Lab Matters Fall 2018 | Page 28

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. 26 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 PublicHealthLabs @APHL