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Table 4 Univariable and multivariable zero-inflated Poisson regression of factors associated with the likelihood of being the first case of a cluster, and the number of subsequent clustered cases for extra-pulmonary TB cases in England, Wales and Northern Ireland, 2010–2014

From: The impact of HIV infection on tuberculosis transmission in a country with low tuberculosis incidence: a national retrospective study using molecular epidemiology

  Total extra-pulmonary cases Clustered cases (%) First extra-pulmonary cases (% of clustered cases) Univariable (number of subsequent cases) Univariable (non-clustered case) Multivariable (number of subsequent cases) Multivariable (non-clustered case)
IRR (95% CI) OR (95% CI) IRR (95% CI) OR (95% CI)
HIV status
 Negative 6739 3389 (50.3) 722 (21.3) 1.00 1.00 1.00 1.00
 Positive 214 99 (46.3) 22 (22.2) 4.16 (3.71–4.67) 1.38 (0.86–2.19) 3.62 (3.12–4.19) 1.93 (1.12–3.33)
Year of TB diagnosis
 2010 1146 590 (51.5) 293 (49.7) 1.00 1.00 1.00 1.00
 2011 1600 805 (50.3) 242 (30.1) 0.77 (0.71–0.84) 1.65 (1.34–2.02) 0.72 (0.66–0.80) 1.45 (1.15–1.84)
 2012 1677 855 (51.0) 122 (14.3) 0.56 (0.48–0.66) 2.84 (2.21–3.64) 0.60 (0.51–0.71) 2.57 (1.93–3.41)
 2013 1342 674 (50.2) 62 (9.2) 0.39 (0.29–0.51) 2.83 (1.94–4.13) 0.45 (0.34–0.61) 2.82 (1.88–4.22)
 2014 1188 564 (47.5) 25 (4.4) 0.90 (0.74–1.10) 6.86 (4.36–10.80) 1.11 (0.82–1.51) 7.82 (4.67–13.11)
Sex
 Female 2959 1492 (50.4) 323 (21.6) 1.00 1.00 1.00 1.00
 Male 3990 1995 (50.0) 421 (21.1) 1.25 (1.15–1.35) 1.11 (0.94–1.31) 1.22 (1.12–1.34) 0.99 (0.81–1.21)
 Missing 4 1 (25.0) (0.0)     
Age (years)
 15–24 984 555 (56.4) 111 (20.0) 2.26 (2.01–2.54) 1.10 (0.85–1.42) 1.66 (1.46–1.89) 1.07 (0.80–1.45)
 25–34 2382 1192 (50.0) 266 (22.3) 1.00 1.00 1.00 1.00
 35–44 1489 727 (48.8) 156 (21.5) 1.67 (1.49–1.87) 1.27 (1.01–1.60) 1.43 (1.26–1.61) 1.32 (1.00–1.75)
 45–54 822 423 (51.5) 83 (19.6) 1.37 (1.19–1.59) 1.19 (0.89–1.58) 1.39 (1.18–1.63) 1.46 (1.02–2.10)
 55–64 489 257 (52.6) 52 (20.2) 1.73 (1.48–2.02) 1.18 (0.84–1.66) 1.92 (1.60–2.31) 1.45 (0.94–2.24)
 65+ 787 334 (42.4) 76 (22.8) 1.08 (0.92–1.26) 1.34 (1.00–1.81) 0.94 (0.78–1.14) 1.40 (0.92–2.12)
Ethnicity
 White 510 237 (46.5) 49 (20.7) 1.00 1.00 1.00 1.00
 Black African 1285 761 (59.2) 150 (19.7) 1.76 (1.45–2.14) 0.74 (0.51–1.08) 0.85 (0.65–1.10) 0.49 (0.27–0.89)
 Black Other 182 136 (74.7) 17 (12.5) 3.69 (2.92–4.66) 0.62 (0.32–1.19) 2.84 (2.18–3.70) 0.57 (0.26–1.25)
 Indian sub-continent 3905 1844 (47.2) 414 (22.5) 1.21 (1.00–1.46) 0.96 (0.68–1.35) 0.64 (0.49–0.83) 0.64 (0.36–1.12)
 Mixed/other 904 436 (48.2) 101 (23.2) 0.97 (0.78–1.21) 0.80 (0.54–1.20) 0.58 (0.44–0.78) 0.50 (0.27–0.93)
 Missing 167 74 (44.3) 13 (17.6)     
Time since entry to the UK
 UK born 800 474 (59.3) 86 (18.1) 1.00 1.00 1.00 1.00
 Within 2 years 999 480 (48.0) 107 (22.3) 1.75 (1.52–2.01) 1.51 (1.09–2.10) 2.06 (1.70–2.50) 2.56 (1.62–4.05)
