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PubMed2000

Quality assurance by systematic in vivo dosimetry: results on a large cohort of patients.

BACKGROUND: In vivo dosimetry is widely considered to be an important tool for quality assurance in external radiotherapy. INTRODUCTION: In this study we report on our experience over more than 4 years in systematic in vivo dosimetry with diodes. MATERIALS AND METHODS: From November '94 an in vivo entrance dosimetry check was performed for every new patient irradiated at one of our treatment units (Linac 6/100, 6 MV X-rays). Diodes were calibrated in terms of entrance dose; appropriate correction factors had been previously assessed (taking SSDs, field width, wedge, oblique incidence and blocking tray into account) and were individually applied to in vivo diode readings. The in vivo measured entrance dose was compared with the expected one, with a 5% action level; if a larger deviation was found, all treatment parameters were verified, and the in vivo dosimetry check was repeated. During the period November '94-May '99, 2824 measurements on 1433 patients were collected. RESULTS: Nine out of 1433 (0.63%) serious systematic errors (leading to a 5% or more on the delivered dose to the PTV) were detected by in vivo dosimetry; four out of nine would produce a 10% or more error if not detected. The rate of serious systematic errors detected by an independent check of treatment chart and MU calculation was found to be 1.5%, showing that less than 1/3 of the errors escapes this check. One hundred and twelve out of 1433 (7.8%) patients had more than one check: the rate of second checks was significantly higher for breast patients (31/250, 12.4%) against non-breast patients (81/1183, 6.8%, P=0.003). A number of patients demonstrated a persistent relatively large error even after two or more checks. For almost all patients the cause of the deviation was assessed; the most frequent cause was the difficulty in correctly positioning the patient and/or the diode. When analyzing the distribution of the deviations between measured and expected entrance doses (excluding first checks in the case of repetition of the in vivo dosimetry control) the mean deviation was 0.4% with a standard deviation equal to 3.0%. The rates of deviations larger than 5 and 7% were 9.9 and 2.6%, respectively. When considering the same data taking the average deviation in the case of opposed beams, the SD became 2.6% and the rates of deviations larger than 5 and 7%, respectively, 5.2 and 0.8%. When dividing the beams according to their orientation, significantly higher rates of large deviations (>5 and 7%) were found for oblique and posterior-anterior (PA) fields against lateral and anterior-posterior (AP) fields (P<0.05). Similarly, higher rates of large deviations were found for wedged fields against unwedged fields (P<0.03) and for blocked fields against unblocked fields (P<0.01). When dividing the data according to the anatomical district, accuracy was worse for breast (mean deviation 0.1%, 1 SD: 3.5%) and neck AP-PA fields (mean deviation 1%, 1 SD: 3,4%). Better accuracy was found for vertebrae (0.1%, 1 SD 2. 1%) and brain patients (-0.7%, 1 SD: 2.6%). During the considered period, in vivo dosimetry was also able to promptly detect a systematic error caused by a wrong resetting of the simulator height couch indicator, with a consequent error in the estimate of patient thickness of about 4 cm. CONCLUSIONS: In our experience, systematic in vivo dosimetry demonstrated to be a valid tool for quality assurance, both in detecting systematic errors which may escape the data transfer/MU calculation check and in giving an effective way of estimating the accuracy of treatment delivery.

Cohort Studies↗

PubMed1997

Cardiovascular morbidity and mortality among hypertensive patients in general practice: the evaluation of long-term systematic management.

