Variation in decision-making is apparent amongst health professionals in a range of health care settings. In the United Kingdom (UK) there is wide variation in referral to secondary care at general practice and practitioner level , with two fold differences between the top and bottom deciles of general practices for hospital admissions, after standardising for population age, sex and deprivation [2, 3]. In the United States the percentage of cases classified as urgent in one study varied from 11% to 63% for four nurses, two accident and emergency doctors and two family practitioners . Some of the variation in practice has been explained by differences in case mix. For example socio-demographic patient factors such as social class and the proportion of the population chronically ill explained about half of the variation in hospital admission levels between general practices in the UK . However, attempts to explain the remaining variation by exploring the effect of health professional characteristics on decision-making have resulted in little more of the variation being explained [1, 2, 5, 6]. Investigators of variation in decision-making have recommended moving away from examining the demographic characteristics of health professionals and turning instead to exploring psychological and sociological factors , in particular health professional risk-taking in the face of uncertainty .
Computerised decision support systems (CDSS) are sometimes used by health professionals with the aim of supporting safety and consistency in their clinical decision-making. In the United Kingdom CDSS is routinely used in NHS Direct in England and Wales, and NHS 24 in Scotland, both of which offer 24-hour national telephone clinical assessment by nurses. One might expect there to be less variation in clinical decision-making between nurses in these services because of the use made of CDSS. However, protocols and computer programmes do not necessarily remove variability in health care [8, 9], and in fact we have previously noted that the level of variation in nurses' decision-making in NHS Direct has been similar to that of health professionals in other services .
Attempts have been made to explain variation in decision-making when CDSS is used. The type of software, and the length of nursing experience of individuals using the software, explains some of the variation in decision-making . Within the same study, an attempt was also made to explore the decision-making process between nurse and CDSS, and possible influences on it, using qualitative interviews with nurses [10, 11]. This helped to explain why variation occurred in decisions made, even when CDSS was used. It was found that, although the CDSS recommends the action which patients should take, nurses can explicitly override this recommendation, or they can influence the recommendation made by the CDSS through the way in which they choose to navigate the system . Within this qualitative study, differences in nurses' attitudes to risk was identified as a possible explanatory factor for variation in the decisions made. Some nurses were very concerned about the risks of under-triaging and missing a serious illness, while others were concerned about over-triaging and overloading a busy service . Nurses viewed the CDSS as a safety net but they also recognised its limitations and the need for nurse expertise. There was variation between nurses in terms of the emphasis they placed on their own professional expertise and intuition, and the expertise embodied within the CDSS. Given the perceived safety net role of the CDSS, a low risk approach for some nurses was to adhere to the software recommendations. Finally, nurses' talk revealed differences in tolerance of uncertainty in their clinical decision-making, which has been identified elsewhere as a possible explanatory factor of variation in decision-making .
In light of this, the aims of this study were to assess nurse attitudes to risk in telephone clinical assessment using CDSS, and to examine how far measured differences in attitudes between nurses explained the variation in decisions made. The study was undertaken in NHS 24. As well as offering a 24-hour service, NHS 24 is the frontline service for all out of hours general practice services and therefore a large proportion of calls to it are typically made in the evenings or at weekends. Nurse advisors use CDSS to clinically assess and triage callers and can advise them to self-care, to contact their general practitioner or out-of-hours service immediately or later, or to attend accident and emergency departments urgently or as an emergency via a 999 ambulance. That is, they offer advice on the urgency with which help should be sought, pass that call on if required, or offer advice about the management of a health problem. Typical examples would be a parent of a young child calling to ask whether the child needs to see a doctor immediately, or an adult calling to ask for advice on managing a self-limiting condition. To help nurses develop the skills required for such telephone triage, NHS 24 runs an extensive in-house training programme covering the use of the CDSS system, and the identification and response to potentially high risk clinical situations. In this study the dichotomous outcome variable of whether or not calls were sent to self-care was chosen because advice to 'self-care only' presents both callers and nurses with the clearest risk – that the patient will not be seen by a health professional and may be falsely reassured and their care delayed . Our hypotheses were that nurses who were more concerned about the risk of missing a serious illness, nurses who relied more on the software, and nurses with low tolerance of uncertainty in their clinical decision-making, would be more risk averse and send fewer calls to self care.