TABLE 1.
DESCRIPTION OF ACID FAST BACILLI SMEAR-NEGATIVE ACTIVE TUBERCULOSIS SUSPECTS
| Characteristic | Total | Noncases (n = 595) | Culture-Positive Cases (n = 65) | P Value |
|---|---|---|---|---|
| Age, years, median (IQR) | 54 (43–64) | 54 (44–65) | 50 (36–62) | 0.06 |
| Male, % | 61 | 61 | 69 | 0.17 |
| Race/ethnicity, % | ||||
| White | 6 | 6 | 9 | 0.38 |
| African American | 6 | 6 | 8 | |
| Asian | 79 | 80 | 71 | |
| Hispanic | 9 | 8 | 12 | |
| US born, % | 10 | 9 | 18 | 0.02 |
| Positive QFT-G result*, % | 55 | 52 | 72 | <0.01 |
| IFN-γ concentration, IU/ml, median (IQR) | 0.46 (0.06–2.42) | 0.37 (0.05–2.38) | 1.1 (0.36–3.77) | <0.01 |
| Quintiles of IFN-γ concentration (IU/ml), % | ||||
| <0.04 | 22 | 6 | <0.001 | |
| 0.04–0.23 | 20 | 9 | ||
| 0.23–0.9 | 19 | 34 | ||
| 0.9–3.12 | 20 | 22 | ||
| 3.12–10 | 19 | 29 | ||
| Active disease on CXR, % | 19 | 16 | 43 | <0.001 |
| Clinical symptoms, % | ||||
| Night sweats or weight loss | 17 | 15 | 32 | <0.001 |
| Cough | 29 | 28 | 35 | 0.20 |
| Hemoptysis | 5 | 5 | 8 | 0.33 |
| Previous active TB, % | 15 | 16 | 5 | 0.01 |
| Contact to active TB case, % | 2 | 2 | 6 | 0.03 |
| Predisposing medical condition†, % | 13 | 13 | 11 | 0.60 |
| Homelessness, % | 8 | 8 | 12 | 0.18 |
| BCG vaccination, % | 20 | 20 | 18 | 0.79 |
| Diabetes mellitus, % | 9 | 10 | 5 | 0.19 |
| Clinician suspicion for active TB at initial evaluation, % | ||||
| Low | 73 | 79 | 26 | <0.001 |
| Intermediate | 13 | 12 | 20 | |
| High |
14 |
9 |
54 |
|
Definition of abbreviations: BCG = bacillus Calmette-Guérin vaccine; CXR = chest radiograph; IQR = Interquartile range; QFT-G = QuantiFERON-TB Gold; TB = tuberculosis.
Values are percentages unless otherwise stated.
*
Positive at the manufacturer-recommended cut point of 0.35 IU/ml.
†
Predisposing medical condition: diabetes mellitus, silicosis, cancer, or condition requiring use of immunosuppressive medications.