OBJECTIVE: To evaluate systematic management of hypertensive patients with regard to cardiovascular morbidity and mortality. DESIGN: In a matched cohort study (1978-1993) the number of cardiovascular events among hypertensive patients under continuous systematic management in four general practices was compared with those occurring among hypertensive patients from eight "usual care" general practices. SUBJECTS: The source population consisted of employees of a major electronic company in Eindhoven with hypertension as determined at an occupational health examination. The index group (n = 120) consisted of employees who were participating in the systematic management program in four practices. A reference group of 120 patients was selected from hypertensive employees who were registered in eight "usual care" practices by matching for age, gender, fasting blood glucose, and frequency of occupational health examinations. The total cohort consisted primarily of males (78%), whose ages ranged from 50 to 65 years. MAIN OUTCOME MEASURES: Risk difference (RD) per 1000 patient years regarding left ventricular hypertrophy, heart failure, angina pectoris, myocardial infarction, transient ischaemic attack, stroke, peripheral arterial disease, nephropathy, retinopathy, cardiac death, death due to stroke, and non-cardiovascular death was determined. In addition to morbidity and mortality, systematic hypertension management was evaluated with regard to cardiovascular risk factors throughout a period of maximally 12 successive years (1978-1989). Morbidity and mortality data were derived from general practice records and archives; data on risk factors were assessed at bi-annual occupational health examinations. RESULTS: The total follow-up duration amounted to 2628 patient years. The mean follow-up duration in the index group was 10.8, in the reference group 11.1 years. As compared to the "usual care" reference group, the index group showed less left ventricular hypertrophy (RD 8.2, 95% CI 1.4-15.0), less angina pectoris (RD 9.7, 95% CI 2.0-17.4) and less peripheral arterial disease (RD 3.7, 95% CI 0.5-7.1). The difference in mean decrease in blood pressure during follow-up was 11.3 mmHg systolic and 5.9 mmHg diastolic in favour of the index group. No significant differences between the index and the reference groups were found with regard to the changes in other risk factors. CONCLUSION: In our study systematic management of hypertensive patients aged 50 to 65 in general practice was associated with a statistically significant, and clinically relevant decrease in cardiovascular morbidity and blood pressure. Although causality cannot be determined from this non-randomized cohort study, the findings do support the view that systematic management of hypertensive patients in general practice is valuable.

Cardiovascular Diseases↗

PubMed2006

Overview of systematic reviews on invasive treatment of stable coronary artery disease.

OBJECTIVES: The aim of the study was to evaluate the validity of the systematic reviews as a source of best evidence and to present and interpret the evidence of the systematic reviews on effectiveness of surgery and percutaneous interventions for stable coronary artery disease. METHODS: Electronic databases were searched without language restriction from January 1966 to March 2004. The databases used included the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, DARE, the Health Technology Assessment Database, MEDLINE(R), MEDLINE(R) In-Process & Other Non-Indexed Citations. We included systematic reviews of randomized clinical trials on patients with stable coronary heart disease undergoing percutaneous coronary intervention or coronary artery bypass surgery in comparison with medical treatment or a comparison between invasive techniques. At least one of the following outcomes had to be reported: death, myocardial infarction, angina pectoris, revascularization. The methodological quality was assessed using a modified version of the scale devised by Oxman and Guyatt (1991). A standardized data-extraction form was used. The method used to evaluate clinical relevance was carried out with updated method guidelines from the Cochrane Back Research Group. Quantitative synthesis of the effectiveness data is presented. RESULTS: We found nineteen systematic reviews. The median score of validity was 13 points (range, 6-17 points), with a maximum of 18 points. Coronary artery bypass surgery gives better relief of angina, and the need for repeated procedures is reduced after bypass surgery compared with percutaneous interventions. There is inconsistent evidence as to whether bypass surgery improves survival compared with percutaneous intervention. A smaller need for repeated procedures exists after bare metal stent and even more so after drug-eluting stent placement than after percutaneous intervention without stent placement. However, according to the current evidence, these treatment alternatives do not differ in terms of mortality or myocardial infarction. CONCLUSIONS: We found some high-quality systematic reviews. There was evidence on the potential of invasive treatments to provide symptomatic relief. Surgery seems to provide a longer-lasting effect than percutaneous interventions with bare metal stents or without stents. Evidence in favor of drug-eluting stents so far is based on short-term follow-up and mostly on patients with single-vessel disease.

Angioplasty, Balloon, Coronary↗

PubMed2003

The assessment of systematic reviews in dentistry.

