Table 3.
Results of log-linear modelling and estimated prevalence of injecting drug use (IDU) in HCV-diagnosed persons, for both full and stratified datasets; the latter were stratified by sex, birth cohort and period of HCV diagnosis. 95% confidence intervals were derived using the profile likelihood
| n | IDU risk, from data sources, n (%) | IDU risk, total n (95% CI) | Estimated prevalence | Saturated model? | |
|---|---|---|---|---|---|
| Full dataset | 25 521 | 18 782 (73·6) | 21 266 (20 582–22 140) | 83·3% | Y |
| Stratified analysis | |||||
| Sex | |||||
| Female | 8177 | 5694 (69·6) | 6230 (6130–6341) | 76·2% | Na |
| Male | 17 344 | 13 088 (75·5) | 14 669 (14 235–15 229) | 84·6% | Nb |
| Birth cohort | |||||
| <1960 | 5168 | 1958 (37·9) | 2554 (2366–2801) | 49·4% | Nc |
| 1960–69 | 8894 | 6841 (76·9) | 8089 (7575–8865) | 91·0% | Y |
| 1970–79 | 8812 | 7781 (88·3) | 8226 (8146–8316) | 93·4% | Nd |
| 1980+ | 2647 | 2202 (83·2) | 2405 (2347–2474) | 90·8% | Ne |
| Health board | |||||
| GGC | 10 679 | 8174 (76·5) | 8856 (8698–9045) | 82·9% | Nf |
| Other | 14 842 | 10 608 (71·5) | 12 573 (11 914–13 491) | 84·7% | Y |
| Period of HCV diagnosis | |||||
| <1995 | 2290 | 1211 (52·9) | 1411 (1304–1600) | 61·6% | Ng |
| 1995–99 | 7163 | 5454 (76·1) | 6554 (6039–7389) | 91·5% | Y |
| 2000–04 | 8168 | 6479 (79·3) | 6912 (6830–7004) | 84·6% | Nh |
| 2005–09 | 7900 | 5638 (71·4) | 6192 (6075–6326) | 78·4% | Ni |
Y, Yes; N, no; CI, confidence interval; GGC, Greater Glasgow & Clyde.
‘Saturated model?’, Y refers to a log-linear model in which all main effects and all possible two- and three-way interactions were retained after applying the backward stepwise selection.
All two-way interactions only (residual d.f. = 4, deviance = 2·53).
All two-way interactions and a:b:d, a:c:d, and b:c:d only (residual d.f. = 1, deviance = 1·70).
All two-way interactions and a:c:d only (residual d.f. = 3, deviance = 1·66).
All two-way interactions only (residual d.f. = 4, deviance = 1·90).
All two-way interactions except a:c and b:c (residual d.f. = 6, deviance = 3·47).
All two-way interactions and a:b:c and a:c:d only (residual d.f. = 2).
All two-way interactions and a:b:c and a:c:d only (residual d.f. = 2, deviance = 2·33).
All two-way interactions except b:c (residual d.f. = 5, deviance = 5·50).
All two-way interactions and a:b:c and b:c:d only (residual d.f. = 2, deviance = 0·42).
[a, HCV Diagnosis; b, HIV Test; c, Scottish Morbidity Records hospital discharge/deaths data (SMR01/Deaths); d, Scottish drug misuse database (SDMD).]