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Levetiracetam: a new therapeutic option for refractory epilepsy.

Levetiracetam (LEV) is the most recently licensed antiepileptic drug (AED) for adjunctive therapy of partial seizures. Its mechanism of action is uncertain but it exhibits a unique profile of anticonvulsant activity in models of chronic epilepsy. Three randomised, double-blind, placebo-controlled trials enrolling 904 patients with refractory partial epilepsy have demonstrated the efficacy of LEV as adjunctive therapy, with a responder rate (> or = 50% reduction in seizure frequency) of 28-41%. Long-term efficacy studies suggest retention rates of 60% after one year, with 13% of patients seizure-free for six months of the study and 8% seizure-free for one year. Adverse effects of LEV, including somnolence, lethargy and dizziness, were generally mild and the frequency of incidents was not significantly different between the active treatment and placebo groups in clinical trials. LEV has no clinically significant pharmacokinetic interactions (PKI) with other AEDs, or with commonly prescribed medications. Preliminary data suggest that LEV has efficacy in primary generalised epilepsy and further randomised trials are under way. The combination of potent antiepileptic properties with a relatively mild adverse effect profile makes LEV an attractive adjunctive therapy for partial seizures.

Animals↗

Effect of prize draw incentive on the response rate to a postal survey of obstetricians and gynaecologists: a randomised controlled trial. [ISRCTN32823119].

BACKGROUND: Response rates to postal questionnaires are falling and this threatens the external validity of survey findings. We wanted to establish whether the incentive of being entered into a prize draw to win a personal digital assistant (PDA) would increase the response rate for a national survey of consultant obstetricians and gynaecologists. METHODS: A randomised controlled trial was conducted. This involved sending a postal questionnaire to all Consultant Obstetricians and Gynaecologists in the United Kingdom. Recipients were randomised to receiving a questionnaire offering a prize draw incentive (on response) or no such incentive. RESULTS: The response rate for recipients offered the prize incentive was 64% (461/716) and 62% (429/694) in the no incentive group (relative rate of response 1.04, 95% CI 0.96 - 1.13) CONCLUSION: The offer of a prize draw incentive to win a PDA did not significantly increase response rates to a national questionnaire survey of consultant obstetricians and gynaecologists.

Computers, Handheld↗

In-hospital care pathways for stroke.

BACKGROUND: Stroke care pathways have the potential to promote organised and efficient patient care that is based on best evidence and guidelines, but evidence to support their use is unclear. OBJECTIVES: We aimed to assess the effects of care pathways, compared with standard medical care, among patients with acute stroke who had been admitted to hospital. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register (last searched in June 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2003), MEDLINE (1975 to June 2003), EMBASE (1980 to June 2003), CINAHL (1982 to June 2003), ISI Proceedings: Science & Technology (1990 to November 2003), and HealthSTAR (1994 to May 2001). We also handsearched the Journal of Integrated Care Pathways (2001 to 2003), formerly Journal of Managed Care (1997 to 1998) and Journal of Integrated Care (1998 to 2001). Reference lists of articles were searched. SELECTION CRITERIA: We considered randomised controlled trials and non-randomised studies that compared care pathway care with standard medical care. DATA COLLECTION AND ANALYSIS: One reviewer selected studies for inclusion and the other independently checked the decisions. Two reviewers independently assessed the methodological quality of the studies. One reviewer extracted the data and the other checked the extracted data. MAIN RESULTS: Three randomised controlled trials (340 patients) and 12 non-randomised studies (4081 patients) were included. There was significant statistical heterogeneity in the analysis of many of the outcomes. We found no significant difference between care pathway and control groups in terms of death or discharge destination. Patients managed with a care pathway were: (a) more dependent at discharge (P = 0.04); (b) less likely to suffer a urinary tract infection (Odds Ratio (OR) 0.51, 95% Confidence Interval (CI) 0.34 to 0.79); (c) less likely to be readmitted (OR 0.11, 95% CI 0.03 to 0.39); and (d) more likely to have neuroimaging (OR 2.42, 95% CI 1.12 to 5.25). Evidence from randomised trials suggested that patient satisfaction and quality of life were significantly lower in the care pathway group (P = 0.02 and P < 0.005 respectively). REVIEWERS' CONCLUSIONS: Use of stroke care pathways may be associated with positive and negative effects. Since most of the results have been derived from non-randomised studies, they are likely to be influenced by potential biases and confounding factors. There is currently insufficient supporting evidence to justify the routine implementation of care pathways for acute stroke management or stroke rehabilitation.

