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PubMed2005

Standard line slopes as a measure of a relative matrix effect in quantitative HPLC-MS bioanalysis.

A simple experimental approach for studying and identifying the relative matrix effect (for example "plasma-to-plasma" and/or "urine-to-urine") in quantitative analyses by HPLC-MS/MS is described. Using as a database a large number of examples of methods developed in recent years in our laboratories, the relationship between the precision of standard line slopes constructed in five different lots of a biofluid (for example plasma) and the reliability of determination of concentration of an analyte in a particular plasma lot (or subject) was examined. In addition, the precision of standard line slopes was compared when stable isotope-labeled analytes versus analogs were used as internal standards (IS). Also, in some cases, a direct comparison of standard line slopes was made when different HPLC-MS interfaces (APCI versus ESI) were used for the assay of the same compound, using the same IS and the same sample preparation and chromatographic separation conditions. In selected cases, the precision of standard line slopes in five different lots of a biofluid was compared with precision values determined five times in a single lot. The results of these studies indicated that the variability of standard line slopes in different lots of a biofluid [precision of standard line slopes expressed as coefficient of variation, CV (%)] may serve as a good indicator of a relative matrix effect and, it is suggested, this precision value should not exceed 3-4% for the method to be considered reliable and free from the relative matrix effect liability. Based on the results presented, in order to assess the relative matrix effect in bioanalytical methods, it is recommended to perform assay precision and accuracy determination in five different lots of a biofluid, instead of repeat (n=5) analysis in the same, single biofluid lot, calculate standard line slopes and precision of these slopes, and to use <3-4% slope precision value as a guide for method applicability to support clinical studies. It was also demonstrated that when stable isotope-labeled analytes were used as internal standards, the precision of standard line slopes in five different lots of a biofluid was </=2.4% irrespective of the HPLC-MS interface utilized. This clearly indicated that, in all cases studied, the use of stable isotope-labeled IS eliminated relative matrix effect. Also, the utilization of the APCI interface instead of ESI led to the elimination of the relative matrix effect in all cases studied. When the precision of standard line slope values exceeds the 3-4% limit, the method may require improvements (a more efficient chromatography, a more selective extraction, a stable isotope-labeled IS instead of an analog as an IS, and/or a change in the HPLC-MS interface) to eliminate the relative matrix effect and to improve assay selectivity.

Body Fluids↗
PubMed1998

WHO cytokine standardization: facilitating the development of cytokines in research, diagnosis and as therapeutic agents.

The development and widespread application of recombinant DNA technology has dramatically increased the number of cytokines available for clinical evaluation. New and novel cytokines are being discovered, cloned and entered into clinical trials at such a rate that it is often the case that the biological activities of these proteins are poorly understood during their development as therapeutic agents. In addition, manufacturers of any one cytokine can produce the protein from different cellular sources resulting in materials that exhibit markedly different specific activities. When estimating the amount of biological activity of different preparations with different specific activities by bioassay, mass units cannot be used and biological activity is therefore expressed as 'biological potency units'. The biological unit requires definition by a standard that is assay-independent (especially when measuring a particular type of biological activity). In many cases, a variety of assay methods will be available and the material chosen for a standard should ideally be suitable for use with as many of them as possible. Once the unit is defined, this can be used in any laboratory, thus providing a means of ensuring uniformity throughout the world in the designation of potency of different biological preparations. The World Health Organisation (WHO) standardization programme involves the production of biologically stable, well characterised potency and immunoassay standards that are available world-wide using a single international unitage. Over the years, WHO international standards have been used to dramatically reduce the variation in estimates of cytokine preparations within and between laboratories for immunoassays and bioassays. WHO international standards are primary reference preparations against which secondary, or working standards (including regional standards, national standards, pharmacopoeial standards and in-house working standards) can be calibrated.

Cytokines↗
PubMed2002

Evaluation and application of bismuth as an internal standard for the determination of lead in wines by simultaneous electrothermal atomic absorption spectrometry.