The aim of this study was to assess the quality of systematic reviews of effectiveness of interventions in dentistry. The Database of Abstracts of Reviews of Effectiveness and the Cochrane Database of Systematic Reviews were searched to identify systematic reviews examining the effectiveness of interventions for oral, dental and craniofacial disorders and diseases. Sixty-five reviews were identified and assessed independently by two reviewers. The area most frequently evaluated within the reviews was pain relief/prevention (20/65, 31%) followed by caries and oral medicine. The quality assessment of the identified systematic reviews highlighted key areas where improvements could be made. One major weakness of the reviews was that the search strategies employed were not always adequate. Only 12 reviews (19%) demonstrated an attempt to identify all relevant studies. Other areas of weakness include the screening and quality assessment of primary studies, the pooling of data and examination of heterogeneity, and the interpretation of findings. This investigation shows that the quality of systematic reviews in dentistry could be improved. If future clinical decisions are to be based upon systematic reviews, it is imperative that the reviews address clinically relevant, focused questions and follow a 'transparent', well-designed protocol.

Databases, Bibliographic↗

PubMed2001

Evaluating the quality of systematic reviews in the emergency medicine literature.

STUDY OBJECTIVE: The objective of this study was to examine the scientific quality of systematic reviews published in 5 leading emergency medicine journals. METHODS: MEDLINE and EMBASE databases were electronically searched to identify published systematic reviews. Searches were only conducted in emergency medicine journals during the past 10 years; 4 of the journals were also hand searched. Potential reviews were assessed independently by 2 reviewers for inclusion. Data regarding methods were extracted from each review independently by 2 reviewers. All systematic reviews were retrieved and rated for quality by using the 10 questions from the overview quality assessment questionnaire. RESULTS: Twenty-nine reviews were identified from more than 100 citations. The overall scientific quality of the systematic reviews was low (mean score, 2.7; 95% confidence interval 2.1 to 3.2; maximum possible score, 7.0). Selection and publication biases were rarely addressed in this collection of reviews. For example, the search strategies were only identified in 9 (31%) reviews, whereas independent study selection (6 [21%]) and quality assessment of included studies (9 [31%]) were infrequently performed. Overall, the majority of reviews had extensive flaws, and only 3 (10%) had minimal flaws. CONCLUSION: The results of the study indicate that many of the systematic reviews published in the emergency medicine literature contain major flaws; reviews with poor methodology may limit the validity of reported results. Further efforts should be made to improve the design, reporting, and publication of systematic reviews in emergency medicine.

Emergency Medicine↗

PubMed2004

Adjustment of systematic microarray data biases.

MOTIVATION: Systematic differences due to experimental features of microarray experiments are present in most large microarray data sets. Many different experimental features can cause biases including different sources of RNA, different production lots of microarrays or different microarray platforms. These systematic effects present a substantial hurdle to the analysis of microarray data. RESULTS: We present here a new method for the identification and adjustment of systematic biases that are present within microarray data sets. Our approach is based on modern statistical discrimination methods and is shown to be very effective in removing systematic biases present in a previously published breast tumor cDNA microarray data set. The new method of 'Distance Weighted Discrimination (DWD)' is shown to be better than Support Vector Machines and Singular Value Decomposition for the adjustment of systematic microarray effects. In addition, it is shown to be of general use as a tool for the discrimination of systematic problems present in microarray data sets, including the merging of two breast tumor data sets completed on different microarray platforms. AVAILABILITY: Matlab software to perform DWD can be retrieved from https://genome.unc.edu/pubsup/dwd/

Algorithms↗

PubMed2003

Methodologic issues in systematic reviews and meta-analyses.

Systematic reviews of original research are increasing in number. Systematic reviews are distinct from narrative reviews because they address a specific clinical question, require a comprehensive literature search, use explicit selection criteria to identify relevant studies, assess the methodologic quality of included studies, explore differences among study results, and either qualitatively or quantitatively synthesize study results. Systematic reviews that quantitatively pool results of more than one study are called meta-analyses. Several organizations are collaboratively involved in producing high quality systematic reviews and meta-analyses. Familiarity with how to do a systematic review and meta-analysis will lead to greater skill in using this type of article. For clinicians, teachers, and investigators, systematic reviews and meta-analyses are useful sources of evidence.

Decision Making↗

PubMed2004

'When measurements mean action' decision models for portal image review to eliminate systematic set-up errors.

