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PubMed1996

The importance of quality of primary studies in producing unbiased systematic reviews.

BACKGROUND: Traditional and largely qualitative reviews of evidence are now giving way to much more structured systematic overviews that use a quantitative method to calculate the overall effect of treatment. The latter approach is dependent on the quality of primary studies, which may introduce bias if they are of poor methodologic quality. OBJECTIVE: To test the hypothesis that the inclusion of poor-quality trials in meta-analyses would bias the conclusions and produce incorrect estimates of treatment effect. METHODS: An overview of randomized trials of antiestrogen therapy in subfertile men with oligospermia was performed to test the hypothesis. Data sources included online searching of MEDLINE and Science Citation Index databases between 1966 and 1994, scanning the bibliography of known primary studies and review articles, and contacting experts in the field. After independent, blind assessment, nine of 149 originally identified studies met the inclusion criteria and were selected. We assessed study quality independently. Outcome data from each study were pooled and statistically summarized. RESULTS: There was a marginal improvement in pregnancy rate with antiestrogen treatment (odds ratio, 1.6; 95% confidence interval, 0.9 to 2.6). Sensitivity analyses on the basis of methodologic quality demonstrated that poor-quality studies produced a positive effect with treatment, whereas no benefit was observed with high-quality studies. CONCLUSION: The results of a meta-analysis are influenced by the quality of the primary studies included. Methodologically, poor studies tend to exaggerate the overall estimate of treatment effect and may lead to incorrect inferences.

Bias↗

PubMed1996

Meta-analysis, clinical trials, and transferability of research results into practice. The case of cholesterol-lowering interventions in the secondary prevention of coronary heart disease.

OBJECTIVE: To evaluate, in the comprehensive scenario of "evidence-based" medicine, the transferability of the results of published randomized clinical trials and meta-analyses on cholesterol-lowering interventions to clinical practice. METHOD: Overview of randomized clinical trials on cholesterol-lowering interventions in the secondary prevention of coronary heart disease. RESULTS: The present overview on secondary prevention of coronary heart disease included 34 trials with cholesterol-lowering interventions in 24968 individuals. There was a 12.5% mortality in the group that was allocated active intervention and a 17.2% mortality in the control group (risk reduction, 13%; 95% confidence interval, -19% to -6%). Coronary and cardiovascular odds of deaths were significantly reduced. No clear association was found between noncoronary mortality and cholesterol-lowering interventions. Baseline total cholesterol levels had no clear influence on total mortality. Intermediate (10%-20%) and high ( > 20%) total cholesterol reductions were associated with similar reductions in the odds of death (-23% and -30%, respectively). No conclusion could be reached for patients who were less represented in the studies (ie, women and elderly persons). Patients with more complicated baseline clinical conditions (eg, congestive heart failure) had little nonsignificant benefit from cholesterol-lowering interventions. CONCLUSIONS: The effect of cholesterol-lowering interventions at least in the secondary prevention of coronary heart disease can be considered as established, but the transferability of such results to real-life patients remains the critical, unanswered question.

Anticholesteremic Agents↗

PubMed1996

Lung cancer.

In small cell lung cancer, combination chemotherapy including platinum compounds (cisplatin and carboplatin) and the podophyllotoxins (teniposide and etoposide) continues to be the backbone of therapy. Complete plus partial responses to combination chemotherapy occur in 80-90% of all patients. Median survival is at present 11-17 months depending on the initial tumour stage. Overall 5-year survival is approximately 5%. The duration of treatment has been shortened to 5-6 months. The results of the use of hematopoietic growth factors have hitherto been disappointing with respect to survival, while a definite effect on the degree and number of infections has been documented, when aggressive chemotherapy is administered. For epidermoid-, adenoid- and large cell carcinoma, results are emerging indicating that preoperative and preirradiatory chemotherapy in stage IIIa non-small cell lung cancer might have a substantial role in the overall management based on results from phase III trials. The studies are, however, rather modest in number and longer follow-up is necessary before recommendations for general use can be made. For patients with advanced non-small cell lung cancer (stage IIIb and IV), meta-analyses have yielded a small survival benefit (6 weeks) in favour of patients receiving chemotherapy vs. best supportive care. The treatment of this type of NSCLC should, however, still be considered to be experimental in order to define new innovative treatments. No improvement of the therapy of mesotheliomas has been reported.

Carcinoma, Non-Small-Cell Lung↗

PubMed1995

[How far should blood pressure be lowered in essential hypertension to optimize the results?].

