QuantiFERON-TB Gold Plus test result interpretation
How are QFT-Plus test results interpreted?
QFT-Plus test results are interpreted based upon the quantification of IFN-gamma production in each of the four QFT-Plus Blood Collection Tubes (Table 1).
A positive QFT-Plus result indicates that M. tuberculosis infection is likely. A negative QFT-Plus result indicates that M. tuberculosis infection is NOT likely. An Indeterminate result indicates that the likelihood of M. tuberculosis infection cannot be determined.
Optional QFT-Plus Analysis Software can be used to analyze raw test data and calculate the results.
Diagnosing or excluding tuberculosis disease, and assessing the probability of TB infection, requires a combination of epidemiological, historical, medical, and diagnostic findings that should be taken into account when interpreting QFT-Plus results.
QFT-Plus result interpretation table
| Nil (IU/ml) | TB1 minus Nil (IU/ml) |
TB2 minus Nil (IU/ml) |
Mitogen minus Nil (IU/ml) |
QFT-Plus Result | Report/interpretation |
| ≤8.0 | ≥0.35 and ≥25% on Nil |
Any | Any | Positive | M.tuberculosis infection likely |
| Any | ≥0.35 and ≥25% on Nil |
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| <0.35 or ≥0.35 and <25% of Nil |
<0.35 or ≥0.35 and <25% of Nil |
≥0.50 | Negative | M.tuberculosis infection NOT likely | |
| <0.35 or ≥0.35 and >25% of Nil |
<0.35 or ≥0.35 and <25% of Nil |
<0.50 | Indeterminate | Likelihood of M.tuberculosis infection cannot be determined |
|
| >8.0 | Any | ||||
For complete details of QFT-Plus test interpretation, consult the QuantiFERON-TB Gold Plus (QFT-Plus) Package Insert.