SEARCH · PubMed Health

Results for “systematics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources

PubMed2006

Systematic reviews of surgical interventions.

All physicians are familiar with the type of general review articles found in many medical journals. Systematic reviews are different. They apply a strict, scientific methodology to the reviewing process to produce a review that is comprehensive, reliable, and as free from bias as possible. As a result, systematic reviews occupy the highest position in the "levels of evidence" tables associated with the practice of evidence-based health care. Systematic reviews relevant to surgery are no less relevant than systematic reviews in other areas of health care. They should be a prerequisite of any new research, a key component in decision making, and an opportunity for all surgical practitioners to get involved in the conduct and interpretation of research.

Bias↗

PubMed2005

Molecular systematics of Eumolpinae and the relationships with Spilopyrinae (Coleoptera, Chrysomelidae).

The 3400 species of Eumolpinae constitute one of the largest subfamilies of leaf beetles (Chrysomelidae). Their systematics is still largely based on late 19th century monographs and remains highly unsatisfactory. Only recently, some plesiomorphic lineages have been split out as separate subfamilies, including the southern hemisphere Spilopyrinae and the ambiguously placed Synetinae. Here we provide insight into the internal systematics of the Eumolpinae based on molecular phylogenetic analyses of three ribosomal genes, including partial mitochondrial 16S and nuclear 28S and complete nuclear 18S rRNA gene sequences. Sixteen morphological characters considered important in the higher-level systematics of Eumolpinae were also included in a combined analysis with the molecular characters. All phylogenetic analyses were performed using parsimony by optimizing length variation directly on the tree, as implemented in the POY software. The data support the monophyly of the Spilopyrinae outside the clade including all sampled Eumolpinae, corroborating their treatment as a separate subfamily within the Chrysomelidae. The systematic placement of the Synetinae remains ambiguous but consistent with considering it a different subfamily as well, since the phylogenetic analyses using all the available evidence show the representative sequence of the subfamily also unrelated to the Eumolpinae. The Megascelini, traditionally considered a separate subfamily, falls within the Eumolpinae. Several recognized taxonomic groupings within Eumolpinae, including the tribes Adoxini or Typophorini, are not confirmed by molecular data; others like Eumolpini seem well supported. Among the morphological characters analyzed, the presence of a characteristic groove on the pygidium (a synapomorphy of the Eumolpini) and the shape of tarsal claws (simple, appendiculate or bifid) stand out as potentially useful characters for taxonomic classification in the Eumolpinae.

Animals↗

PubMed2005

Effectiveness of exercise therapy: a best-evidence summary of systematic reviews.

The purpose of this project was to summarise the available evidence on the effectiveness of exercise therapy for patients with disorders of the musculoskeletal, nervous, respiratory, and cardiovascular systems. Systematic reviews were identified by means of a comprehensive search strategy in 11 bibliographic databases (08/2002), in combination with reference tracking. Reviews that included (i) at least one randomised controlled trial investigating the effectiveness of exercise therapy, (ii) clinically relevant outcome measures, and (iii) full text written in English, German or Dutch, were selected by two reviewers. Thirteen independent and blinded reviewers participated in the selection, quality assessment and data-extraction of the systematic reviews. Conclusions about the effectiveness of exercise therapy were based on the results presented in reasonable or good quality systematic reviews (quality score > or = 60 out of 100 points). A total of 104 systematic reviews were selected, 45 of which were of reasonable or good quality. Exercise therapy is effective for patients with knee osteoarthritis, sub-acute (6 to 12 weeks) and chronic (> or = 12 weeks) low back pain, cystic fibrosis, chronic obstructive pulmonary disease, and intermittent claudication. Furthermore, there are indications that exercise therapy is effective for patients with ankylosing spondylitis, hip osteoarthritis, Parkinson's disease, and for patients who have suffered a stroke. There is insufficient evidence to support or refute the effectiveness of exercise therapy for patients with neck pain, shoulder pain, repetitive strain injury, rheumatoid arthritis, asthma, and bronchiectasis. Exercise therapy is not effective for patients with acute low back pain. It is concluded that exercise therapy is effective for a wide range of chronic disorders.

Chronic Disease↗

PubMed1992

Detection of clinically significant prostate cancer by transrectal ultrasound-guided systematic biopsies.

