QuantiFERON®-TB Gold Plus, 4 Tubes, Draw Site Incubated (QUAN4I)

LAB7208

36971

1 mL whole blood collected in each of the following tubes:
QFT-Nil control (gray cap, white or gold ring) tube
QFT-TB1 antigen (green cap, white or gold ring) tube
QFT-TB2 antigen (yellow cap, white or gold ring) tube
QFT-Mitogen control (purple cap, white or gold ring) tube

0.8 mL in each tube

Note: Specimen collection locations >3350 feet above sea level should use the QuantiFERON® collection kit designed for "High Altitude" (tubes with a gold ring on tube top)

For each patient, collect 1 mL of blood by venipuncture directly into each of the 4 QFT-PLUS blood collection tubes. These tubes should be at 17-25° C at the time of draw.

If a "butterfly needle" is being used, a "purge" tube should be used to ensure that the tubing is filled with blood prior to the QFT-PLUS tubes being used.

Immediately after filling the tubes, shake them 10 times just firmly enough to ensure the entire surface of the tube is coated with blood, to solubilize antigens on tube walls.

Each of the four tubes must be transferred to a 37° C +/- 1° C incubator as soon as possible and within 16 hours of collection for 16-24 hours. If the blood is not incubated immediately after collection, re-mixing of the tubes by inverting 10 times must be performed immediately prior to incubation. The specimen rack should sit off the floor of the incubator and the tubes should be upright.

Following incubation either:
A. Centrifuge each of the 4 incubated collection tubes for 15 minutes at 2000-3000 RCF(G). Label with patient name, identification number, and date of collection. Deliver to Quest Diagnostics at 2-8° C. Samples will be stable for 28 days at 2-8° C (refrigerated).
*OR*
B. Immediately transport the 4 collection tubes to Quest Diagnostics between 4 and 27° C. Samples will be stable for 72 hours at 4-27° C (refrigerated or at room temperature).

The Centers for Disease Control and Prevention (CDC) has provided guidance on clinical considerations for tuberculosis (TB) testing such as QuantiFERON®-TB Gold Plus in conjunction with COVID-19 mRNA vaccines. Please refer to the QuantiFERON®-TB Gold Plus FAQ link (https://education.questdiagnostics.com/faq/FAQ204) for more detailed information on the latest CDC guidelines regarding TB testing and COVID-19 vaccines.

QFT-Nil control (gray cap, white or gold ring) tube
QFT-TB1 antigen (green cap, white or gold ring) tube
QFT-TB2 antigen (yellow cap, white or gold ring) tube
QFT-Mitogen control (purple cap, white or gold ring) tube

Refrigerated (cold packs)

Uncentrifuged specimens
Room temperature: 72 hours after incubation
Refrigerated: 72 hours after incubation
Frozen: Unacceptable

Centrifuged specimens
Room temperature: Unacceptable
Refrigerated: 28 days
Frozen: Unacceptable

Non-incubated specimens • Received frozen

Negative

This test is a blood-based interferon-gamma release assay (IGRA) used as an aid in the diagnosis of Mycobacterium tuberculosis infection. It is an immune response-based, indirect test for M tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations. Additional testing is needed to determine if a person who has tested positive has latent tuberculosis (TB) infection or TB disease.

This in vitro diagnostic test uses a peptide cocktail simulating ESAT-6, CFP-10, and TB7.7 proteins to stimulate cells in heparinized whole blood. Detection of interferon-γ (IFN-γ) by ELISA is used to identify in vitro responses to those peptide antigens that are associated with Mycobacterium tuberculosis infection.

This test uses a 4-tube blood collection method, which requires incubation before submitting to the lab. For the single-tube QFT-Plus testing option, see test code #36970.

Guidelines recommend testing for individuals who 1) have been exposed to a person with latent or active TB, including the general population and healthcare workers; 2) are from TB-endemic countries, which include most countries in Latin America, the Caribbean, Africa, Asia, and Eastern Europe, and Russia; 3) work in high-risk settings, such as correctional facilities, long-term care (LTC) facilities, nursing homes, and homeless shelters; or 4) have HIV or have an injection drug substance use disorder [1].

All of these individuals can be tested with either a traditional tuberculin skin test (TST) or an IGRA. However, the American Thoracic Society (ATS), the Infectious Disease Society of America (IDSA), and the Centers for Disease Control and Prevention (CDC) jointly prefer an IGRA test for individuals who have been vaccinated against bacillus Calmette-Guérin (BCG) or are not likely to return for the follow-up portion of the TST (and in both cases are at least 5 years old and likely to have TB infection and are at low or moderate risk of disease progression, or in whom it has been determined that TB testing is necessary [1]. The QuantiFERON-TB Gold test has specificity >99% in low-risk individuals and sensitivity of 92% in individuals with active disease [2].

In contrast to the TST, IGRA testing for TB requires only 1 patient visit (instead of 2). Also, IGRAs are not associated with the booster phenomenon, in which previously infected individuals generate a false-positive on a TST; and prior BCG vaccination does not generate a false-positive result. Note that for children aged 2 and above, either TST or IGRA can be used [3,4].

The CDC does not recommend dual testing with both a TST and an IGRA, unless the goal is to confirm a positive result, or when a high-risk individual’s test results are negative and there is clinical suspicion of TB. In this clinical situation, dual testing is used for confirmatory purposes [4].

For more information about TST versus IGRA testing, please visit the QuantiFERON®-TB Gold FAQs page.

Note: Specimens collected for this test must be transferred to a 37 °C incubator as soon as possible (within 16 hours of collection). An alternative, single-tube test option (QuantiFERON®-TB Gold Plus, 1 Tube; test code 36970) allows the specimen to be stabilized for up to 48 hours before incubation.

References
1. Lewinsohn DM, et al. Clin Inf Dis. 2017;64:111-115.
2. QuantiFERON®-TB Gold Elisa [package insert]. Germantown, MD: Qiagen; August 2016.
3. American Academy of Pediatrics. In: Kimberlin DW, et al, eds. Red Book: 2018 Report of the Committee on Infectious Diseases, 31st ed. Itasca, IL: American Academy of Pediatrics;2018: 829-853.
4. CDC. Fast facts: Interferon-gamma release assays (IGRAs)-blood tests for TB infection. Published November 2011. https://www.cdc.gov/tb/publications/factsheets/testing/igra.htm