Early studies of the seventies and eighties showed an inverse relationship between blood pressure reduction and incidence of complications and death. Afterwards, in the late eighties, some authors showed that reductions of diastolic blood pressure beyond 85 or 90 mm Hg increased coronary heart disease mortality (J shaped curve). Meta-analyses and recent epidemiological studies have shown that cardiovascular morbidity decreases along with reductions in diastolic blood pressure, if it is kept within normal limits (70-89 mm Hg). Cardiovascular mortality decreases significantly with blood pressure reductions of 7 to 8 mmHg. Some authors have suggested that diastolic blood pressure should be reduced to 85 mmHg or less in individuals with several cardiovascular risk factors, to obtain a better risk reduction. This hypothesis waits for confirmation from follow-up studies.

Blood Pressure↗

PubMed1996

Efficacy of glucose-based oral rehydration therapy.

OBJECTIVE: This article reviews and synthesizes evidence in the published literature on the safety and efficacy of oral rehydration therapy (ORT) among young children with pediatric gastroenteritis in developed nations. METHODOLOGY: We searched the literature for randomized, controlled trials comparing the safety and efficacy of ORT with intravenous (IV) rehydration treatment and/or oral rehydration solutions (ORSs) of different sodium content. We combined the failure rates of each set of studies in statistical meta-analyses and conducted tests of homogeneity of treatment effect over all the studies and for subgroups of children defined by the trial type, the sodium content of the ORS, and the setting of care. We also conducted a multivariate logistic regression on the probability of failure to determine the relative importance of these factors, controlling for other characteristics of the trials. Other outcomes were also tabulated and discussed. These include the relative incidence of hypernatremia and hyponatremia induced by treatment; weight gain; the volume, frequency, and duration of diarrhea; for inpatient trials, the length of stay; and for outpatient trials, rates of hospitalization. RESULTS: The evidence suggests that among pediatric patients with gastroenteritis in developed countries, failure of ORT, defined as the need to rehydrate children intravenously, is infrequent. We found a combined overall ORT failure rate of 3.6%. We found no statistically significant difference in failure rates by trial type or the sodium content of the ORS. However, we did find some supporting evidence for a lower failure rate among children treated in outpatient settings. In addition, compared with patients rehydrated intravenously, pediatric patients treated with ORT were not found to be at higher risk of iatrogenic hypernatremia or hyponatremia. The evidence from the literature fails to show a consistent trend in favor of either high- or low-sodium solutions for rehydration of pediatric patients. CONCLUSIONS: There seems to be a great potential for improving the medical treatment of children with acute gastroenteritis by the greater use of ORT.

Adolescent↗

PubMed1996

Implications of the links between hypertension and myocardial infarction for choice of drug therapy in patients with hypertension.

Meta-analyses of major outcome trials have demonstrated that the benefits of antihypertensive treatment for reduction of the incidence of stroke are entirely consistent with the benefits predicted from epidemiologic data; however, there remains a shortfall in the expected reduction of the incidence of coronary heart disease. Several explanations have been proffered to account for this shortfall, including the potential deleterious metabolic effects of long-term antihypertensive treatment; this has led to the speculation that antihypertensive agents with beneficial ancillary properties might confer additional significant advantage. However, with the exception of the angiotensin-converting enzyme inhibitors, few of these agents have translated into clinical benefit for humans. In addition, sound reasons exist to justify a focus on maintaining and improving the "quality" of blood pressure control. Current evidence suggests that optimal benefit is likely to result from the use of pharmacologic strategies that lower blood pressure consistently over a 24-hour period while at the same time maintaining the "normal" circadian pattern of blood pressure. This result will only be achieved with drugs and drug regimens that genuinely offer long duration of action with the additional potential benefit of maintaining a significant blood pressure lowering effect beyond the end of the dosage interval. This factor is particularly important because many patients with hypertension demonstrate poor adherence to prescribed dosage regimens.

Antihypertensive Agents↗

PubMed1995

[Magnesium sulfate in acute myocardial infarction].