Systematic biopsies are a useful, sensitive means to detect carcinoma of the prostate. However, multiple biopsies pose a risk for detecting clinically insignificant prostate cancer, that is those cancers less than 0.5 cc in volume, which occur in approximately 32% of all white men more than 50 years old. Systematic biopsies were positive for cancer in 442 of 816 patients and 60 (14%) demonstrated only a minute focus of cancer (3 mm. or less) in 1 of the 6 biopsy specimens. In 27 patients with these minute foci who underwent radical prostatectomy a wide range of cancer volumes was observed; 30% of these 27 cancers were less than 0.5 cc (15% less than 0.2 cc) and may not have required therapy. Thus, the overall risk of detecting an insignificant cancer is 4.0% with systematic biopsies. Performance of confirmatory biopsies in patients with a minute focus (3 mm. or less) of cancer on initial systematic biopsies resulted in cancers less than 0.5 cc being removed in only 1 of 10 radical prostatectomies (10%, none was less than 0.2 cc). Thus, with the addition of confirmatory biopsies the risk of detecting insignificant cancer is 1.4%. Conservative management is recommended for patients without significant cancer on repeat biopsies in whom initial biopsies have revealed only a minute focus of cancer in 1 of the biopsy cores. We believe that concern is also warranted for patients who have 3 mm. or less of cancer demonstrated by several nonsystematic biopsies directed at a suspicious hypoechoic lesion in whom the digital rectal examination is normal.

Antigens, Neoplasm↗

PubMed1992

Systematic transrectal ultrasound guided prostate biopsy after negative digitally directed prostate biopsy.

The diagnostic accuracy of digitally directed prostate biopsies was evaluated by performing systematic ultrasound guided biopsies on 44 patients who had previously had a negative prostate biopsy by systematic digitally directed technique. All 44 patients still had palpable abnormalities. Core biopsies (2 to 4) were obtained from each lateral lobe of the prostate with 2 additional cores directed at hypoechoic lesions. Only 4 of the 44 ultrasound directed biopsies (9.1%) were positive for cancer. These results confirm the postulate that random systematic digitally directed biopsy is highly accurate in making the diagnosis of prostate cancer. They also suggest that performing biopsies in a systematic pattern is more important than the method used to guide the biopsy needle.

Biopsy↗

PubMed1987

A systematic approach to the immunohistologic classification of lymphoproliferative disorders.

From the study of over 3,000 immunologically well characterized cases, we have developed a systematic approach for the immunohistologic evaluation of lymphoproliferative disorders (LPD). By using a basic screening panel of antibodies on fresh-frozen sections, LPD can be reliably immunophenotyped. Fourteen patterns of immunoreactivity have been identified that can be used in differential diagnosis and the establishment of the correct diagnosis. A comprehensive table has been developed for systematically recording for each case the results of immunohistologic evaluation of fresh-frozen sections. The information recorded is easily computerized for later studies of large numbers of cases. We also propose a strategy for the further characterization of rare cases that are not easily defined with the basic screening panel of immunologic reagents. The proposed systematic approach allows the rapid recognition of the predominant immunologic pattern, the determination of the differential diagnoses, and the establishment of the correct diagnosis. In many cases, the final diagnosis can be predicted on the basis of patterns of immunoreactivity in the fresh-frozen section prior to the evaluation of the paraffin-embedded histologic material. Moreover, this systematic approach may provide an additional method to classify LPD more precisely and reproducibly.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1994

Prospective evaluation of prostate-specific antigen density and systematic biopsies for early detection of prostatic carcinoma.

