How to combine research studies

Dealing with imperfect information All marketing research studies are subject to sampling errors. After all, even if we use a reasonably large sample size of 1,000, our margin of error is ±3% or a spread of 6 percentage points. Consequently, if 2% of your customers are dissatisfied with the service provided by your firm in one study and this figure increases to 5% in the next study conducted 6 months later, it is not even clear whether your firm is really achieving a better performance. Even worse, if in the next survey the figure may go back where it was before. Obviously this raises questions: has your performance gone down (or up)? is nothing really happening? While such questions are usually answered with the help of other information that may be available to the researcher or to management, it is clear that the data 'don't' speak for themselves'. If we have unlimited money (and not enough intelligence to match) we can do enormously large studies at great expense. But that is not the real solution. Firstly, no matter how large a study is, there will always be sampling error, albeit small. Secondly, such resource outlay is seldom justified in marketing research where no meaningful marketing decisions can (or more importantly, should) be taken on the basis of a few percentage point difference in response to survey questions. Consolidating what we know What we really need may not be very large scale studies but methods which will enable us consolidate the knowledge we gathered over a period of time. This called 'meta-analysis'. Meta-analysis has several advantages. Meta-analysis may be able to offer definitive conclusions out a series of less than definitive studies. It saves resources by avoiding redundant studies-there is no need to carry out new studies if the main objective of the proposed study can be met through a re-analysis of the existing studies. Even when one-shot studies provide reliable information, there is no substitute for cumulative knowledge. Meta analysis provide cumulative knowledge. Meta-analysis can combine studies which may not be directly comparable. For example, in one study you may have used a five-point scale and in another study a seven-point scale. These and other advantages of meta-analysis make it particularly attractive to those who constantly have to work under the constraints of limited resources. Combined tests The fundamental technical concern in any meta analysis relates to the procedures that can be used to combine different studies. Let us start with an example of a new marketing manager in a corporation confronted with four different studies carried out prior to her arrival. The results are given in Exhibit 1

Uptake of systematic reviews and meta-analyses based on individual participant data in clinical practice guidelines: descriptive study.

To establish the extent to which systematic reviews and meta-analyses of individual participant data (IPD) are being used to inform the recommendations included in published clinical guidelines

Neutrophil-to-lymphocyte ratio as a bladder cancer biomarker: assessing prognostic and predictive value in SWOG 8710

No abstract available

Preoperative chemotherapy for non-small cell lung cancer: a systematic review and meta-analysis of individual participant data

BACKGROUND: Individual participant data meta-analyses of postoperative chemotherapy have shown improved survival for patients with non-small-cell lung cancer (NSCLC). We aimed to do a systematic review and individual participant data meta-analysis to establish the effect of preoperative chemotherapy for patients with resectable NSCLC. METHODS: We systematically searched for trials that started after January, 1965. Updated individual participant data were centrally collected, checked, and analysed. Results from individual randomised controlled trials (both published and unpublished) were combined using a two-stage fixed-effect model. Our primary outcome, overall survival, was defined as the time from randomisation until death (any cause), with living patients censored on the date of last follow-up. Secondary outcomes were recurrence-free survival, time to locoregional and distant recurrence, cause-specific survival, complete and overall resection rates, and postoperative mortality. Prespecified analyses explored any variation in effect by trial and patient characteristics. All analyses were by intention to treat. FINDINGS: Analyses of 15 randomised controlled trials (2385 patients) showed a significant benefit of preoperative chemotherapy on survival (hazard ratio [HR] 0.87, 95% CI 0.78-0.96, p=0.007), a 13% reduction in the relative risk of death (no evidence of a difference between trials; p=0.18, I2=25%). This finding represents an absolute survival improvement of 5% at 5 years, from 40% to 45%. There was no clear evidence of a difference in the effect on survival by chemotherapy regimen or scheduling, number of drugs, platinum agent used, or whether postoperative radiotherapy was given. There was no clear evidence that particular types of patient defined by age, sex, performance status, histology, or clinical stage benefited more or less from preoperative chemotherapy. Recurrence-free survival (HR 0.85, 95% CI 0.76-0.94, p=0.002) and time to distant recurrence (0.69, 0.58-0.82, p<0.0001) results were both significantly in favour of preoperative chemotherapy although most patients included were stage IB-IIIA. Results for time to locoregional recurrence (0.88, 0.73-1.07, p=0.20), although in favour of preoperative chemotherapy, were not statistically significant. INTERPRETATION: Findings, which are based on 92% of all patients who were randomised, and mainly stage IB-IIIA, show preoperative chemotherapy significantly improves overall survival, time to distant recurrence, and recurrence-free survival in resectable NSCLC. The findings suggest this is a valid treatment option for most of these patients. Toxic effects could not be assessed. FUNDING: Medical Research Council U

Meta-Analysis of the Relationship Between Ethnicity, Obesity, and Type 2 Diabetes of Adults in Urban Populations of Central America

The purpose of this meta-analysis was to examine the impact of ethnicity and obesity as it relates to Type-2 Diabetes (T2D) in specific Central American countries. A meta-analysis was conducted to determine the association of ethnicity, obesity, and T2D. Four studies that qualified for inclusion were identified by searching MEDLINE and PubMed databases. The studies on the association of ethnicity and T2D had a combined population resulted in 265,858 study participants. Two studies on the association of obesity and T2D had 197,899 participants. An analysis of the data was conducted utilizing the relative risk ration, odds ratio, and forest plots. The comparison of the relative risk of T2D across ethnic categories by studies range for Blacks was 1.59 to 2.74, Asians was 1.43 to 2.08, and Hispanics .92 to 2.91. The ethnic difference in the prevalence of diabetes was almost two-fold higher in all ethnic groups than among the Caucasians with a significance level of 95%. A comparison of relative risk of T2D across weight categories was significantly higher among those with a diagnosed of diabetes in all reported areas. The odds ratio was very close to the risk ratio in both ethnicity and obesity to the development of T2D. The meta-analysis findings documented that an association does exist between ethnicity and obesity to the development of type 2 diabetes

The risk of falling

Abstract: In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30–40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics—which is able to promote regeneration of bones—was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes

Does coffee consumption alter plasma lipoprotein(A) concentrations? A systematic review

Coffee consumption alters plasma lipid and cholesterol concentrations, however, its effects on lipoprotein(a) (Lp(a)) have received little study. The aim of this PRISMA compliant systematic review was to examine the role of coffee on serum Lp(a). This study was prospectively registered (PROSPERO 2015:CRD42015032335). PubMed, Scopus, Web of Science and Cochrane Central were searched from inception until 9th January 2016 to detect trials and epidemiological studies investigating the impact of coffee on serum Lp(a) concentrations in humans. We identified six relevant publications describing nine experimental trials of various designs. There were a total of 640 participants across all studies and experimental groups. In short-term controlled studies, consumption of coffee, or coffee diterpenes was associated with either a reduction in serum Lp(a) of 11 mg/dl (6 trials, 275 participants), or no effect (2 trials, 56 participants). Conversely, one cross-sectional study with 309 participants showed serum Lp(a) was elevated in chronic consumers of boiled coffee who had a median Lp(a) of 13.0 mg/dl (range 0-130) compared with consumers of filtered coffee who had median Lp(a) 7.9 mg/dl (range 0-144) The effect of coffee on Lp(a) is complex and may follow a biphasic time-course. The type of coffee and the method of preparation appear to be important to determining the effect on Lp(a