TABLE 1

Characteristics of cases developing tuberculosis (TB) after diagnosis of latent tuberculosis infection (LTBI), 2015–2013

PT completedPT stoppedNo PTTotal
Total LTBI notified#8871 (62%)1167 (8%)4203 (30%)14 241 (100%)
Total TB cases#57 (43%)21 (16%)56 (42%)134 (100%)
Interval between LTBI and TB diagnosis years
 Mean (median)1.33 (0.45)1.88 (0.92)1.38 (0.88)1.44 (0.77)
 Range0.08–7.270.12–6.550.10–7.010.08–7.27
 Interquartile range0.15–1.820.56–2.740.42–1.660.29–1.77
 28 days to 1 year38 (67%)12 (57%)34 (61%)84 (63%)
 1–2 years5 (9%)3 (14%)11 (20%)19 (14%)
 2–5 years12 (21%)4 (19%)8 (14%)24 (18%)
 ≥5 years2 (4%)2 (10%)3 (5%)7 (5%)
Age group
 0–4 years6 (11%)1 (5%)1 (2%)8 (6%)
 5–34 years36 (63%)9 (43%)23 (41%)68 (51%)
 35–54 years13 (23%)9 (43%)25 (45%)47 (35%)
 ≥55 years2 (4%)2 (10%)7 (13%)11 (8%)
Reason for TB examination
 Presenting with TB symptoms30 (53%)9 (43%)21 (38%)60 (45%)
 Contact investigation20 (35%)3 (14%)8 (14%)31 (23%)
 Screening TB risk group+4 (7%)1 (5%)21 (38%)32 (24%)
 Post-exposure screening of travellers and healthcare workers1 (2%)0 (0%)1 (2%)2 (1%)
 Radiological screening in LTBI§3 (5%)6 (29%)19 (34%)28 (21%)
 Other or unspecified2 (4%)2 (10%)5 (9%)9 (7%)
Diagnosis
 Pulmonary TB31 (54%)17 (81%)46 (82%)94 (70%)
 Primary TB infectionƒ12 (21%)0 (0%)4 (7%)16 (12%)
 Other extrapulmonary TB14 (25%)4 (19%)6 (11%)24 (18%)
Microscopy result
 Sputum positive7 (12%)4 (19%)8 (14%)19 (14%)
 Bronchoalveolar lavage positive2 (4%)3 (14%)3 (5%)8 (6%)
 Negative14 (25%)8 (38%)29 (52%)51 (38%)
 Unknown/not performed34 (60%)6 (29%)16 (29%)56 (42%)
Culture
 Positive27 (47%)13 (62%)36 (64%)76 (57%)
 Negative8 (14%)5 (24%)8 (14%)21 (16%)
 Unknown/not done22 (39%)3 (14%)12 (21%)37 (28%)
Drug resistance##
 Pan-sensitive24 (89%)12 (92%)31 (86%)67 (88%)
 Isoniazid resistant1 (4%)1 (8%)3 (8%)5 (7%)
 MDR2 (7%)0 (0%)2 (6%)4 (6%)
DNA fingerprint
 Cluster¶¶23 (40%)10 (48%)32 (57%)65 (49%)
 Unique++4 (7%)3 (14%)4 (7%)11 (8%)
 Culture negative or unknown30 (53%)8 (38%)20 (36%)58 (43%)
Comorbidity
 No comorbidity33 (58%)14 (67%)32 (57%)79 (59%)
 Comorbidity§§5 (9%)4 (19%)7 (13%)16 (12%)
 Unknown12 (21%)3 (14%)17 (30%)32 (24%)
TB treatment outcome
 Completed53 (93%)19 (90%)52 (93%)124 (93%)
 Stopped1 (2%)1 (5%)1 (2%)3 (2%)
 Died due to TB0 (0%)0 (0%)1 (2%)1 (1%)
 Died due to other causes0 (0%)1 (5%)1 (2%)2 (2%)
 Failed0 (0%)0 (0%)1 (2%)1 (1%)
 Transferred out1 (2%)0 (0%)0 (0%)1 (1%)
 Unknown2 (4%)0 (0%)0 (0%)2 (2%)
  • PT: preventive treatment; MDR: multidrug resistant (isoniazid and rifampicin). #: row percentages are shown; : column percentages are shown; +: targeted active case finding in high-risk groups for TB, i.e. prison inmates, drug users or homeless persons; §: biannual screening in eligible persons with LTBI not receiving preventive treatment; ƒ: International Statistical Classification of Diseases and Related Health Problems category Tuberculosis 010; ##: percentages of culture-positive isolates are shown; ¶¶: identical DNA fingerprint of mycobacterial isolate; ++: unique DNA fingerprint of mycobacterial isolate; §§: diseases associated with a higher risk of progression to tuberculosis (HIV (n=1), malignancy (n=1), diabetes (n=5), immune suppressive medication (n=4), alcohol abuse (n=4), unspecified cause (n=1)).