Significant controversies persist in regard to the need for systematic biopsies in patients with serum prostate-specific antigen (PSA) levels above 4 ng/mL (Hybritech assay), especially if they show no signs of prostatic cancer on digital rectal examination (DRE) or transrectal ultrasonography (TRUS). We evaluated 565 consecutive patients referred to us for prostatism, suspicious lesions on DRE, or an elevated serum PSA level. These patients do not represent a purely screened population. A detection rate of 38.4 percent was achieved by performing directed biopsies of suspicious lesions on DRE and/or TRUS, and systematic biopsies of all patients with serum PSA levels above 4 ng/mL. Among 142 patients with serum PSA between 4.1 and 10 ng/mL, but without suspicion for cancer on DRE and TRUS (DRE- TRUS-), a large number of patients (6.2) were subjected to systematic biopsies to detect one cancer. A receiver-operating characteristics curve for PSA density (PSAD) applied to this population confirmed that the best cut-off point for biopsies was a PSAD of 0.15, below which only two of twenty-three cancers would have been missed, sparing biopsies in 77 of 142 patients. A similar approach was applied to DRE- TRUS- patients with serum PSA levels above 10 ng/mL. The number of cancers in those with serum PSA between 10.1 and 14 ng/mL was too low to establish a PSAD cut-off point. In patients with serum PSA above 14 ng/mL, the best PSAD cut-off point for biopsies was 0.3, below which two of thirteen cancers would have been missed, sparing biopsies in 19 of 39 patients. We conclude that PSAD can safely reduce the number of patients subjected to systematic biopsies without significantly compromising cancer detection.

Adult↗

PubMed1997

Systematic sextant biopsies in the prediction of extracapsular extension at radical prostatectomy.

OBJECTIVES: To evaluate the clinical utility of transrectal ultrasound-guided systematic sextant needle biopsies in the prediction of extracapsular extension (ECE) at radical prostatectomy. METHODS: A retrospective analysis of 104 men who underwent systematic biopsy and radical prostatectomy at our institution was performed. All patients underwent preoperative staging by transrectal ultrasound and transrectal ultrasound-guided systematic sextant biopsy. The presence of pathologic ECE was correlated to the number of positive core biopsies on each side of the prostate by chi-square analysis. Sensitivity, specificity, positive and negative predictive values, and likelihood ratios (LRs) were calculated for both positive (two or three biopsies positive per side) and negative (no or one positive biopsy per side) test results. RESULTS: Forty-two (20.2%) of 208 sides demonstrated evidence of ECE at radical prostatectomy. Chi-square analysis demonstrated a significant correlation between the number of positive biopsies and the presence of ECE at radical prostatectomy (P = 0.001). Overall, the finding of multiple positive core biopsies (two or three per side) had predictive value with regard to the presence of ECE (sensitivity 62%, specificity 77%, positive predictive value 40%, negative predictive value 89%). The corresponding LRs were 2.5 for a positive and 0.5 for a negative test result. CONCLUSIONS: The probability of ECE at radical prostatectomy can be more accurately assessed preoperatively by the combined use of transrectal ultrasound and systematic sextant needle biopsies.

Aged↗

PubMed2001

Electronic portal image assisted reduction of systematic set-up errors in head and neck irradiation.

PURPOSE: To quantify systematic and random patient set-up errors in head and neck irradiation and to investigate the impact of an off-line correction protocol on the systematic errors. MATERIAL AND METHODS: Electronic portal images were obtained for 31 patients treated for primary supra-glottic larynx carcinoma who were immobilised using a polyvinyl chloride cast. The observed patient set-up errors were input to the shrinking action level (SAL) off-line decision protocol and appropriate set-up corrections were applied. To assess the impact of the protocol, the positioning accuracy without application of set-up corrections was reconstructed. RESULTS: The set-up errors obtained without set-up corrections (1 standard deviation (SD)=1.5-2mm for random and systematic errors) were comparable to those reported in other studies on similar fixation devices. On an average, six fractions per patient were imaged and the set-up of half the patients was changed due to the decision protocol. Most changes were detected during weekly check measurements, not during the first days of treatment. The application of the SAL protocol reduced the width of the distribution of systematic errors to 1mm (1 SD), as expected from simulations. A retrospective analysis showed that this accuracy should be attainable with only two measurements per patient using a different off-line correction protocol, which does not apply action levels. CONCLUSIONS: Off-line verification protocols can be particularly effective in head and neck patients due to the smallness of the random set-up errors. The excellent set-up reproducibility that can be achieved with such protocols enables accurate dose delivery in conformal treatments.

Algorithms↗

PubMed2000

Science in practice: can health care reform projects in central and eastern Europe be evaluated systematically?

