QuantiFERON-TB Gold Plus | Back to Test Directory | ||||
Test Description |
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Interferon gamma release assay to determine latent Mycobacterium tuberculosis infection | |||||
Performed | Avg. Turnaround Time | Method | |||
Coralville, 8 a.m. - 5 p.m., M - F |
1 - 3 business days | Chemiluminescent Immunoassay (CLIA) - DiaSorin | |||
Fee | CPT Code(s) | ||||
$115.51 | 86480 | ||||
Specimen Requirements | |||||
Specimen Type: | Minimum 1 mL plasma in each tube; 4 tubes total | ||||
Collection Instructions: | QuantiFERON-TB Gold Plus tubes are calibrated to accept 1 mL of whole blood. Recommend a purge tube with use of butterfly needle. Fill to the black indicator mark on each tube. DO NOT overfill or underfill.
Not incubated (Call SHL for approval 319-335-4275): Immediately after filling shake tubes 10 times firmly. Specimen must arrive at SHL within 16 hours of collection. Ship at room temperature. Do not refrigerate or freeze. |
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Temperature and Stability: | Non-incubated specimens: 16 hours at room temperature. Incubated specimens: 3 days at room temperature. | ||||
Unacceptable Conditions: | Non-incubated tubes must arrive at SHL the same day as collection by 5 PM M-F. Incubated tubes must arrive at SHL within 3 days after incubation. | ||||
Expected Results: | QuantiFERON-TB Gold Plus: Negative, Indeterminate, Positive. Values in IU/mL of Nil, TB1 Antigen minus Nil, TB2 Antigen minus Nil, and Mitogen minus Nil. | ||||
Shipping Instructions | |||||
Use the SHL QuantiFERON-TB Gold Plus collection tubes, shipping materials, and container. Transport at ambient/room temperature. DO NOT REFRIGERATE OR FREEZE. Ship to the Coralville location. | |||||
Comments | |||||
QFT-Plus Positive: M. tuberculosis infection is likely. TB1 antigen and/or TB2 antigen minus Nil is > or = 0.35 IU/mL AND > or = 25% of Nil. Positive results in patients at low risk for TB should be interpreted with caution and repeat testing on a new sample should be considered. False positive results may occur in patients with prior infection with M. marinum, M. szulgai, or M. kansasii. QFT-Plus Negative: M. tuberculosis infection is NOT likely. TB1 antigen and/or TB2 antigen minus Nil is < 0.35 OR > or = 0.35 IU/mL AND < 25% of Nil. A single negative result does not exclude TB infection. In patients at high risk for M. tuberculosis infection, a second test should be considered. QFT-Plus Indeterminate: Likelihood of M. tuberculosis infection cannot be determined. Indeterminate due to a low IFN-gamma level in the mitogen (positive control) tube may occur due to a low lymphocyte count, reduced lymphocyte activity, or inability of the patient’s lymphocytes to generate IFN-gamma. Indeterminate due to a high level of IFN-gamma in the Nil (negative control) tube may occur due to heterophile antibody effects or nonspecific, circulating IFN-gamma in the patient’s blood sample. Repeat testing on a new specimen is suggested. See CDC guidelines for diagnosing and treating TB disease. | |||||
Alternate Names | |||||
Interferon-Gamma Release Assay for Tuberculosis, Latent Tuberculosis Infection (LTBI), QFT-Plus. |