The main aim of clinical practice guidelines is to improve healthcare processes and health outcomes. Their effective implementation will promote consistency in daily clinical practice and hence facilitate optimal utilization of healthcare resources. They are increasingly being used to assist both clinical and healthcare policy decision-making [5]. As defined by the US Institute of Medicine, clinical practice guidelines are “statements that include recommendations intended to optimize patient care that are informed by a systematic review of evidence and an assessment of the benefits and harms of alternative care options” [6]. Guidelines are viewed as powerful tools to improve the quality of care. They can contribute to decreased variability in healthcare decisions between physicians, and stimulate effective care, communication and collaboration between different healthcare professionals, as well as between healthcare professionals and patients.

Before the wider use of guidelines, clinical practice was usually guided by non-systematic observations based on clinical experience. The knowledge of basic disease mechanisms and pathophysiology was considered sufficient to guide clinical decision-making [7]. Systematic development of guidelines within a well-defined program started in the late 1970s. Guidelines were seen as tools to improve the quality of care, and were mainly consensus-based. The U.S. National Institutes of Health initiated the development of these so-called “consensus statements.” The consensus conference had a central role within this process [8]. During the 1980s, various other organizations outside the USA adopted this program to develop their own consensus statements and standards for good medical care.

In the early 1990s, a shift emerged to more evidence-based clinical practice based on content-expertise and clinical experience-based decision-making. In 1992 evidence-based medicine (EBM) was introduced by the EBM Working Group. EBM is the process of integrating clinical expertise with the best research evidence to make high-quality decisions about the care of individual patients (Evidence-Based Medicine Working Group 1992). This emphasized the importance of systematic literature searches and evidence summaries in the development of guidelines. The Cochrane Collaboration was founded in 1993 to improve the availability of the best evidence in healthcare by facilitating the preparation and maintenance of systematic reviews. Cochrane systematic reviews help clinicians evaluate all the evidence addressing a particular clinical problem, using standardized methodology for searching and appraising the literature and for reporting the results [9].

In 1996 the second fundamental principle of EBM was presented. This principle suggested that decision makers must always balance the benefits and risks, inconvenience and costs associated with alternative management strategies in the decision making process, and also include consideration of the patients’ values [10, 11].

The principles of EBM dominate contemporary guideline programs. The method of evidence-based guideline development has become the international standard by which contemporary clinical practice guidelines should integrate the best available evidence and clinical judgment, as well as the patients’ perspectives.

Guidelines are a combination of a summary of evidence-based knowledge and recommendations. It is very challenging for a healthcare professional to remain up-to-date since more than two million new scientific papers are published each year. There is far too much information available and the conclusions of published work may be conflicting since all the accessible information is rarely summarized. Guidelines can facilitate in bridging the gap between research and clinical practice.

Clinical practice guidelines can improve the quality of clinical decisions. They are useful for clinicians who are uncertain about how to proceed, and also enable the patient to make well- informed healthcare decisions and to consider their personal needs and preferences in selecting the best option [5].

The greatest potential benefit of guidelines is the improvement of health outcomes. Guidelines recommending proven effective interventions and discouraging ineffective ones may reduce morbidity and mortality, and thus improve quality of life. Guidelines also make it more likely that patients receive uniform high-quality care, thereby reducing variability in daily healthcare practice. It has been shown that the consistency of healthcare is low—the frequency with which procedures are performed varies considerably between clinicians and geographical regions [5, 12]. Several international reviews have shown that the majority of implemented guidelines have resulted in significant improvements in the process and structure of care [13–15].

Finally, clinical practice guidelines can contribute to reduced healthcare costs by standardizing care and hence increasing the efficiency of care provision and reducing unnecessary or inefficient components of healthcare. Guidelines reduce expenses for hospitalization, drug prescriptions, surgery, and other procedures [5].

Many clinical practice guidelines have been developed by expert groups without complete appraisal of the evidence. This method relies on the group’s knowledge of existing evidence and the clinical experience of its members. However, the knowledge of clinicians of published work is often incomplete due to poor presentation and dissemination of research findings and difficulties to keep fully up-to-date with the published literature. Guidelines developed without formal literature reviews and critical appraisal of the evidence may be biased towards supporting current practice rather than promoting newer and more evidence-based practice [16].

Traditionally, the incorporation of evidence into guideline development was achieved by providing narrative reviews of topic areas by experts in the field. However, the general methodology of this type of review is not transparent, since there are no explicit research strategies and inclusion criteria, and formal methods of synthesizing the evidence are lacking. Authors may cite studies selectively supporting their own opinion and fail to cite other studies providing alternative evidence. Therefore guidelines developed after non-systematic literature reviews may be prone to selection bias and provide false reassurance [16].

Evidence-based guidelines attempt to be as complete and focused as possible in summarizing the available evidence. The best way to summarize the evidence is a systematic review. However, since this is very time consuming and costly, a decision should be taken during the guideline process for which particular issues a systematic review should be performed. A systematic review aims to minimize the occurrence of bias through an explicit search strategy to identify all available evidence, selection and assessment of the methodological quality of the evidence, and reduction of random error by using quantitative methods (i.e., meta-analysis). The Cochrane Collaboration is the largest provider of systematic reviews for healthcare and includes approximately 6,000 systematic reviews in the Cochrane Library. The Cochrane Collaboration developed standardized methods to perform systematic reviews. The Cochrane Childhood Cancer Group (CCCG) in Amsterdam has been registered within the Cochrane Collaboration since 2006 (www.​ccg.​cochrane.​org). The goal of the CCCG is to conduct and maintain systematic reviews on diagnosis of and interventions for cancer in children and young adults with respect to prevention, treatment, supportive care, psychosocial care, palliative and terminal care, nursing care, and late adverse effects of treatment.

However the translation of evidence into recommendations is not always straightforward since data can be interpreted in different ways depending on clinical experiences. In addition, one should keep in mind that evidence is only one component of the development of evidence-based guidelines and needs to be considered alongside clinical expertise and patient values. Transparency about the process is essential [9, 16].