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PubMed2005

Multiple, linked human immunodeficiency virus type 1 drug resistance mutations in treatment-experienced patients are missed by standard genotype analysis.

To investigate the extent to which drug resistance mutations are missed by standard genotyping methods, we analyzed the same plasma samples from 26 patients with suspected multidrug-resistant human immunodeficiency virus type 1 by using a newly developed single-genome sequencing technique and compared it to standard genotype analysis. Plasma samples were obtained from patients with prior exposure to at least two antiretroviral drug classes and who were on a failing antiretroviral regimen. Standard genotypes were obtained by reverse transcriptase (RT)-PCR and sequencing of the bulk PCR product. For single-genome sequencing, cDNA derived from plasma RNA was serially diluted to 1 copy per reaction, and a region encompassing p6, protease, and a portion of RT was amplified and sequenced. Sequences from 15 to 46 single viral genomes were obtained from each plasma sample. Drug resistance mutations identified by single-genome sequencing were not detected by standard genotype analysis in 24 of the 26 patients studied. Mutations present in less than 10% of single genomes were almost never detected in standard genotypes (1 of 86). Similarly, mutations present in 10 to 35% of single genomes were detected only 25% of the time in standard genotypes. For example, in one patient, 10 mutations identified by single-genome sequencing and conferring resistance to protease inhibitors (PIs), nucleoside analog reverse transcriptase inhibitors, and nonnucleoside reverse transcriptase inhibitors (NNRTIs) were not detected by standard genotyping methods. Each of these mutations was present in 5 to 20% of the 20 genomes analyzed; 15% of the genomes in this sample contained linked PI mutations, none of which were present in the standard genotype. In another patient sample, 33% of genomes contained five linked NNRTI resistance mutations, none of which were detected by standard genotype analysis. These findings illustrate the inadequacy of the standard genotype for detecting low-frequency drug resistance mutations. In addition to having greater sensitivity, single-genome sequencing identifies linked mutations that confer high-level drug resistance. Such linkage cannot be detected by standard genotype analysis.

Anti-HIV Agents↗

PubMed1995

Comparison of standards for assessing patients' capacities to make treatment decisions.

OBJECTIVE: This study investigated the proportion of psychiatric and medical patients who are impaired in their decision-making abilities in relation to each of several major legal standards for determining competence to consent to treatment. METHOD: The subjects were hospitalized patients with diagnoses of schizophrenia (N = 75), major depression (N = 92), and ischemic heart disease (N = 82) and equal numbers of community comparison subjects matched on age, race, gender, education, and occupation. Three instruments measuring abilities related to the legal standards for competence were administered to each group. Impaired functioning was defined as scores two standard deviations below the means for all subjects combined or lower. RESULTS: Although similar percentages of subjects with impaired performance were found for each of the measures, different groups of patients were identified as impaired depending on the measure used. The proportion of patients identified as impaired increased when compound standards were used, i.e., when impairment was defined as poor performance on any of two or three measures. Despite previous suggestions that the legal standards might form a hierarchy of rigorousness, the data did not support this hypothesis. CONCLUSIONS: Choice of standards for determining competence, including compound standards, will affect the identity and proportion of patients classified as impaired. Clinicians should be aware of applicable standards in their jurisdictions. Use of compound standards requires independent evaluation of performance on abilities related to each relevant standard, because standards do not appear to be hierarchical. Policies relating to the characterization of persons as incompetent must be fashioned with caution.

Comprehension↗

PubMed1989

Occupational exposure standards for pharmaceutical agents.