The aim of the present paper is to evaluate how the use of decision models in the review of portal images can eliminate systematic set-up errors during conformal therapy. Sixteen patients undergoing four-field irradiation of prostate cancer have had daily portal images obtained during the first two treatment weeks and weekly thereafter. The magnitude of random and systematic variations has been calculated by comparison of the portal image with the reference simulator images using the two-dimensional decision model embodied in the Hotelling's evaluation process (HEP). Random day-to-day set-up variation was small in this group of patients. Systematic errors were, however, common. In 15 of 16 patients, one or more errors of >2 mm were diagnosed at some stage during treatment. Sixteen of the 23 errors were between 2 and 4 mm. Although there were examples of oversensitivity of the HEP in three cases, and one instance of undersensitivity, the HEP proved highly sensitive to the small (2-4 mm) systematic errors that must be eliminated during high precision radiotherapy. The HEP has proven valuable in diagnosing very small (<4 mm) errors. When combined with the potential for rapid diagnosis of larger (>4 mm) systematic errors using one-dimensional decision models, HEP can eliminate the majority of systematic errors during the first 2 treatment weeks.

Aged↗

PubMed1997

Value of systematic transition zone biopsy in the detection of prostate cancer.

BACKGROUND: We evaluated routine transition zone biopsies for the detection of prostate cancer. METHODS: Systematic sextant transrectal biopsies, including 2 systematic transition zone biopsies (sextant biopsy group), were performed on 196 consecutive patients. Biopsies were based on indications from digital rectal examination and/or a serum PSA level greater than 4.0 ng/mL. During the same period, 21 patients with persistently elevated PSA levels and earlier negative systematic biopsies also had the sextant biopsy (re-biopsy group). The sextant biopsy group was compared with 124 cases in our previous cancer detection program who had systematic quadrant biopsies targeted to the peripheral zone (quadrant biopsy group). RESULTS: Between the sextant and quadrant biopsy groups, the difference in rate of cancer detection was not significant statistically. Of the sextant biopsy group, 64 (33%) demonstrated malignancy, including 9 (4.6%) with cancer found exclusively in the peripheral zone and 55 (28%) both in the peripheral and transition zones. No cancer was found exclusively in the transition zone. Of the re-biopsy group, all 4 cancers (19%) were detected in the transition zone, 2 of them exclusively in the transition zone. CONCLUSION: Routine transition zone biopsies did not increase the detection rate of prostate cancer. Systematic transition zone biopsies proved useful to the patients with persistently elevated PSA values and negative results in previous systematic peripheral zone biopsies.

Aged↗

PubMed2006

Two physiotherapists, one librarian and a systematic literature review: collaboration in action.

AIM: This paper explores the processes of collaboration between a librarian and two academic physiotherapists working on a systematic review jointly funded by the University of the West of England (UWE), Bristol, and the Royal National Hospital for Rheumatic Diseases (RNHRD), Bath, UK. The aim of this paper is to describe and evaluate some of the processes of collaboration between the three authors in their work in progress on a funded systematic literature review on the topic of hydrotherapy and pain. METHODS: The vehicle for describing and analysing these processes is a joint (National Health Service Trust and University) funded systematic literature review currently in progress on the topic of hydrotherapy and pain. RESULTS: Systematic review methodology is becoming increasingly complex and is rapidly developing its own research base. Librarian input is a key element in a successful systematic review. CONCLUSIONS: Systematic reviews play a critical role in informing healthcare delivery and research in the UK. The individual nature and inherent complexity of each review demands close collaboration between librarians, academics and clinicians. In addition to enhancing the reviews themselves, there are many other personal and institutional benefits of collaborative working. Consideration may need to be given to library staff structures and roles if these benefits are to be maximized and sustained.

Cooperative Behavior↗

PubMed2004

A process for systematically reviewing the literature: providing the research evidence for public health nursing interventions.