A method for the direct determination of Pb in wines by simultaneous multi-element atomic absorption spectrometry (SIMAAS) using a transversely heated graphite atomizer, Zeeman-effect background corrector and internal standardization is proposed. Bismuth was used as an internal standard and Pd(NO3)2 plus Mg(NO3)2 as chemical modifier to stabilize both the analyte and the internal standard. The implementation of two pyrolysis steps avoided any build-up of carbonaceous residues on the graphite platform. All diluted samples (1 + 1 v/v) in 0.2% v/v HNO3 and reference solutions (5.0-50 microg l(-1) Pb in 0.2% v/v HNO3) were spiked with 25 microg l(-1) Bi. For a 20 microl aliquot dispensed into the graphite tube, a good correlation (r = 0.9997) was obtained between the ratio of the analyte signal to the internal standard signal and the analyte concentration of the reference solutions. The electrothermal behaviour of Pb and Bi in red, white and rosé wines were compared. In addition, absorbance variations due to changes in experimental conditions, such as atomizer temperature, integration time, injected sample volume, radiation beam intensity, graphite tube surface, dilution and sample composition, were minimized by using Bi as internal standard. Relative standard deviations of measurements based on integrated absorbance varied from 0.1 to 3.4% and from 0.5 to 7.3% (n = 12) with and without internal standard correction, respectively. Good recoveries (91-104%) for Pb spikes were obtained. The characteristic mass was 45 pg Pb and the limit of detection based on integrated absorbance was 0.9 microg l(-1) Pb. Internal standardization increased the lifetime of the tube by 25%. Direct determinations of Pb in wines with and without internal standardization approaches were in agreement at the 95% confidence level. The repeatability and the tube lifetime were improved when using Bi as internal standard. The improvement in accuracy using an internal standard was only observed when the analytical results were affected by errors.

Bismuth↗
PubMed2006

Evidence of reference standard related bias in studies of plain radiograph reading performance: a meta-regression.

The aim is to determine the effect of reference standard related bias on estimates of plain radiograph reading performance using studies conducted in clinical practice. Data were extracted on study eligibility, clinical and reference standard characteristics and reading performance. The choice of reference standards and the prevalence of bias are presented descriptively. Associations between bias and reading performance are estimated using a regression model that produces relative diagnostic odds ratios (RDOR) with 95% confidence intervals (CIs). Three of the 20 eligible studies addressed all five reference standard related biases; 15 studies addressed three or more. When the reference standard report is influenced by knowledge of an observer's opinion this is associated with a significant overestimation in reading performance (RDOR, 3.7; 95% CI, 1.6 to 8.3; p = 0.01). There is limited evidence that reading performance is inflated when the observer is aware of the reference standard report before commenting on the radiograph (RDOR, 1.7; 95% CI, 0.6 to 5.1) and deflated when a less valid reference standard is used (RDOR, 0.5; 95% CI, 0.1 to 2.5). There is no evidence that reading performance is affected by application of the reference standard depending on an observer's opinion and using different reference standards in the same study. In conclusion we found variation in the choice and application of reference standards in studies of plain radiograph reading performance, but only when reference standards report in the knowledge of an observer's opinion does this contribute to a significant overestimation in reading performance.

Awareness↗
PubMedDate not supplied

How valid are our reference standards of nutrition?

The validity of anthropometric measurements in the assessment of nutritional status depends on the use of appropriate standards. The most commonly used standards for triceps skinfold thickness and mid-arm muscle circumferences are based on Jelliffe's and Frisancho's tables. In this study we compared these two standards in a population of healthy subjects and patients with a variety of pathological disorders. The study showed that the correlation between these two standards was poor. When Frisancho's standards were used as "gold standards," the positive predictive value of Jelliffe's standards for triceps skinfold thickness was only 22% and for mid-arm muscle circumference only 53%; the false positive results for triceps skinfold thickness and mid-arm muscle circumference were 28% and 27%, respectively. This study emphasizes the need to develop appropriate standards for the studied population. Until such standards are available, workers assessing nutritional status in population studies would be advised to interpret their findings with caution, and, on the basis of this study, we recommend the use of Frisancho's standard in preference to Jelliffe's standards.

