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PubMed1991

A prototype for integrative review and meta-analysis of nursing research.

Meta-analysis has gained international recognition as a statistical approach to research synthesis. What is missing in research reviews, however, is the systematic compilation of results from non-experimentally designed studies. An approach is described which extends the rigours of integrative research review and meta-analysis to descriptive studies. A model for conceptualizing a systematically derived research synthesis is presented with selected accompanying generic elements. The model serves as a prototype for application to a variety of topical areas of interest. Generic elements contained in the prototype may be tailored to specific topics with relative ease. Resources and time required for topic development from conceptualization through to dissemination can be considerably reduced by adaptation of the generic elements.

Clinical Nursing Research↗
PubMed1999

Meta-analysis as a source of evidence in gastroenterology: a critical approach.

Meta-analysis is increasingly used in hepatogastroenterology. Meta-analysis is of value to provide a systematic review of related trials and to display their results in an objective, easily understandable manner. When the trials are sufficiently homogeneous, meta-analysis can document the superiority, (a), or the lack of superiority (b) of a treatment with respect to another (e.g., (a) Interferon plus ribavirin vs Interferon for chronic hepatitis; (b) 5-ASA vs sulfasalazine for maintaining remission in ulcerative colitis). However the interpretation of meta-analysis requires caution. Meta-analysis can be unreliable or unstable if based on a few, small trials (e.g., Tamoxifen vs non-active treatment for hepatocellular carcinoma), or if distorted by confounding variables and publication bias (e.g., glucocorticoids vs standard treatment in alcoholic hepatitis). Eventually, qualitative heterogeneity makes the pooled results of meta-analysis meaningless or questionable (e.g., endoscopic sclerotherapy for prevention of first variceal bleeding in cirrhosis) and should prompt the search for its sources to plan future studies. Finally, meta-analysis of trials measuring the treatment effect of a drug vs a placebo when an active drug is available for comparison provides the limited informative content for the physician of the individual trials (e.g. 5-ASA vs placebo for maintaining remission in ulcerative colitis).

Clinical Trials as Topic↗
PubMed1992

How effective are current drugs for Crohn's disease? A meta-analysis.

We have conducted a meta-analysis of 12 placebo controlled trials to determine the efficacy of single drug therapy in Crohn's disease for both induction (seven trials) and maintenance (five trials) of remission. A total of 767 and 796 patients were studied, respectively. Various clinical criteria of success were analyzed. The Dersimonian-Laird method for meta-analysis was used to calculate the risk difference (RD). Therapeutic advantage, defined as the difference between drug and placebo response, was also determined. Using various criteria of success, we found that single drug therapy conferred an 11-29% therapeutic advantage (RD = 0.13-0.33) over placebo for the induction of remission. In trials for maintenance, no therapeutic advantage was found for single drug therapy over placebo. All forms of maintenance therapy followed nearly identical linear rates of relapse over time, showing an approximately 90% maintenance of remission rate at 3 months, which decreased to 25% at 36 months. In conclusion, meta-analysis has established a standard of reference against which future drug trials can be compared. This standard of reference for drug and placebo rates, as well as the corresponding risk differences and therapeutic advantages can help determine the relative value of newer agents in the therapy of Crohn's disease.

Crohn Disease↗
PubMed1995

Misunderstanding meta-analysis.

Although it is increasingly common, meta-analysis is still a relatively new addition to the toolbox of research strategies. Partially because of its newness and partially because its early enthusiasts may have overstated its presumed contributions, a number of common misunderstandings have developed about the meta-analytic approach. These misunderstandings have to do with the way that meta-analysis is conducted and interpreted and its relation to primary research and narrative review. This article aims to highlight these misunderstandings and offer an alternative view of meta-analysis. It is hoped that meta-analytic research of the future will be a partnership with primary research and that meta-analysis will be valued not so much for its definitiveness as for the creative speculations it allows about patterns that appear across studies.

Data Collection↗
PubMed1990

Cigarette smoking-associated changes in blood lipid and lipoprotein levels in the 8- to 19-year-old age group: a meta-analysis.

In this meta-analysis it was demonstrated that, when compared with nonsmokers of similar age, smokers in the 8- to 19-year-old age group have significantly higher serum levels of triglyceride (+11.8%), very-low-density lipoprotein (VLDL)-cholesterol (+12.4%) and low-density lipoprotein (LDL)-cholesterol (+4.1%) and significantly lower serum levels of high-density lipoprotein (HDL)-cholesterol (-8.5%) and total cholesterol (-3.7%). All of these smoking-associated changes are in the same direction as those found in adults, with the exception of total cholesterol levels, which are significantly increased in adult smokers. The extent to which mean triglyceride, LDL-cholesterol, and HDL-cholesterol levels are shifted is significantly greater in the 8- to 19-year-old smokers than in adult smokers. The changes in mean total cholesterol levels among smokers in both age groups represent only the net shifts in the lipoprotein fractions and are therefore likely to be a less sensitive indicator of the possible lipid-related excess coronary artery disease risk in smokers.

