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Table 3 Univariable and multivariable zero-inflated Poisson regression of factors associated with the likelihood of transmitting TB, and the number of subsequent clustered cases for 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 pulmonary cases Clustered pulmonary cases (%) First 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 11,366 6910 (60.8) 1950 (28.2) 1.00 1.00 1.00 1.00
 Positive 545 311 (57.1) 106 (34.1) 0.76 (0.68–0.87) 0.94 (0.72–1.23) 0.75 (0.65–0.86) 1.10 (0.79–1.53)
Year of TB diagnosis
 2010 2028 1205 (59.4) 716 (59.4) 1.00 1.00 1.00 1.00
 2011 2696 1638 (60.8) 546 (33.3) 0.63 (0.59–0.66) 1.69 (1.46–1.96) 0.64 (0.60–0.68) 1.52 (1.29–1.80)
 2012 2650 1670 (63.0) 379 (22.7) 0.39 (0.35–0.43) 1.87 (1.56–2.24) 0.38 (0.34–0.43) 1.53 (1.25–1.88)
 2013 2354 1456 (61.9) 230 (15.8) 0.42 (0.35–0.49) 2.79 (2.20–3.53) 0.40 (0.34–0.48) 2.38 (1.83–3.11)
 2014 2183 1252 (57.4) 185 (14.8) 0.64 (0.52–0.79) 4.53 (3.34–6.14) 0.59 (0.47–0.74) 4.04 (2.87–5.69)
Sex
 Female 4562 2661 (58.3) 765 (28.7) 1.00 1.00 1.00 1.00
 Male 7333 4552 (62.1) 1285 (28.2) 1.04 (0.99–1.09) 0.86 (0.76–0.96) 1.01 (0.95–1.06) 0.81 (0.70–0.93)
 Missing 16 8 (50.0) 6 (75.0)     
Age (years)
 15–24 2254 1504 (66.7) 405 (26.9) 0.93 (0.87–1.00) 0.78 (0.65–0.92) 0.86 (0.79–0.93) 0.78 (0.63–0.96)
 25–34 3250 1947 (59.9) 575 (29.5) 1.00 1.00 1.00 1.00
 35–44 2089 1314 (62.9) 395 (30.1) 1.30 (1.22–1.39) 0.89 (0.75–1.05) 1.33 (1.24–1.43) 0.99 (0.81–1.22)
 45–54 1566 1000 (63.9) 252 (25.2) 0.90 (0.83–0.99) 0.89 (0.73–1.08) 0.96 (0.87–1.07) 1.08 (0.84–1.38)
 55–64 999 633 (63.4) 167 (26.4) 1.19 (1.09–1.30) 1.10 (0.87–1.39) 1.01 (0.91–1.13) 1.36 (1.01–1.82)
 65+ 1753 823 (46.9) 262 (31.8) 1.04 (0.96–1.13) 1.61 (1.34–1.94) 1.03 (0.93–1.14) 1.97 (1.53–2.53)
Ethnicity
 White 3481 2205 (63.3) 522 (23.7) 1.00 1.00 1.00 1.00
 Black African 1926 1270 (65.9) 370 (29.1) 0.96 (0.89–1.02) 0.76 (0.64–0.91) 1.23 (1.12–1.36) 0.91 (0.70–1.19)
 Black Other 406 322 (79.3) 68 (21.1) 0.89 (0.77–1.02) 0.51 (0.35–0.74) 0.86 (0.74–1.01) 0.58 (0.37–0.93)
 Indian sub-continent 4174 2354 (56.4) 758 (32.2) 0.94 (0.88–0.99) 1.15 (1.00–1.33) 0.93 (0.85–1.01) 1.19 (0.94–1.51)
 Mixed/other 1621 894 (55.2) 273 (30.5) 0.60 (0.55–0.66) 1.03 (0.85–1.26) 0.68 (0.60–0.77) 1.10 (0.83–1.46)
 Missing 303 176 (58.1) 65 (36.9)     
Time since entry to the UK
 UK born 3631 2526 (69.6) 540 (21.4) 1.00 1.00 1.00 1.00
 Within 2 years 1536 833 (54.2) 311 (37.3) 0.70 (0.64–0.75) 1.10 (0.91–1.32) 0.65 (0.59–0.71) 1.27 (0.99–1.63)
 2–5 years 1549 815 (52.6) 267 (32.8) 0.75 (0.69–0.81) 1.24 (1.02–1.50) 0.76 (0.69–0.84) 1.35 (1.05–1.74)
