Suchergebnisse

Lyons (2011) offered several critiques of the social network analyses of
Christakis and Fowler, including issues of confounding, model inconsistency,
and statistical dependence in networks. Here we show that in some settings,
social network analyses of the type employed by Christakis and Fowler will
still yield valid tests of the null of no social contagion, even though
estimates and confidence intervals may not be valid. In particular, we show
that if the alter's state is lagged by an additional period, then under the
null of no contagion, the problems of model inconsistency and statistical
dependence effectively disappear which allow for testing for contagion. Our
results clarify the setting in which even "flawed" social network analyses
are still useful for assessing social contagion and social
influence.

BACKGROUND: We evaluated the effectiveness of integrated care centers (ICCs), which provided single-venue HIV testing, prevention, and treatment services for people who inject drugs (PWID) and men who have sex with men (MSM), in India. METHODS: We conducted baseline respondent-driven sampling (RDS) surveys in 27 sites across India, and selected 22 of these (12 PWID and 10 MSM) for a cluster randomised trial on the basis of high HIV prevalence and logistical considerations. We used stratified (PWID and MSM), restricted randomisation to allocate sites to either the ICC intervention or usual care (11 sites per arm). We implemented ICCs in 11 cities (6 PWID ICCs embedded within opioid agonist treatment centers and 5 MSM PWIDs embedded within locations of government-sponsored health services), with a single ICC per city in all but 1 city. After a 2-year intervention phase, we conducted evaluation RDS surveys of target population members 18 years or older at all sites. The primary outcome was self-reported HIV testing in the prior 12 months (recent testing) in the evaluation survey. We used a biometric identification system to estimate ICC exposure (visited an ICC at least once) among evaluation survey participants at intervention sites. This trial is registered with ClinicalTrials.gov (NCT01686750). FINDINGS: ICCs provided HIV testing for 14,689 unique clients during the intervention phase. In the evaluation phase (August 2016 to May 2017) we surveyed 11,721 PWID and 10,005 MSM participants using RDS. In the primary population-level analysis, recent HIV testing was 31% higher in ICC than usual care sites (adjusted prevalence ratio [aPR] 1·31, 95% confidence interval [CI] 0·95, 1·81, p=0·09). Among survey participants at intervention sites, ICC exposure was lower than expected (median exposure 40% at PWID sites and 24% at MSM sites). In intervention sites, survey participants who visited an ICC were 3·5-fold (95% CI 2·9, 4·1) more likely to report recent HIV testing than participants who had not. Post-hoc analyses ...