Adult↗
PubMed1994

Do provider practices conform to the new pediatric immunization standards?

OBJECTIVE: Standards for pediatric immunization practices were issued by the Centers for Disease Control and Prevention, Atlanta, Ga, in May 1992. This article provides baseline data on immunization practices related to eight of the standards. DESIGN: Survey of pediatric providers before publication of the standards. SETTING: Baltimore, Md. PARTICIPANTS: Forty of the 41 health centers, clinics, and private practices serving children in designated high-risk census tracts participated in the survey. One hundred seventy-three of the 251 eligible physicians and nurse practitioners at the sites responded. MAIN OUTCOME MEASURES: Conformity with the eight standards was measured as a percentage of either sites or physicians and nurse practitioners across the sites. RESULTS: Conformity with the standards varied, ranging from nearly universal conformity with the need to educate parents and guardians about immunizations (standard 5) to less than 3% for simultaneous administration of all vaccine doses when a child is first eligible (standard 8). For most of the standards, considerable variability was found between and within public and private sites. CONCLUSIONS: Providers often followed practices that did not conform to the new standards (prior to issuance). Some of the standards are ambiguous and require clarification before they can be fully applied. The impact of the standards on immunization rates and pediatric primary health care has yet to be tested empirically.

Baltimore↗
PubMed1989

Gamma globulin-derived standards for the determination of molecular weights, transfer, and immunodetection efficiencies in protein blotting procedures.

Molecular weight markers which are detectable using labeled antispecies antibodies or labeled Protein A have been prepared for use as standards on protein blots. The standards were prepared by the controlled reduction followed by subsequent alkylation of gamma globulin. Separate sets of standards were prepared using gamma globulins derived from human, mouse, rabbit, and sheep species. Standards were also prepared using monoclonal-derived gamma globulins from human myeloma fluid and mouse ascites fluid. Standards produced from monoclonal-derived gamma globulins produced very sharp bands on sodium dodecyl sulfate-polyacrylamide gels and proved to be excellent standards for this technique alone. However, the markers were uniquely suitable for use as standards in protein blotting procedures because their detection was achieved by the procedure used to detect the transferred antigen(s). The detection of immunoglobulin G (IgG)-derived standards on protein blots from all the species listed above was demonstrated using appropriate horseradish peroxidase (HRP)-conjugated antispecies antibodies. The use of other detection systems (biotin-labeled antibody and subsequent detection with HRP-steptavidin, HRP-Protein A) was also validated with human IgG-derived standards. Furthermore, the standards were shown to be suitable for use on both nitrocellulose and cationized nylon-based supports and could be used when adjacent samples were run under reducing conditions. Hence the gamma globulin-derived standards serve as both a control to check the adequacy of transfer and immunodetection systems and as markers which enable the molecular weights of detected antigens to be calculated.

Animals↗
PubMed1996

Comparison of the standard and reduced pH Syrian hamster embryo (SHE) cell in vitro transformation assays in predicting the carcinogenic potential of chemicals.