Adolescent↗
PubMed2026

Socioeconomic differences in the effectiveness of oral health programs for dental caries prevention in Europe: A systematic review and meta-analysis.

AIM: The meta-analysis systematically summarized evidence on how socioeconomic status (SES), access to dental care, and oral health programs (OHP) affect caries prevalence and severity among children and adults in Europe. METHODS: Four electronic databases (PubMed, Scopus, Cochrane Library and Embase) were systematically screened from 1947-2026, supplemented by cross-referencing and manual searches, without language restrictions. Study selection, data extraction and quality assessment were done in duplicate. Methodological quality was assessed using the NHLBI Study Quality Assessment Tools according to study design. Certainty of evidence was graded using GRADE Profiler 3.6. Mean differences (MD) were calculated for changes in DMFT, and odds ratios (OR) for the presence of dental caries in individuals using fixed-or random-effects models. RESULTS: Electronic searching identified 1800 articles; 23 studies were included in the review (>169,000 participants) and 14 in the meta-analyses (>88,000). Nine studies evaluated the effectiveness of OHP stratified by SES, and ten examined OHP in low-SES populations. Among low-SES individuals, participation in OHP was associated with a significantly lower increase in DMFT (MD[95% CI]=-0.63[-0.94;-0.31];very low certainty) and significantly lower odds of having dental caries (OR[95% CI]=0.61[0.52;0.73];very low) compared with non-participation. Among program participants, individuals with low SES showed a significantly greater increase in DMFT than those with high SES (MD[95% CI]=0.79[0.30;1.21];very low) and had significantly higher odds of having dental caries (OR[95% CI]= 2.88[1.97;4.22];very low). CONCLUSION: Participation in OHP may be associated with reducing dental caries in European populations, but benefits are unequally distributed and increase with higher SES. However, this conclusion is based on a limited number of well-conducted trials.

Humans↗
PubMed2000

Meta-analysis in hematology and oncology.

In 1992, a review article about meta-analysis identified only 15 meta-analyses of randomized, controlled trials of cancer therapy. Since then, the total number of meta-analyses in this field has increased almost sixfold. More importantly, the number of randomized, controlled trials in this discipline has also grown tremendously. The expansion in the literature will provide a fertile ground for future meta-analyses. The quality of the recent publications has also improved. An ongoing world-wide effort, the Cochrane Collaboration, is systematically assembling and synthesizing several hundred thousand randomized, controlled trials to improve the delivery of health care. Meta-analysis has many important advantages. It allows the viewing of the complete picture of the evidence. The advent of meta-analysis has sensitized researchers to issues of quality and has improved methodology in clinical research. Detection and explanation of bias and heterogeneity are prime objectives of meta-analysis in clinical research. An array of methods has been developed that allows a better understanding of bias and heterogeneity, beyond simple averaging of results from diverse studies. Meta-analyses of individual patient data, in particular, may promote the development of international collaborations. Several examples of their application are already available in oncology. Meta-analysis may point out deficiencies in the study design of past and current studies, suggest the need for new studies, and inform researchers about the size and design of these studies. In the end, meta-analysis helps to integrate evidence and make recommendations for medical care and medical practice.

Clinical Trials as Topic↗
PubMed2002

[Meta-analysis and evidence based medicine].

Meta-analysis is a statistical method for combining the results of available research studies to increase statistical power. The steps of meta-analysis are identification of question, search and selection of trials and analysis. Evidence based medicine (EBM) is integrating individual clinical expertise with the best available external clinical evidence from systematic research. The practice of EBM consists of formulated clinical question, systematic review, critical appraisal, application for patients and performance review. We must notice the results of meta-analysis and evidence are keeping up to date. We should use them with critical appraisal skill and should not criticize without good understanding.

Evidence-Based Medicine↗
PubMed1998

Cancer among farmers: a meta-analysis.

