Table 4.
Yield number of tests, and cost per patient according to the sequence of tests for 332 patients suspected of having tuberculosis.a
| Tests | Yield | Incremental yield of culture (%) |
Xpert, n (%) | LAM, n (%) | Induction of sputum, n (%) |
Mycobacterial culture, n (%) |
DST, n (%) | Cost/patient ($US) |
|---|---|---|---|---|---|---|---|---|
| Xpert Spotb Culture |
24.3 | 1.2 | 88 (26.5) | 0 (0) | 0 (0) | 48 (14.5) | 2 (0.6) | 10.5 |
| LAM Xpert Spotb |
50.9 | N/A | 73 (22.0) | 332 (100) | 0 (0) | 0 (0) | 0 (0) | 10.5 |
| LAM Xpert Spotb Culture |
52.1 | 1.2 | 73 (22.0) | 332 (100) | 0 (0) | 47 (14.2) | 2 (0.6) | 12.5 |
| LAM Xpert SIc |
92.3 | N/A | 261 (78.6) | 332 (100) | 188 (56.7) | 0 (0) | 0 (0) | 37.2 |
| Xpert SIc Culture |
95.0 | 4.5 | 332 (100) | 0 (0) | 244 (73.5) | 170 (51.2) | 7.5d (2.3) | 49.6 |
| LAM Xpert SIc Culture |
95.9 | 3.6 | 261 (78.6) | 332 (100) | 188 (56.7) | 160 (48.2) | 6d (1.8) | 42.0 |
LAM, urine lateral flow lipoarabinomannan test; DST, drug susceptibility testing by line probe assay; N/A, not applicable.
Where multiple tests are shown, it is assumed that testing is performed in series and terminates when a test is positive. Columns represent the proportion of patients who would receive each test if the sequence was followed in this way. Total costs per patient are calculated based on these proportions and the costs of each test.
Xpert Spot = test only performed if the patient could produce sputum spontaneously.
Xpert SI = includes spontaneously produced sputum and induced sputum.
Includes patients where two sputum cultures taken on the same day gave discordant results and it was not possible to determine whether the first or second was positive. For the purposes of evaluation, it was assumed that there was a 50% chance that the first sample was positive in each case.