Compared to the wide range of occupational exposure standards available in different countries for industrial chemicals, there are only a few similar standards set for pharmaceutical agents. These substances produce physiological effects in relatively small doses, and there are documented ill-effects from worker exposures, hence the need for such standards. There are different approaches to setting occupational exposure standards for pharmaceutical agents. One derived from the nuisance dust standard may be used, although that may not be wholly appropriate. An approach has been previously suggested for ethinyl estradiol, and this requires the minimal effective dose, a safety factor, an assumption of equal absorption by inhalation as by the oral route, and the volume of air inhaled over an 8-hour day. Toxicological and pharmacological information for zeranol, an animal growth promoter with estrogenic properties, is used with these criteria to obtain an airborne standard. It can be shown that depending on what assumptions are made, there can be more than a tenfold difference in standards reached. There are other difficulties with setting standards for pharmaceutical agents, depending on the group of substances involved. Airborne standards are useful for medicines that are inhaled. A "skin" notation may be needed for those that can be absorbed via the dermal route. Biological standards should also be considered. Provision of standards for pharmaceutical agents will go some way towards protecting exposed pharmaceutical workers.

Air Pollutants, Occupational↗

PubMed2006

Angled forceps used for transbronchial biopsy in which standard forceps are difficult to manipulate: a comparative study.

OBJECTIVES: To evaluate the usefulness of the Sasada transbronchial angled forceps (STAF) in patients with peripheral pulmonary lesions (PPLs), which are difficult to manipulate with standard forceps. METHODS: We have invented the STAF, a forceps with an angled tip. One hundred ten patients with PPLs that were difficult to reach with standard forceps were retrospectively evaluated. The patients first underwent bronchoscopy with a standard forceps and then with the STAF. The specimens obtained with standard forceps and those obtained with STAF were separately fixed and analyzed histologically. We compared the histologic diagnosis of the specimens obtained by STAF with that obtained by the specimens obtained with standard forceps. Statistical significance was calculated with the McNemar chi(2) statistic. RESULTS: The diagnostic yield of all lesions from the specimens obtained with STAF (86 of 110 lesions; 78.2%) was significantly higher than that of lesions from the specimens obtained with standard forceps (43 of 110 lesions; 39.1%; p < 0.001). Among malignant lesions, the yield obtained with STAF (60 of 72 lesions; 83.3%) was significantly higher than that obtained with standard forceps (32 of 72 lesions; 44.4%; p < 0.001). Among benign lesions, the yield obtained with STAF (26 of 38 lesions; 68.4%) was also significantly higher than that obtained with standard forceps (11 of 38 lesions; 28.9%; p < 0.001). Among the different lesion areas, the right upper lobe plus the left upper division gave the greatest difference in yield (STAF, 46 of 60 lesions; 76.7%; standard forceps, 22 of 60 lesions; 36.7%; p < 0.001). Among the different size ranges, the diagnostic yields obtained with STAF were significantly higher than that obtained with standard forceps except for the size range of < or = 10 mm. There were two complications, pneumothorax and bronchial bleeding, both of which were controlled easily. CONCLUSIONS: The STAF was shown to be useful for obtaining specimens that were sufficient for histologic diagnosis from PPLs that were difficult to manipulate with standard forceps.

Adenocarcinoma↗

PubMed1976

The first international standard for human urinary FSH and for human urinary LH (ICSH), for bioassay.

This paper describes the preparation and nature of the First International Standard for Human Urinary Follicle Stimulating Hormone and for Human Urinary Luteinizing Hormone, for Bioassay, and of two batches of working standard which were prepared from the same material. A collaborative study of these materials was carried out by six laboratories in six different countries. The FSH and LH activities of the Standard were assayed in terms of those of the Second International Reference Preparation of Human Menopausal Gonadotrophins, Urinary, for Bioassay, which it replaces. The results from 20 valid FSH assays and 30 valid LH assays (using four different methods) obtained in this way gave a weighted combined potency estimate for FSH of 53.7 IU, with 95 % fiducial limits of 47.2-61.1 IU, and for LH of 46.2 IU, with 95 % fiducial limits of 43.3-49.3 IU. Accelerated degradation studies of the Standard stored at elevated temperatures suggested that the stability of both FSH and LH activities under normal storage conditions would be satisfactory. The FSH and LH activities of the two batches of working standard (WS-A and WS-B) were compared with those of the Standard and were not found to differ significantly, except for the LH activity of WS-B which appeared to be slightly higher than that of the Standard. Accelerated degradation studies did not show any significant differences in stability between the Standard and batches of working standards. On the basis of these results the Standard has been established by WHO and allocated a potency for FSH of 54 IU per ampoule and for LH 46 IU per ampoule. The International Units for FSH, Human Urinary, for Bioassay and for LH (ICSH), Human Urinary, for Bioassay are thus defined as the activities contained in 0.1138 mg and 0.13369 mg of the International Standard, respectively.