Since the beginning of the 1990s, health care reform projects have taken place in many of the former Communist countries, but these projects are rarely evaluated systematically. Evaluation, however, is an important tool for increasing their rationality and continuity. The aim of this paper is to identify the difficulties in the efforts towards systematic evaluation and draw lessons for the future. For this aim, the requirements for a more rigorous, controlled evaluation are compared with our experiences of evaluating a health care reform project in the Slovak republic. From this comparison a number of discrepancies arise: it was difficult to set clear and realistic goals at the start of the project; the outcomes of the project could not always be measured, nor could 'the process' always be distinguished from the outcomes. Systematic evaluation was further hampered by an insufficient degree of structuration of the project, in advance and during the implementation, and by the absence of a tradition and infrastructure for data collection. On the basis of the experiences and relevant literature, recommendations for future evaluations are formulated. The main lesson is that, given the context, often it will not be possible to use an ambitious evaluation design, and concessions need to be made. At the same time, continuous efforts towards more systematic evaluation procedures should be made, but it is wise and more sustainable to do this in an incremental way.

Costs and Cost Analysis↗

PubMed1996

How to systematically review the medical literature.

In contrast to traditional narrative reviews, systematic reviews are true hypothesis-driven research. Meta-analysis is a form of systematic review in which studies are selected and combined by use of a predefined protocol to reduce bias and subjectivity. A sensitivity analysis shows how results vary through the use of different assumptions, tests, and criteria. The most valid synthesis of information occurs when published and unpublished materials are subjected to the same rigorous evaluation and when results are calculated with and without unpublished sources of data. A good systematic review captures the reader's attention through a skillful blend of numbers and narrative and qualifies for publication as original research in a peer-reviewed journal. Otolaryngologists have published systematic reviews of varying quality since 1990. This article should help improve the quality and validity of future efforts.

Bias↗

PubMed2003

Electronic searching of the literature for systematic reviews of screening and diagnostic tests for preterm birth.

BACKGROUND: Published systematic reviews on prediction of preterm birth have tended to focus on a limited number of tests and their search strategies have often been relatively simple. Evaluation of all available tests in a systemic review will require a broad search strategy. AIM: To describe a case study of electronic searching for a systematic review of accuracy studies evaluating all tests for predicting preterm birth. METHODS: The search strategy, developed to capture literatures concerning all the tests en-masse consisted of formulation of an appropriate combination of search terms, pilot searches to refine the search term combination, selection of relevant databases, and citation retrieval from the refined searches for selection of potentially relevant papers. Electronic searches were carried out on general bibliographic databases (Biosis, Embase, Medline, Pascal and Scisearch), specialised databases (Database of Abstracts of Reviews of Effectiveness, Medion, National Research Register, Cochrane Controlled Trial Register and Cochrane Database of Systematic Reviews). RESULTS: A total of 30076 citations were identified. Of these 8855 (29%) citations were duplications either within a database or across databases. Of the remaining 21221 citations, 3333 were considered potentially relevant to the review after assessment by two reviewers. These citations covered 19 different tests for predicting preterm birth. CONCLUSIONS: This case study suggests that with use of a concerted effort to organise and manage the electronic searching it is feasible to undertake broad searches for systematic reviews with multiple questions.

Databases, Bibliographic↗

PubMed2003

Systematic reviews with individual patient data meta-analysis to evaluate diagnostic tests.

Systematic literature reviews with meta-analysis of reported data in diagnostic research studies about the accuracy of tests assist clinicians in decision-making. However, there are limitations to this approach as the analysis of such data often does not allow reviewers to explore the diagnostic information gained from combinations of tests. In recent years meta-analysis of individual patient data (IPD) has been introduced as gold standard analytic approach in systematic reviews of randomised controlled trials. Application of IPD meta-analysis in systematic reviews of diagnostic tests can allow advanced analysis to decipher the real value of testing. In particular, the additional information provided by testing can be examined in light of the information already known from history and examination. To our knowledge there are no IPD meta-analyses in diagnostic research so far. This commentary aims to highlight the benefits of IPD meta-analysis in the diagnostic domain and demonstrates how strategies for diagnostic work-up of women with postmenopausal bleeding could be improved using this approach in systematic reviews of diagnostic research on accuracy of ultrasound and hysteroscopy.