A comprehensive review of the Syrian Hamster Embryo (SHE) cell transformation literature was performed in order to catalogue the chemical/physical entities which have been evaluated for in vitro cell transformation potential. Both reduced pH (pH 6.7) and standard pH (pH 7.1-7.3) SHE cell testing protocols were considered. Based upon this analysis, over 472 individual chemical/physical agents and 182 combinations of chemical/physical agents have been tested under the standard pH conditions, while over 56 chemical/physical agents have been tested under reduced pH conditions. Of the 472 chemical/physical agents tested at the standard pH, 213 had in vivo carcinogenicity data available. Of these 213 chemical/physical agents, 177 were carcinogens while 36 were non-carcinogens. The results of testing the SHE transformability of these 213 chemical/physical agents indicates that the standard pH SHE cell transformation assay had a concordance of 80% (171/213), a sensitivity of 82% (146/177), and a specificity of 69% (25/36). Of these 213 chemical/physical agents, 53% (112/213) were tested more than once often in more than one laboratory, with a 82% (92/112) interlaboratory agreement rate, thus providing confirmatory results. Carcinogenicity data were available for 48 of the 56 chemical/physical agents tested for SHE cell transformation under the reduced pH conditions. The SHE cell transformation assay under reduced pH conditions had a concordance of 85% (41/48), a sensitivity of 87% (26/30), and a specificity of 83% (15/18). For Salmonella-negative carcinogens, the standard pH SHE assay correctly predicted carcinogenicity 75% (48/64) of the time while the reduced pH SHE assay correctly predicted carcinogenicity for Salmonella-negative carcinogens 78% (14/18) of the time. For chemical/physical agents tested under both the reduced pH and standard pH conditions, the standard pH and reduced pH SHE cell assays had a 69% (22/32) agreement rate. Under the reduced pH conditions, the SHE assay correctly predicted rodent carcinogenicity in 86% (25/29) of the chemicals tested under both reduced and standard pH conditions. Under standard pH conditions, the SHE assay correctly predicted rodent carcinogenicity in 69% (20/29) of the chemicals tested under both reduced and standard pH conditions. Collectively, these data indicate that the SHE cell transformation assay is predictive for rodent carcinogenicity under either reduced or standard pH conditions. Importantly, the assay displays better performance and appears to have improved carcinogen prediction capability under reduced pH conditions.

Animals↗
PubMed1995

American National Standard for nonautomated sphygmomanometers. Summary report.

The Association for the Advancement of Medical Instrumentation develops voluntary standards for medical devices so that manufacturers might provide information on their product and basic safety and performance criteria that should be considered in qualifying the instrument for clinical use. American National Standards are generated through a consensus process by committees of experts in research, development, and design from user, industry, and government communities. Draft standards are made available for public review and become American National Standards after review by the American National Standards Institute. This report is a summary of the American National Standard that establishes both the safety and performance requirements of pneumatic and other nonautomated sphygmomanometers (especially mercury gravity and aneroid sphygmomanometers) used in the indirect measurement of blood pressure. This standard was developed by a consensus panel from academia, industry, and government; it updates the previous standard approved by the American National Standards Institute in 1986. This summary report does not cover all of the provisions of the revised 1994 American National Standard, thus users, researchers, and instrument designers should refer to the standard for detailed requirements.

Blood Pressure Determination↗
PubMed2006

An investigation into health informatics and related standards in China.

OBJECTIVE: To describe the current status of and future plans for health informatics and related standards in China and analyze the problems raised in the process of standardization for health informatics. METHODS: Data were collected through investigation and interviews, complemented by a comprehensive review of relevant literatures and regulations/law documents about health informatics and related standards in China. RESULTS: Health informatics has been greatly developed in China. Significant resources were committed to construct and improve the health information system. Approximately 35-40% of hospitals have constructed hospital information system. Over 80% of medical organizations above the county/district level, 27% of town level hospitals and all CDC above the county/district level can transmit real-time epidemic situation reporting through public health information system. However, lack of standards became a bottleneck to utilize and improve health informatics. China has adopted some vocabulary, classification, coding standards and message standards. Moreover, several national standardization actions for health informatics have been taken. In the process of standardization, the main barriers consist of financial, technical, cultural and language problems, legal and ethical concerns and others. CONCLUSIONS: Informatics has the potential to play an important role in China's healthcare reform process and standards are the basis for the information sharing and interoperability. Governments and partners of health informatics have realized the importance of standards and taken the initiatives in trying to solve the problem of lacking standards, but much work still needs to be done.

China↗
PubMed2005

Matched case-control study of quality of life and xerostomia after intensity-modulated radiotherapy or standard radiotherapy for head-and-neck cancer: initial report.

