Swift, Melanie melanie.swift at Vanderbilt.Edu
Mon Apr 25 09:58:09 PDT 2016

By your use of the term "borderline" I'm guessing you use T-Spot. But in case you were using it in a more generic sense, there is a good article by Wendy Thanassi et al delineating a retesting zone for QFT-GIT using the 0.35 - 1.11 IU/ml results. Wendy spoke at our AOHC a couple of weeks ago and shared a helpful algorithm using 1.1 as the cutoff for the first test and 0.7 as the cutoff for the retest. Again, that probably won't help you much if you are using T-spot.

The CDC lists this situation as a time when you might want to do both a TST and an IGRA. If the TST is negative and the person is low risk and the IGRA remains borderline, it's less like to be an LTBI case than if the TST is positive also.

You really should sit down with your medical director and develop a protocol based on the quantitative result, and the specific IGRA you use (T-Spot or QTF-GIT.) Hopefully he or she participates on this listserve also!

Here are some references that may be helpful in writing your protocol:


Melanie Swift, MD
Director, Vanderbilt Occupational Health Clinic

From: MCOH-EH [mailto:mcoh-eh-bounces at mylist.net] On Behalf Of Senior, Cathy (Employee Health)
Sent: Monday, April 25, 2016 11:12 AM
Subject: [MCOH-EH] IGRA

We use Interferon Gamma Release Assays ( IGRA) to test for tuberculosis on all new employees.  I have one new employee that I have tested twice (with approx one month in between testing) and both times the results were borderline.  Has anyone else had this come up and if so what did you do next?  This employee has no symptoms and no high risk activity such as traveling outside the country or having contact with anyone with known Tb.

Cathy Senior RN BSN CDE
Employee Health Director
Penn Highlands DuBois
100 Hospital Avenue
P.O. Box 447
DuBois Pa 15801
Phone 814-375-3392
Fax 814-372-2610
cesenior at phhealthcare.org<mailto:cesenior at phhealthcare.org>

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