Diagnostic Tests, Routine↗

PubMed2001

Multi-isocenter stereotactic radiotherapy: implications for target dose distributions of systematic and random localization errors.

PURPOSE: This investigation examined the effect of alignment and localization errors on dose distributions in stereotactic radiotherapy (SRT) with arced circular fields. In particular, it was desired to determine the effect of systematic and random localization errors on multi-isocenter treatments. METHODS AND MATERIALS: A research version of the FastPlan system from Surgical Navigation Technologies was used to generate a series of SRT plans of varying complexity. These plans were used to examine the influence of random setup errors by recalculating dose distributions with successive setup errors convolved into the off-axis ratio data tables used in the dose calculation. The influence of systematic errors was investigated by displacing isocenters from their planned positions. RESULTS: For single-isocenter plans, it is found that the influences of setup error are strongly dependent on the size of the target volume, with minimum doses decreasing most significantly with increasing random and systematic alignment error. For multi-isocenter plans, similar variations in target dose are encountered, with this result benefiting from the conventional method of prescribing to a lower isodose value for multi-isocenter treatments relative to single-isocenter treatments. CONCLUSIONS: It is recommended that the systematic errors associated with target localization in SRT be tracked via a thorough quality assurance program, and that random setup errors be minimized by use of a sufficiently robust relocation system. These errors should also be accounted for by incorporating corrections into the treatment planning algorithm or, alternatively, by inclusion of sufficient margins in target definition.

Algorithms↗

PubMed2000

Data collection instrument and procedure for systematic reviews in the Guide to Community Preventive Services. Task Force on Community Preventive Services.

INTRODUCTION: A standardized abstraction form and procedure was developed to provide consistency, reduce bias, and improve validity and reliability in the Guide to Community Preventive Services: Systematic Reviews and Evidence-Based Recommendations (the Guide). DATA COLLECTION INSTRUMENT: The content of the abstraction form was based on methodologies used in other systematic reviews; reporting standards established by major health and social science journals; the evaluation, statistical and meta-analytic literature; expert opinion and review; and pilot-testing. The form is used to classify and describe key characteristics of the intervention and evaluation (26 questions) and assess the quality of the study's execution (23 questions). Study procedures and results are collected and specific threats to the validity of the study are assessed across six categories (intervention and study descriptions, sampling, measurement, analysis, interpretation of results and other execution issues). DATA COLLECTION PROCEDURES: Each study is abstracted by two independent reviewers and reconciled by the chapter development team. Reviewers are trained and provided with feedback. DISCUSSION: What to abstract and how to summarize the data are discretionary choices that influence conclusions drawn on the quality of execution of the study and its effectiveness. The form balances flexibility for the evaluation of papers with different study designs and intervention types with the need to ask specific questions to maximize validity and reliability. It provides a structured format that researchers and others can use to review the content and quality of papers, conduct systematic reviews, or develop manuscripts. A systematic approach to developing and evaluating manuscripts will help to promote overall improvement of the scientific literature.

Data Collection↗

PubMed1999

Assessing "best evidence": issues in grading the quality of studies for systematic reviews.

BACKGROUND: Evidence-based medicine, clinical practice guidelines, quality and value of health services, and science-based decision making are becoming mainstays of the health care sector. As part of the evidence-based movement, systematic reviews of the literature on clinical questions are becoming increasingly common. Part of the structured approach to evaluating the literature involves assessing the quality of individual studies included in systematic reviews. REVIEW QUESTIONS: To clarify issues in this area, in 1998 the Agency for Health Care Policy and Research commissioned a small project to determine how its 12 Evidence-based Practice Centers were carrying out this part of their systematic reviews (called evidence reports). The number of potential checklists, scales, and similar tools for grading the methodology or the clinical relevance of individual reports is large; the reliability, the validity, the feasibility, and the utility of these tools are either unmeasured or quite variable. CONCLUSIONS: Numerous methodologic questions await definitive research and answers, but in the meantime teams developing authoritative systematic reviews can take certain steps to ensure that their approaches to grading the quality of articles meet applicable scientific standards. Clinicians, program administrators, and health policymakers can then be confident in the overall strength of the evidence and study conclusions.

Bias↗

PubMed2004

[Bibliometric analysis of systematic reviews in the Neonatal Cochrane Collaboration. Its role in evidence-based decision making in neonatology].