Critical Pathways↗

Self-management education for chronic obstructive pulmonary disease.

BACKGROUND: In asthma, self-management programmes have been proven to be effective. In COPD, their value is not clear. OBJECTIVES: To assess the efficacy of COPD self-management/ education programmes on health outcomes and use of health services SEARCH STRATEGY: We searched the Cochrane Airways Group trial registers, MEDLINE (January 1985 to October 2001), reference lists, and abstracts of medical conferences. We also contacted research groups in the field for ongoing trials and unpublished material. SELECTION CRITERIA: Controlled trials (randomised and non-randomised) of self-management education in patients with COPD. Studies focusing mainly on physical pulmonary rehabilitation were excluded. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data. Investigators were contacted for additional information. MAIN RESULTS: The reviewers included 12 articles describing 8 randomised-controlled trials and 1 controlled clinical trial. Self-management education was compared with usual care in 8 studies. The studies in this review assessed a broad-spectrum of outcome measures with different follow-up times. Synthesis of the results using meta-analysis was always not possible. The studies showed no effect of self-management education on hospital admissions, emergency room visits, days lost from work and lung function. Inconclusive results were observed on health-related quality of life (HRQoL): studies using the disease specific SGRQ showed a better quality of life in the patients in the intervention group, but only in the activity component where there was heterogeneity between the results of the two included studies. A potential reason for the absence of convincing effects on HRQoL is the limited use of COPD-specific instruments. Inconclusive results were observed on COPD-symptoms and use of other health care resources such as doctor and nurse visits. Self-management education reduced the need for rescue medication, and led to an increased use of courses of oral steroids and antibiotics for respiratory symptoms. REVIEWER'S CONCLUSIONS: The data available for this review are insufficient for forming recommendations. Further research on the effectiveness of self-management programmes should be focussed on behavioural change evaluated in well designed randomised controlled trials with standardised outcomes designed for use in COPD patients, and with long follow-up time so that definite conclusions can be made.

Humans↗

Paracetamol versus nonsteroidal anti-inflammatory drugs for rheumatoid arthritis.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) are usually preferred for simple analgesics such as paracetamol for rheumatoid arthritis. It is not clear, however, whether the trade-offs between benefits and harms of NSAIDs are preferable to those of paracetamol (paracetamol is also called acetaminophen). OBJECTIVES: To compare the benefits and harms of paracetamol with NSAIDs in patients with rheumatoid arthritis. SEARCH STRATEGY: Medline Silverplatter, Embase databases were searched up until Sept 2002. Reference lists of identified articles were also searched. SELECTION CRITERIA: Randomised double-blind studies comparing paracetamol with an NSAID. DATA COLLECTION AND ANALYSIS: Decisions on inclusion of trials and data extraction were performed by the two authors independently. MAIN RESULTS: Four cross-over studies, published between 1968 and 1982, involving 121 patients, and four different NSAIDs were included. The generation of the allocation sequence and the use of methods to conceal the allocation were not described in any of the studies. The studies were double-blind but it was not clear whether the blinding was effective. Methods for collecting adverse effects were not described. The NSAIDs were preferred more often than paracetamol by the patients or the investigator. In the largest trial, 20 out of 54 patients (37%) preferred ibuprofen and 7 out of 54 (13%) paracetamol. Investigators preference (as established by joint tenderness, grip strength and joint circumference) was 17 out of 35 for diclofenac versus 5 out of 35 for paracetamol in another trial. However, because of the weaknessess in the trials, no firm conclusion can be drawn. REVIEWER'S CONCLUSIONS: When considering the trade off between the benefits and harms of non-steroidal anti-inflammatory drugs and paracetamol/acetaminophen, it is not known whether one is better than the other for rheumatoid arthritis. But people with rheumatoid arthritis and the researchers in the study did prefer non-steroidal anti-inflammatory drugs more than acetaminophen/paracetamol. There is a need for a large trial, with appropriate randomisation, double-blinding, test of the success of the blinding, and with explicit methods to measure and analyse pain and adverse effects.

