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PubMed2001

Definition and assessment of sampling and analytical accuracy.

Two independent definitions for quantifying measurement accuracy and two limiting schemes for their assessment are examined in this paper. Gauss' mean square error MSE is compared to the symmetric-range accuracy A, describing the range of measurements about a measurand. Both measures of accuracy account for systematic error (bias) and imprecision so as to quantify the closeness of estimates to the actual values being measured. Remarkably, it is found that the accuracy functions are closely equivalent for most method applications. Furthermore, details are presented on how to compute confidence limits on measurement accuracy so as to account for error in method evaluation. The confidence limits are qualitatively different in the case that the method undergoes extensive initial evaluation in comparison to a continual re-evaluation at each method application. To this end the statistical theories of tolerance as well as more familiar types of confidence intervals are applied.

Bias↗
PubMed1984

Pooled analyses of randomized trials of streptokinase and heparin in phlebographically documented acute deep venous thrombosis.

Although thrombolysis with streptokinase has been compared with heparin anticoagulation for treating acute proximal deep venous thrombosis in several randomized trials, no individual study has had a sample of sufficient size to determine with adequate power both efficacy and safety. Therefore, results were pooled from six randomized studies in which phlebography was used to confirm the diagnosis and to assess therapy. Thrombolysis was achieved 3.7 times more often among patients treated with streptokinase than among patients treated with heparin (95 percent confidence limits 2.5, 5.7; p less than 0.0001). Only three studies allowed comparison of these drugs for major bleeding complications, which were 2.9 times greater with streptokinase than with heparin (95 percent confidence limits 1.1, 8.1; p = 0.04). Thus, in aggregate, streptokinase-treated patients achieved thrombolysis but also seemed to experience major bleeding complications more frequently than those assigned at random to receive heparin. Future trials of sufficient sample size should be undertaken to evaluate efficacy and safety. Such trials, which should include newer fibrinolytic agents, are necessary to determine optimal therapy for acute proximal deep venous thrombosis.

Clinical Trials as Topic↗
PubMed2005

Risk of a right pneumonectomy: role of bronchopleural fistula.

BACKGROUND: The purpose of this study is to compare the morbidity and mortality of right versus left pneumonectomy. METHODS: We used a retrospective review of pneumonectomies performed during the period 1990 to 2000 and included a meta-analysis of relevant literature. RESULTS: There were 187 pneumonectomies: 68 right, 119 left. The primary study end point was in-hospital death. There were 11 deaths: 7 (10.3%) right, 4 (3.3%) left (p = 0.10). Six deaths were attributable to bronchopleural fistula and its subsequent complications. The risk of bronchopleural fistula was higher on the right (9 [13.2%]) versus left (6 [5.0%]; p = 0.0472), as was the mortality associated with bronchopleural fistula (4 of 9 [44%] right versus 2 of 6 [33%] left). Right pneumonectomies were more likely to require an intrapericardial or extended dissection (p = 0.003), hand-sewn bronchial closure (p < 0.0001), or the closure buttressed (p < 0.0001). By univariate analysis, factors associated with an increased mortality were bronchopleural fistula (p < 0.0001), hand-sewn closure (p = 0.001), and a history of smoking (p = 0.01). By multivariate analysis, the most important factor was bronchopleural fistula (odds ratio, 43.3; 95% confidence limits, 4.2 to 441.9; p = 0.002). A meta-analysis combining our results with those from the literature found increased mortality of right pneumonectomy with a relative risk of 3.39 (95% confidence limits, 2.10 to 5.48; p < 0.00001). CONCLUSIONS: Right pneumonectomy is associated with a higher mortality even in the absence of induction therapy. This is primarily related to the increased risk of bronchopleural fistula on the right. The increased number of bronchopleural fistulas on the right may be attributable to more extensive resection. Addressing technical factors that contribute to early bronchopleural fistula may reduce the mortality of right pneumonectomy.

Adult↗
PubMed1976

Alcohol consumption and nonfatal myocardial infarction.

