In this study, we have used two different 'off-the-shelf' methods of identifying opinion leaders across a range of different professional groups in the UK. The study utilised existing instruments that had previously been validated in cross sectional surveys and in randomised trials. The study used replicated surveys across different types of professionals within the UK, which allowed us to identify wide variations across different professional groups and sites in the extent of nominating SOLs and the complexity of networks. Furthermore, this has been one of the first studies to examine whether opinion leaders are polymorphic or monomorphic.
Responses to the sociometric instruments demonstrated a wide variation across different professional groups and sites in the extent of nominating SOLs and the complexity of social networks [8
]. These results suggest that the extent of social networks and potential coverage of the study population in primary and secondary care is highly idiosyncratic, and adequate coverage rates cannot be assumed. In contrast, relatively complex networks with good coverage rates were observed in both national specialty groups.
Both SOLs and SDOLs had characteristics of opinion leaders although the odds ratios and mean differences in continuous variables were higher in SOLs. Approximately one-third of generic SOLs also were nominated as condition-specific SOLs, and the condition-specific coverage rate of these SOLs was poor. Similarly, generic SDOLs were relatively unlikely to identify themselves as condition-specific SDOLs. These results suggest that opinion leaders are monomorphic, and that separate identification exercises would be needed for different conditions.
Case studies frequently identify the importance of individuals (opinion leaders, change agents, product champions) in leading and supporting change in the health service. However, these terms are not necessarily well defined, nor mutually exclusive. In this study there was poor agreement in the responses to the sociometric and self-designating instruments. SDOLs were relatively unlikely to have been identified as SOLs and vice versa. There are at least two possible interpretations of this. If the instruments are trying to identify the same construct of opinion leaders, one is performing poorly. Alternatively, the instruments may be identifying different constructs of opinion leaders. The sociometric instrument was rigorously developed [6
] and has face validity, but remains the only instrument of its type and thus has not been validated against a comparable instrument. It emphasises opinion leaders who are knowledgeable, humanistic, and good communicators – characteristics identified by physicians as likely to influence their choice of educational influential (Table ). Work in Norway [9
] showed that general practitioners supported the concepts espoused in the sociometric instrument. The instrument demonstrates the extent of social networks and coverage of identified opinion leaders and has been successfully used to identify opinion leaders in randomised trials, which have demonstrated behaviour change. The self-designating instrument emphasises opinion leaders who are commonly consulted by colleagues and who give a lot of information (Table ), and while the sociometric instrument may identify one construct of opinion leader, other types of leadership also may be influential (e.g., professional or academic leaders). However, there is scope for further exploration of the validity of the self-designating instrument within professional settings. These considerations highlight the potential conceptual and terminological confusion surrounding opinion leadership. Whilst this term is used in a specific technical way within the diffusions of innovation, marketing and social influence literatures, it is commonly used to describe any influential individual (educational, academic or political).
Response rates to the survey overall were moderate (57.8%). The response rate to the sociometric instrument was lower. During pilot work for this study, interviews with primary care respondents – after they had completed the instruments – suggested that they had some difficulties with the concept of opinion leaders, and the questionnaire was also seen as being rather abstract [8
]. We have identified eleven studies that have used the sociometric instrument from the systematic review by Thomson, [5
] and a forward citation search for the original study by Hiss and colleagues (1978). The majority of previous studies provided inadequate details of the methods of identifying opinion leaders, partly due to editorial pressures on space (Soumerai S, personal communication.). The number of opinion leaders identified varied. In the studies by Stross [10
]], Lomas [13
] and Soumerai [14
], the individual with the greatest number of nominations per institution was identified as an opinion leader. In the other studies, a larger number of opinion leaders were identified (similar to the current study). These differences are probably due to different strategies for analysing the sociometric instrument. Coverage rates are rarely reported, although Lomas [13
] and Soumerai [14
] both report that the identified opinion leaders received the clear majority of votes within their hospital. As a result, it is difficult to assess the coverage likely to be needed if the strategy is successful. All of these factors have important implications for the utility of the method in a service setting, as it would be difficult to justify as a single strategy a method that potentially only drew on just more than half of the population and could not cover the non-responding half. We used convenience samples for this work, so it is important that the study is replicated in other settings and populations of clinicians. Indeed, it would be interesting to repeat it in the same populations in a few years to see if recent UK health reforms, with their emphasis on localities of general practitioners, have changed the situation.
The concept of opinion leadership has a good theoretical basis and strong face validity. Some trials of recruiting opinion leaders to support the implementation of research findings have observed significant improvements in clinical care. However, this study has highlighted some of the likely problems of recruiting opinion leaders. First, opinion leaders appear to be monomorphic – separate identification exercises would be required for each clinical area or targeted behaviour. Second, the identification of opinion leaders and their coverage, if the underlying social networks were highly variable and idiosyncratic (except in the national specialty groups), suggests that recruitment of opinion leaders is unlikely to be an effective general strategy across all settings and professional groups. The more specialised the group, the more opinion leaders may be a useful strategy.