J.J. van Binsbergen

Systematic reviews incorporating evidence from nonrandomized study designs: reasons for caution when estimating health effects.

Systematic reviews that include nonrandomized studies (NRS) face a number of logistical challenges. However, the greatest threat to the validity of such reviews arises from the differing susceptibility of randomized controlled trials (RCTs) and NRS to selection bias. Groups compared in NRS are unlikely to be balanced because of the reasons leading study participants to adopt different health behaviours or to be treated differentially. Researchers can try to minimize the susceptibility of NRS to selection bias both at the design stage, for example, by matching participants on key prognostic factors, and during data analysis, for example, by regression modelling. However, because of logistical difficulties in matching, imperfect knowledge about the relationships between prognostic factors and between prognostic factors and outcome, and measurement limitations, it is inevitable that estimates of effect size derived from NRS will be confounded to some extent. Researchers, reviewers and users of evidence alike need to be aware of the consequences of residual confounding. In poor quality RCTs, selection bias tends to favour the new treatment being evaluated. Selection bias need not necessarily lead to systematic bias in favour of one treatment but, even if it acts in an unpredictable way, it will still give rise to additional, nonstatistical uncertainty bias around the estimate of effect size. Systematic reviews of NRS studies run the risk of compounding these biases. Nutritional choices and uptake of health education about nutrition are very likely to be associated with potential confounding factors. Therefore, pooled estimates of the effects of nutritional exposures and their confidence intervals are likely to be misleading; reviewers need to take into account both systematic and uncertainty bias.

The development of a minimal intervention strategy to address overweight and obesity in adult primary care patients in The Netherlands.

BACKGROUND Currently, overweight and obesity do not receive the attention they deserve from the Dutch GPs, mostly because of a lack of an effective intervention strategy to tackle this difficult health problem. OBJECTIVE To develop a minimal intervention strategy (MIS) addressing overweight and obesity among adult primary care patients, resulting in a prototype. METHODS Following the intervention mapping protocol, the MIS is based on literature study, existing interventions, psychosocial theories, stakeholder interviews and a questionnaire study among stakeholders. This led to the development of a prototype of the MIS materials: a screening flow chart and a treatment flow chart, a manual and patient education materials. A pre-test among 42 general practitioners and practice nurses was conducted to investigate the usefulness of the MIS materials at first sight. RESULTS The stakeholder interviews and the questionnaire study resulted in insight on what the MIS should look like. For instance, the stakeholders indicated that the treatment needs to focus on helping patients to eat more healthy and exercise more, using techniques like motivational interviewing. The pre-test showed that most participants were enthusiastic about the materials, although they made some suggestions on improvements. CONCLUSION The MIS materials seem to be useful and promising. A future pilot test is needed to investigate its usefulness in daily practice and to further improve the materials in preparation for a process and effect evaluation.

Primary care and public health a natural alliance? The introduction of the guidelines for obesity and undernutrition of the Dutch College of General Practitioners

The prevalence of obesity and overweight is increasing globally and forms a huge public health problem. On the other hand, the prevalence of malnutrition or undernutrition is substantial, especially in nursing homes or in the elderly at home. Primary care and public health are separate disciplines. But in the field of nutrition and other lifestyle-related interventions, there are many direct and indirect interfaces for over- as well as undernutrition. The Dutch College of General Practitioners (NHG) published the Practice Guideline Obesity in adults and children to lead GPs in this process and to bridge the gap with public health. The same applies for the recently published National Primary Care Cooperation Agreement Undernutrition on the collaboration of primary care workers to enhance awareness and early intervention in case of nutritional impairment. This article goes into the background as well as the content of these two NHG products and the implications for daily practice. An attempt is made to connect primary care and public health in this matter. Particularly in the case of obesity, a close relationship with public health is of vital importance.