Acetaminophen↗

Continuous positive airway pressure delivery interfaces for obstructive sleep apnoea.

BACKGROUND: Continuous positive airway pressure (CPAP) is the mainstay of therapy for moderate to severe obstructive sleep apnoea (OSA). However, compliance with CPAP has been less than ideal. There are many different CPAP interfaces now available for the treatment of OSA. The type of CPAP delivery interface is likely to influence a patient's acceptance of CPAP therapy and long term compliance. OBJECTIVES: This review aims to compare the efficacy of the various CPAP delivery interfaces available for the treatment of obstructive sleep apnoea. SEARCH STRATEGY: Searches were carried out on the Cochrane Airways Group Specialised Register, CENTRAL, MEDLINE, EMBASE & CINAHL up to January 2006. SELECTION CRITERIA: All randomised, controlled trials comparing different forms of CPAP delivery interface for the treatment of OSA were considered for inclusion. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed studies for inclusion into the review and extracted data. Attempts were made to contact study authors to obtain additional, unpublished data. MAIN RESULTS: A total of four studies fulfilled the inclusion criteria. Two studies compared nasal mask with the Oracle oral mask and showed no significant difference in compliance at one month (mean difference [95%CI]: 0.17 hours per night [-0.54 to 0.87]). There were also no significant differences in any of the physiological parameters (e.g. AHI, arousal index, minimum oxygen saturation), Epworth Sleepiness Scale (ESS), or symptoms of OSA. A single study comparing nasal mask with nasal pillows showed a significant difference in compliance when expressed as the percentage of days used in favour of nasal pillows (nasal pillows mean+/-SD 94.1+/-8.3%; nasal mask 85.7+/-23.5%, P=0.02), however there were no significant differences in the mean daily use for all days or when use was greater than 0 minutes per day. Nasal pillows were also associated with fewer overall adverse effects (P<0.001) and greater interface satisfaction (P=0.001). No significant differences in AHI, ESS or quality of life scores were seen. One study comparing nasal mask with face mask showed that compliance was significantly greater with use of a nasal mask (mean difference 1.0 hour per night [95%CI 0.3-1.8]). Nasal mask was also associated with significantly lower ESS scores and was the preferred interface in almost all patients. AUTHORS' CONCLUSIONS: Due to the limited number of studies available comparing various interface types, the optimum form of CPAP delivery interface remains unclear. The results of our review suggest that nasal pillows or the Oracle oral mask may be useful alternatives when a patient is unable to tolerate conventional nasal masks. The face mask can not be recommended as a first line interface, but may be considered if nasal obstruction or dryness limits the use of a nasal mask. Further randomised studies comparing the different forms of CPAP delivery interface now available for the treatment of OSA, in larger groups of patients and for longer durations, are required.

Continuous Positive Airway Pressure↗

Treatment of hepatocellular carcinoma by means of radiopharmaceuticals.

Several techniques have been developed for radionuclide therapy of hepatocellular carcinoma (HCC). Medical literature databases (Pubmed, Medline) were screened for available literature and articles were critically analysed as to their scientific relevance. In a palliative setting, intra-arterial administration of 131I-Lipiodol yields responses in 17-92% of patients. According to a randomised study, 131I-Lipiodol was far better tolerated than classic chemo-embolisation. The additive value of a single 131I-Lipiodol administration following partial liver resection for HCC was evaluated and evidence is available that adjuvant radionuclide treatment reduces the recurrence rate. Data concerning the role of 131I-Lipiodol in bridging patient to liver transplantation are scarce but suggest a potential benefit in terms of reducing the drop-out rate while patients are listed for transplantation. 188Re- and 90Y-labelled conjugates are emerging and initial clinical data are promising. Treatment of HCC with 90Y-labelled microspheres is likely as efficacious as treatment with radiolabelled Lipiodol but pretreatment 99mTc-MAA scintigraphy is required in order to exclude patients with significant lung shunting. Several antibodies targeting antigens expressed on HCC have been radiolabelled, almost exclusively with 131I, and evaluated in a preclinical or clinical setting. The use of radiolabelled Lipiodol and microspheres allows for selective targeting of HCC with limited toxicity. Prospective, randomised controlled trials demonstrating that both treatment modalities may provide a survival benefit in a palliative setting are mandatory. In addition, future research should focus on the complementary role of radionuclide treatment in patients at risk for recurrent disease following partial liver resection or while awaiting liver transplantation.

