Validity and utility of community health workers' estimation of kava use

Estimating illicit substance use in epidemiological studies is challenging, particularly across ethical, cultural and language barriers. While developing the methods for a case-control study of the effects of heavy kava consumption among Aboriginal people in remote Northern Territory (NT), we examined the validity and utility of alternative methods for estimating exposure.

We assessed the level of agreement between a consensus of Aboriginal health workers in two different communities using interviews conducted with community members and health workers and individuals' self-reported kava consumption. Exposure measures included history of kava use, current kava use and history of heavy use. Agreement between a health worker consensus classification and individuals' self-report was analysed and agreement among several health workers in a consensus classification without self-report was assessed.

Health workers concurred about an individual's history of kava use (k=0.83), current use (k=0.43) and also level of use (k=0.33). There was very good agreement between health workers' consensus and self-reported history of use (k=0.77). Agreement among health workers about current kava use was poor (k=0.08), while there was fair agreement between health workers and self-reported heavy kava users (k=0.36). Data from review of clinic patient notes supported agreement between consensus classification and self-reported history and level of use (k=0.39).

Self-reported kava use may be a poor estimate of current use especially when obtained from interviews away from a confidential clinic setting. Consensus classification by knowledgeable Aboriginal health workers provided comprehensive coverage, efficiently and with greater reliability and assisted to identify 'excessive' kava use.