This study illustrated that Dutch GPs have a positive attitude towards the national guidelines for general practice. In addition, they reported high rates of adherence and the perceived barriers were overall limited. However, rates of adherence and perceived barriers differed substantially across recommendations in guidelines. The most perceived barriers-that are widely applicable across recommendations-are patient related, suggesting that GPs believe that current guidelines do not always adequately incorporate patient preferences, needs and abilities.
GPs in our study had a positive attitude towards the NHG guidelines in general. Other studies focusing on physicians' attitudes towards guidelines [21
] and in particular those of GPs [23
], demonstrated overall positive attitudes as well. Moreover, the positive attitude found among our sample of Dutch GPs may be related to the fact that almost all GPs are a member of the NHG and that their guidelines are presented as 'guidelines for GPs developed by GPs'. This can result in a strong sense of ownership among the target group. Although the overall adherence rate reported by GPs was rather high, we further uncovered that the rates of adherence varied largely across recommendations. These findings are consistent with a comprehensive study based on data from medical records among 195 GPs working in 104 general practices in the Netherlands, showing that GPs overall adherence is about 74%, with levels of adherence varying largely between diagnoses [7
In line with the overall positive attitude to guidelines and high rate of adherence, the reported barriers among our GPs were overall limited. Furthermore, we found a negative association between perceived adherence and all types of barriers; recommendations that were more adhered to in practice, received lower rates on barriers. We found that barriers related to knowledge were not perceived as a barrier, whereas some of the barriers related to attitude and external factors prevented GPs from applying recommendations consistently in practice. The most perceived barriers to adherence across key recommendations were patient ability and behaviour, patient preferences and lack of applicability in general and more specifically to individual patients. These findings suggest that GPs believe that preferences, abilities and needs of individual patients are not well incorporated in guidelines that focus on the 'average patient', complicating adherence to guideline recommendations in practice.
Other studies also indicated that lack of applicability can be a barrier to guideline adherence, particularly to patients with comorbidity [11
]. That guidelines do in fact provide little guidance on the treatment of patients with comorbidities was confirmed in several studies [[26
], Lugtenberg M, Burgers JS, Clancy C, Westert GP, Schneider EC: Current guidelines have limited applicability to patients with comorbid conditions: a systematic analysis of evidence-based guidelines, submitted]. Aside from comorbidities, generally, GPs can have difficulties balancing the needs of the individual patients with the aggregated needs of the population and deviate from guidelines by adjusting practice to the patients' individual needs [24
]. To address these main barriers, it may not only be useful to involve patients in the process of guideline development [27
], but also to adapt the guidelines to facilitate the integration of individual patients' preferences in clinical decision making [30
]. It may be useful to provide tools such as decision aids to support the flexible use of guidelines to individual patients in practice.
Whereas lack of knowledge regarding guideline recommendations was mentioned as a barrier in the focus group study [11
], it was not identified as a barrier in this study. Discrepancies between qualitative and quantitative studies have been found before and may be related to the superficial nature of a survey compared to the more problem-oriented focus in qualitative studies [24
]. On the other hand, the aim of the focus group study was to identify the range of barriers, whereas the survey aimed to explore the relevance of the barriers among a larger sample of the target group. Other barriers that did not seem to be relevant across all recommendations were lack of evidence and lack of outcome expectancy, which is in line with the overall positive attitude of Dutch GPs towards NHG guidelines. Dutch GPs seem to value the NHG guidelines and do not question their scientific basis and content. Finally, lack of reimbursement was among the lowest scoring barriers. This may be related to the well-recognised role of GPs and appropriate financial structure within the Dutch healthcare system [31
The main strength of our study is that we specifically focused on key recommendations in assessing adherence and barriers to guideline adherence. Our study shows that factors that influence adherence vary markedly across recommendations, resulting in specific patterns of barriers for individual key recommendations. It also shows that identifying barriers at the recommendation level is a useful approach. Some barriers may seem unimportant at guideline level, but appear to be very relevant for particular recommendations. A 'one size fits all approach' to guideline implementation will therefore be ineffective. Instead, interventions should be tailored to the barriers of specific recommendations. Although it is usually not feasible to develop interventions to address all barriers for all recommendations in guidelines, results from a detailed analysis may help in deciding where to focus the efforts. Also, substantial improvements can be achieved by focusing on barriers that are widely applicable across recommendations.
Some limitations of our study need to be mentioned. Although our response rate is only slightly below mean response rates of surveys among physicians [33
], it may nevertheless limit the ability to generalise our findings. Those with a positive attitude towards guidelines may be overrepresented in our sample. To minimize this possible bias, we offered accreditation points for completing the questionnaire, creating an incentive to participate for all GPs. In addition, although GPs in the in the age group of 55-64 years were somewhat overrepresented, overall, our sample corresponded quite well with the total population of Dutch GPs in terms of basic characteristics [20
]. Secondly, perceived barriers depend on GPs perceptions' of the situation and may not accurately reflect the (whole spectrum of) barriers. Similarly, perceived adherence rates may be subject to the phenomenon of social desirability, resulting in overestimations of adherence rates [35
]. On the other hand, there are indications that self-reporting among physicians is a valid and reliable source for assessing clinical performance, with high levels of consistency with data from medical records [36
Thirdly, we used an existing framework to classify the barriers. Whereas the use of a predefined framework is useful in analysing a wide range of barriers, the classification of barriers can also be disputed. Based on our qualitative focus group study [11
] we suggest that lack of applicability should be a more prominent category, including different reasons such as patients with comorbidities and that patient factors should also include patients' abilities, needs and behaviour, rather than solely their preferences. Fourthly, our analysis of barriers is based on four guidelines, while GPs in the Netherlands currently have more than 90 guidelines at their disposal. The inclusion of other guidelines could potentially yielded different patterns of barriers. As a diverse set of recommendations of both acute and chronic conditions were included, we expect the identified barriers to be quite representative across all guidelines in general practice.