Animals↗

Data required for the evaluation of newborn screening programmes.

Tandem mass spectrometry offers the chance to improve newborn screening (NBS) for phenylketonuria and to expand screening programmes at minimal additional costs. So far, however, there are only limited data available on the incidence of a broader range of disorders presently being considered, their natural course, the benefits achievable and potential harm associated with screening. Based on a literature search and experience from the Bavarian extended screening trial, these questions are addressed using medium-chain acyl-CoA dehydrogenase deficiency (MCADD) as an example. The data retrieved are sufficient for estimation of the incidence of MCADD cases identifiable by NBS and for diagnosis following clinical symptoms. Clinically detected cases ascertained by active surveillance in populations with highly developed and freely accessible health care systems consistently amount to only 33% of those identified by NBS. This difference cannot be explained by the difference in the proportion of the homozygous 985A-->G mutation, which accounts for about 50% of cases identified in NBS. Further research is needed to assess the contribution of MCADD to unexplained deaths in infancy. Retrospective cohort studies enrolling at least 500,000 children would allow for a more precise estimate of the natural course of disease in particular with regard to less severe adverse outcomes. The most relevant gap in knowledge concerns the long-term outcome of children identified following symptoms and by newborn screening. Since randomised controlled trials are unlikely to be feasible on this issue, a standardised documentation protocol should be implemented in follow-up studies for cases identified either by high risk screening or newborn screening. A proposal for the content of such observational studies is made.

Acyl-CoA Dehydrogenase↗

Health technology assessment in its local contexts: studies of telehealthcare.

Health technology assessment (HTA) is one of the major research enterprises of late modernity, reaching into fields of previously autonomous professional practice, and critically interrogating the organisation and delivery of health care. The 'evaluation' of new health technologies within the field of HTA is increasingly a normative political expectation, as discourses of 'evidence-based' practice run through health policy in the UK and elsewhere. Despite its importance in governing the direction of innovation in health care delivery, there are hardly any empirical studies of HTA in practice. In this paper, we draw on two ethnographic studies of telehealthcare implementation and evaluation in the UK to explore the practical conduct of HTA, and we focus specifically on the social organisation and conduct of randomised controlled trials of these new technologies. The paper examines how evaluation forms a mediating set of practices that make the embedding or normalisation of a new technology possible; and present a simple model of the social and technical contingencies within the evaluation process.

Anthropology, Cultural↗

Changes in local clinical practice following an experiment in medical care: evaluation of evaluation.

The changes in clinical practice following a randomised controlled trial of early discharge for inguinal hernia and varicose veins are reviewed. A significant reduction in mean length of stay was recorded in the study area between 1970 (the year before the start of the study) and 1975 (two complete years after the study). This change was not found in two adjacent health districts.

Adolescent↗

Current and future options for the treatment of chemotherapy-induced anaemia.

Chemotherapy-induced anaemia (CIA) is a significant source of morbidity in patients receiving treatment for cancer. There are three products currently available for the treatment of CIA: epoetin alfa, epoetin beta and darbepoetin alfa. Several organisations have published recommendations for the use of these agents. Several randomised, controlled trials have been conducted comparing the most popular dosing regimens of epoetin alfa and darbepoetin alfa, with conflicting results. Information regarding survival and adverse event data related to these agents continues to create debate. This review considers four new agents that are under development for the treatment of CIA.

Anemia↗

[Interactions between radiation and hormonal therapy in breast cancer: simultaneous or sequential treatment].

