4 hours;
P <.001), discontinuations of isolation (2.9 vs 2.5
days; P =.001), as well as reduced hospital discharge
(6.0 days vs 4.9 days; P =.003). Significant reductions
were also observed in cost, with the testing strategy associated
with an average cost-savings of $13,347 per isolated TB-negative
patient.
The authors highlight several limitations of the study’s
design, including its use of patient data from a single center,
which may limit generalizability of the findings.
In an accompanying
editorial, Max Salfinger, MD, commented on how these findings may impact
clinical practice. “Twenty years after the first US Food
and Drug Administration (FDA)-approved NAAT, the evidence showed
that clinicians and infection preventionists, as well as
hospital administrators, should work with all stakeholders to
identify barriers at their institution (eg, outdated electronic
ordering algorithms, not acknowledging system-wide savings when
only focused on laboratory expense) preventing a wider
implementation of NAAT testing,” he wrote. “In
addition, they should validate this new algorithm, so their
institutions can reap the potential substantial savings that
result from using a NAAT for patients with possible TB in
airborne infection isolation.”
Source:
Contagion