BACKGROUND: Several groups have outlined methodologies for systematic literature reviews of the effectiveness of interventions. The Effective Public Health Practice Project (EPHPP) began in 1998. Its mandate is to provide research evidence to guide and support the Ontario Ministry of Health in outlining minimum requirements for public health services in the province. Also, the project is expected to disseminate the results provincially, nationally, and internationally. Most of the reviews are relevant to public health nursing practice. AIMS: This article describes four issues related to the systematic literature reviews of the effectiveness of public health nursing interventions: (1) the process of systematically reviewing the literature, (2) the development of a quality assessment instrument, (3) the results of the EPHPP to date, and (4) some results of the dissemination strategies used. METHODS: The eight steps of the systematic review process including question formulation, searching and retrieving the literature, establishing relevance criteria, assessing studies for relevance, assessing relevant studies for methodological quality, data extraction and synthesis, writing the report, and dissemination are outlined. Also, the development and assessment of content and construct validity and intrarater reliability of the quality assessment questionnaire used in the process are described. RESULTS: More than 20 systematic reviews have been completed. Content validity was ascertained by the use of a number of experts to review the questionnaire during its development. Construct validity was demonstrated through comparisons with another highly rated instrument. Intrarater reliability was established using Cohen's Kappa. Dissemination strategies used appear to be effective in that professionals report being aware of the reviews and using them in program planning/policymaking decisions. CONCLUSIONS: The EPHPP has demonstrated the ability to adapt the most current methods of systematic literature reviews of effectiveness to questions related to public health nursing. Other positive outcomes from the process include the development of a critical mass of public health researchers and practitioners who can actively participate in the process, and the work on dissemination has been successful in attracting external funds. A program of research in this area is being developed.

Confounding Factors, Epidemiologic↗

PubMed2005

A new method of incorporating systematic uncertainties in intensity-modulated radiotherapy optimization.

Uncertainties in tumor position during intensity-modulated radiotherapy (IMRT) plan optimization are usually accounted for by adding margins to a clinical target volume (CTV), or additionally, to organs at risk (OAR). The former approach usually favors target coverage over OAR protection, whereas the latter does not account for correlation in target and OAR movement. We investigate a new approach to incorporate systematic errors in tumor and organ position. The method models a distribution of systematic errors due to setup error and organ motion with displaced replicas of volumes of interest, each representing the patient geometry for a possible systematic error, and maximizes a score function that counts the number of replicas meeting dose or biological constraints for both CTV and OAR. Dose constraints are implemented by logistic functions of Niemierko's generalized model of equivalent uniform dose (EUD). The method is applied to prostate and nasopharynx IMRT plans, in which CTV and OAR each consists of five replicas, one representing no error (the position in the planning CT) and the other four discrete systematic setup displacements in one dimension with equal probability. The resulting IMRT plans are compared with those from two other EUD-based optimizations: a standard planning target volume (PTV) approach consisting of a single replica of each OAR in the planned position and a single PTV encompassing all CTV replicas, and a PTV-PRV approach consisting of a single PTV and a single planning risk volume (PRV) for each OAR encompassing all replicas. When systematic error is present, multiple-replica optimization provides better critical organ protection while maintaining similar target coverage compared with the PTV approach, and provides better CTV-to-OAR therapeutic ratio compared with the PTV-PRV instances where there is substantial PTV-PRV overlap. The method can be used for other systematic errors due to organ motion and deformation.

Body Burden↗

PubMed2005

Global priority setting for Cochrane systematic reviews of health promotion and public health research.

BACKGROUND: Systematic reviews of health promotion and public health interventions are increasingly being conducted to assist public policy decision making. Many intra-country initiatives have been established to conduct systematic reviews in their relevant public health areas. The Cochrane Collaboration, an international organisation established to conduct and publish systematic reviews of healthcare interventions, is committed to high quality reviews that are regularly updated, published electronically, and meeting the needs of the consumers. AIMS: To identify global priorities for Cochrane systematic reviews of public health topics. METHODS: Systematic reviews of public health interventions were identified and mapped against global health risks. Global health organisations were engaged and nominated policy-urgent titles, evidence based selection criteria were applied to set priorities. RESULTS: 26 priority systematic review titles were identified, addressing interventions such as community building activities, pre-natal and early infancy psychosocial outcomes, and improving the nutrition status of refugee and displaced populations. DISCUSSION: The 26 priority titles provide an opportunity for potential reviewers and indeed, the Cochrane Collaboration as a whole, to address the previously unmet needs of global health policy and research agencies.

Evidence-Based Medicine↗

PubMed1999

The treatment of attention-deficit hyperactivity disorder: an annotated bibliography and critical appraisal of published systematic reviews and metaanalyses.

