Measuring exposure to cannabis use and other substance use in remote aboriginal populations in northern Australia: Evaluation of a 'community epidemiology' approach using proxy respondents

We evaluate a method to describe changing substance use patterns in northern Australia's remote Aboriginal communities (Arnhem Land, Northern Territory). Substance use was assessed in random samples in two communities A (n = 194) and B (n = 176). Five Aboriginal health workers made assessments independently of each other in community A. A different group of three health workers made independent assessments in community B. Sub-samples were opportunistically recruited for interview (community A, n = 77; community B, n = 55). In community C, 10 1 people were interviewed and were also assessed by four local health workers working together. Proportional agreements (kappa-kappa statistic) among health workers for a history of substance use and current use, varied from kappa=0.207 for petrol sniffing (P=0.006) up to kappa=0.749 for cannabis use (P<0.001), all better than would be expected by chance. In communities A and 13, agreement between health workers' consensus and self-reported substance use was weaker (0.103<kappa<0.482) probably because of under-reporting in interviews. In community C, where interviews were conducted in a confidential clinic setting, agreement between health workers' concensus and self-report varied from kappa=0.273 for petrol sniffing (P<0.001) up to 0.819 for tobacco use (P<0.001). Aboriginal health worker consensus classification clarified equivocal self-report data.