Biological Assay↗

PubMed2005

Comparing the utility of a standard pediatric resuscitation cart with a pediatric resuscitation cart based on the Broselow tape: a randomized, controlled, crossover trial involving simulated resuscitation scenarios.

BACKGROUND: Access to resuscitation equipment is a critical component in delivering optimal care in pediatric arrest situations. Historically, children's hospitals and clinics have used a standard pediatric resuscitation cart ("standard cart") in which drawers are organized by intervention (eg, intubation module, intravenous module), requiring multiple drawers to be opened during a code. Many emergency departments, however, use a pediatric resuscitation cart based on the Broselow tape ("Broselow cart") in which each drawer is color coded and organized by patient length and weight ranges; each drawer contains all necessary equipment for resuscitation of a patient in that specific length/weight range. A literature review has revealed no studies examining the utility of either cart. OBJECTIVES: To compare which resuscitation cart organization (standard versus Broselow) allows for faster access to equipment, more accurate selection of appropriately sized equipment, and better user satisfaction. Methodology. We performed a prospective, randomized, controlled, crossover trial in which 21 pediatric health care providers were assigned the role of obtaining the appropriate equipment during 2 standardized, simulated codes alternately using either a standard or Broselow cart. Time to and accuracy of the selection of appropriate medical equipment along with posttesting satisfaction were measured. All simulations were performed in the Center for Advanced Pediatric Education at Stanford University Medical Center (Stanford, CA), a training facility designed to replicate the real medical environment with the technology to allow for videotaping of scenarios. RESULTS: Of the 21 subjects, 62% found the Broselow cart "easy" or "very easy" to use versus 33% for the standard cart. Of the 21 subjects, 67% preferred the Broselow cart, 10% preferred the standard cart, and 23% indicated no preference. Intubation supplies and nasogastric tubes were found significantly faster when using the Broselow cart (mean time: 29.1 and 20 seconds, respectively) versus the standard cart (mean time: 38.7 and 38.2 seconds, respectively). Correct equipment was provided a statistically significant 99% of the time with the Broselow cart versus 83% of the time with the standard cart. Ten percent of the subjects had prior experience with the Broselow cart versus 62% having experience with the standard cart. CONCLUSIONS: Despite less prior experience with the Broselow cart, subjects in this study found it easier to use and preferred it over the standard cart. In addition, subjects located intubation equipment and nasogastric tubes significantly faster when using the Broselow cart, and correct equipment was provided significantly more often with the Broselow cart. These data suggest that sites caring for pediatric patients should consider modeling their resuscitation carts after the Broselow cart to enhance provider confidence and patient safety.

Cardiopulmonary Resuscitation↗

PubMedDate not supplied

The SGML standardization framework and the introduction of XML.

Extensible Markup Language (XML) is on its way to becoming a global standard for the representation, exchange, and presentation of information on the World Wide Web (WWW). More than that, XML is creating a standardization framework, in terms of an open network of meta-standards and mediators that allows for the definition of further conventions and agreements in specific business domains. Such an approach is particularly needed in the healthcare domain; XML promises to especially suit the particularities of patient records and their lifelong storage, retrieval, and exchange. At a time when change rather than steadiness is becoming the faithful feature of our society, standardization frameworks which support a diversified growth of specifications that are appropriate to the actual needs of the users are becoming more and more important; and efforts should be made to encourage this new attempt at standardization to grow in a fruitful direction. Thus, the introduction of XML reflects a standardization process which is neither exclusively based on an acknowledged standardization authority, nor a pure market standard. Instead, a consortium of companies, academic institutions, and public bodies has agreed on a common recommendation based on an existing standardization framework. The consortium's process of agreeing to a standardization framework will doubtlessly be successful in the case of XML, and it is suggested that it should be considered as a generic model for standardization processes in the future.

