Background
Methods
Results
Enrolment and characteristics of the study group
Total arrivals at Tanum | Study group | |||||
---|---|---|---|---|---|---|
No. | % | 95% CI | No. | % | 95% CI | |
Total | 2813 | 912 | ||||
Sex | ||||||
Male
| 1983 |
70.5
| 68.8 – 72.2 | 685 |
75.1
| 72.2 – 77.8 |
Female
| 830 |
29.5
| 27.8 – 31.2 | 227 |
24.9
| 22.2 – 27.8 |
Origin | ||||||
Europe
| 473 |
16.8
| 15.5 – 18.2 | 115 |
12.6
| 10.6 – 14.9 |
Asia*
| 1304 |
46.3
| 44.5 – 48.2 | 418 |
45.8
| 42.6 – 49.1 |
Africa
| 1021 |
36.3
| 34.5 – 38.1 | 371 |
40.7
| 37.5 – 44.0 |
America
| 7 |
0.2
| 0.1 – 0.5 | 4 |
0.4
| 0.2 – 1.1 |
Unknown
| 8 |
0.3
| 0.1 – 0.6 | 4 |
0.4
| 0.2 – 1.1 |
*Includes Turkey (no = 15 of study group)
|
TST and QFT results
Agreement between QFT and TST
TST | QFT | TST cut-off ≥ 6 mm | TST cut-off ≥ 10 mm | TST cut-off ≥ 15 mm |
---|---|---|---|---|
No. (%) | No. (%) | No. (%) | ||
Positive | Positive | 232 (25) | 190 (21) | 104 (11) |
Negative | Negative | 420 (46) | 527 (58) | 611 (67) |
Positive | Negative | 228 (25) | 121 (13) | 37 (4) |
Negative | Positive | 32 (4) | 74 (8) | 160 (18) |
Total agreement | 652 (72) | 717 (79) | 715 (78) | |
Kappa (95% CI) | 0.43 (0.37 – 0.49) | 0.51 (0.45 – 0.57) | 0.39 (0.32 – 0.47) |
Predictors of positive tests
A. Predictors of positive QFT | Univariate | Multivariate | |||||
---|---|---|---|---|---|---|---|
Variable | Characteristic | Total No. | No. QFT+ | OR (95%CI) | p-value |
a OR (95%CI) | p-value |
BCG – scar | no scar | 246 | 68 | 1 | 0.53 | ||
scar | 658 | 196 | 1.1 (0.8–1.5) | ||||
Sex | male | 685 | 202 | 1 | 0.53 | ||
female | 227 | 62 | 0.9 (0.6–1.3) | ||||
Age group | 18–29 years | 471 | 129 | 1 | < 0.001 | 1 | < 0.001 |
30–39 years | 291 | 75 | 0.9 (0.7–1.3) | 1.1 (0.8–1.5) | |||
40–49 years | 115 | 40 | 1.4 (0.9–2.2) | 1.8 (1.1–2.9) | |||
50+ years | 35 | 20 | 3.5 (1.8–7.1) | 4.6 (2.2–9.5) | |||
Origin | Asia | 418 | 82 | 1 | < 0.001 | 1 | < 0.001 |
Europe | 115 | 22 | 1.0 (0.6–1.6) | 1.0 (0.6–1.7) | |||
Africa | 371 | 159 | 3.1 (2.2–4.2) | 3.3 (2.4–4.6) | |||
Exposure | no | 898 | 255 | 1 | 0.01 | 1 | 0.02 |
yes | 14 | 9 | 4.5 (1.5–13.7) | 4.0 (1.3 – 12.9) | |||
Previous diagnosis of tuberculosis | no | 904 | 259 | 1 | 0.05 | ||
yes | 8 | 5 | 4.2 (1 – 17.5) | ||||
Log likelihood = -502.86642, p-value final model = 0.000, No. of observations in final model = 904
| |||||||
B. Predictors of TST ≥ 15 mm | Univariate | Multivariate | |||||
Variable | Characteristic | Total No. | No. TST ≥15 mm | OR (95%CI) | p-value |
a OR (95%CI) | p-value |
BCG – scar | no scar | 246 | 39 | 1 | 0.85 | ||
scar | 658 | 101 | 1.0 (0.6–1.4) | ||||
Sex | male | 685 | 85 | 1 | < 0.001 | 1 | < 0.001 |
female | 227 | 56 | 2.3 (1.6–3.4) | 1.9 (1.3–2.8) | |||
Age group | 18–29 years | 471 | 63 | 1 | 0.31 | 1 | < 0.002 |
30–39 years | 291 | 44 | 1.2 (0.8–1.7) | 1.5 (1–2.3) | |||
40–49 years | 115 | 23 | 1.6 (1–2.7) | 1.9 (1.1–3.3) | |||
50+ years | 35 | 11 | 3.0 (1.4–6.4) | 4.3 (1.9–9.5) | |||
Origin | Asia | 418 | 32 | 1 | < 0.001 | 1 | < 0.001 |
Europe | 115 | 21 | 2.7 (1.5–4.9) | 2.4 (1.3–4.5) | |||
Africa | 371 | 88 | 3.8 (2.4–5.8) | 3.8 (2.4–6) | |||
Exposure | no | 898 | 136 | 1 | 0.05 | ||
yes | 14 | 5 | 3.1 (1–9.4) | ||||
Previous diagnosis of tuberculosis | no | 904 | 138 | 1 | 0.10 | ||
yes | 8 | 3 | 3.3 (0.8–14.1) | ||||
Log likelihood = -359.05381, p-value final model = 0.000. No. of observations in final model = 904
|
Implications for screening
Screening programme approach | Referral criteria | Proportion (%) referred for treatment | Proportion (%) LTBI* cases detected (detection rate) | Proportion (%) non-infected referred for treatment (false positive rate) |
---|---|---|---|---|
Only TST | TST ≥ 6 mm | 50 | 89 | 42 |
TST ≥ 10 mm | 34 | 75 | 27 | |
TST ≥ 15 mm | 15 | 47 | 0 | |
Only QFT | QFT positive | 29 | 88 | 0 |
Two step (first TST, then QFT) | TST ≥ 6 mm and QFT positive, or TST ≥15 mm | 29 | 89 | 0 |
TST ≥ 10 mm and QFT positive or TST ≥ 15 mm | 25 | 75 | 0 | |
TST ≥ 15 mm (with or without QFT positives afterwards) | 15 | 47 | 0 |