PURPOSE: We conducted a meta-analysis of 37 studies to assess whether farmers had elevated rates for several cancers, as was concluded in a previous meta-analysis of 21 studies. METHODS: We identified studies from the reference list of the previous meta-analysis and from a MEDLINE search through December 31, 1994. The primary purpose of our analysis was to identify and, if possible, understand the sources of heterogeneity in the literature. Stratified analyses of studies and linear modeling with inverse variance weights were used to assess the impact of study characteristics on results. We calculated summary relative risks as a weighted average of the log relative risks across studies using inverse variance weights. Fixed and random effects models were used as appropriate. RESULTS: The results for most cancers were markedly heterogeneous by study design and, for fewer cancers, by geographic location, and whether the studies focused on crop and livestock farmers. There was some indication of publication bias due to underreporting of near null or sub null findings. Lip cancer was the only cancer that was clearly elevated among farmers. CONCLUSIONS: The results do not suggest that farmers have elevated rates of several cancers. However, the known heterogeneity of exposures by type of farming, geographic area, time period, and other factors limits the informativeness of meta-analyses of these studies for assessing potential carcinogenic exposures in agriculture.

Agricultural Workers' Diseases↗
PubMed1998

Out of step with the Lancet homeopathy meta-analysis: more objections than objectivity?

The meta-analysis of homeopathy trials that appeared in the Lancet in 1997 seemed to endorse the experience of practitioners and patients that homeopathic medicines have specific clinically relevant effects. However, results from later unsuccessful trials, and negative inferences from a review of trials for a condition excluded from the meta-analysis--delayed onset muscle soreness (DOMS)--have since been presented to suggest that the meta-analysis may well have overestimated the positive effects of homeopathy, and that the "placebo question is still not resolved." This article reviews the evidence underlying this challenge to the meta-analysis and homeopathy, and demonstrates that it would be valid if it were based on: a comprehensive literature search; appropriate classification of primary studies; clear discrimination between clinical effectiveness and placebo questions; sound and transparent review methods; and a reliable and unconfounded clinical treatment model for testing the ultramolecular hypothesis. It is suggested that different models are needed to answer different questions.

Bias↗
PubMed2002

Evaluation of the effectiveness of a pre-brushing rinse in plaque removal: a meta-analysis.

OBJECTIVES: A meta-analysis technique was used to pool data from studies to assess the effectiveness of the pre-brushing rinse PLAX on existing plaque and gingivitis. METHODS: Studies were identified using MEDLINE and other sources, and grouped according to whether PLAX was used in short- or long-term treatment. The quality of trials was assessed by 2 independent readers. The DerSimonian and Laird random effects model was used. Meta-analyses were performed according to duration and type of PLAX treatment. In "1-day" studies, the effect of PLAX after rinsing and after rinsing and brushing was evaluated, whereas in longitudinal studies, this was done at several follow-up times. RESULTS: A total of 19 studies were included and mean quality scores ranged from 0.13 to 0.60, for the study protocol from 0.18 to 0.70 and for data analysis and presentation from 0.05 to 0.53. In "1-day" studies, PLAX significantly reduced plaque after rinsing (difference=0.143; 95% CI=0.02-0.27;p=0.022), whereas no significant reduction was observed in post-brushing measures. In "longitudinal" studies, plaque was significantly reduced at 1-2 (difference=0.168; 95% CI=0.09-0.24; p<0.0001), 3-4 (difference=0.179; 95% CI=0.01-0.35; p=0.043), 12 (difference=0.288; 95% CI=0.21-0.37; p<0.0001) and 24 (difference=0.377; 95% CI=0.19-0.57; p=0.0001) weeks. The meta-analysis that evaluated gingivitis showed a significant reduction in inflammation with PLAX treatment at 12 (difference=0.209; 95% CI=0.17-0.25; p<0.0001) and 24 (difference=0.257; 95% CI=0.22-0.29; p<0.0001) weeks follow-up. CONCLUSIONS: Although PLAX use appears to offer some benefit in plaque and gingivitis reduction, the clinical magnitude of the difference and the benefit on oral health are likely to be small.

Anti-Infective Agents, Local↗
PubMed2001

Application and validation of a computerized cough acquisition system for objective monitoring of acute cough: a meta-analysis.