Cohort Studies↗

PubMed2001

[Standards, options and recommendations for blood tumor markers in thyroid cancers].

CONTEXT: The "Standards, Options and Recommendations" (SOR) project, started in 1993, is a collaboration between the Federation of the French Cancer Centers (FNCLCC), the 20 French Cancer Centers and specialists from French Public Universities, General Hospitals and Private Clinics. The main objective is the development of clinical practice guidelines to improve the quality of health care and outcome for cancer patients. The methodology is based on literature review and critical appraisal by a multidisciplinary group of experts, with feedback from specialists in cancer care delivery. OBJECTIVES: To define, according to the definitions of the Standards, Options and Recommendations project, the characteristics of the main tumor markers in thyroid cancer and the potential role of these markers in the management of patients with this malignancy. METHODS: Data were identified by searching Medline and the personal reference lists of members of the expert groups. Once the guidelines were defined, the document was submitted for review to 55 independent reviewers, and to the medical committees of the 20 French Cancer Centers. RESULTS: The main recommendations are: 1) Thyroglobulin is a serum tumor marker for the monitoring of operated thyroid differentiated neoplasms (standard). 2) It is essential to know if the patient is under TSH stimulation or under thyroid suppression therapy to interpret thyroglobulin results (standard). 3) Thyroglobulin assay must be performed regularly during the monitoring of differentiated thyroid neoplasms (standard, level of evidence B2), should be coupled with the measurement of anti-thyroglobulin antibodies concentration using a sensitive method (standard, level of evidence B2). 4) Thyroglobulin assay should not be performed to detect or diagnose differentiated thyroid neoplasms (standard, level of evidence B2). 5) The methods used to assay thyroglobulin must have a limit of detection lower than 3 mug.l- 1 (standard, expert agreement). 6) Calcitonin is a marker for medullary thyroid cancer (standard). 7) Its assay, associated with RET gene study if indicated, enables medullary thyroid cancer to be diagnosed. 8) The pentagastrin test is essential to diagnose familial forms of medullary thyroid cancer. 9) All analyses for each patient must be performed in the same laboratory, using the same technique (standard, expert agreement). 10) Calcitonin and carcinoembryonic-antigen are serum markers for the monitoring of medullary thyroid cancer and allow the detection of recurrent disease (standard).

Antibodies, Neoplasm↗

PubMed2002

Comparison of hand assisted and standard laparoscopic radical nephroureterectomy for the management of localized transitional cell carcinoma.