A study of the relathonship between alcohol consumption and nonfatal myocardial infarction, involving 399 cases and 2486 reference subjects, indicated absence of any major overall association (rate ratio point estimate of 0.9 with 95% confidence limits of 0.6 and 1.2), but there was some evidence of a lower rate in subjects consuming six or more drinks per day (rate ratio point estimate of 0.6 with 95% confidence limits of 0.3 and 1.1). Confounding by several potential confounders was controlled by stratification according to a confounder-summarizing score.

Adult↗
PubMed1988

Test-retest reliability of the Arden Grating Test: inter-tester variability.

The aim of this study was to investigate the test-retest reliability of the Arden Grating Test (AGT), and to assess the extent to which any variance in AGT score on retest can be attributed to intra-subject and inter-tester differences. Twelve patients with various pathologies and whose contrast sensitivity covered a wide range were each tested twice by six testers. It was shown that variance attributable to testing by different clinicians accounted for approximately 25% of the total variance, and that the 95% confidence limits about any observed score were +/- 15 AGT units, which is about one quarter of the total dynamic range of the test. The large range of scores encompassed by the 95% confidence limits represents considerable unreliability, the consequence of which is a high misclassification rate, i.e. many false positives and false negatives, especially in the context of primary vision screening for which it was designed.

Adult↗
PubMed1984

Soft tissue sarcomas in agriculture and forestry workers.

The National Cancer Register maintained by the Office of Population Censuses and Surveys (OPCS) was used to investigate the relative risks of soft tissue sarcomas among farmers, agricultural workers, and related occupational groups. The relative risk for the group as a whole was 1.15 (95% confidence limits 0.83-1.59). One of the four subgroups (which comprises farmers, farm managers, and market gardeners) experienced a relative risk of 1.7 which just achieves significance at the 5% level (95% confidence limits 1.00-2.88). The risks in the other three subgroups were respectively 1.0 (agricultural workers, 003), 0.7 (gardeners and groundsmen, 005), and 1.0 (foresters and woodmen, 006). No attempt has been made in this study to determine exposure to phenoxy herbicides in cases or controls. The significance of these findings is discussed.

Adolescent↗
PubMedDate not supplied

Prevalence and causes of blindness and low vision in Dambatta local government area, Kano State, Nigeria.

In 1995 a population based cross sectional blindness prevalence survey was conducted in Dambatta local government area (LGA). 3596 people were examined. The prevalence of blindness was 1.14% with 95% confidence limit of (0.8-1.48%). The causes of blindness are cataract 54%, Trachoma 17%, Glaucoma 15%, Corneal opacity 7%, other blinding conditions 7%. The prevalence of low vision was 2.05% with 95% confidence limit (1.60-2.50%). One percent of the population were severely visually impaired (WHO category 2). The causes of low vision are cataract 55%, corneal opacity 14%, uncorrected aphakia 11%, Glaucoma 7%, Refractive error 5%, other conditions 8 percent. Cataract was the leading cause of uniocular blindness with 53%, others were phthisis bulbi 17%, Trauma 14%, corneal opacity 10%, and others 7 percent. Cataract was the single most important cause of blindness, low vision and uniocular blindness accounting for 54%, 55%, and 53%, respectively. Uncorrected aphakia accounted for 11% of the low vision group, 80% of these had couching. This study showed that 93% of the blindness was avoidable in the sense that it could have been primarily prevented or, is treatable. 92% of the causes of low vision are avoidable.

Blindness↗
PubMed1991

Atrioventricular septal defects. Analysis of short- and medium-term results.

Atrioventricular septal defects were repaired in 87 patients from 1981 to 1988. Interventricular communications were present in 73 patients, and major associated anomalies were present in 17 (tetralogy of Fallot in four, double-outlet right ventricle in two, multiple ventricular septal defects in 11). Five deaths occurred in the hospital (5.7%; 70% confidence limits, 3.2% to 9.7%). A preoperative New York Heart Association class V functional condition was the only incremental risk factor (p = 0.02) for death in the hospital. No patient (0%; 70% confidence limits, 0% to 2.15%) had complete heart block. Actuarial survival rate at 80 months was 81.4%. The only incremental risk factor (p = 0.005) leading to reoperation was a preoperative valve incompetence. Actuarial rate at 80 months for freedom from reoperation was 84.2% in the overall group of patients after repair of atrioventricular septal defect. We conclude that an improvement in survival and success rates should be found when a policy of earlier repair is followed.