CONTEXT: The Agency for Health Care Policy and Research charged the McMaster Evidence-based Practice Center with conducting a comprehensive systematic review of the literature on the treatment of attention-deficit hyperactivity disorder (ADHD), with input from various groups of stakeholders. One strategy used to avoid duplication of work included a critical appraisal of existing systematic reviews and metaanalyses. OBJECTIVE: To identify and appraise published metaanalyses and systematic reviews on the treatment of ADHD and to produce an annotated bibliography. DATA SOURCES: Medline, Cumulative Index in Nursing and Allied Health (CINAHL), Healthstar, Psycinfo, and Embase were searched to September 1998; the Cochrane Database (1998 issue 3), selected Internet sites, and the files of investigators were also reviewed. STUDY SELECTION: Review articles described as systematic reviews or metaanalyses or including a Methods section were identified independently by 3 reviewers. DATA EXTRACTION: Two reviewers extracted, by consensus, relevant information on the name, methodological quality, ADHD-related aspects (comorbid disorders, family characteristics) of those reviews; data on the population, study setting, interventions, and outcomes evaluated by the reviews were also retrieved. RESULTS: Thirteen reviews, published from 1982 to 1998, were included. Eight included metaanalysis and 5 a qualitative review. Nonpharmacological treatments were mentioned in 6 reviews and combination therapies in 3. One review focused on the treatment of adults. Forty-seven drugs and 20 adverse effects were mentioned. Most reviews had major methodological flaws. CONCLUSIONS: Most published systematic reviews and metaanalyses on the treatment of ADHD have limited value for guiding clinical, policy, and research decisions. A rigorous, systematic review following established methodological criteria is warranted.

Attention Deficit Disorder with Hyperactivity↗

PubMed2004

Assessing harmful effects in systematic reviews.

BACKGROUND: Balanced decisions about health care interventions require reliable evidence on harms as well as benefits. Most systematic reviews focus on efficacy and randomised trials, for which the methodology is well established. Methods to systematically review harmful effects are less well developed and there are few sources of guidance for researchers. We present our own recent experience of conducting systematic reviews of harmful effects and make suggestions for future practice and further research. METHODS: We described and compared the methods used in three systematic reviews. Our evaluation focused on the review question, study designs and quality assessment. RESULTS: One review question focused on providing information on specific harmful effects to furnish an economic model, the other two addressed much broader questions. All three reviews included randomised and observational data, although each defined the inclusion criteria differently. Standard methods were used to assess study quality. Various practical problems were encountered in applying the study design inclusion criteria and assessing quality, mainly because of poor study design, inadequate reporting and the limitations of existing tools. All three reviews generated a large volume of work that did not yield much useful information for health care decision makers. The key areas for improvement we identified were focusing the review question and developing methods for quality assessment of studies of harmful effects. CONCLUSIONS: Systematic reviews of harmful effects are more likely to yield information pertinent to clinical decision-making if they address a focused question. This will enable clear decisions to be made about the type of research to include in the review. The methodology for assessing the quality of harmful effects data in systematic reviews requires further development.

Anticonvulsants↗

PubMed2005

Towards systematic reviews that inform health care management and policy-making.

OBJECTIVES: To identify ways to improve the usefulness of systematic reviews for health care managers and policy-makers that could then be evaluated prospectively. METHODS: We systematically reviewed studies of decision-making by health care managers and policy-makers, conducted interviews with a purposive sample of them in Canada and the United Kingdom (n = 29), and reviewed the websites of research funders, producers/purveyors of research, and journals that include them among their target audiences (n = 45). RESULTS: Our systematic review identified that factors such as interactions between researchers and health care policy-makers and timing/timeliness appear to increase the prospects for research use among policy-makers. Our interviews with health care managers and policy-makers suggest that they would benefit from having information that is relevant for decisions highlighted for them (e.g. contextual factors that affect a review's local applicability and information about the benefits, harms/risks and costs of interventions) and having reviews presented in a way that allows for rapid scanning for relevance and then graded entry (such as one page of take-home messages, a three-page executive summary and a 25-page report). Managers and policy-makers have mixed views about the helpfulness of recommendations. Our analysis of websites found that contextual factors were rarely highlighted, recommendations were often provided and graded entry formats were rarely used. CONCLUSIONS: Researchers could help to ensure that the future flow of systematic reviews will better inform health care management and policy-making by involving health care managers and policy-makers in their production and better highlighting information that is relevant for decisions. Research funders could help to ensure that the global stock of systematic reviews will better inform health care management and policy-making by supporting and evaluating local adaptation processes such as developing and making available online more user-friendly 'front ends' for potentially relevant systematic reviews.

