Search PubMed⌕ Search

Biomedical subjects

D G Altman

Publications and source records attributed to D G Altman.

At least 73 records · Page 4Linked to original sources
PubMed1999

The Cochrane Collaboration.

The Cochrane Collaboration is an international organisation that aims to help people make well-informed decisions about health care by preparing, maintaining and ensuring the accessibility of systematic reviews of the benefits and risks of health care interventions. We describe the structure and activities of the Cochrane Collaboration, especially focusing on the carrying out of systematic reviews of randomised trials. We describe the place of surgery and surgeons within the Cochrane Collaboration.

Evidence-Based Medicine↗
PubMed1999

The relationship between tobacco access and use among adolescents: a four community study.

The objective of this study was to examine the effectiveness of a longitudinal community intervention on the reduction of tobacco sales to minors and subsequent effects on tobacco consumption by youths. The study was conducted in Monterey County, CA. Four rural communities were randomized into treatment and comparison arms of the study and middle and high school students in each of these communities completed surveys assessing knowledge, attitude, and behavior. The main outcome measures were retail tobacco sales to minors as measured through store visits (tobacco purchase surveys) and self-reported consumption of tobacco. Over a three-year period, a diverse array of community interventions were implemented in the intervention communities. These included community education, merchant education, and voluntary policy change. In the treatment communities, the proportion of stores selling tobacco to minors dropped from 75% at baseline to 0% at the final post-test. In the comparison communities, the proportions were 64% and 39%, respectively. Although the availability of tobacco through commercial outlets was reduced substantially in intervention communities, youths reported still being able to obtain tobacco from other sources. Predicted treatment effects on reported use of tobacco among youths were observed cross-sectionally and longitudinally for younger students (7th graders). The intervention did not impact tobacco use among older students (9th and 11th graders) although the trends were in the predicted direction for 9th graders. A significant intervention effect was found for sex--females in the intervention communities were less likely to use tobacco post-intervention than females in the comparison communities. Tobacco sales to minors can be reduced through a broad-based intervention. To prevent or reduce tobacco use by youths, however, multiple supply-and demand-focused strategies are needed.

Adolescent↗
PubMed1999

Risk of bacterial infection associated with allogeneic blood transfusion among patients undergoing hip fracture repair.

BACKGROUND: The relationship between allogeneic blood transfusion and bacterial infection remains uncertain. An increased risk of bacterial infection would represent the most important risk of allogeneic transfusion, because viral disease transmission has become so rare. STUDY DESIGN AND METHODS: A retrospective cohort study of 9598 consecutive hip fracture patients at least 60 years old who underwent surgical repair was performed. The primary outcome was serious bacterial infection, defined as bacteremia, pneumonia, deep wound infection, or septic arthritis or osteomyelitis. Secondary outcomes included two individual infections, pneumonia and urinary tract infection (UTI), and the cost of infection. Hospital cost of infection was assessed by linking the study population to Medicare data. RESULTS: Fifty-eight percent of patients received at least one transfusion. Serious bacterial infection occurred in 437 patients (4.6%); 28.8 percent of this group died during the hospital stay. Pneumonia occurred in 361 patients (3.8%) and UTI occurred in 1157 patients (12.1%). The adjusted risk of serious bacterial infection associated with transfusion was 1.35 (95% CI, 1.10-1.66). The adjusted risk for pneumonia was 1.52 (95% CI, 1.21-1.91), and that for UTI was 1.03 (95% CI, 0.91-1.17). A dose-response relationship was present for serious bacterial infection (p = 0.001) and pneumonia (p = 0.001). The cost of hospitalization was $14,000 greater for patients with serious infection than for patients without infection. CONCLUSION: Blood transfusion is associated with a 35-percent greater risk of serious bacterial infection and a 52-percent greater risk of pneumonia. Postoperative infections are costly. The risk of bacterial infection may be the most common life-threatening adverse effect of allogeneic blood transfusion.

Aged↗
PubMed1999

Estimating sample sizes for continuous, binary, and ordinal outcomes in paired comparisons: practical hints.

Paired data occur in crossover trials and matched case-control studies, and it is rare to find studies reporting sample size calculations associated with these types of studies, despite recommendations from editors that sample size calculations should be justified. In this article we describe some simple formulas and strategies for calculating the number of patients that should be entered into a matched or paired study when the outcome measures are continuous, binary, or ordinal.

Aged↗
PubMed1999

Newspaper and wire service coverage of tobacco farmers.

This study examined print media coverage of tobacco farmers from the perspective of agenda setting, or the extent to which information is available to the public and perceived as important. A content analysis of 743 articles published between January 1, 1995 and June 30, 1997 was completed. The number of articles increased from 1995 to 1997. Of the topics analyzed, articles on tobacco settlement (7.1% of total) and diversification (15.6% of total) were the least prevalent. Because the settlement discussions did not occur until 1997 (when it comprised 26.4% of the total in the first 6 months), diversification was consistently the least covered topic. The two most frequent topics covered were tobacco companies (36.2%) and the tobacco price support program (32.3%). Except for one 6 month interval, there were substantially more articles in local/regional publications than in national publications. Public health professionals have called for tobacco farmers to diversify to non-tobacco enterprises. Yet, there is little discussion of diversification in print media. Without more attention to diversification, the public and policy makers will be ill-informed about opportunities and obstacles in this regard.

