Table 3.
Tuberculosis screening package performance comparison (ordered by proportion of patients correctly assigned)
| Completed packagea (n varies) | Intent-to-screenb (n=435) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Package | Patients correctly assignedc (n=435) | Sensitivity of tests % | Specificity of tests % | Positive predictive value of package | Negative predictive value of package | Failed to complete packaged (n) | TB-positive cases missed (n) | US$2007 per person intended-to-screene | ||
| More patients correctly assigned than no screening |  |
2 MODS | 435 (100%) | 27/27 (100%) | 408/408 (100%) | 27/27 (100%) | 408/408 (100%) | 19 | 0 | $13.62 |
| 1 MODS | 426 (97.9%) | 18/27 (67%) | 408/408 (100%) | 18/18 (100%) | 408/417 (97.8%) | 0 | 9 | $7.31 | ||
| 2 Smears | 415 (95.4%) | 7/27 (26%) | 408/408 (100%) | 7/7 (100%) | 408/428 (95.3%) | 19 | 20 | $5.57 | ||
| 1 LJ | 414 (95.2%) | 15/25 (60%) | 399/399 (100%) | 15/15 (100%) | 408/420 (97.1%) | 11 | 12 | $6.39 | ||
| 2 LJ | 412 (94.7%) | 22/25 (88%) | 390/390 (100%) | 22/22 (100%) | 408/413 (98.8%) | 39 | 5 | $11.77 | ||
| No Screening (all would get IPT) | 408 (93.8%) | 0/27 (0%) | 408/408 (100%) | n/a | 408/435 (93.8%) | 0 | 27 | $0.00 | ||
| Fewer patients correctly assigned than no screening |  |
Clinical Exam + 2 MODS | 393 (90.3%) | 27/27 (100%) | 366/408 (89.7%) | 27/69 (39.1%) | 366/366 (100%) | 19 | 0 | $14.14 |
| Clinical Exam + 2 Smears | 380 (87.4%) | 14/27 (52%) | 366/408 (89.7%) | 14/56 (25%) | 366/379 (96.6%) | 19 | 13 | $6.09 | ||
| Clinical Exam | 378 (86.9%) | 12/27 (44%) | 366/408 (89.7%) | 12/54 (22%) | 366/381 (96.1%) | 0 | 15 | $1.52 | ||
| Clinical Exam + 2 Smears + 2 LJ | 371 (85.3%) | 23/25 (92%) | 348/390 (89.2%) | 23/65 (35%) | 366/370 (98.9%) | 39 | 4 | $14.86 | ||
| CXR | 351 (80.7%) | 14/25 (56%) | 337/399 (84.5%) | 14/76 (18%) | 346/359 (96.4%) | 17 | 13 | $9.17 | ||
| Southern Africa Algorithmf (430 total patients) | 350 (81.4%) | 11/21 (52%) | 338/358 (94.4%) | 12/33 (36%) | 382/397 (96.2%) | 87 | 15 | $17.03 | ||
| CXR + Clinical Exam | 330 (75.9%) | 18/25 (72%) | 310/399 (77.7%) | 20/111 (18%) | 317/324 (97.8%) | 17 | 7 | $9.70 | ||
| CXR + Clinical Exam + 2 Smears | 330 (75.9%) | 18/25 (72%) | 310/399 (77.7%) | 20/111 (18%) | 317/324 (97.8%) | 30 | 7 | $13.26 | ||
| CXR + Clinical Exam + 2 Smears + 2 LJ | 320 (73.6%) | 22/23 (96%) | 295/381 (77.4%) | 25/116 (22%) | 317/319 (99.4%) | 50 | 2 | $22.03 | ||
TB-positive cases were defined as patients having any positive microbiologic test. Patients who provided fewer than two sputum samples did not have an adequate culture reference standard and thus were excluded from the table. Positive clinical exam=higher risk of active TB, according to referring clinician. Positive chest radiograph (CXR)=findings consistent with active TB for which further testing would be recommended prior to isoniazid preventive therapy. Southern Africa algorithm27=preliminary screening by tuberculin skin test (TST); then, for only those with positive TST: clinical exam, chest radiograph, two smears, and two LJ.
Excludes patients who did not undergo one or more components of the package (e.g. CXR), or who had one contaminated (indeterminate) and one negative LJ; denominators vary according to completion rate of the package. This is the “as screened” analysis which provides efficacy data for completed packages.
Within a package, a positive result for any component was considered to be a positive result for the package. This “intention-to-screen” analysis describes overall performance in all those who entered into screening, and incorporates the effect of loss-to-follow-up.
Indicates those correctly assigned as TB-positive or TB-negative by the package, with the reference standard being any positive microbiologic test. Patients who failed to complete all components of a package were considered not correctly assigned, unless at least one component test was positive in the context of a positive culture result.
This is the only column that includes the 19 patients who provided only one sputum sample; these patients were considered to have failed to complete all packages involving two sputum samples.
This value was attained by summing the cost of diagnosis and patient costs from Supplemental Tables 1 and 2, then dividing the result by the 435 patients presented in Table 3. The median of the patient costs, including transport, was used.
Five patients did not undergo TST and thus were excluded from analysis of this package.