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Test Code MTB Mycobacterium tuberculosis by ELISA

Aliases

Quantiferon TB Gold Plus, QFT4

Useful For

Mycobacterium tuberculosis by ELISA is an indirect test for M. tuberculosis infection.

Patient Preparation

No special patient preparation required

Special Collection Instructions

  1. A set of 4 collection tubes are located in lab areas and are lab collect.
  2. Draw 1 mL of blood. Note the mark on the side of each tube indicating proper draw volume.
  3. Invert the tubes 10 times after collection to coat the sides with blood.
  4. Place the correct label on each tube, i.e. MTB Gray label on gray tube, etc.
  5. Allow the color bar on the side of each tube to remain visible when labeling.
  6. Deliver to the lab as soon as possible for special handling.

Collection Method

Venous collection

Minimum Volume

1 mL in each of the four MTB tubes

Container

Quantiferon Gold Kit

Preferred Specimen

Plasma in Nil, TB1, TB2, and Mitogen tubes

Acceptable Specimens

Plasma in Nil, TB1, TB2, and Mitogen tubes

Reference or Target Ranges

  • Negative – M. tuberculosis infection not likely, Non-Responsive to ESAT-6, CFP-10 and/or TB7.7 antigens.
  • Indeterminate – Likelihood of M. tuberculosis infection cannot be determined.
  • Positive – M. tuberculosis infection likely.

Reportable Units

Positive/Indeterminate/Negative

Critical Value

Not defined for this assay

Reasons for Rejection

Hemolysis Threshold N/A
Icterus Threshold N/A
Lipemia Threshold N/A
Other
  • Contaminated
  • Improperly labled
  • Improper specimen type.
  • Sample contains less than 0.8 mL or more than 1.2 mL of blood.
  • Samples are more than 16 hours old before incubation.
  • Sample is incubated less than 16 or greater than 24 hours.
  • Sample is more than 72 hours old following incubation prior to centrifugation.
  • Sample has been subjected to temperatures outside the 17 to 24 C range.

Specimen Stability

Ambient N/A
Refrigerated (2°C to 8°C) N/A
Frozen(<-20°C to 0°C) N/A
Other Specimen stability is dependent upon proper collection and handling.

Performance Information

Approved Days for Collection Monday - Friday
Days and Time Performed Monday – Friday 8 AM – 4:30 PM
Expected Turn Around Time Within 3 days of arrival in lab
Stat Availabilty No
Performing Bench Special Chemistry
Methodology/Method Description DiaSorin Liasion XL – Enzyme-linked immunosorbent assay (ELISA)

Special Handling

  1. Invert tubes 10 times just prior to incubation to remix the blood and antigens.
  2. Transfer to a 37 C incubator as soon as possible and within 16 hours of collection.
  3. Incubate for 16 to 24 hours at 37 C.
  4. Following incubation tubes may be held at room temp for 72 hours prior to centrifugation.

Additional Information/Important Notes

Results from QFT-Plus testing must be used in conjunction with each individual’s epidemiological history, current medical status, and other diagnostic evaluations.
 

See general guidance on the diagnosis and treatment of TB disease and LTBI (CDC Guidelines).
 

The performance of the USA format of the QFT-Plus test has not been extensively evaluated with specimens from the following groups of individuals:

  • Pregnant women
  •  
  • Individuals younger than age 17 years
  •  
  • Individuals who have impaired or altered immune functions.

CPT Codes

86480