PURPOSE: To compare quality of life (QOL) and xerostomia between head-and-neck cancer patients who received standard radiotherapy (RT) and patients matched by factors known to affect QOL who received intensity-modulated RT (IMRT). METHODS AND MATERIALS: This was a prospective, longitudinal study of patients with head-and-neck cancer requiring bilateral neck irradiation who received IMRT at the University of Michigan and patients who received standard RT at affiliated clinics. Each patient received a validated head-and-neck cancer-related QOL questionnaire (HNQOL) consisting of four multi-item domains--Eating, Communication, Pain, and Emotion--and a validated patient-reported xerostomia questionnaire (XQ). In both questionnaires, the answers were scored 0-100, with higher scores denoting worse QOL or xerostomia. The questionnaires were given before therapy and at 1, 3, 6, 12, 18, and 24 months after the completion of therapy. Each standard RT patient was matched with several IMRT patients according to tumor site, stage, RT status (postoperative or definitive), and age. A linear mixed-effects model was fit to compare outcomes between the two treatment groups and to model trends over time. To account for matching, the differences in scores between the matched sets of patients were fit as a random intercept. Also, matching was taken into account in the model by using the standard error of the within-paired-groups differences. RESULTS: Between 1997 and 2002, 10 patients who had received standard RT and answered the XQ and HNQOL through at least 1 year were included in the study. Each of these patients was matched with a subgroup of 2-5 patients (median, 3) who had received IMRT, had similar patient and tumor characteristics, and answered the same questionnaires. A total of 30 patients were included in the IMRT group. During the initial months after therapy, the XQ and HNQOL summary scores worsened significantly in both groups compared with the pretherapy scores. Starting at 6 months, improvements of both XQ and HNQOL scores were found over time in the IMRT patients (p = 0.01 and 0.04, respectively), compared with no trend of improvement in the standard RT patients (p = 0.5 and 0.9, respectively). The trend of improvement over time in QOL in the IMRT patients was noted in most of the HNQOL domains (Eating: p = 0.07, Pain: p = 0.05, Emotion: p = 0.04, and Communication: p = 0.13), compared with no trend of improvement in most of the domains in the standard RT patients. As the scores of the IMRT (but not the standard RT) patients improved over time, the differences between the groups in the mean XQ and HNQOL summary scores widened. At 12 months, median XQ and HNQOL scores were lower (better) in the IMRT compared with the standard RT patients by 19 and 20 points, respectively, adjusted for the pretherapy values (p = 0.2). In both groups, the pretherapy XQ and HNQOL summary scores were significantly related to the respective posttherapy scores (p = 0.02 and p < 0.01, respectively). CONCLUSIONS: After initial posttherapy declines in both groups, xerostomia and QOL improved over time after IMRT but not after standard RT. The potential benefits gained from IMRT in xerostomia or in QOL, compared with standard RT, are best reflected late (> or = 6 months) after therapy.

Adult↗
PubMed2004

Potential benefits of the new Leapfrog standards: effect of process and outcomes measures.

OBJECTIVE: The Leapfrog Group standards for evidence-based hospital referral underwent significant revision in 2003. In addition to other changes, risk-adjusted mortality and process of care measures now augment or replace volume standards for some procedures. The objective of this study was to estimate the potential benefits of these newly expanded standards. METHODS: Leapfrog's 2003 standards were based on minimum volume standards alone for 2 operations (esophagectomy, pancreatectomy), volume standards and a process measure (perioperative beta blockade) for 1 operation (abdominal aortic aneurysm repair), and volume standards coupled with risk-adjusted mortality rates for 2 operations (coronary artery bypass grafting [CABG] and percutaneous coronary intervention [PCI]). We used data from the 2000 Nationwide Inpatient Sample to determine eligible surgical populations, volume-outcome associations, and risk-adjusted hospital mortality rates for the 5 operations. A recent meta-analysis was used to estimate the effectiveness of perioperative beta-blocker use. RESULTS: Approximately 23,790 patients died in 2000 in the United States undergoing 1 of the 5 procedures. We estimate that full implementation of the Leapfrog standards would have averted 7818 of these deaths: CABG (4089), PCI (3016), elective abdominal aortic aneurysm repair (356), esophageal resection (180), and pancreatic resection (177). For CABG and PCI, standards based on risk-adjusted mortality rates would save at least 5 times more lives than those based on volume criteria alone. CONCLUSIONS: Widespread implementation of the 2003 Leapfrog standards for evidence-based referral could avert a large number of surgical deaths. For some procedures, standards comprised of process of care or direct outcome measures would be more effective than those based on volume alone.

