Table 3.
Factors associated with transmission clustering.
| Factor/threshold | 1st Percentile (0.04 ns s−1) | 15th Percentile (0.07 ns s−1) | 30th Percentile (0.08 ns s−1) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| OR | 95% CI | P value | OR | 95% CI | P value | OR | 95% CI | P value | |
| Calendar year of genotyping (per more recent) | 1.04 | (1.01–1.06) | 0.0011 | 0.98 | (0.96–1) | 0.1163 | 0.98 | (0.95–1.01) | 0.2626 |
| Italian country area of residence (ref. Central) | |||||||||
| Northern | 0.52 | (0.46–0.6) | <0.0001 | 0.73 | (0.63–0.85) | <0.0001 | 1.09 | (0.85–1.39) | 0.4936 |
| Southern | 0.58 | (0.45–0.75) | <0.0001 | 0.78 | (0.6–1.01) | 0.0578 | 1.07 | (0.68–1.68) | 0.7860 |
| Unknown | 0.86 | (0.56–1.34) | 0.5151 | 1.05 | (0.63–1.76) | 0.8583 | 0.65 | (0.32–1.32) | 0.2341 |
| Mode of HIV-1 transmission (ref. IDU) | |||||||||
| Heterosexual | 1.64 | (1.29–2.09) | <0.0001 | 1.08 | (0.86–1.36) | 0.4993 | 0.27 | (0.17–0.44) | <0.0001 |
| Male homosexual | 1.58 | (1.24–2.01) | 0.0002 | 1.05 | (0.82–1.33) | 0.7112 | 0.16 | (0.1–0.25) | <0.0001 |
| Other/unknown | 1.52 | (1.19–1.94) | 0.0007 | 1.05 | (0.84–1.32) | 0.6658 | 0.33 | (0.21–0.52) | <0.0001 |
| Gender (ref. female) | |||||||||
| Male | 1.88 | (1.56–2.26) | <0.0001 | 1.00 | (0.83–1.19) | 0.9564 | 0.54 | (0.4–0.73) | <0.0001 |
| Unknown | 2.27 | (1.73–2.97) | <0.0001 | 1.08 | (0.82–1.42) | 0.5801 | 0.52 | (0.32–0.83) | 0.0058 |
| Country of birth (ref. Italy) | |||||||||
| Other than Italy | 0.64 | (0.45–0.91) | 0.0142 | 0.53 | (0.37–0.75) | 0.0004 | 0.28 | (0.18–0.43) | <0.0001 |
| Unknown | 1.03 | (0.86–1.23) | 0.7390 | 1.13 | (0.93–1.36) | 0.2096 | 1.12 | (0.82–1.53) | 0.4867 |
| Age (ref. >46 years old) | |||||||||
| ≤36 | 1.49 | (1.23–1.81) | <0.0001 | 1.20 | (0.98–1.47) | 0.0790 | 1.49 | (1.1–2.04) | 0.0111 |
| >36 and ≤41 | 1.06 | (0.88–1.26) | 0.5617 | 1.00 | (0.83–1.21) | 0.9656 | 1.70 | (1.26–2.29) | 0.0006 |
| >41 and ≤46 | 0.99 | (0.84–1.18) | 0.9366 | 1.00 | (0.84–1.19) | 0.9965 | 1.44 | (1.1–1.9) | 0.0082 |
| Unknown | 1.02 | (0.82–1.26) | 0.8910 | 1.10 | (0.87–1.38) | 0.4303 | 1.50 | (1.01–2.21) | 0.0424 |
| ART status (ref. ART-naive) | |||||||||
| ART-experienced | 0.68 | (0.56–0.84) | 0.0003 | 1.08 | (0.85–1.37) | 0.5361 | 1.18 | (0.82–1.7) | 0.3708 |
| Unknown | 0.72 | (0.59–0.89) | 0.0020 | 1.04 | (0.82–1.31) | 0.7447 | 0.93 | (0.65–1.32) | 0.6677 |
| Time from first HIV+ test (ref. >14 years) | |||||||||
| ≤3 years | 2.56 | (1.87–3.51) | <0.0001 | 1.78 | (1.3–2.45) | 0.0004 | 1.33 | (0.75–2.36) | 0.3261 |
| >3 and ≤9 years | 1.70 | (1.27–2.26) | 0.0003 | 1.14 | (0.87–1.5) | 0.3524 | 0.87 | (0.52–1.45) | 0.6022 |
| >9 and ≤14 years | 1.30 | (1–1.7) | 0.0537 | 1.18 | (0.93–1.51) | 0.1804 | 0.99 | (0.62–1.57) | 0.9519 |
| Unknown | 1.38 | (1.04–1.81) | 0.0232 | 0.90 | (0.7–1.17) | 0.4394 | 0.77 | (0.47–1.24) | 0.2809 |
| Presence of at least one drug-resistance mutation* | |||||||||
| NRTI | 0.68 | (0.6–0.78) | <0.0001 | 0.72 | (0.62–0.82) | <0.0001 | 0.99 | (0.8–1.24) | 0.9378 |
| NNRTI | 0.93 | (0.83–1.04) | 0.2271 | 0.99 | (0.88–1.12) | 0.8875 | 0.95 | (0.78–1.16) | 0.6196 |
| PI | 0.93 | (0.82–1.07) | 0.3092 | 0.80 | (0.7–0.92) | 0.0012 | 0.77 | (0.61–0.97) | 0.0274 |
| HIV-1 RNA per one Log10 copies per ml higher | 1.08 | (1.01–1.15) | 0.0344 | 1.01 | (0.94–1.09) | 0.7574 | 1.04 | (0.92–1.17) | 0.5722 |
| CD4+ count per 50 cells/mm3 higher | 1.03 | (1.01–1.04) | 0.0002 | 1.02 | (1.01–1.04) | 0.0057 | 1.03 | (1–1.06) | 0.0616 |
ART, antiretroviral therapy; CI, confidence interval; IDU, injecting drug user; NNRTI, non-nucleoside reverse transcriptase inhibitors; NRTI, nucleoside/tide reverse transcriptase inhibitors; ns s−1, nucleotide substitutions per site; OR, odds-ratio; PI, protease inhibitors.
*Mixtures of wild-type and resistant mutants are classified as resistant
Adjusted OR of transmission clustering evidence (clustered versus un-clustered isolates) from fitting a multivariable logistic generalized-estimating-equations model, by considering different percentile thresholds.