STUDY OBJECTIVE: The purpose of the meta-analysis was to understand the antitussive effect of treatment with dextromethorphan hydrobromide, 30 mg, vs placebo over a 3-h treatment period in patients with cough due to uncomplicated upper respiratory tract infection (URTI), and to show that the computerized system for acquisition and analysis of cough sound was consistent and reproducible across the individual studies. STUDY DESIGN: The six studies used for the meta-analysis were randomized, double-blind, parallel-group, single-dose, placebo-controlled studies with a 3-h postdose cough evaluation period. SETTING: One study was conducted in Durban, South Africa, and five studies were conducted in Bombay, India. Four studies took place in clinics, and two studies were in-home studies. PATIENTS: Seven hundred ten adult patients with cough due to uncomplicated URTI who were otherwise healthy and who satisfied the inclusion/exclusion criteria for the meta-analysis. MEASUREMENTS AND RESULTS: For each patient, a standard baseline was calculated pretreatment, then a 3-h continuous cough recording was made after treatment was initiated. Five efficacy variables were measured in 30-min intervals: cough bouts, cough components, cough effort, cough intensity, and cough latency. The meta-analysis showed consistent results across most of the studies for each of the efficacy variables. It demonstrated significantly greater overall reductions in cough bouts, cough components, and cough effort, and an increase in cough latency for patients treated with dextromethorphan hydrobromide, 30 mg, vs those treated with placebo. CONCLUSION: The results of a meta-analysis of the six clinical studies show that the antitussive effect of a single dose of dextromethorphan hydrobromide, 30 mg, has been established. The consistent nature of the results shows that the computerized cough acquisition and analysis system is a valid and reproducible methodology for evaluating cough associated with URTI.

Adolescent↗
PubMed1996

G-CSF for the prophylaxis of neutropenic fever in patients with small cell lung cancer receiving myelosuppressive antineoplastic chemotherapy: meta-analysis and pharmacoeconomic evaluation.

Standard meta-analytical and pharmacoeconomic techniques were used to study the clinical effectiveness and the cost-effectiveness ratio of the prophylactic (or pre-emptive) administration of G-CSF to patients with small cell lung cancer treated with conventional myelosuppressive cytotoxic chemotherapy. In the first part of our study, we conducted a meta-analysis of the randomized clinical trials evaluating G-CSF for this clinical indication. Three trials were identified by our literature search and were included in the meta-analysis (overall number of patients = 606). The end-points for evaluating G-CSF included mortality from infection and the cumulative incidence of neutropenic fever over six cycles of chemotherapy. The results of our meta-analysis demonstrate that prophylactic G-CSF did not affect mortality but significantly reduced the incidence of neutropenic fever from 68.3% to 38.7% (pooled odds ratio = 0.29, 95% CI: 0.21-0.40; P < 0.001). In the second part of our study, we carried out a pharmacoeconomic analysis to estimate the cost-effectiveness ratio of pre-emptive G-CSF (i.e. the 'average' cost associated with the prevention of an episode of neutropenic fever). This cost-effectiveness ratio was US$ 14,372 using the Italian price of the drug converted into dollars, or US$ 41 088 using the US price. Finally, we estimated the revenue-neutral price of G-CSF based on American data of the cost-of-illness. The price ranged from US$ 395 to US$ 569 per cycle, a figure higher than the value (US$ 150) previously reported in the literature.

Antineoplastic Agents↗
PubMed2000

Meta-analysis: methods, strengths, and weaknesses.

Meta-analysis is a systematic, quantitative approach to the combination of data from several clinical trials that address the same question. This analytic approach can help resolve questions that remain unclear from the results of individual trials. Meta-analysis is of particular interest in oncology because of the small differences in efficacy between therapeutic alternatives. The large number of patients included in meta-analyses permit small to moderate benefits of a treatment to be reliably detected and larger treatment benefits to be quantified more accurately. Despite these apparent benefits, the use of meta-analysis has met with a great deal of resistance and has generated much controversy in clinical journals. After a brief description of the basic methods of conducting meta-analyses, this article will explore both their advantages and disadvantages.

Bias↗
PubMed2000

Adverse events and treatment discontinuations in clinical trials of fluoxetine in major depressive disorder: an updated meta-analysis.