Evidence-Based Medicine↗
PubMed2002

The effects of standard enforcement on Michigan safety belt use.

The purpose of this study was to assess the effects of standard enforcement legislation on safety belt use in Michigan through a series of seven statewide direct observation surveys. A secondary purpose of the study was to compare the results in Michigan to the results in other states that have changed the provision of their mandatory safety belt use law from secondary to standard enforcement. The study found that standard enforcement has been effective in increasing safety belt use in Michigan. Immediately following the implementation of standard enforcement, Michigan's belt use rate increased to 83.5%, 13.4 percentage points higher than the highest rate previously observed. One year after the change, safety belt use in Michigan was still nearly 10 percentage points greater than the highest observed rate before standard enforcement legislation was enacted. Results indicated that safety belt use decreased slightly in the year following the implementation of standard enforcement. This appears to be an overall trend across all observed groups, and not due to any single demographic category. The results also suggest that standard enforcement legislation appears to have a greater effect on groups with historically low belt use, such as young people, males, passengers, and Black/African-Americans. When compared with other states that have made the change from secondary to standard enforcement, the increase in the safety belt use rate in Michigan was comparable to the increase seen in states with relatively high safety belt use prior to standard enforcement. However, states that had low safety belt use rates prior to adopting standard enforcement legislation observed a larger percentage point increase in the year following their change to standard enforcement.

Automobile Driving↗
PubMed2003

Standard vs. radical pancreaticoduodenectomy for periampullary adenocarcinoma: a prospective, randomized trial evaluating quality of life in pancreaticoduodenectomy survivors.

This study was designed to assess the health-related quality of life (QOL) of patients who had been randomly assigned to either standard or radical pancreaticoduodenectomy for periampullary adenocarcinoma. Pancreaticoduodenectomy has been performed in increasing numbers for periampullary adenocarcinoma. The appropriate extent of resection (standard vs. radical [extended]) remains controversial, particularly as concerns survival benefit. Past reports comparing standard vs. radical resection have suggested that the more extensive resection is attended by negative functional outcomes (diarrhea and weight loss) and poorer QOL, diminishing the impact of any possible survival advantage of the radical resection. A prospective, randomized single-institution trial comparing standard pancreaticoduodenectomy (pylorus preservation preferred) to radical pancreaticoduodenectomy (including distal gastrectomy and retroperitoneal lymphadenectomy) evaluated 299 patients with periampullary adenocarcinoma between April 1996 and June 2001. A standard Functional Assessment of Cancer Therapy-Hepatobiliary (FACT-Hep) QOL survey designed for hepatobiliary cancer was sent to 150 of these patients surviving pancreaticoduodenectomy. QOL and functional status were assessed via a series of subscale scores for physical, social, emotional, and functional well-being. A total of 105 QOL surveys (70%) were returned and analyzed, with 55 of the patients having been randomized to the standard group and 50 to the radical group. The patients were evaluated at a mean of 2.2 years after pancreaticoduodenectomy. The two groups were statistically similar with regard to multiple parameters including age at operation (64.6 years), race, intraoperative blood transfusions, pathologic diagnosis and staging, and perioperative complications. The radical group had a significantly higher percentage of men (66% vs. 44%; P = 0.02), a longer operative time (369 minutes vs. 327 minutes; P < 0.001), and a longer postoperative length of hospital stay (13.6 days vs. 10.1 days; P < 0.01). The FACT-Hep total QOL scores were similar between the standard and radical groups: 143.5 vs. 147.3, respectively. Additionally, the individual FACT-G subscale scores evaluating physical (22.1 vs. 23.3), social (24.5 vs. 24.4), emotional (19.2 vs. 19.6), and functional well-being (20.6 vs. 22.4) were comparable between the standard and radical groups. Subgroup analyses based on pathologic diagnosis (pancreatic, ampullary, distal bile duct, etc.) failed to reveal any differences in QOL assessment between the standard and radical pancreaticoduodenectomy groups. Finally, QOL measures were similar when comparing time since operation (<2 years' follow-up vs. >2 years' follow-up) and age (< or =65 years vs. >65 years). This is the largest report comparing QOL assessment in survivors of pancreaticoduodenectomy randomized between standard and radical resection. These data demonstrate no differences in long-term QOL between standard and radical resection. These results imply that no negative long-term QOL measures are associated with radical pancreaticoduodenectomy (as performed in this study) for periampullary adenocarcinoma.

