Reclassification tables to calculate the NRI for binary T-SPOT.TB results in smear-negative children with and without culture-confirmed TB, using the risk categories <10%, 10–30% and >30%*
| Clinical+CXR+TST+T-SPOT.TB (expanded model) | ||||
|---|---|---|---|---|
| Clinical+CXR+TST (baseline model) | <10% | 10–30% | >30% | Total |
| Confirmed TB (N=54) | ||||
| <10% | 4 | 5 | 0 | 9 |
| 10–30% | 4 | 9 | 6 | 19 |
| >30% | 1 | 4 | 21 | 26 |
| Total | 9 | 18 | 27 | 54 |
| Not confirmed TB (N=437) | ||||
| <10% | 318 | 12 | 0 | 330 |
| 10–30% | 26 | 29 | 12 | 67 |
| >30% | 2 | 10 | 28 | 40 |
| Total | 346 | 51 | 40 | 437 |
Numbers in bold indicate correctly-reclassified patients that are used to calculate the NRI.
*The risk categories are based on the predicted probabilities from the logistic regression model. The T-SPOT.TB correctly reclassified 3% of culture-confirmed cases (11/54 above the diagonal minus 9/54 below the diagonal). The T-SPOT.TB correctly reclassified 4% of non-confirmed cases (38/437 below the diagonal minus 24/437 above the diagonal). Thus, the overall NRI is 7%.
CXR, chest radiography; NRI, net reclassification improvement; PTB, pulmonary tuberculosis; TST, tuberculin skin test.