 5–10 years 1543 897 (58.1) 283 (31.5) 0.82 (0.76–0.89) 1.10 (0.91–1.33) 0.76 (0.69–0.83) 1.25 (0.97–1.60)
 More than 10 years 2423 1460 (60.3) 423 (29.0) 0.89 (0.83–0.95) 1.23 (1.04–1.46) 0.84 (0.77–0.91) 1.10 (0.87–1.40)
 Missing 1229 690 (56.1) 232 (33.6)     
TB lineage
 Beijing 706 525 (74.4) 93 (17.7) 1.00 1.00 1.00 1.00
 Euro-American 5306 3233 (60.9) 898 (27.8) 0.51 (0.47–0.56) 1.05 (0.80–1.39) 0.46 (0.41–0.50) 1.11 (0.80–1.54)
 Central Asian Strain 2955 1948 (65.9) 547 (28.1) 0.72 (0.66–0.79) 1.05 (0.79–1.40) 0.78 (0.70–0.86) 1.01 (0.72–1.43)
 East Asian Indian 1271 551 (43.4) 235 (42.6) 0.42 (0.37–0.48) 1.59 (1.16–2.17) 0.52 (0.45–0.59) 1.54 (1.06–2.23)
 Other/unknown 1673 964 (57.6) 283 (29.4) 0.48 (0.43–0.53) 1.17 (0.86–1.59) 0.43 (0.38–0.48) 1.18 (0.82–1.69)
 Missing 2       
IMD decile
 1 2581 1654 (64.1) 440 (26.6)
 2 2238 1383 (61.8) 396 (28.6)
 3 1851 1117 (60.3) 335 (30.0)
 4 1425 873 (61.3) 247 (28.3)
 5 1039 609 (58.6) 191 (31.4)
 6 737 437 (59.3) 125 (28.6)
 7 525 306 (58.3) 80 (26.1)
 8 486 276 (56.8) 82 (29.7)
 9 390 224 (57.4) 63 (28.1)
 10 305 171 (56.1) 54 (31.6)
 Missing 334 171 (51.2) 43 (25.1)
 For each decile increase 0.96 (0.95–0.97) 1.02 (0.99–1.04) 0.96 (0.95–0.97) 1.00 (0.97–1.03)
Drug misuse
 No 10,165 6061 (59.6) 1768 (29.2) 1.00 1.00 1.00 1.00
 Yes 639 507 (79.3) 82 (16.2) 1.14 (1.02–1.27) 0.61 (0.45–0.83) 0.88 (0.76–1.01) 0.84 (0.56–1.28)
 Missing 1107 653 (59.0) 206 (31.5)     
Alcohol misuse
 No 10,039 6043 (60.2) 1747 (28.9) 1.00 1.00 1.00 1.00
 Yes 670 470 (70.1) 87 (18.5) 1.85 (1.71–2.01) 0.97 (0.74–1.26) 1.69 (1.54–1.86) 1.18 (0.84–1.66)
 Missing 1202 708 (58.9) 222 (31.4)     
Homelessness
 No 10,398 6277 (60.4) 1799 (28.7) 1.00 1.00 1.00 1.00
 Yes 567 393 (69.3) 85 (21.6) 0.90 (0.80–1.02) 0.74 (0.55–0.99) 0.63 (0.54–0.72) 0.88 (0.59–1.30)
 Missing 946 551 (58.2) 172 (31.2)     
Imprisonment
 No 9990 5978 (59.8) 1725 (28.9) 1.00 1.00 1.00 1.00
 Yes 553 423 (76.5) 82 (19.4) 1.07 (0.96–1.20) 0.86 (0.76–0.96) 1.10 (0.97–1.26) 0.85 (0.57–1.26)
 Missing 1368 820 (59.9) 249 (30.4)     
Smear status
 Smear positive 4959 3137 (63.3) 901 (28.7) 1.00 1.29 1.00 1.00
 Smear negative or unknown 6952 4084 (58.7) 1155 (28.3) 0.87 (0.83–0.92) 1.94 (1.78–2.12) 0.83 (0.79–0.88) 1.17 (1.02–1.34)
  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 case of a cluster. Both analyses were restricted to clusters where the first case was pulmonary. 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 5694 TB cases after 1052 were excluded due to missing data on one or more of sex (n = 14), ethnicity (n = 192), time since entry to the UK (n = 771) or IMD score (n = 206)
  3. Cases missing data were considered not to have these social risk factors