Adenocarcinoma↗
PubMed2003

Low-dose or standard-dose proton pump inhibitors for maintenance therapy of gastro-oesophageal reflux disease: a cost-effectiveness analysis.

BACKGROUND: Studies on the use of low-dose proton pump inhibitor for the maintenance therapy of gastro-oesophageal reflux disease have shown that it might be comparable with standard-dose proton pump inhibitor treatment and superior to standard-dose histamine-2 receptor antagonist therapy. AIM: To compare the impact of standard-dose histamine-2 receptor antagonist, low-dose proton pump inhibitor and standard-dose proton pump inhibitor treatment for the maintenance therapy of gastro-oesophageal reflux disease on symptom control and health care resource utilization from the perspective of a public health organization in Hong Kong. METHODS: A Markov model was designed to simulate, over 12 months, the economic and clinical outcomes of gastro-oesophageal reflux disease patients treated with standard-dose histamine-2 receptor antagonist, low-dose proton pump inhibitor and standard-dose proton pump inhibitor. The transition probabilities were derived from the literature. Resource utilization was retrieved from a group of gastro-oesophageal reflux disease patients in Hong Kong. Sensitivity analysis was conducted to examine the robustness of the model. RESULTS: The standard-dose proton pump inhibitor strategy was associated with the highest numbers of symptom-free patient-years (0.954 years) and quality-adjusted life-years gained (0.999 years), followed by low-dose proton pump inhibitor and standard-dose histamine-2 receptor antagonist. The direct medical cost per patient in the standard-dose proton pump inhibitor group (904 US dollars) was lower than those of the low-dose proton pump inhibitor and standard-dose histamine-2 receptor antagonist groups. CONCLUSIONS: The standard-dose proton pump inhibitor strategy appears to be the most effective and least costly for the maintenance management of patients with gastro-oesophageal reflux disease in Hong Kong.

Cost-Benefit Analysis↗
PubMed2002

Comparison of a new reduced lead set ECG with the standard ECG for diagnosing cardiac arrhythmias and myocardial ischemia.

In a few patients, 12-lead electrocardiograms (ECGs) derived from reduced-lead-set configurations do not match the standard ECG. Constructing an ECG from a reduced number of standard leads should minimize this problem because some of the resultant 12 leads would always include "true" standard leads. The purpose of this study was to compare the ability of a new reduced-lead-set 12-lead ECG ("interpolated" ECG) with the standard ECG to diagnose cardiac arrhythmias and acute myocardial ischemia. The interpolated ECG uses six standard electrode sites (limb leads plus V(1) and V(5)), from which the remaining four precordial leads (V(2), V(3), V(4), and V(6)) are constructed. Standard and interpolated ECGs were compared using data from 2 prospective clinical trials involving 649 patients evaluated for 1) chest pain in the emergency department (ischemia group, n = 509) or 2) tachycardias in the cardiac electrophysiology laboratory (arrhythmia group, n = 140). Diagnoses were identical between standard and interpolated ECGs for bundle branch and fascicular blocks, left atrial enlargement, right ventricular hypertrophy, prior inferior myocardial infarction (MI), and the distinction of ventricular tachycardia from supraventricular tachycardia with aberrant conduction. There was 99% agreement for prior anterior MI (kappa, .935, P =.000). The percent agreement for acute myocardial ischemia on the initial ECG recorded in chest-pain patients in the emergency department was 99.2% (kappa, .978, P =.000). Of the 120 patients who had ST events with continuous standard 12-lead ECG monitoring, 116 (97%) also had criteria for transient ischemia with the interpolated ECG (ie, DeltaST >or= 100 microV in >or=1 lead(s) lasting >or=1 minute(s). The interpolated 12-lead ECG is comparable to the standard ECG for diagnosing multiple cardiac abnormalities, including wide-QRS-complex tachycardias and acute myocardial ischemia. The advantages of this ECG method are that the standard electrode sites are familiar to clinicians and that eight of the 12 leads are "true" standard leads. Hence, QRS-axis and morphology criteria for diagnosing wide-QRS-complex tachycardia and bundle branch and fascicular blocks are preserved.