BACKGROUND: A 1993 meta-analysis of US Investigational New Drug clinical trials of fluoxetine reinforced this agent's more favorable adverse-event profile compared with tricyclic antidepressants (TCAs). OBJECTIVES: The present meta-analysis sought to provide a reanalysis of updated adverse-event and discontinuation data for fluoxetine 20 to 80 mg/d compared with TCAs and placebo in the treatment of major depressive disorder (MDD) in adults. A subanalysis to assess the safety profile of the most commonly used effective dose of fluoxetine in MDD (20 mg) was also conducted. METHODS: Data were obtained from 25 double-blind clinical trials involving 4016 patients with MDD randomized to treatment with fluoxetine 20 to 80 mg/d, TCAs, or placebo. The subanalysis included data from 6 trials involving 1258 patients treated with fixed 20-mg doses of fluoxetine or placebo. Spontaneously reported treatment-emergent adverse events, reasons for discontinuation, and events leading to discontinuation were compared between groups. RESULTS: The age of the 4016 randomized patients ranged from 12 to 90 years, with a mean age of 46 years. Most patients were white (92%), and 62% were female. The age of the 1258 patients in the 20-mg fixed-dose population ranged from 18 to 90 years, with a mean age of 54 years; as in the total population, most of these patients were white (92%), and 57% were female. The adverse-event profiles of fluoxetine and TCAs in these trials were consistent with the typical profiles of selective serotonin reuptake inhibitors and TCAs. At a dose of 20 mg/d, fluoxetine-treated patients had a discontinuation rate due to adverse events that was not statistically significantly different from that in placebo recipients. Discontinuation rates due to lack of efficacy were not significantly different between fluoxetine and TCAs. However, significantly more TCA-treated patients discontinued therapy because of adverse events and significantly fewer completed treatment compared with fluoxetine-treated patients (both, P < 0.001). The most common events (> or = 2%) leading to discontinuation were asthenia, dizziness, insomnia, nausea, nervousness, somnolence, and tremor in fluoxetine-treated patients and abnormal vision, agitation, constipation, dizziness, dry mouth, headache, nausea, nervousness, rash, somnolence, sweating, and tremor in TCA-treated patients. CONCLUSIONS: Data from this large series of clinical trials confirm that fluoxetine is well tolerated in the acute treatment of MDD in adults, especially at a dosage of 20 mg/d, and is better tolerated than the recommended doses of TCAs.

Adolescent↗
PubMed2001

Discontinuation of Pneumocystis carinii prophylaxis in patients infected with human immunodeficiency virus: a meta-analysis and decision analysis.

We performed a meta-analysis and a decision analysis on the discontinuation of prophylaxis for Pneumocystis carinii pneumonia (PCP) in patients infected with human immunodeficiency virus who had adequate immune recovery while receiving highly active antiretroviral therapy. In the meta-analysis (14 studies with 3584 subjects who had discontinued prophylaxis), 8 cases of PCP occurred during 3449 person-years (0.23 cases per 100 person-years [95% confidence interval, 0.10-0.46]). In the decision analysis, mortality and time spent alive without immunodeficiency in the modeled discontinuation strategy were similar to those in the continuation strategy. For patients who received primary prophylaxis, the discontinuation strategy led to slightly fewer episodes of PCP and fewer toxicity-related prophylaxis withdrawals (e.g., 8.6 vs. 34.5 cases per 100 patients during a 10-year period). Patients on the discontinuation strategy were more likely to be receiving trimethoprim-sulfamethoxazole when they became immunodeficient. Comparative results were similar for patients with prior PCP. Discontinuation of PCP prophylaxis in patients with adequate immune recovery is a useful strategy that should be widely considered.

AIDS-Related Opportunistic Infections↗
PubMed1994

Use of immune globulin to prevent symptomatic cytomegalovirus disease in transplant recipients--a meta-analysis.

The objective of this meta-analysis was to review the evidence for the use of immune globulin in the prevention of symptomatic cytomegalovirus (CMV) disease in transplant recipients. A computerized search of Medline from 1980 to October 1991 was conducted using the textword "cytomegalo:" and the subheading "prevention and control" for studies in all languages. Reference lists, a manual search of relevant literature and communication with internationally recognized experts were used to locate additional studies. Of the studies identified, 18 met the inclusion criteria (population: transplant recipients; intervention: immune globulin; outcome: symptomatic cytomegalovirus disease; study design: randomized controlled trial). The meta-analysis of the 18 studies showed a reduction in the incidence of symptomatic CMV disease in the group receiving immune globulin as compared to the untreated group. The common odds ratio was 0.58 (95% C.I. 0.42 to 0.77). Analyses of combining trials by subgroups of polyvalent immune globulin, hyperimmune globulin, bone marrow recipients and solid organ recipients resulted in common odds ratios comparable to the overall common odds ratio. Common odds ratios for the trials reporting cytomegalovirus interstitial pneumonia, cytomegalovirus death, overall death and graft loss ranged from 0.47 to 0.69. Common odds ratios for the effect of immune globulin prophylaxis analyzed by pre-transplant patient/donor cytomegalovirus antibody status ranged from 0.32 to 0.50. In conclusion, the use of immune globulin as passive immunization for the prevention of symptomatic cytomegalovirus disease in the transplant population is supported by this meta-analysis. The response is similar in both bone marrow and solid organ transplant recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytomegalovirus Infections↗