Table 1 Characteristics of the study population

No. of cases

431

1,513

7,202

232

Age, years

49 (34–63)

48 (39–57)

31 (24–43)^a

46 (30–64)

Male, n (%)

236 (55.3)

662 (46.0)

2,222 (34.7)

86 (40.0)

Smoking status (n = 5,231)

359

1,027

3,630

215

 Current

92 (25.6)

198 (19.3)

342 (9.4)

34 (15.8)

 Ex-smoker

52 (14.5)

133 (13.0)

244 (6.7)

29 (13.5)

IGRA result

 Positive

376 (87.2)

1,513 (100)

 Negative

36 (8.4)

7,202 (100)

 Indeterminate

19 (4.4)

232 (100)

Close contact to active TB

0 (0)

52 (3.6)

185 (2.8)

1 (0.5)

History of TB

53 (12.5)

148 (10.3)

75 (1.1)^b

10 (4.7)

NTM infection

7 (1.6)

16 (1.1)

49 (0.8)

3 (1.4)

Corticosteroid use

35 (8.2)

117 (8.1%)

523 (8.0)

105 (48.8)^a

Other immunosuppressants

12 (2.8)

169 (11.8)

584 (9.0)

58 (27.0)^a

Underlying conditions

 Diabetes mellitus

48 (11.3)

137 (9.5)

274 (4.2)^a

29 (13.5)

 Autoimmune disease

18 (4.2)

242 (16.8)

749 (11.5)

86 (40.0)^a

 Hematologic malignancy

8 (1.9)

19 (1.3)

58 (0.9)

19 (8.8)^a

 Solid malignancy

14 (3.3)

44 (3.1)

78 (1.2)

13 (6.0)^a

 HIV infection

8 (1.9)

17 (1.2)

112 (1.7)

7 (3.3)

 Renal insufficiency

18 (4.2)

36 (2.5)

79 (1.2)

12 (5.6)

 Chronic liver disease

3 (0.7)

8 (0.6)

23 (0.4)

6 (2.8)

 COPD

10 (2.4)

37 (2.6)

64 (1.0)

9 (4.2)

 Cardiac disease

45 (10.6)

112 (7.8)

345 (5.3)

27 (12.6)

 Acute infection

9 (2.1)

63 (4.4)

203 (3.1)

46 (21.4)^a

Laboratory results

 Leukocyte (×10³/mm³)

6.5 (5.3–8.3)

6.1 (5.0–7.8)

5.9 (4.9–7.5)

8.8 (5.4–13.8)^a

 Lymphocyte (×10³/mm³)

1.4 (0.9–1.9)

1.8 (1.4–2.3)

1.7 (1.3–2.2)

0.9 (0.5–1.3)^a

 Neutrophil (×10³/mm³)

4.3 (3.1–5.7)

3.7 (2.8–5.1)

3.6 (2.6–5.1)

7.1 (4.0–11.7)^a

 Albumin (mg/dL)

4.0 (3.3–4.5)

4.4 (3.9–4.7)

4.4 (3.9–4.7)

3.3 (2.8–3.8)^a

 CRP (mg/dL)

3.3 (0.6–6.6)

0.7 (0.1–3.3)

1.0 (0.2–3.9)

4.7 (0.9–12.1)