Magnesium sulphate has antiarrhythmic and antithrombotic properties, a coronary and systemic vasodilating action, a direct myocardial protective effect in experimental and clinical models of ischemia-reperfusion injury. Two meta-analyses have pooled the results of several small studies that had analyzed the effect of controlled hypermagnesiemia in acute myocardial infarction before the advent of thrombolytic and antithrombotic therapies. The results have shown a more than 50% mortality reduction, with a minimum estimated benefit of about 30%, and a reduction in ventricular arrhythmias of about 50%. In LIMIT-2, a double-blind trial of 2,316 patients where magnesium was administered as a 8 mMol bolus followed by a 24-hour infusion of 65 mMol, a 24% reduction in mortality was observed. However, these data have not been confirmed in the more than 58,000 patients of the ISIS-4 trial. In this study magnesium, at the same dose of the LIMIT trial, did not reduce 5-week mortality, neither in the general population (7.64% versus 7.24% in control patients, p = n.s.) nor in specific subgroups. The results of ISIS-4 have excluded the routine use of magnesium sulphate in acute myocardial infarction in the era of fibrinolysis and aspirin, beta-blockers and ACE-inhibitors. Nevertheless, magnesium administration could still be considered in certain clinical situations, such as 1) the presence of contraindications to fibrinolysis and aspirin, 2) the treatment of ventricular tachyarrhythmias unresponsive (or as an alternative) to lidocaine, 3) severe hypertension when beta-blockers are not indicated.

Adrenergic beta-Antagonists↗

PubMed1995

Integration of vinorelbine into chemotherapy strategies for non-small-cell lung cancer.

Meta-analyses of randomized clinical studies comparing combination chemotherapy versus "best supportive care" for advanced non-small-cell lung cancer have revealed a small, but statistically significant survival advantage for patients who receive chemotherapy. However, overall increases in lifespan have been short, and the great majority of patients die within 1 year of diagnosis. In the last few years, several new drugs with promising activity have been identified. Of these, vinorelbine has already been shown to increase survival rates in randomized clinical trials. In particular, one such trial showed the combination of vinorelbine and cisplatin to result in statistically superior survival rates, compared with "standard" therapy of cisplatin and vindesine, and with single-agent vinorelbine. A second study comparing vinorelbine to fluorouracil/leucovorin also demonstrated a survival benefit for patients treated with vinorelbine. Therefore, the combination of vinorelbine and cisplatin represents one new option for initial therapy of newly diagnosed stage IV non-small-cell lung cancer.

Antineoplastic Agents↗

PubMed1996

The importance of diet and physical activity in the treatment of conditions managed in general practice.

Evidence from meta-analyses, physiological data and individual studies suggests that diet and exercise are important in the aetiology and treatment of many of the conditions that are managed predominantly in primary care (hypercholesterolaemia, hypertension, diabetes, obesity and excess alcohol intake). However, much of the evidence comes from outside primary care, and it is doubtful whether those studies done in primary care used optimal intervention strategies. A priority for future research should be to demonstrate the feasibility, efficacy and efficiency of lifestyle interventions in a general practice setting.

Adult↗

PubMed1996

Adjuvant drug therapy for operable breast cancer.

Breast cancer-the most common malignancy of lethal potential for women in the developed world-presents as two interrelated problems: (1) local disease in the breast and axillary lymph nodes, and (2) micrometastatic disease in distant sites. During the last century, advances in surgery and radiotherapy have led to high rates of control over local disease. In addition, heightened public awareness and the more widespread use of mammography have led to the more frequent detection of smaller cancers with better prognosis. Nevertheless, the problem of distant recurrence, leading almost inevitably to death, persists. Hence, there is considerable interest in integrating systemic therapy, which since mid-century has been shown to be active against advanced disease, into the treatment of primary breast cancer. The long-standing theoretical prediction of benefit from drug therapy as an adjunct to local control procedures has now been confirmed by several decades of clinical investigation. Long-term follow-up of seminal trials and the conduct of a crucial series of meta-analyses have established the ability of both hormonal therapies and chemotherapy to prolong disease-free and overall survival in nearly all groups of patients. Although the relative and absolute influences of drug therapies remain modest, if these were properly applied to the hundreds of thousands of patients diagnosed worldwide per year, the potential impact on public health would be significant. In addition, recent laboratory advances and clinical trial data have indicated several new directions that promise greater impact against occult disseminated disease. These include novel dosing and scheduling strategies, newer active agents, fresh biochemical targets, and different combinations of chemotherapy with hormonal therapy.

Age Distribution↗

PubMedDate not supplied

[Psychotherapy in children and youths].

