“…In some studies there is the opportunity to obtain both self-report and actual utilisation data (McCallum, Simons, Simons, Sadler, & Wilson, 1995;Shadbolt, McCallum, Bourne, & Singh, 1998). Where these can be obtained for a common period and covering the same set of healthcare services, self-report can be validated against the actual utilisation data as the 'gold standard'.…”