How it Differs

T-SPOT.TB  test vs. 100-year-old Tuberculin Skin Test (TST)

T-SPOT.TB  Test

Tuberculin Skin Test

A single visit is required Yes No; requires at least two visits
No return visit for results Yes No; requires a return visit for reading in
48-72 hours
TB test with high sensitivity1 Yes No; limited sensitivity, especially in the immunosuppressed2
TB test with high specificity1 Yes No; limited specificity²
Does not cross react with most non-tuberculosis mycobacteria1 Yes No; cross reacts with several non-tuberculosis mycobacteria²
Objective test results Yes No; subjectivity with interpretation of results

Comparison of IGRAs

T-SPOT.TB  Test

In-Tube

Standard blood collection tubes are used Yes No; requires three specialized tubes drawn in specific order.
Blood collection tube is filled using standard phlebotomy practices Yes No; specialized tubes must be filled between 0.8mL and 1.2mL or within the black mark on the side of the tube label.³  Over  or under-filling of the tubes outside the range may lead to erroneous results.4
Phlebotomist gently inverts blood tube after drawing specimen, consistent with standard phlebotomoy practices Yes No; once filled, each tube must be mixed by shaking 10 times.³  Over-energetic shaking should be avoided to minimize erroneous results due to gel dislodgement.³
Butterfly needles may be used without the need for a “purge” tube Yes No; when a butterfly needle is used, a purge tube should be used to fill the tubing with blood prior to filling the Nil tube.³
A borderline zone is used, consistent with the recommendations of the 2010 CDC Guidelines Yes No; “Although not included in FDA-approved interpretation criteria for
QFT-GIT…an appropriate borderline category for QFT-GIT might increase its accuracy…”5
Specimens can be maintained at room temperature for up to 32 hours Yes No; tubes must be transferred to an incubator as soon as possible but within 16 hours.³

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¹T-SPOT.TB  Package Insert.
2 Huebner R et al., The tuberculin skin test. Clin Infect Dis  1993; 17: 968-975.
3 Cellestis Technical Note, L05995036B
QuantiFERON®-TB Gold Package Insert, page 9; Doc. No. US05990301J
5 MMWR 2010;59(RR-5):1-25.
T-SPOT is a registered trademark of Oxford Immunotec Ltd.
QFT is a regsitered trademark of Cellestis Ltd.