Test Detail

QuantiFERON-TB Gold Plus

Performed	Avg. Turnaround Time	Method
Test Description		Contact: Serology (319) 335-4291 Test Request Form: Serology/Immunology SHL OpenELIS Code: 951
Interferon gamma release assay to determine latent Mycobacterium tuberculosis infection
Coralville, 8 a.m. - 5 p.m., M - F	1 - 3 business days	Chemiluminescent Immunoassay (CLIA) - DiaSorin
Fee	CPT Code(s)
$121.29	86480
Specimen Requirements
Specimen Type:	QuantiFERON-TB Gold Plus tubes: Minimum 1 mL plasma in each tube; 4 tubes total. Alternatively, one 5-mL Lithium Heparin or Sodium Heparin tube filled with plasma can be used for long distance transport.
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. Incubated at collection site (Recommended): Immediately after filling shake tubes 10 times firmly. Blood must be incubated within 16 hours of collection. Incubate tubes upright at 37 +/- 1 degrees C, for 16 to 24 hours. Ship incubated tubes at room temperature to SHL within 3 days of incubation. If tubes are not incubated immediately after collection, re-shake 10 times prior to incubation at 37 degrees C. Centrifuging specimens will occur at SHL within 3 days of incubation stop date. If specimens will not arrive at SHL within 3 days of incubation than submitting lab must centrifuge specimens (15 minutes at 2000 to 3000 RCF = g). After centrifugation the sample is stable for 28 days refrigerated 2-8 degrees C.
Shipping:
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. 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. Contact the SHL courier to arrange time-sensitive pickup of blood specimens.
Temperature and Stability:	Non-incubated specimens: 16 hours at room temperature. Uncentrifuged incubated specimens: 3 days at room temperature. Centrifuged QuantiFERON-TB Gold Plus tubes: Refrigerate (2-8 degrees C); stable for up to 28 days. Lithium Heparin or Sodium Heparin tube: Hold for 3 hours at room temperature, then refrigerate (2-8 degrees C) up to 48 hours.
Rejection Criteria:	Specimens will be rejected if received under these conditions: Samples not processed correctly. Blood collection under or over filled in each tube. Blood is hemolyzed. Incubation start date and time is greater than 16 hours from collection. Incubation stop date and time is not within required time of 16-24 hours in the incubator. Incubator temperature is not 36-38 degrees C. Specimens are received frozen or refrigerated before centrifugation.
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.
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.