Nutritional deficiency in general practice: a systematic review

Objective:Nutritional deficiency is an independent risk factor for mortality. Despite its clinical relevance, the prevalence in a primary care setting is poorly documented. We performed a systematic review of reported prevalence and clinical assessment of nutritional deficiency in general practice.Methods:From MEDLINE, Current Contents and EMBASE, we derived articles and checked the initially included ones for references on prevalence data. Of the eligible articles, we assessed the quality of research and results.Results:We finally included eight studies. The prevalence ranged from 0 to 13%. However, the study populations were heterogeneous and all studies contained methodological flaws, especially selection bias. In addition, the clinical assessment differed between studies.Conclusion:Literature on the prevalence of nutritional deficiency within general practice is rare and provides disputable prevalence assessments.Sponsorship:The Dutch Dairy Association, Zoetermeer.Objective:Nutritional deficiency is an independent risk factor for mortality. Despite its clinical relevance, the prevalence in a primary care setting is poorly documented. We performed a systematic review of reported prevalence and clinical assessment of nutritional deficiency in general practice.Methods:From MEDLINE, Current Contents and EMBASE, we derived articles and checked the initially included ones for references on prevalence data. Of the eligible articles, we assessed the quality of research and results.Results:We finally included eight studies. The prevalence ranged from 0 to 13%. However, the study populations were heterogeneous and all studies contained methodological flaws, especially selection bias. In addition, the clinical assessment differed between studies.Conclusion:Literature on the prevalence of nutritional deficiency within general practice is rare and provides disputable prevalence assessments.Sponsorship:The Dutch Dairy Association, Zoetermeer.

The Cochrane Library: more systematic reviews on nutrition needed.

The knowledge and relevance of nutrition as well as the demand for well-funded advices increase. The Cochrane Collaboration plays a leading role within the evidence-based medicine and practice. We advocate therefore more specialized nutritional interest within the Cochrane Collaboration. In case ‘Nutrition’ needs more attention within the Cochrane Library, one of the first priorities is deciding about whether to include non-randomized studies into the Specialized Register and generating lists of journals to handsearch for such a Specialized Register. Preparatory to these activities an inventory of Nutritional content within the Cochrane Library is needed. We estimate that reviews directly related to nutrition and those of borderline interest to nutrition represent less than 4% of all published reviews in The Cochrane Library.

ICPC-code approach of nutritional questions in general practice: a look at the future.

The Dutch College of General Practitioners is developing a computerised consult supporting system on nutrition that is integrated in the widely used GP Information System. Connected to every ICPC-code (International Code of Primary Care) for diagnosis relevant nutritional information is available. Short items—simple sentences with respect to the content—provide the main nutritional information, needed to inform the patient within the limited consultation time. Background information is the second level and is reachable by clicking on the coloured items in the first part. After all the patients’ practical advice is the last part of this so-called: ‘P-module of nutrition’.

Limited evidence for effects of diet for type 2 diabetes from systematic reviews.

Objective:Systematic reviews are an appraised method to summarize research in a concise and transparent way, and may enable to draw conclusions beyond the sum of results of individual studies. We assessed the results, quality and external validity of systematic reviews on diet in patients with type 2 diabetes.Design, setting, subjects:We systematically searched for systematic reviews on nutritional interventions in patients with type 2 diabetes that used a reproducible search strategy in at least one major database that applied some form of quality assessment. We assessed quality and the external validity of the retrieved systematic reviews. Outcomes were defined as statistical meta-analyses or narrative results using a predefined and reproducible method.Results:Six systematic reviews met the inclusion criteria, investigating dietary interventions in general (n=3), chromium supplementation (n=1), fish-oil (n=1) or herbs and nutrition supplements (n=1). Quality assessment showed minimal/minor flaws in four cases and major/extensive flaws in two cases. All reviews had insufficient data needed to judge external validity. In reviews with minimal/minor flaws, we found beneficial effects of very-low-calorie diets and fish-oil supplements. However, the external validity of these results could not be assessed sufficiently.Conclusions:Systematic reviews largely failed to produce knowledge beyond the sum of the original studies. Furthermore, judgment of external validity was hampered in most cases owing to missing data. To improve the quality and usefulness of systematic reviews of dietary interventions, we recommend the application of more focused research questions, but with broader inclusion criteria, for example, the use of observational studies.Sponsorship:Internal funding Radboud University Nijmegen Medical Centre.