Child and adolescent psychotherapy form a large proportion of the total amount of psychotherapeutic efforts. Because of the age of the patients, the positive or negative impact is considerable. From the literature we learn that the efforts made to evaluate psychotherapy effects are not in balance with the amount of executed therapies. Meta-analyses of the available controlled therapy-evaluation studies offer a limited but rather encouraging view on the effectiveness of child and adolescent psychotherapy. Also on the differences in effectiveness according to the therapeutic orientation or the treated disturbance some interesting conclusions can be drawn. Unfortunately, these conclusions are based on a limited number of studies, because few clinicians conduct systematic research on therapy effectiveness. Systematic therapy evaluation requires some explicit decisions. The clinician has to decide on the description of the disturbance and the use of a diagnostic system, on the choice of standardized assessment procedures, on the operationalization of his therapeutic techniques and on the availability of norm groups and/or appropriate control conditions. In our psychology and psychotherapy training programs, attention for therapy evaluation is rather limited. Only a small number of students or trainees is explicitly trained in this aspect of therapeutic work. The available literature offers some interesting suggestions to enhance the quantity and the quality of the research in this area.

Adolescent↗

PubMed1996

[Risk of second primary cancer in two-year survivors of small cell lung cancer].

A total of 498 patients with small cell lung cancer received chemotherapy with or without chest irradiation at Osaka Prefectural Habikino Hospital from October 1977 through December 1991. Sixty-one who survived for more than two years were evaluated to determine the incidence and anatomic patterns of redevelopment of small cell lung cancer and development of second primary cancers. The numbers of expected cancers were estimated by cumulating person years of observation from 2 years after the start of treatment for small cell lung cancer to the date of death. Second primary cancers were observed in seven patients (four cases of non-small cell lung cancer, two of gastric cancer, and one of prostate cancer). The risk of a second primary cancer was 3.2 times greater than in the general population (95% Cl: 1.3-6.6). the relations between occurrence of a second primary cancer and family history of cancer, smoking history, smoking cessation after treatment of small cell lung cancer, and thoracic irradiation were studied. Occurrence of a second primary cancer correlated with family history (relative risk 7.5, 95% Cl: 1.5-22) and smoking cessation (relative risk 3.2, 95% Cl: 1.2-6.9). Long-term survivors were more likely to have a second primary cancer than a relapse of small cell lung cancer. Therefore, long-term survivors should be closely monitored for second primary cancers. Meta-analyses of studies done at several institutions may provide more detailed information on the occurrence of second primary cancers after small cell lung cancer.

Adenocarcinoma↗

PubMed1996

Calcium channel blockers in the dock: innocent or guilty?

Several studies have recently been published which have raised doubts over the long-term safety of calcium channel blockers (CCB). These have included retrospective case control studies in hypertension and meta-analyses of small scale studies in unstable angina and myocardial infarction (MI). Most of the reports were primarily concerned with the use of the short acting dihydropyridine nifedipine. Despite wide media coverage of these reports, the results are by no means irrefutable and, because of the nature of the studies themselves, are open to several criticisms. Calcium channel blockers are currently being evaluated in large-scale, prospective, randomised controlled studies, but results are unlikely to be available within the next few years. Meanwhile, the consensus view seems to be that short acting dihydropyridines should in general be avoided and have no place in the management of unstable angina and post MI. In the setting of stable angina, long acting dihydropyridines should generally be used in conjunction with a beta-blocker. In hypertensive patients, long acting dihydropyridines may be used as alternative antihypertensive agents in patients in whom the first line agents (diuretics and beta-blockers) are poorly tolerated, contra-indicated or ineffective.

Calcium Channel Blockers↗

PubMed1996

Geriatric work-up in the Nordic countries. The Nordic approach to comprehensive geriatric assessment.

A group established by the Nordic professors of geriatrics has developed a position document presenting a shared and updated review of geriatric work-up as a way of comprehensive geriatric assessment in the Nordic countries. The main intention is that the document will serve as support and help for the clinician concerned with hospital based geriatric medicine. It may also be useful for quality control and teaching. Not least, it may be useful for health professionals other than geriatricians. To some extent, the position of geriatric medicine in the Nordic countries varies between the countries. However, the background for developing a Nordic version of geriatric work-up is shared attitudes and principally the same organization of the health care system, and collaboration within geriatrics for many years. Several trials on comprehensive geriatric assessment and management performed in different settings have shown favourable outcomes. Results from controlled Nordic trials are compiled and summaries of meta-analyses are presented. The concept of Nordic geriatric work-up is based on a model defining health and disease in old age as dimensions of pathology, impairments, functional limitations, and disability, all being modified by extra- and intraindividual factors. Handicap is defined as the disability gap. Different health professionals have varying responsibilities in the geriatric team-work, but all should be dedicated to establish common goals. The geriatric work-up is presented with success factors and barriers, stating important differences between multidisciplinary and interdisciplinary processes. Checklists and assessment scales may be very useful when performing a geriatric work-up, but they should be used with caution. Specific scales covering different functional areas of the geriatric patient are recommended for clinical practice. Such scales must be valid, reliable, acceptable to the patient, responsive to change, and should be in an appropriate format, as well as easy to administer. Prior to the use among geriatric teams in the Nordic countries the scales should be translated into all the Nordic languages, and the translated versions should ideally have been subjected to validity and reliability testing. However, so far no scale meets these demands regarding all the five Nordic languages.