 2–5 years 1450 694 (47.9) 156 (22.5) 0.72 (0.61–0.84) 1.16 (0.85–1.59) 0.99 (0.81–1.22) 1.72 (1.10–2.70)
 5–10 years 1200 588 (49.0) 134 (22.8) 0.87 (0.74–1.01) 1.20 (0.87–1.65) 1.16 (0.94–1.42) 1.83 (1.15–2.89)
 More than 10 years 1692 869 (51.4) 185 (21.3) 0.95 (0.83–1.09) 1.15 (0.85–1.56) 1.28 (1.04–1.57) 1.42 (0.91–2.23)
 Missing 812 383 (47.2) 76 (19.8)     
TB lineage
 Beijing 335 245 (73.1) 34 (13.9) 1.00 1.00 1.00 1.00
 Euro-American 2007 1067 (53.2) 236 (22.1) 0.46 (0.39–0.54) 1.21 (0.79–1.87) 0.41 (0.34–0.49) 1.16 (0.70–1.93)
 Central Asian Strain 2325 1337 (57.5) 255 (19.1) 0.75 (0.65–0.87) 1.36 (0.89–2.09) 0.76 (0.64–0.90) 1.37 (0.82–2.26)
 East Asian Indian 1403 495 (35.3) 133 (26.9) 0.48 (0.41–0.58) 2.18 (1.40–3.42) 0.55 (0.45–0.67) 2.07 (1.23–3.48)
 Other 881 342 (38.8) 85 (24.9) 0.66 (0.56–0.79) 2.17 (1.36–3.47) 0.62 (0.51–0.75) 1.92 (1.12–3.30)
 Missing 2       
IMD decile
 1 1352 706 (52.2) 160 (22.7)
 2 1407 747 (53.1) 156 (20.9)
 3 1157 587 (50.7) 136 (23.2)
 4 876 441 (50.3) 72 (16.3)
 5 616 297 (48.2) 75 (25.3)
 6 446 215 (48.2) 45 (20.9)
 7 313 147 (47.0) 26 (17.7)
 8 242 122 (50.4) 30 (24.6)
 9 220 83 (37.7) 17 (20.5)
 10 169 72 (42.6) 12 (16.7)
 Missing 155 71 (45.8) 15 (21.1)
 For each decile increase 0.93 (0.92–0.95) 1.03 (1.00–1.07) 0.97 (0.95–0.99) 1.03 (0.99–1.08)
Drug misuse
 No 6371 3180 (49.9) 675 (21.2) 1.00 1.00 1.00 1.00
 Yes 63 44 (69.8) 7 (15.9) 0.41 (0.21–0.82) 0.34 (0.10–1.18) 0.49 (0.27–0.90) 0.31 (0.06–1.66)
 Missing 519 264 (50.9) 62 (23.5)     
Alcohol misuse
 No 6221 3117 (50.1) 654 (21.0) 1.00 1.00 1.00 1.00
 Yes 106 58 (54.7) 13 (22.4) 1.44 (1.13–1.83) 0.89 (0.47–1.66) 1.79 (1.34–2.38) 1.09 (0.47–2.51)
 Missing 626 313 (50.0) 77 (24.6)     
Homelessness
 No 6373 3203 (50.3) 679 (21.2) 1.00 1.00 1.00 1.00
 Yes 99 56 (56.6) 7 (12.5) 0.29 (0.12–0.72) 0.71 (0.21–2.33) 0.23 (0.09–0.58) 0.62 (0.10–3.94)
 Missing 481 229 (47.6) 58 (25.3)     
Imprisonment
 No 6220 3119 (50.1) 657 (21.1) 1.00 1.00 1.00 1.00
 Yes 96 61 (63.5) 8 (13.1) 0.06 (0.03–0.13) 1.11 (0.94–1.31) 0.17 (0.04–0.82) 0.36 (0.01–8.94)
 Missing 637 308 (48.4) 79 (25.6)     
  1. IRR: incidence rate ratio (Poisson part) for an increased number of subsequent clustered cases. OR: odds ratio (zero-inflated part) for the odds of being a non-clustered case, compared to being the first extra-pulmonary case of a cluster. IMD: index of multiple deprivation score. IMD score deciles represent relative levels of deprivation of income, employment, health, education, housing and services, crime and living environment for small areas in England and Wales, where 1 = most deprived and 10 = least deprived [29, 30]
  2. Adjusted for all variables shown in the table. The multivariable model included 3576 extra-pulmonary TB cases after 633 were excluded due to missing data on one or more of sex (n = 3), ethnicity (n = 106), time since entry to the UK (n = 505), IMD score (n = 99) or TB lineage (n = 1)
  3. Cases missing data were considered not to have these social risk factors