A questionnaire to measure melanoma risk, knowledge and protective behaviour: Assessing content validity in a convenience sample of Scots and Australians

BACKGROUND The aim of this study was to assess the content validity of a questionnaire to measure melanoma risk, knowledge and protective behaviour in a convenience sample of Scots and Australians. Australia has the highest melanoma incidence worldwide but has developed a culture of skin cancer avoidance with a long history of skin cancer primary prevention campaigns of proven effectiveness. Scotland has lower incidence, but has shown a greater rate of increase between 1985 and 2007. There is an urgent need in Scotland, therefore, to identify those groups at greatest risk and provide them with effective preventative advice. METHOD A self-administered postal survey was completed by four groups formed from convenience samples in two geographical locations (Northeast Scotland and Western Australia). In univariate analysis scores on personal risk, level of concern, protective behaviour, and knowledge were compared by nationality, previous skin cancer diagnosis and personally knowing someone with melanoma. Multivariate linear regression analysis modelled the influence of potential predictor variables upon each of the scores. RESULTS 540 people completed the questionnaire, 273 Scots (50.6%). 133 (24.6%) Scots and 83 (15.4%) Australians previously had melanoma or non-melanoma skin cancer, whilst 120 (22.2%) Scots and 190 (35.2%) Australians personally knew someone with melanoma. Australians had higher knowledge (p < 0.001), level of concern (p < 0.001) and protective behaviour (p < 0.001) scores than the Scottish. Australian nationality was the strongest independent predictor of a higher knowledge score (p < 0.001), followed by a previous skin cancer diagnosis (p = 0.003), personal knowledge of someone with melanoma (p = 0.011), female gender (p = 0.005) and higher education status (p < 0.001) (R(2) = 0.163). CONCLUSION The questionnaire detected higher levels of knowledge and skin cancer protective behaviours in Australians than in Scottish people. This was expected and supports the content validity of the questionnaire and its value as a future research tool in the Scottish population.