How can a proposed Cochrane diet and nutrition field work effectively

The Cochrane Database currently provides relatively little evidence-based guidance about nutrition relevant to general practitioners. This situation could be improved by the establishment of a new Cochrane Field to identify relevant studies, prioritize topics to include nutrition, work with Cochrane methodologists on the inclusion of observational studies, and disseminate results of Cochrane reviews to general practitioners and their patients.A Diet and Nutrition Field could be established as a separate entity or as a Subgroup of the existing Primary Health Care (PHC) Field. The Field would be appropriate if the intent is to immediately cover nutritional interventions of all sorts, in all settings. However, if the focus is nutritional evidence for use by primary care clinicians, organization as a subField would provide a simpler registration process, allow Cochrane activities to begin sooner, and would allow members to focus on primary-care-relevant nutritional issues, conserving their resources and energy. A mechanism exists for conversion to a freestanding Field if the scope later expands.Of the core Field functions, identification and assembly of relevant trials into a specialized register would be among the most important. Special registers are generated by focused literature searches augmented by hand-searching of key journals. Given the importance of studies with observational designs, a nutrition field register will require some additional work on search strategies and inclusion criteria.Other key functions would include ensuring effective communication both with members of other Cochrane entities and with the scientific and clinical community with interests in diet and nutrition.

Nutritional deficiency in Dutch primary care: data from general practice research and registration networks.

Objective:To explore incidence and prevalence rates of nutritional deficiency in adults in general practice.Methods:Six Dutch general practice research and registration networks supplied incidence and prevalence rates of nutritional deficiency by the International Classification of Primary Care (ICPC) or ‘E-list’ labels (‘loss of appetite, feeding problem adult, iron, pernicious/folate deficiency anaemia, vitamin deficiencies and other nutritional disorders, weight loss’). In case of disease-related nutritional deficiency, we asked whether this was labelled separately (‘co-registered’) or included in the registration of the underlying disease.Results:‘Iron deficiency anaemia’ had highest incidence (0.3–8.5/1000 person years), and prevalence rates (2.8–8.9/1000 person years). Nutritional deficiency was mostly documented in the elderly. In two networks ‘co-registration’ was additional, two only documented the underlying disease and two did not specify ‘co-registration’. No clear difference was found between networks considering the difference in ‘co-registration’.Conclusion:Nutritional deficiency is little documented in general practice, and generally is not registered separately from the underlying disease.

Van verzadigd naar onverzadigd vet

SamenvattingHornstra G, Grooten HNA, Van Binsbergen JJ. Van verzadigd naar onverzadigd vet. Huisarts Wet 2012;55(2):64–7.Wat is de rol van voeding bij de selectieve en zorggerelateerde preventie van hart- en vaatziekten en diabetes mellitus type 2? Welke rol spelen de verschillende vetten daarbij? Het advies van de Gezondheidsraad luidt vooral om minder verzadigde vetten te eten. Uit de wetenschappelijke literatuur blijkt echter dat extra gezondheidswinst mogelijk is als men verzadigde vetten in de voeding vervangt door onverzadigde vetten. In dit artikel gaan we dieper in op de wetenschappelijke achtergronden van deze opvatting. Bij een normaal lichaamsgewicht is de vetkwaliteit van de voeding belangrijker dan de vetkwantiteit.AbstractHornstra G, Grooten HNA, Van Binsbergen JJ. From saturated to unsaturated fat. Huisarts Wet 2012;55(2):64–7.What is the role of diet in the prevention of cardiovascular diseases and diabetes mellitus type 2? And what is the role of the different types of fat? The Health Council of the Netherlands advises eating less saturated fat, but the scientific literature suggests that an additional health benefit can be achieved if people replace saturated fat in their diet with unsaturated fat. In this article, we go into the scientific basis for this. In normal-weight individuals, it is the quality rather than the quantity of dietary fat that is important.