INFECTIOUS DISEASES
Louisville Goes for the “Gold” in IGRA TB Testing
By Leslie A. Wolf, PhD, laboratory technical director, Louisville Metro Department of Public Health and Wellness
Our regional TB clinic staff were frustrated
by IGRA turnaround times, and we were
spending a lot of money to send out
these test requests used to aid contact
investigations. In 2016, the Louisville
Metro Department of Public Health and
Wellness (LMPHW) laboratory purchased
equipment, blood collection supplies
and test kits to verify the QuantiFERON ®
TB Gold (QFT-TB Gold) IGRA with initial
funding provided by APHL. Public health
laboratories (PHLs) in Fairfax County, VA
and Los Angeles County, CA provided
QFT-TB Gold samples to the laboratory for
verification and quality control purposes.
Benefits and Challenges
With the QFT-TB Gold test, clients have
one visit for the blood draw and do
not have to return for a second visit
as they do with the TB skin test. This
is especially helpful when performing
contact investigations in the field. For
the providers, results are timely with a
reduction in turnaround time from 7 days
to 2 days, and results are quality-assured
because laboratory technologists are able
to monitor pre- and post-analytic metrics
such as rates of positivity, indeterminate
and unsatisfactory specimens. Between
9/6/2016 and 8/31/2018, LMPHW
received 568 test requests from the TB
clinic. Of these, 19.6% were positive,
0.18% had indeterminate results and
1.06% were unsatisfactory. Prior to the
LMPHW performing IGRA testing, these
metrics were difficult to monitor and
improvements were hard to make.
Two challenges associated with bringing
the QFT-TB Gold test into the laboratory
are laboratory hours of operation and
incubation times. Since the laboratory
is only open Monday through Friday
from 8:00 am to 5:00 pm, samples must
be received by 4:30 pm to get processed
for overnight incubation. And Since the
laboratory is not open on Saturday, tests
requested on Friday must be sent to a
reference laboratory. Another challenge is
billing for the QFT-TB Gold test, primarily
related to clients’ insurance status and
reducing barriers by not charging a fee.
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LAB MATTERS Fall 2018
LMPHW Laboratory Technologist Maura Murphy performs QFT TB Plus testing. Photo: LMPHW
While overall, LMPHW is saving money
by having the test available in-house, the
laboratory budget takes a hit. vendor trained two additional staff and
the new QFT-TB PLUS assay was instituted
in July 2018.
Transition to QFT-TB PLUS Future Endeavors
Earlier this year, the manufacturer
decided to discontinue the QFT-TB Gold
test and replace it with QFT-TB Gold Plus
(QFT-TB PLUS). As we heard the news,
the laboratory gathered information
about how to proceed: we reviewed the
vendor information, listened to available
webinars and attended a roundtable
at the 2018 APHL Annual Meeting. We
developed a game plan based on our
remaining QFT-TB Gold kits and feedback
from our TB clinic staff, then took some
initial steps. As LMPHW continues to use the
new QFT-TB PLUS test for contact
investigations and special circumstances,
performance will be monitored with
usual quality indicators. Another metric
of interest is the number of clients with
discrepant TB1/TB2 results, something
the manufacturer claims could be a
better predictor of disease progression,
since none were observed during the
verification. Finally, long-term outcomes
concerning development of active TB
disease, age of client, immune status and
correlation with other clinical findings
will be excellent practicum projects for
MPH students. n
First, the software for using a four-point
standard curve was installed. Next, using
the training set provided by the vendor,
specimens were run in duplicate on one
day and in singlet a different day to gather
accuracy and precision data. There was
100% agreement with the expected results
and reproducibility, so writing the method
verification summary was completed. TB
clinic staff had been comfortable drawing
three QFT-TB Gold tubes, thus drawing
an additional tube for the QFT-TB PLUS
was not a concern for the nurses. The
procedure manual was updated, the
TB Nurse Amber Vittitoe draws blood from TB Clinic Supervisor
Kristy Henderson. Photo: LMPHW
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