Part III will deal with health care measures and indicators which we consider in the phases of the temporal dimension: input, process and outcome.We shall use the term ‘measures'to denote direct assessments,and ‘indicators’ as indirect assessments (or reasonable proxies) that summarise information relevant to a particular phenomenon. Like other instruments used for health services evaluation, such measures and indicators should have adequate validity, reliability, sensitivity and specificity (Jenkins, 1990). Since direct measures are difficult to collect, indirect proxy variables are more common and such performance indicators have been defined as ‘operationally- defined indirect measures of selected aspects of a system which give some indication of how far it conforms to its intended purpose’(Glover & Kamis-Gould,1996).

The distinction and balance between inputs, processes and outcomes within mental health services are far from clear-cut for three reasons. First, there is no consensus on the definitions of these terms, and their use in the literature is widely variable. The consequence of this is that it is often the case that the three temporal phases are used in a confused way so that processes (such as numbers of admissions) are used as if they were outcome variables. Second, these three categories of variables are inter-connected and need to be seen as different aspects of the wider,dynamic mental health care system. In this case, outcomes cannot be considered in isolation, and in fact patients will often want acceptable care processes andoutcomes, so that attention to outcomes alone will miss a part of what is valued by the recipients of care.