BACKGROUND: Combining radiation and hormone therapy (administration of selective estrogen receptor modulators) has become common clinical practice in recent years for receptor positive breast cancer. Little is known about a possible interaction of both treatment modalities if they are given simultaneously. Tamoxifen (antiestrogen molecule, triphenylethylene derivative) may theoretically render cancer cells less responsive to radiotherapy arresting hormone-receptor-positive cells in G0/G1 phase and increase the risk of breast and lung fibrosis stimulating the secretion of transforming growth factor beta in human fibroblasts. PURPOSE: This article reviews the published data to assess the impact of sequencing of hormonal and radiation therapy on outcomes in breast cancer. METHODS: Computerised searches for publications debating the sequencing of hormonal therapy relative to radiation therapy were done using MEDLINE data. RESULTS: Results of tamoxifen experiments with cell culture regarding radioprotection of tumour clonogens are conflicting. In contrast to in vitro results, in animal studies no protective effect of tamoxifen was observed. In one in vitro study, letrozole (non-steroid selective aromatase inhibitor) had a radiosensitizing effect on breast-cancer lines. No randomised clinical trials to date have studied sequencing of tamoxifen or other selective estrogen receptor modulators and radiotherapy. Results from retrospective clinical studies which included treatment arms with and without tamoxifen showed reduction in tumour recurrence with tamoxifen. Some of these studies have noted increased risk of lung and breast fibrosis with tamoxifen with radiotherapy. Results of three articles examined the effect of tamoxifen sequence showed no adverse effect on local control or survival in sequential versus concurrent tamoxifen and radiation patients. One of the three studies also assessed the risk of complications with respect to the timing of tamoxifen with radiotherapy. There was no difference in the rates of complications between the two groups. The association of radiation and selective aromatase inhibitors or aromatase inactivators has not been addressed in clinical studies. CONCLUSIONS: Combined application of tamoxifen and radiotherapy improves survival and local control in breast cancer. Available clinical studies do not indicate that the simultaneous application of tamoxifen and radiotherapy is disadvantageous, as was suggested by some of the in vitro studies. The risk of subcutaneous breast and lung fibrosis might be slightly increased if tamoxifen is given simultaneously with radiotherapy. Both treatment modalities should be started early after surgery. There is no sufficient evidence to withhold tamoxifen administration during irradiation of breast cancer. The issue of optimal sequencing of hormonal and radiotherapy should be addressed in randomised clinical trials.

Animals↗

[Hormonal supplements for postmenopausal women: no evidence of protection against cardiovascular disease].

Atherothrombotic cardiovascular disease is a leading cause of death in women, especially in the postmenopause. It is controversial whether postmenopausal hormone replacement therapy is protective with regard to cardiovascular disease. On the one hand, observational studies consistently show that the risk of cardiovascular disease is 35 to 50% lower among users of hormonal replacement than among non-users. In addition, hormonal replacement is associated with an improvement of the lipid profile and several other potentially beneficial effects. On the other hand, two recent placebo-controlled randomised trials did not find evidence in favour of cardiovascular protection by hormonal replacement. This discrepancy may be explained by insufficient adjustment for lifestyle factors in observational studies and insufficient consideration of methodological flaws in experimental studies, both of which lead to an overestimation of the protective effect of hormonal replacement. Hormonal replacement may affect the pathophysiology of atherothrombosis in several ways, both positive and negative. Progress in this field requires the isolation of the positive effects.

Aged↗

Field efficacy of a 10 per cent pyriproxyfen spot-on for the prevention of flea infestations on cats.

The clinical application of a new method for using the insect growth regulator, pyriproxyfen, for controlling flea populations in cat-owning homes is evaluated for the first time. In a multicentric, controlled and randomised trial, 107 flea-infested cats were treated with a minimum dose of 10 mg/kg bodyweight pyriproxyfen as a 10 per cent spot-on application on two occasions, with a three-month interval between doses. For comparison, 99 cats received lufenuron suspension orally, once a month, for six months. Flea counts decreased significantly over time in each group and were significantly lower in the pyriproxyfen group than in cats treated with the reference product. The percentage of 'zero-flea' cats increased from 49 per cent on day 30 to 88 per cent on day 180 in the pyriproxyfen group and from 30 to 71 per cent in the lufenuron group at the same time points (P<0.05). Appropriately timed topical applications of pyriproxyfen, therefore, offer a method of flea control in the domestic environment.

Administration, Cutaneous↗

[Chemoradiotherapy and anal canal cancer].

