Table 2.
Demographic factors in transmission clusters.
| Factor strata | Clusters | Random | Adjusted P value | ||
|---|---|---|---|---|---|
| n | % | n | % | ||
| Country area of residence | |||||
| Northern Italy | 183 | 31.28 | 96 | 17.30 | <0.0001 |
| Central Italy | 146 | 24.96 | 90 | 16.22 | 0.0009 |
| Southern Italy | 8 | 1.37 | 7 | 1.26 | 0.8985 |
| Northern and Central Italy | 158 | 27.01 | 230 | 41.44 | <0.0001 |
| Northern and Southern Italy | 19 | 3.25 | 13 | 2.34 | 0.4504 |
| Central and Southern Italy | 9 | 1.54 | 12 | 2.16 | 0.5302 |
| Northern, Central and Southern Italy | 62 | 10.60 | 107 | 19.28 | 0.0001 |
| Mode of HIV transmission | |||||
| Male homosexual | 135 | 27.05 | 77 | 15.88 | <0.0001 |
| Heterosexual | 93 | 18.64 | 72 | 14.85 | 0.1794 |
| IDU | 56 | 11.22 | 79 | 16.29 | 0.0415 |
| Male homosexual and heterosexual | 99 | 19.84 | 48 | 9.90 | <0.0001 |
| Male homosexual and IDU | 13 | 2.61 | 46 | 9.48 | <0.0001 |
| Heterosexual and IDU | 50 | 10.02 | 42 | 8.66 | 0.5564 |
| Male homosexual, heterosexual and IDU | 53 | 10.62 | 121 | 24.95 | <0.0001 |
| ART status | |||||
| Naive | 99 | 19.08 | 48 | 9.78 | 0.0001 |
| Experienced | 227 | 43.74 | 231 | 47.05 | 0.3921 |
| Naive and experienced | 193 | 37.19 | 212 | 43.18 | 0.0883 |
| Presence of at least one resistance mutation to NRTI | |||||
| Yes | 153 | 26.15 | 102 | 18.65 | 0.0069 |
| No | 156 | 26.67 | 87 | 15.90 | <0.0001 |
| Yes and no | 276 | 47.18 | 358 | 65.45 | <0.0001 |
| Presence of at least one resistance mutation to NNRTI | |||||
| Yes | 67 | 11.45 | 58 | 10.34 | 0.5998 |
| No | 243 | 41.54 | 183 | 32.62 | 0.0051 |
| Yes and no | 275 | 47.01 | 320 | 57.04 | 0.0020 |
| Presence of at least one resistance mutation to PI | |||||
| Yes | 61 | 10.43 | 34 | 6.09 | 0.0181 |
| No | 300 | 51.28 | 225 | 40.32 | 0.0007 |
| Yes and no | 224 | 38.29 | 299 | 53.58 | <0.0001 |
| Presence of at least one drug-resistance mutation to any ARV class | |||||
| Yes | 188 | 32.14 | 161 | 28.50 | 0.2574 |
| No | 119 | 20.34 | 58 | 10.27 | <0.0001 |
| Yes and no | 278 | 47.52 | 346 | 61.24 | <0.0001 |
| Years passed from the first HIV-1 positive test | |||||
| Below 3 | 143 | 34.71 | 76 | 18.86 | <0.0001 |
| Between 3 and 9 | 53 | 12.86 | 48 | 11.91 | 0.7235 |
| Between 9 and 14 | 33 | 8.01 | 49 | 12.16 | 0.0851 |
| Above 14 | 26 | 6.31 | 37 | 9.18 | 0.1964 |
| Mixtures with ≥2 factors | 157 | 38.11 | 193 | 47.89 | 0.0121 |
| HIV-1 RNA load (copies per ml) | |||||
| Below 1,000 | 19 | 3.85 | 28 | 6.38 | 0.1300 |
| Between 1,000 and 10,000 | 55 | 11.16 | 61 | 13.90 | 0.2834 |
| Above 10,000 | 212 | 43.00 | 151 | 34.40 | 0.0169 |
| Mixtures with ≥2 factors | 207 | 41.99 | 199 | 45.33 | 0.4017 |
| Mode of HIV transmission and gender | |||||
| Male homosexual | 130 | 26.69 | 76 | 15.90 | 0.0001 |
| Male heterosexual and homosexual | 66 | 13.55 | 19 | 3.97 | <0.0001 |
| Male heterosexual | 45 | 9.24 | 40 | 8.37 | 0.6846 |
| Male IDU | 36 | 7.39 | 48 | 10.04 | 0.2173 |
| Female and male heterosexual | 22 | 4.52 | 10 | 2.09 | 0.0649 |
| Female and male heterosexual, male homosexual | 21 | 4.31 | 8 | 1.67 | 0.0338 |
| Other mixtures | 167 | 34.29 | 277 | 57.95 | <0.0001 |
| ART status and presence of at least one drug-resistance mutation to any ARV class | |||||
| Naive and no-resistance | 78 | 15.00 | 30 | 5.93 | <0.0001 |
| Naive and resistance | 12 | 2.31 | 11 | 2.17 | 0.8985 |
| Naive, treated and no-resistance | 28 | 5.38 | 11 | 2.17 | 0.0169 |
| Naive, treated and resistance | 22 | 4.23 | 24 | 4.74 | 0.7247 |
| Other mixtures | 380 | 73.08 | 430 | 84.98 | <0.0001 |
ART, antiretroviral therapy; ARV, antiretroviral; IDU, injecting drug user; NNRTI, non-nucleoside reverse transcriptase inhibitors; NRTI, nucleoside/nucleotide reverse transcriptase inhibitors; PI, protease inhibitors.
Clusters compositions by different demographic factors, using a clustering threshold of 0.07 nucleotide substitutions per site. Observed proportions have been compared with a data randomization.