Actuarial Analysis↗
PubMedDate not supplied

Regression analysis of use-dilution disinfectant test data as an alternative to current registration practices.

The historical application of probit analysis applied to the use-dilution disinfectant test is discussed. Attention is focused on earlier work which either deleted or incompletely applied confidence limits leading to much current controversy in disinfectant test interpretation. It is proposed that the probit analysis approach applied to disinfectants is indeed feasible and that a more complete application of confidence limits to the assay will yield more reliable data than those currently required for disinfectant product registration with the Environmental Protection Agency. A suggested modified registration protocol using probit analysis is offered as an alternative to the current registration guidelines.

Disinfectants↗
PubMed1982

Analysis of inphase interaction pattern in EEG.

Inphase interactions among EEG signals recorded using eight electrodes were investigated. The inphase interaction parameters are presented in two ways: (1) matrix form in which the number of inphase interactions are tabulated; and (2) histogram in which the number of inphase interactions are plotted pair-wise between two sites as a function of phase delays in milliseconds. The highest number of interactions occurs between 0 and 8 ms in normal brains. The values of interactions parameters are enhanced by various activities. For example, inphase interaction parameters increase in the motor area in the right hemisphere if the EEG is recorded during repeated left fist clenching. Inphase interactions are drastically altered by the presence of a tumor. We studied the inphase interactions of the EEG of a patient having an occipital tumor. The interaction parameters are greatly diminished in this area, indicating a severe impairment of neuronal communications between both hemispheres in the occipital region. The confidence limits of the changes in inphase interaction parameters during fist clenching are tested statistically using the Student's test. The test shows that the interaction parameters increase, in general, with 1-5% confidence limits in respective cortex areas as a result of fist clenching.

Brain↗
PubMed1977

Reserpine and breast cancer in women in germany.

Exposure to reserpine was compared in 181 women interviewed prior to biopsy and found to have breast cancer and 307 women found to have a benign disorder of the breast. The age-adjusted relative risk of breast cancer in those who had taken reserpine was 0.6 (95% confidence limits: 0.4 and 1.1). When the 181 breast cancer patients were compared with a second control group of 101 women with a benign condition requiring surgery, the relative risk was 0.9 (95% confidence limits: 0.4 and 1.7). Neither long-term exposure nor its timing, gave any evidence of an association with breast cancer. The findings in this study do not support the hypothesis that rauwolfia derivatives initiate or promote breast cancer.

Adult↗
PubMed2005

Physiologically precise simulation of multiple lung gas exchange during anaesthesia by simultaneous gas infusion and extraction.

UNLABELLED: A lung gas exchange simulator was tested which produces simultaneous uptake and/or elimination of multiple gases by an artificial test lung with physiologically realistic gas expired and exhaust gas flows, using a combination of infusion of diluting/enriching gases into the lung with lung gas extraction. A deterministic algorithm is incorporated which calculates required gas infusion and extraction flow rates for any set of possible target gas exchange values with any given set of fresh gas flows and concentrations. Six different scenarios were simulated, comprising a range of gas exchange values for each gas species which lie within a physiologically realistic range for anaesthetized patients. For each of these experiments the system was tested for 15 consecutive measurements over 25 min by measurement of gas exchange in the system using the Haldane transformation. RESULTS: the mean bias and standard error of the mean bias (SE, in parentheses) relative to the target value was: +0.001 (0.002) l min(-1) for O(2) uptake, -0.002 (0.005) l min(-1) for CO(2) production, -0.001 (0.002) l min(-1) for uptake of nitrous oxide and +0.3 (0.1) ml min(-1) for uptake of a volatile anaesthetic agent (isoflurane). The confidence limits of the mean bias were within 5% of the target value for all gases and scenarios with the exception of those where a low uptake of anaesthetic gas was specified. The confidence limits of the mean bias for the lower uptakes of isoflurane were within 10% of the target value for these scenarios and within 15% for the low uptake of N(2)O. Good accuracy and precision of this approach to lung gas exchange simulation were demonstrated, resulting in a versatile simulator.

Algorithms↗
PubMed1998

Phenytoin auto-induction.