PURPOSE: Hand assisted laparoscopy affords the surgeon tactile sensation and blunt dissection, which are currently limited using the standard laparoscopic technique. Therefore, we compared standard and hand assisted laparoscopic radical nephroureterectomy for localized upper tract transitional cell carcinoma. MATERIALS AND METHODS: The medical records of 27 patients who underwent standard (11) or hand assisted (16) laparoscopic radical nephroureterectomy between April 1998 and January 2001 were retrospectively reviewed. The parameters of efficacy, efficiency, safety and convalescence were compared. RESULTS: Mean patient age was 64 and 66 years (p = 0.72) in the standard and hand assisted groups, and the mean American Society of Anesthesiologists score was 2.5 and 2.7 (p = 0.64), respectively. All standard and 15 of the 16 hand assisted (94%) procedures were successfully completed via laparoscopy. Total operative time was more than 1 hour shorter for hand assisted than for laparoscopic radical nephroureterectomy (4.9 versus 6.1 hours, p = 0.055). Mean estimated blood loss was similar in the standard and hand assisted groups (190 and 201 ml., p = 0.78). In each group 1 patient required blood transfusion. Mean specimen weight was significantly higher in hand assisted cases (576 versus 335 gm., p = 0.036). Mean time to oral intake was similar in patients who underwent standard and hand assisted laparoscopic radical nephroureterectomy (13 and 20 hours, respectively, p = 0.45). The mean analgesic requirement was also similar (29 and 33 mg. morphine sulfate, respectively, p = 0.83). Mean hospital stay in uncomplicated cases was similar for standard and hand assisted surgery (2.9 and 2.5 days, respectively). Overall hospital stay in the 2 cohorts was also similar (3.3 and 4.5 days, respectively, p = 0.59). Four patients per group experienced postoperative complications. There were no deaths in the standard group but 1 patient (6%) in the hand assisted group died postoperatively. Mean time to partial and complete convalescence in the standard and hand assisted groups was 2.4 and 5.2, and 3.5 and 8.0 weeks, while mean followup was 27.4 and 9.6 months, respectively. CONCLUSIONS: Compared with standard laparoscopy hand assisted laparoscopy decreases operative time without significantly altering short-term parameters of convalescence. However, long-term convalescence after hand assisted laparoscopic radical nephroureterectomy is 1 to 3 weeks longer (p = 0.27). Longer followup in the hand assisted cohort is necessary to determine whether there are any differences in the 2 methods in regard to cancer control.

Aged↗

PubMed1996

[Development of standards for quality management in interventional cardiology].

Standardization is one of the fundamental methods for quality management. Standards describe first requirements for adequate delivery of diagnostic and therapeutic services (e.g. in the format of guidelines and protocols), second they define core data sets for documentation of real clinical outcome and of process and structure quality or third they define normal values (standards in the strict sense) or thresholds for critical parameters. This standardization is increasingly performed by the professional societies in international collaboration. We report on the parallel development of methodology. Presently standards for documentation and guidelines are being developed for the areas of cardiac interventional and surgical therapy. Three main methods are described. First, the common approach to guideline definition becomes more formalized as exemplified by the consensus approaches of the RAND group and of physicians in The Netherlands. Second, the definition of core data sets for quality assurance is increasingly based on the statistical evaluation of large interventional databases with the goal of developing predictive models of outcome. Since some of these methods are not yet fully reliable, it is still necessary to combine the results of predictive modelling with consensus on clinical practice. Figure 1 describes one of these approaches to data standards definition. These methods are currently developed within the new Cardiovascular Data Standards Initiative of the American College of Cardiology (ACC) that is open for international collaboration. Figure 2 describes a parallel approach for standardization of digital image communication in angiocardiography. As shown in Figure 3, these data set standards and imaging standards will be applied not only in quality assurance, but also in shared care. Third, the PRESTIGE project of the European Commission is developing computerized tools that support terminology support, guideline authoring, guideline dissemination and protocol-directed care. We show that the elements described can be put to use within the unifying framework depicted in Figure 4. This guideline approach that is fully integrated into daily care delivery provides the physician with instant feedback from the guideline and, in addition, with periodic quality reports based on a comparison of the local clinical reality with the recommendations from the guideline. In our extended concept, these deviations are in addition symmetrically used to trigger, where necessary, the process of evaluation of the guideline. The often poor acceptance of guidelines should be improved both by integrating them into daily practice and by providing a feedback to the guideline authoring committee. We conclude that standardization activities are now entering into a new era due to increased involvement of physicians, international collaboration, integrated approaches to quality management, and improved computerized tools.

Angioplasty, Balloon, Coronary↗

PubMed2005

Multielement trace determination in SiC powders: assessment of interlaboratory comparisons aimed at the validation and standardization of analytical procedures with direct solid sampling based on ETV ICP OES and DC arc OES.