INTRODUCTION: The Cochrane Neonatal Collaborative Review Group (CNRG) is one of the most important collaborative review groups registered in the Cochrane Collaboration (CC) and provides a growing and readily accessible source of information to help neonatologists base their care on detailed, critical, and up-to-date reviews of the best available evidence. The objective of this article was to perform a bibliometric analysis (quantitative and qualitative) of the systematic reviews (SR) published in the Neonatal Cochrane Collaboration (NCC) and to identify the subject areas studied by the CNRG in which decision-making in clinical practice is based on the best available evidence. METHODS: We performed a bibliometric analysis of the Cochrane Database of Systematic Reviews in Neonatology, Issue 2, 2003 (n = 147 SR). The following variables were registered in each SR: subject area of the study, authors (number and country), dates (last review and update), characteristics of the clinical trials included (number and type), characteristics of included newborns (number and gestational age), reviewers' conclusions and potential conflicts of interest. RESULTS: The main subject areas of studies in the NCC were respiratory diseases (69 SR) and gastroenterology-nutrition (23 SR). Reviews were relatively scarce on some subjects that are very important in clinical practice in neonatology, such as cardiovascular diseases (10 SR), neurology (10 SR) and infectious diseases (6 SR). All the SR dealt with interventions for the treatment or prevention of diseases of the newborn infant (mainly preterm) and we found no reviews on diagnostic tests. Eighty-two per cent of the SR were signed by 2 or 3 authors, and we found four Bradford's zones of productivity. Ninety-two percent of the authors of SR were from four countries (Australia, United States, United Kingdom and Canada). Seventy-nine percent of all SR were published between 2000 and 2002, and 48 % have been updated. The median number of clinical trials per SR was 5 (range 0-30) and the median number of newborns included per SR was 559 (range 0-5448). Sixty percent of SR also included quasi-randomized clinical trials, and 67 % of SR included only preterm infants. In 54 % of the SR, the reviewers' conclusion was sufficient to infer probable effects (favorable or unfavorable) in clinical practice, and potential conflicts of interest were registered in 22 %. DISCUSSION: Although CC reviews are based on specific guidelines, errors and biases occur, suggesting the need to "review the reviews". The bibliometric analysis of the NCC shows that the quality of published SR varies, and the main conclusion is that almost half of the reviewers' conclusions are insufficient to infer probable effects in clinical practice. There is a lack of scientific evidence on many therapies in neonatology and, at the moment, the SR published in the NCC enable evidence-based decision making mainly in the subject area of respiratory diseases and gastroenterology-nutrition. Challenges for the future include the need for bigger and better clinical trials in this field (with long-term outcomes among surviving children), the preparation of systematic reviews on topics not yet covered, and keeping an increasing number of reviews up-to-date. Every decision in neonatology should be based on a systematic appraisal of the best evidence available in the context of the prevailing values and resources at our disposal.

Bibliometrics↗

PubMed2001

Factors affecting the utilization of systematic reviews. A study of public health decision makers.

OBJECTIVE: To determine the extent to which public health decision makers used five systematic reviews to make policy decisions, and to determine which characteristics predict their use. METHODS: This cross-sectional follow-up study of public health decision makers in Ontario collected primary data using a telephone survey and a short, self-administered organizational demographics questionnaire completed by the administrative assistant for each Medical Officer of Health. Independent variables included characteristics of the innovation, organization, environment, and individual. Data were entered into a computerized database developed specifically for this study, and multiple logistic regression analysis was conducted. RESULTS: The participation rate was very high, with 85% of public health units and 96% of available decision makers completing the survey. In addition, 63% of respondents stated they had used at least one of the systematic reviews in the previous 2 years to make a decision. The most important predictors of use were one's position, expecting to use a review in the future, and perceptions that the reviews were easy to use and that they overcame the barrier of limited critical appraisal skills. CONCLUSIONS: Utilization of the systematic reviews in Ontario was very high. The utilization rates found in this study were significantly higher than those reported in previous utilization studies. One's position was found to be the strongest predictor of use, identifying program managers and directors as the most appropriate audience for systematic reviews.

Cross-Sectional Studies↗