Information regarding phenytoin auto-induction is sparse and conflicting. However, confirmation of the presence or absence of auto-induction by phenytoin could have important implications in phenytoin therapy and research. This was an open, randomized, three-way crossover study in which each of the eighteen volunteers received three different formulations of phenytoin, which was allocated in a random order. The period effect between each crossover was determined to assess the effect of the previous exposure to phenytoin on the area under the concentration-time curve (AUC). The point estimate ratio of AUC(o-t) for the third dose relative to the first dose was 81.19% with 90% t-confidence limits of 74.37% to 88.00% and p = 0.3847. The point estimate ratio of AUC(o-infinity) for the third dose relative to the first dose was 76.25% with 90% t-confidence limits of 65.3% to 87.2% and p = 0.7169. These results suggest that the AUC (o-infinity) and AUC(o-t) measured after the third dose of phenytoin was statistically significantly smaller than those measured after the first dose. This decrease in AUC after the third dose of phenytoin is probably caused by enhanced elimination of the drug as a result of enzyme induction.

Adolescent↗
PubMed2002

Randomized, controlled human challenge study of the safety, immunogenicity, and protective efficacy of a single dose of Peru-15, a live attenuated oral cholera vaccine.

Peru-15 is a live attenuated oral vaccine derived from a Vibrio cholerae O1 El Tor Inaba strain by a series of deletions and modifications, including deletion of the entire CT genetic element. Peru-15 is also a stable, motility-defective strain and is unable to recombine with homologous DNA. We wished to determine whether a single oral dose of Peru-15 was safe and immunogenic and whether it would provide significant protection against moderate and severe diarrhea in a randomized, double-blind, placebo-controlled human volunteer cholera challenge model. A total of 59 volunteers were randomly allocated to groups to receive either 2 x 10(8) CFU of reconstituted, lyophilized Peru-15 vaccine diluted in CeraVacx buffer or placebo (CeraVacx buffer alone). Approximately 3 months after vaccination, 36 of these volunteers were challenged with approximately 10(5) CFU of virulent V. cholerae O1 El Tor Inaba strain N16961, prepared from a standardized frozen inoculum. Among vaccinees, 98% showed at least a fourfold increase in vibriocidal antibody titers. After challenge, 5 (42%) of the 12 placebo recipients and none (0%) of the 24 vaccinees had moderate or severe diarrhea (> or = 3,000 g of diarrheal stool) (P = 0.002; protective efficacy, 100%; lower one-sided 95% confidence limit, 75%). A total of 7 (58%) of the 12 placebo recipients and 1 (4%) of the 24 vaccinees had any diarrhea (P < 0.001; protective efficacy, 93%; lower one-sided 95% confidence limit, 62%). The total number of diarrheal stools, weight of diarrheal stools, incidence of fever, and peak stool V. cholerae excretion among vaccinees were all significantly lower than in placebo recipients. Peru-15 is a well-tolerated and immunogenic oral cholera vaccine that affords protective efficacy against life-threatening cholera diarrhea in a human volunteer challenge model. This vaccine may therefore be a safe and effective tool to prevent cholera in travelers and is a strong candidate for further evaluation to prevent cholera in an area where cholera is endemic.

Adolescent↗
PubMed1999

Haemodynamic measurements (continuous cardiac output and systemic vascular resistance) in critically ill patients: transoesophageal Doppler versus continuous thermodilution.

Ten critically ill patients underwent this prospective study to assess the reliability of the continuous thermodilution versus transoesophageal Doppler techniques in the determination of continuous cardiac output (CO) and systemic vascular resistance (SVR). A total of 145 pairs of CO and SVR measurements were obtained by both a pulmonary artery catheter with a heated filament and a transoesophageal Doppler apparatus (ODM II). Total CO ranged from 2.4 and 13 l.min-1; the bias of all measurements was 0.01 +/- 0.48 l.min-1, and the 95% confidence limits (mean difference +/- 2 SD) were 0.97/0.96 l.min-1. Total SVR ranged from 309 and 2643 dyn.s.cm-5; the bias of all measurements was 18 +/- 127 dyn.s.cm-5, and the 95%, confidence limits were 272/236 dyn.s.cm-5. Transoesophageal Doppler accurately measures continuous CO and SVR in critically ill patients. It should be viewed as complementary to pulmonary catheterization.