The members of the committee NMP 264 "Chemical analysis of non-oxidic raw and basic materials" of the German Standards Institute (DIN) have organized two interlaboratory comparisons for multielement determination of trace elements in silicon carbide (SiC) powders via direct solid sampling methods. One of the interlaboratory comparisons was based on the application of inductively coupled plasma optical emission spectrometry with electrothermal vaporization (ETV ICP OES), and the other on the application of optical emission spectrometry with direct current arc (DC arc OES). The interlaboratory comparisons were organized and performed in the framework of the development of two standards related to "the determination of mass fractions of metallic impurities in powders and grain sizes of ceramic raw and basic materials" by both methods. SiC powders were used as typical examples of this category of material. The aim of the interlaboratory comparisons was to determine the repeatability and reproducibility of both analytical methods to be standardized. This was an important contribution to the practical applicability of both draft standards. Eight laboratories participated in the interlaboratory comparison with ETV ICP OES and nine in the interlaboratory comparison with DC arc OES. Ten analytes were investigated by ETV ICP OES and eleven by DC arc OES. Six different SiC powders were used for the calibration. The mass fractions of their relevant trace elements were determined after wet chemical digestion. All participants followed the analytical requirements described in the draft standards. In the calculation process, three of the calibration materials were used successively as analytical samples. This was managed in the following manner: the material that had just been used as the analytical sample was excluded from the calibration, so the five other materials were used to establish the calibration plot. The results from the interlaboratory comparisons were summarized and used to determine the repeatability and the reproducibility (expressed as standard deviations) of both methods. The calculation was carried out according to the related standard. The results are specified and discussed in this paper, as are the optimized analytical conditions determined and used by the authors of this paper. For both methods, the repeatability relative standard deviations were <25%, usually ~10%, and the reproducibility relative standard deviations were <35%, usually ~15%. These results were regarded as satifactory for both methods intended for rapid analysis of materials for which decomposition is difficult and time-consuming. Also described are some results from an interlaboratory comparison used to certify one of the materials that had been previously used for validation in both interlaboratory comparisons. Thirty laboratories (from eight countries) participated in this interlaboratory comparison for certification. As examples, accepted results are shown from laboratories that used ETV ICP OES or DC arc OES and had performed calibrations by using solutions or oxides, respectively. The certified mass fractions of the certified reference materials were also compared with the mass fractions determined in the interlaboratory comparisons performed within the framework of method standardization. Good agreement was found for most of the analytes.

Calibration↗

PubMed1993

Thrombin treated plasma employed as a standard for determination of soluble fibrin.

The Coa-set Fibrin Monomer test (CFM-test) is a quantitative method for determination of soluble fibrin in plasma. The fibrin standard of the CFM-test is produced by bathroxobin conversion of purified fibrinogen to fibrin. Plasma treated with minute amounts of thrombin may be considered as a more physiological way of preparing fibrin monomers. Therefore, we have employed such thrombin treated plasma (TTP) as an alternative fibrin standard for the CFM-test. The fibrin concentration of the TTP was determined indirectly by quantitation of released fibrinopeptide A. The TTP was stable during freezing, thawing and storage for 3 months at -70 degrees C. The standard curve obtained using TTP as a standard was linear in the range of 0-275 nmol/l fibrin in plasma, but the slope of the line was less steep than the original standard curve. This difference was probably due to the greater plasminogen activating effect of bathroxobin digested fibrinogen compared to soluble fibrin generated in plasma by thrombin, as observed in a previous study. Because of the less steep slope of the alternative standard curve, fibrin levels in plasma samples from 20 healthy volunteers and 25 patients were found to be higher employing TTP as a standard. Preparation of a fibrin standard by incubation of plasma with minute amounts of thrombin will to some extent mimic the process of fibrin generation in vivo. Since we have found a satisfactory stability of such a standard during freezing, thawing and storage, we think the TTP standard might be useful for quantitation of soluble fibrin in plasma.

Blood Preservation↗

PubMed1991

The calibration of 35S or 32P with 14C-labeled brain paste or 14C-plastic standards for quantitative autoradiography using LKB Ultrofilm or Amersham Hyperfilm.