Aged↗
PubMed2003

Comparison of the 1-hr and 8-hr National Ambient Air Quality Standards for ozone using Models-3.

In 1997, the U.S. Environmental Protection Agency revised the National Ambient Air Quality Standard governing ozone (O3), adding an 8-hr standard of 0.08 ppm and phasing out the 1-hr requirement of 0.12 ppm. The 8-hr standard is intended to provide greater protection for human health. This research examines spatial and temporal patterns of exceedances of the standards using monitoring data and modeled estimates. The Penn State/National Center for Atmospheric Research Mesoscale Model and Models-3 framework were used to estimate hourly O3 concentrations for 4-km resolution in the Maryland/Virginia/Delaware/Washington, DC, and northern Georgia domains. Results reveal that the spatial and temporal nature of compliance is considerably different under the 8-hr standard. In the modeling simulations, the 8-hr standard was exceeded 2-5.2 times more often and in a 1.8-16.2 times larger area than the 1-hr standard. The 8-hr standard was exceeded in areas that generally comply with the 1-hr standard and are not well covered by the monitoring network. These results imply that a larger population resides in areas with unhealthy O3 levels than noncompliance with the original 1-hr standard suggests. For the MD/VA/DE/DC domains, 80 and 98% of the total population live in areas with 8-hr National Ambient Air Quality Standards (NAAQS) exceedances for the 1990 and 1995 episodes, respectively.

Cities↗
PubMed1999

Standardized management of intracranial pressure: a preliminary clinical trial.

OBJECTIVE: To test a standardized protocol for management of intracranial pressure (ICP) after severe head injury (i.e., traumatic brain injury), consistent with published guidelines. METHODS: We compared prospective use of a standardized protocol for ICP management in 12 patients with severe head injuries and retrospective ICP management using preprinted hospital orders in combination with ad hoc physician orders in 12 historical control patients with severe head injuries. With the standardized protocol, flow-chart decision logic diagrams were applied at patient bedside by critical care practitioners, with nursing shift review. RESULTS: ICP and its variation during the first 6 intensive care unit days was less for the standardized protocol- than for the preprinted order-managed group (p <0.001), indicating better process control with the standardized protocol. ICP exceeded 25 mm Hg for less time for the standardized protocol group (182 hours; 15+/-23 hours/patient) than for prescribed order group (429 hours; 36+/-28 hours/patient) (p = 0.03). On average, ICP exceeded 20 mm Hg for 2.3 days for the standardized protocol-managed group and for 4.7 days for the prescribed order-managed group. Cerebral perfusion pressure was significantly greater and its variation less for the standardized protocol- than for the preprinted order-managed group. Fewer interventions were made for ICP management for the standardized protocol- than for the preprinted order-managed patients (601 vs. 876), suggesting more effective nursing time using the standardized protocol. CONCLUSION: ICP management was more consistent, and intracranial hypertension was better controlled, in patients managed according to a standardized, data-driven protocol for escalation and weaning of therapies in response to immediate patient needs. We recommend computerized implementation and a randomized clinical trial to compare the protocol with prescribed orders.

Algorithms↗