Local control and sphincter preservation are the two challenges of anal canal cancer treatment. These tumors are radio- and chemo-sensitive and treatment moved from surgical approach, with abdominoperineal resection, to definitive radiation therapy with or without concurrent chemotherapy. Randomised trials proved the benefit of combined modality with chemoradiotherapy and of mitomycine C (MMC) compared with radiotherapy alone, with a toxic death rate of about 2%. Indications of chemoradiotherapy are locally advanced tumor T2 > or = 4 cm, T3-4 or N1-3 but the best modalities of combined treatment are still under debate. Standard chemotherapy is 5 flurouracile (5FU) + MMC, but cisplatinum (CDDP) is an effective and well tolerated substitute for MMC. Favourable results with CDDP-containing regimen in term of toxicity and carcinologic control have been reported in phase II and retrospective studies. Total radiation dose, overall duration of radiation therapy, duration of the gap and indications of additional boost are not clear, but it is demonstrated that overall duration of treatment should be as short as possible to improve the therapeutic radio. Phase II and III studies are ongoing, to evaluate the best chemotherapy regimen between 5FU+MMC and 5FU+CDDP, the benefit of neoadjuvant or maintenance chemotherapy and the interest of increased total dose. Next future could be the utilisation of oral 5FU. This article is a review of past randomised trials, phases II and retrospective study on radiochemotherapy of anal canal carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗

New strategies in anaemia management: ACORD (Anaemia CORrection in Diabetes) trial.

Anaemia is a key component of diabetic nephropathy, but its importance has only recently been recognised. Recombinant human erythropoietin (epoetin) is an established treatment for renal anaemia, and may help to reduce complications associated with diabetic nephropathy, such as cardiovascular disease. The limited experience with the use of epoetin in this patient group prompts the urgent need for clinical data on anaemia correction in early diabetic nephropathy, particularly with regard to benefits on cardiovascular risk reduction. The Anaemia CORrection in Diabetes (ACORD) study will investigate the effects of anaemia correction on cardiac structure and function in patients with early diabetic nephropathy. This 15-month multicentre study will recruit 160 adult patients with diabetes, mild or moderate chronic kidney disease (with creatinine clearance >or=30 ml/min at screening) and moderate anaemia (haemoglobin [Hb], 10.5-13.0 g/dl). Patients will be randomised to one of two groups: the early treatment group will receive subcutaneous epoetin beta (NeoRecormon) at study entry to maintain target Hb levels of 13-15 g/dl, while the control group will reflect current practice and will not receive epoetin therapy until Hb levels decline below 10.5 g/dl. The primary efficacy variable, change in left ventricular mass index, will be evaluated at 15 months following randomisation; secondary efficacy variables will include changes in cardiac structure and function over the study period. The ACORD study should provide valuable information on the benefits of anaemia correction in patients with early diabetic nephropathy. The study will also increase awareness of the importance of treating anaemia associated with diabetes.

Anemia↗

[Calcaneal fractures--the most frequent tarsal fractures].

Operative treatment of intra-articular calcaneal fractures with anatomical reduction and early mobilisation has lead to a considerable improvement of the functional results of these severe injuries over the recent two decades. New tendencies like modified approaches tailored according to the vascular anatomy, arthroscopic control of joint reduction in conjunction with open or percutaneous procedures, early flap coverage for severe open fractures or closed fractures with full thickness skin necrosis, the use of interlocking plates that further minimises the need of bone grafting and subtalar arthrolysis at the time of hardware removal for fibrous overgrowth have the potential for further improvement of the outcome. The observation from several comparative studies that operative treatment leads to superior results in displaced intra-articular calcaneal fractures has been qualified in a recent prospective, randomised multicentre trial. This paper presents and the authors' experience with the demanding operative treatment of these fractures together with new developments aiming at improving the clinical results.

Arthroscopy↗

Evidence-based medicine: how good is the evidence?

The "evidence" in EBM must be of high quality in order to be useful, but this is not always the case. Even the "gold standard" of evidence-based medicine, the randomised clinical trial, is bedevilled by low inclusion rates and potentially important recruitment biases. "Real world" trials often do not give the same results as these highly artificial controlled clinical studies. Meta-analysis, the next most important level of evidence in EBM, may be unreliable, sometimes giving different results to subsequent large randomised trials. There is a bias in the hypotheses tested in large clinical trials, as the costs involved are usually covered by commercially interested companies. For this reason, trials of non-patentable compounds or therapies of no commercial interest may not be performed. The process of journal review and publication is capricious, slow and may have a selection bias towards positive studies, meaning that communication channels for the "evidence" are often unsatisfactory. For many rarer conditions and situations, there is simply no "high level" evidence, such as in paediatrics and subspecialty surgery.

Bias↗