Aged↗
PubMed1987

Cough and wheezing from beclomethasone dipropionate aerosol are absent after triamcinolone acetonide.

STUDY OBJECTIVE: To test the hypothesis that patients with asthma who develop cough and wheezing after the use of beclomethasone aerosol would have a better tolerance for triamcinolone aerosol. DESIGN: Randomized, double-blinded, crossover trial. SETTING: Pulmonary function laboratory. PATIENTS: Volunteer sample of 24 patients attending an asthma clinic who had developed cough, with or without wheezing, after inhaling beclomethasone aerosol. All patients completed the study. INTERVENTIONS: Aerosols were used in habitual manufacturers' preparations and canisters, but both were administered in three puffs through the delivery system used for triamcinolone. The preparations differed in drug (beclomethasone dipropionate or triamcinolone acetonide), propellant (trichloromonofluoromethane and dichlorodifluoromethane, or dichlorodifluoromethane alone, respectively) and dispersant (oleic acid or dehydrated alcohol, respectively). PATIENTS inhaled three puffs of one aerosol on one day and three of the other on the next. MEASUREMENTS AND MAIN RESULTS: Forced expiratory volume in one second (FEV1) was measured before and after each aerosol application. The FEV1 decreased a mean of 17.7% from baseline after inhalation of beclomethasone, and 0.8% after triamcinolone (difference, 16.9; 95% confidence limits, 12.36 to 21.34; p less than 0.001). Coughs were counted after each puff. The mean number of coughs after beclomethasone aerosol inhalation was 35.8, and after triamcinolone, 0.5 (difference, 35.3; 95% confidence limits, 22.62 to 47.98, p less than 0.001). CONCLUSIONS: Asthmatic patients who are unable to inhale beclomethasone aerosol due to cough or wheezing can inhale triamcinolone aerosol without difficulty. Our investigation does not determine the exact cause of the coughing and wheezing with the beclomethasone aerosol, but we suspect the dispersant as the source.

Adult↗
PubMedDate not supplied

Mathematical approach to some methodological difficulties in settling newborn IgE reference levels (study in a Portuguese population).

The authors used statistical procedures to attempt to solve the usual methodological difficulties inherent in the determination of neonatal IgE reference values. The problem of un detectable values was overcome by theoretical estimation of their distribution, through the regression of the probits of the cummulative frequencies of the determinations on the natural logarithms of the known concentrations. Thus, the geometrical mean and 95% confidence limits were established, and population selection was replaced by exclusion of aberrant observations in successive steps, with recalculation of reference values. The final geometrical mean obtained was 0.21 I.U./ml with 95% confidence limits of 0.03 and 1.54 I.U./ml. These results have been compared with the work presented by other authors, observed differences probably reflecting distinct methodologies.

Female↗
PubMed1980

Wall thickness of ventricular chambers in transposition of the great arteries: surgical implications.

One hundred four specimens of complete transposition of the great arteries (TGA) were studied. The free wall thickness of the left (LV-T) and right (RV-T) ventricular chambers and the left ventricular/right ventricular (LV/RV) thickness ratio for all hearts were analyzed. A control group of 63 normal hearts was also studied. Specimens of TGA were divided into four groups: (1) TGA with intact ventricular septum (TGA + IVS); (2) TGA with ventricular septal defect (TGA + VSD); (3) TGA with a large patent ductus arteriosus (TGA + PDA); (4) TGA with pulmonary stenosis (TGA + PS). In Group I, LV-T was under the 95% confidence limits for normality after 8 months of age, and in Group II, the same was true after 18 months of age. For all groups the RV-T was above the 95% confidence limits for normality from the first month of age. The LV/RV ratio was under 1 in every group. Group I showed a significant decrease in the LV/RV ratio after the neonatal period (p less than 0.005). The potential failure of the left ventricle after anatomic correction of TGA is explained by a multifactorial hypothesis. In view of the ventricular wall thickness findings, we do not recommend the anatomic correction after 8 months of age in Group I or after 18 months in Group II.

Age Factors↗