Canada↗

PubMedDate not supplied

New strategies on molecular biology applied to microbial systematics.

Systematics is the study of diversity of the organisms and their relationships comprising classification, nomenclature and identification. The term classification or taxonomy means the arrangement of the organisms in groups (rate) and the nomenclature is the attribution of correct international scientific names to organisms and identification is the inclusion of unknown strains in groups derived from classification. Therefore, classification for a stable nomenclature and a perfect identification are required previously. The beginning of the new bacterial systematics era can be remembered by the introduction and application of new taxonomic concepts and techniques, from the 50's and 60's. Important progress were achieved using numerical taxonomy and molecular taxonomy. Molecular taxonomy, brought into effect after the emergence of the Molecular Biology resources, provided knowledge that comprises systematics of bacteria, in which occurs great evolutionary interest, or where is observed the necessity of eliminating any environmental interference. When you study the composition and disposition of nucleotides in certain portions of the genetic material, you study searching their genome, much less susceptible to environmental alterations than proteins, codified based on it. In the molecular taxonomy, you can research both DNA and RNA, and the main techniques that have been used in the systematics comprise the build of restriction maps, DNA-DNA hybridization, DNA-RNA hybridization, sequencing of DNA sequencing of sub-units 16S and 23S of rRNA, RAPD, RFLP, PFGE etc. Techniques such as base sequencing, though they are extremely sensible and greatly precise, are relatively onerous and impracticable to the great majority of the bacterial taxonomy laboratories. Several specialized techniques have been applied to taxonomic studies of microorganisms. In the last years, these have included preliminary electrophoretic analysis of soluble proteins and isoenzymes, and subsequently determination of deoxyribonucleic acid base composition and assessment of base sequence homology by means of DNA-RNA hybrid experiments beside others. These various techniques, as expected, have generally indicated a lack of taxonomic information in microbial systematics. There are numberless techniques and methodologies that make bacteria identification and classification study possible, part of them described here, allowing establish different degrees of subspecific and interspecific similarity through phenetic-genetic polymorphism analysis. However, was pointed out the necessity of using more than one technique for better establish similarity degrees within microorganisms. Obtaining data resulting from application of a sole technique isolatedly may not provide significant information from Bacterial Systematics viewpoint.

Bacteria↗

PubMed2006

A comparison of cluster and systematic sampling methods for measuring crude mortality.

OBJECTIVE: To compare the results of two different survey sampling techniques (cluster and systematic) used to measure retrospective mortality on the same population at about the same time. METHODS: Immediately following a cluster survey to assess mortality retrospectively in a town in North Darfur, Sudan in 2005, we conducted a systematic survey on the same population and again measured mortality retrospectively. This was only possible because the geographical layout of the town, and the availability of a good previous estimate of the population size and distribution, were conducive to the systematic survey design. RESULTS: Both the cluster and the systematic survey methods gave similar results below the emergency threshold for crude mortality (0.80 versus 0.77 per 10,000/day, respectively). The results for mortality in children under 5 years old (U5MR) were different (1.16 versus 0.71 per 10,000/day), although this difference was not statistically significant. The 95% confidence intervals were wider in each case for the cluster survey, especially for the U5MR (0.15-2.18 for the cluster versus 0.09-1.33 for the systematic survey). CONCLUSION: Both methods gave similar age and sex distributions. The systematic survey, however, allowed for an estimate of the town's population size, and a smaller sample could have been used. This study was conducted in a purely operational, rather than a research context. A research study into alternative methods for measuring retrospective mortality in areas with mortality significantly above the emergency threshold is needed, and is planned for 2006.

Adolescent↗