The relationship between 14C-labeled brain paste or plastic standards and 35S- or 32P-labeled brain paste was characterized with quantitative autoradiography. Film was exposed to both sets of 14C-labeled standards and 35S- and 32P-labeled standards for 15-148 h and the film was analyzed with computer densitometry. Subsequently, the tissue pastes were scraped from the slides, dissolved in tissue solubilizer and radioactivity determined by scintillation spectroscopy. A linear relationship was observed between the plastic and brain paste 14C standards as well as between both sets of 14C-labeled standards and 35S-labeled brain paste standards. The 32P-labeled standards demonstrated a poor linear relationship with the 14C-labeled standards and greater variability in the autoradiographic estimates than was seen with 35S or 14C. Results were similar for both Ultrofilm and Hyperfilm with all the radioisotopes. These findings demonstrate a simple linear relationship between plastic and brain paste 14C-labeled standards and between either 14C-labeled standards and 35S-labeled brain paste for use in quantitative autoradiography.

Animals↗

PubMed1988

The value and hazards of standardization in clinical epidemiologic research.

The statistical standardization of rates produces a single summary value that converts crude rates of occurrence into "standardized" rates that are adjusted for differences in the composition of compared populations. Although the process is well described in the epidemiologic literature and is regularly applied in comparisons of large populations, many investigators are not familiar with three important hazards that are magnified for the smaller groups studied in clinical epidemiologic research. This report contains a new "symmetrical" outline of the direct and indirect standardization processes, and an illustration of three pragmatic hazards: (1) Because the direct standardizing factor uses the observed stratum-specific rates, and because any stratum-specific rates that depend on small denominators may be misleading or unstable, the indirect method is preferred when the observed strata have small denominators. (2) Both the direct and indirect standardizing methods are highly vulnerable both to the choice of reference population and to the boundaries chosen when strata are demarcated or consolidated. The standardized rates can be altered dramatically according to differences in the stratum proportions of the reference population, or to distinctions produced when standardizing strata are consolidated. (3) If the stratum-specific rates and stratum proportions have different patterns of variation across the strata of the compared groups, the use of a single summary value--no matter what method of standardization is applied--may obscure cogent patterns of variation and significant differences in the stratum-specific rates. These hazards can be overcome if the studied group and the reference population are carefully compared for inconsistent variations in the stratum-specific rates and proportions before any standardizing procedure is applied. In many instances, the best approach may be to compare the unaltered stratum-specific rates, without standardization.

Adult↗

PubMed2003

Analysis of natural gas: the necessity of multiple standards for calibration.

The importance of natural gas as an international trading commodity and the cost to consumers has made the accuracy of determinations for the components of natural gas very important. Pricing of natural gas is based on the heating value of the gas determined from either calorimetry measurements or calculations based on individual component concentrations determined by gas chromatography (GC). Due to the expense of accurate calibration standards, many analysts and laboratories will use a single calibration standard to perform natural gas determinations. Therefore, the purpose of this study was to determine whether an analyst could accurately measure the components of natural gas, in particular methane, using a single standard, or whether a suite of standards is necessary to calibrate the analytical instrument. A suite of eight gravimetric primary standards was prepared covering a concentration range for methane of 64-94 mol%, with uncertainties of +/-0.05% relative (95% confidence interval). These natural gas primary standards also contained nitrogen, carbon dioxide, ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, and n-hexane with varying concentrations from 0.02 to 14%. A single analytical method was used in which only the amount of sample injected onto the column was altered. The results show that when injecting a 0.5 ml sample volume a second-order regression through the standards is necessary for the determination of methane. The results for nitrogen, ethane and propane also show the same trend. Only those individual standards whose methane concentration is within 1% of the test mixture predicted a concentration within 0.05% of the regression value. Those individual primary standards whose methane concentration is different by more than +/-1% of the test mixture predicted values differing by +/-0.5 to +/-2.0% from the regression value. These differences lie well outside the predicted concentration uncertainty interval of +/-0.20%. A smaller sample volume, 0.1 ml, resulted in a set of data that could be fit using linear regression. Each of the eight primary standards individually predicted the methane in the test mixture to be within +/-0.11% of the predicted value from linear regression. The data confirm that it is imperative to fully characterize the analytical system before proceeding with an analysis.