Agriculture↗
PubMed1999

What randomized trials and systematic reviews can offer decision makers.

It is important to recognize the studies that yield the most reliable evidence upon which to base treatment decisions. Randomized trials have a particular place in providing high-quality unbiased comparisons of different treatments, when carried out to a high methodological standard. Empirical evidence shows that such trials are not always done well, and also that poor methodology is associated with biased findings. Consumers of the published literature need to be able to recognize which trials can be trusted. Systematic reviews and meta-analyses offer an organized approach to assessing all the relevant literature on a topic, particularly when several randomized trials address the same treatment comparison. Like trials, systematic reviews and meta-analyses need to be carried out to a high standard. They offer particular potential for providing the most useful information for clinical decision making. Critical aspects of these types of study are considered in this paper.

Bias↗
PubMed1999

Measuring agreement in method comparison studies.

Agreement between two methods of clinical measurement can be quantified using the differences between observations made using the two methods on the same subjects. The 95% limits of agreement, estimated by mean difference +/- 1.96 standard deviation of the differences, provide an interval within which 95% of differences between measurements by the two methods are expected to lie. We describe how graphical methods can be used to investigate the assumptions of the method and we also give confidence intervals. We extend the basic approach to data where there is a relationship between difference and magnitude, both with a simple logarithmic transformation approach and a new, more general, regression approach. We discuss the importance of the repeatability of each method separately and compare an estimate of this to the limits of agreement. We extend the limits of agreement approach to data with repeated measurements, proposing new estimates for equal numbers of replicates by each method on each subject, for unequal numbers of replicates, and for replicated data collected in pairs, where the underlying value of the quantity being measured is changing. Finally, we describe a nonparametric approach to comparing methods.

Clinical Laboratory Techniques↗
PubMed1998

Statistical reviewing for medical journals.

This paper reviews the difficulties associated with being a statistical reviewer for a medical journal. As background, I consider first the use of statistical reviewers by medical journals, medical journals' policies on statistical peer review, and the limited evidence of its effectiveness. The assessment of a manuscript is considered under the headings of design, methods of analysis, presentation and interpretation, with many illustrative examples of the difficulties to be overcome. I emphasize the judgemental nature of many aspects. I suggest how to present and structure the reviewer's report to the editor. Finally, I consider wider issues, including the various other ways in which statisticians can interact with medical journals.

Peer Review, Research↗
PubMed1998

Randomised trial of educational visits to enhance use of systematic reviews in 25 obstetric units.

OBJECTIVE: To evaluate the effectiveness of an educational visit to help obstetricians and midwives select and use evidence from a Cochrane database containing 600 systematic reviews. DESIGN: Randomised single blind controlled trial with obstetric units allocated to an educational visit or control group. SETTING: 25 of the 26 district general obstetric units in two former NHS regions. SUBJECTS: The senior obstetrician and midwife from each intervention unit participated in educational visits. Clinical practices of all staff were assessed in 4508 pregnancies. INTERVENTION: Single informal educational visit by a respected obstetrician including discussion of evidence based obstetrics, guidance on implementation, and donation of Cochrane database and other materials. MAIN OUTCOME MEASURES: Rates of perineal suturing with polyglycolic acid, ventouse delivery, prophylactic antibiotics in caesarean section, and steroids in preterm delivery, before and 9 months after visits, and concordance of guidelines with review evidence for same marker practices before and after visits. RESULTS: Rates varied greatly, but the overall baseline mean of 43% (986/2312) increased to 54% (1189/2196) 9 months later. Rates of ventouse delivery increased significantly in intervention units but not in control units; there was no difference between the two types of units in uptake of other practices. Pooling rates from all 25 units, use of antibiotics in caesarean section and use of polyglycolic acid sutures increased significantly over the period, but use of steroids in preterm delivery was unchanged. Labour ward guidelines seldom agreed with evidence at baseline; this hardly improved after visits. Educational visits cost pound860 each (at 1995 prices). CONCLUSIONS: There was considerable uptake of evidence into practice in both control and intervention units between 1994 and 1995. Our educational visits added little to this, despite the informal setting, targeting of senior staff from two disciplines, and donation of educational materials. Further work is needed to define cost effective methods to enhance the uptake of evidence from systematic reviews and to clarify leadership and roles of senior obstetric staff in implementing the evidence.

Costs and Cost Analysis↗
PubMed1998

Methodological challenges in the evaluation of prognostic factors in breast cancer.

Many studies are carried out in an effort to find factors that help explain the large unexplained variation in prognosis of breast cancer patients. The principles of good study design and analysis are less well appreciated for prognostic factor studies than for therapeutic trials. The oncology literature is full of results from studies of varying quality, often with conflicting findings. As a consequence, despite the large number of studies, there is still uncertainty about the importance of most prognostic factors. Few recently proposed prognostic factors for breast cancer have become widely accepted. This paper reviews the important methodological issues underlying such research. These issues are illustrated with examples from published studies and recent reviews of papers published in cancer journals. Guidelines are proposed for conducting and evaluating prognostic factor studies which should improve the quality of research in this important area.

Breast Neoplasms↗