Aged↗

PubMed1996

Controversies: synthetic or natural surfactant treatment for respiratory distress syndrome? The case for synthetic surfactant.

The choice of surfactant for prophylactic or "rescue" treatment of RDS is dependent on a number of different considerations: a) Randomised controlled trials have shown that natural and synthetic surfactants increase survival whether used prophylactically or as rescue. No statistically significant difference in mortality has been shown when the two types of surfactant have been compared in randomised trials. b) Possible adverse effects of surfactant treatment include: (i) Intraventricular haemorrhage (IVH). Two randomised trials of natural surfactant have shown a significant increase in IVH with natural surfactant treatment. In meta-analyses, IVH has not been significantly reduced despite decreased mortality. Acute changes in cerebral haemodynamics and EEG have been demonstrated following natural surfactant administration. These changes are less marked or absent with synthetic surfactant. (ii) The antigenicity of animal surfactant has not been shown to have clinical consequences. (iii) Prions are infectious particle (resistant to some sterilising techniques) which are responsible for slow encephalopathies, some of which have crossed species barriers. Contamination of bovine surfactant with prion particles from nervous tissue has been a theoretical concern. Synthetic surfactant has no risk of prion contamination. (iv) One natural surfactant has been shown to contain platelet activating factor (PAF). Synthetic surfactants can be made with greater chemical purity. c) Natural surfactants improve oxygenation faster than do synthetic surfactants. A rapid effect is not necessarily better with respect to later outcomes. d) Synthetic surfactant preparations are generally cheaper per dose than natural surfactant preparations. Synthetic surfactant treatment increases survival with less concern about adverse effects and generally lower cost per dose than natural surfactant.

Cerebrovascular Circulation↗

PubMed1996

Infection and prematurity: evidence-based approaches.

The real cost savings arising from effectively preventing or treating preterm birth ascribable to prevalent reproductive tract infections are demonstrated in the lives of children saved from premature death and personal, biologic and economic impairment. Three meta-analyses demonstrate neonatal and maternal benefits from adjunctive antibiotic treatment of mothers suffering preterm premature rupture of membranes. The effects of adjunctive antibiotic treatment of women with preterm labor are inconsistent, but single-agent regimens using erythromycin and clindamycin are effective and provide coverage for group B streptococcus. Providers and payers now have evidence-based, clinically proven and cost-saving opportunities to prevent important numbers of preterm births, as well as preventing individual children suffering from being 'born too soon'.

Anti-Bacterial Agents↗

PubMed1996

Who needs antiplatelet therapy?

A series of overviews or meta-analyses of randomized clinical trials prepared by the Antiplatelet Trialists' Collaboration were published in the British Medical Journal in January 1994. They demonstrated that prolonged courses of medium-dose aspirin were very effective at preventing both fatal and non-fatal myocardial infarction and stroke in patients at high risk of occlusive vascular disease. The aim of this review is to provide the general practitioner with a practical guide to the use of aspirin in patients at high and low risk of occlusive vascular disease and to discuss appropriate dosages and contraindications to treatment in the light of all the recent evidence.

Aspirin↗

PubMed1996

Random versus nonrandom assignment in controlled experiments: do you get the same answer?

Psychotherapy meta-analyses commonly combine results from controlled experiments that use random and nonrandom assignment without examining whether the 2 methods give the same answer. Results from this article call this practice into question. With the use of outcome studies of marital and family therapy, 64 experiments using random assignment yielded consistently higher mean post-test effects and less variable posttest effects than 36 studies using nonrandom assignment. This difference was reduced by about half by taking into account various covariates, especially pretest effect size levels and various characteristics of control groups. The importance of this finding depends on (a) whether one is discussing meta-analysis or primary experiments, (b) how precise an answer is desired, and (c) whether some adjustment to the data from studies using nonrandom assignment is possible. It is concluded that studies using nonrandom assignment may produce acceptable approximations to results from randomized experiments under some circumstances but that reliance on results from randomized experiments as the gold standard is still well founded.

Family Therapy↗