Calibration↗

PubMed2004

Standard cancer patient population for age standardising survival ratios.

Standard adult cancer patients populations are derived in this paper as a tool for the calculation of age-standardised cancer survival figures. Previously used standards in survival analysis have been site- and/or study-specific. Here, multivariate methods have been used to define the smallest possible number of general standard cancer patient populations which are simple to use and provide standardised survival values close to the raw ones for the largest possible number of cancer sites. The analysis was based on data for over 1.1 million cancer patients included in the EUROCARE-2 study. The proposed standard populations consist of three age distributions, appropriate for cancers with incidence patterns: (1) increasing with age - the vast majority of cancers; (2) broadly constant with age and (3) mainly affecting young adults. The three standard distributions are presented by both broad and five-year age classes. The latter can be used to determine which of the three standards would be used for sites not included in the cluster analysis because their survival is generally calculated in unusual age groups. Overall, standard 1 is appropriate for over 91% of cases, standard 2 for just over 7%, and standard 3 for less than 2%. The proposed standards were tested on European (EUROCARE-2 and EUROCARE-3) and US (Surveillance, Epidemiology and End Results Program, SEER) relative survival data. There was very good correspondence between the raw (population weighted) and age-standardised survival figures.

Adolescent↗

PubMed2000

Relationship between the standards of removable partial denture construction, clinical acceptability, and patient satisfaction.

STATEMENT OF PROBLEM: Little is known about the importance of published fabrication standards in determining the outcome of treatment with mandibular distal extension removable partial dentures in patients of community practices. PURPOSE: This study describes mandibular partial dentures worn by patients from King County, Wash., and examines the validity of standards of design and fabrication by relating the standards to measures of clinical acceptability and patient satisfaction. MATERIAL AND METHODS: Eighty-two people treated in private dental practices who responded to a mail survey about satisfaction with a partial denture were examined. Eight standards of fabrication, overall clinical acceptability of the prosthesis, and tissue health were evaluated clinically. Patient satisfaction was assessed by questionnaire. Associations between variables were assessed by contingency tables and odds ratios. RESULTS: Half the prostheses met 4 or fewer of the 8 standards, and these were responsible for nearly all the displacement of tissue by the framework. Forty-three percent of the dentures (35/82) were rated clinically acceptable. Of the remaining dentures, 38 could be made acceptable by modifications. The remaining 9 dentures needed replacement. Sixty-three percent of the patients examined were satisfied with the dentures. There was a relationship between tissue health and the fabrication standards related to rest form, base extension, stress distribution, and framework fit. This study found no relation between tissue health and other design or fabrication features. None of the standards were found to be related to patient satisfaction. CONCLUSION: This study found partial support for the validity of design/fabrication standards for removable partial dentures. The most important standards are rest form, base extension, and stress distribution. The standards appear to be unrelated to patient satisfaction.

Dental Stress Analysis↗

PubMed2004

Double standards: memory loading in temporal reference memory.

Three experiments compared human performance on temporal generalization tasks with either one or two different, and distinct, standard durations encoded. In the first two experiments participants received presentations of two different standards at the beginning of each trial block and were instructed to encode either one or both of them. When instructed to encode one standard they then had to judge whether each of a number of comparison stimuli was or was not that standard. When instructed to encode both they were then tested using just one of the standards but the participants were unaware, at the time of encoding, which standard would later be used as a reference. No marked effect of the number of temporal standards encoded was found. In Experiment 3 participants received either one or two temporal standards and had to use both when two were presented. This manipulation produced flatter generalization gradients when two standards were encoded than when just one was, and modelling attributed this difference mainly to an increase in reference memory variability in the double-standard case. This suggests that the variability of representation of durations in temporal reference memory can be systematically increased by increasing temporal reference memory load.

Adolescent↗