The Standard for Reporting of Diagnostic Accuracy statement promotes the reporting of confidence intervals (CIs) for indices of diagnostic test accuracy. However, these indices must be combined with an estimate of pretest probability to properly interpret the results of such tests, thus yielding positive and negative predictive values. For small sample sizes, CI estimation for predictive values based on the classical logit transformation has been found to be very conservative. A method based on computer simulation has therefore been suggested as an alternative.
ACI procedure for predictive values that yields limits completely contained in those provided by the logit transformation is proposed and evaluated.
The proposed approach to CI construction maintains nominal coverage very well even when sample sizes are small.
Accurate CIs for positive and negative predictive values can be obtained without using computer simulation.
As part of a study to determine whether maternal mortality in Canada is under- reported, we explored the validity of including deaths not directly related to pregnancy. We linked live birth and stillbirth registrations to death registrations of women of reproductive age from 1988 through 1992. We calculated standardized mortality ratios, by cause, from deaths in women known to have been pregnant and deaths in same-aged women not known to have been pregnant within the same time period. Women known to have been pregnant were approximately half as likely to die as would be expected in each of two six-month time periods: from 20 weeks gestation to 42 days postpartum (SMR 0.4, 95% CI 0.3-0.5), and from 42 days to 225 days postpartum (SMR 0.5, 95% CI 0.5-0.6). Furthermore, pregnant and recently pregnant women were not more likely to die from specific causes, with the exception of diseases of the arteries, arterioles, and capillaries (SMR 3.5, 95% CI 1.3-7.7) during pregnancy or within 42 days of pregnancy termination. The only other SMR that was > 1 was for death from cerebrovascular disorders during pregnancy and up to 42 days postpartum, although not significantly so (SMR 1.4, 95% CI 0.8-2.2). No other cause-specific SMRs were > 1. Moreover, recently pregnant women were found to be much less likely to commit suicide or to be the victims of homicide. We found no empirical justification for including deaths not directly related to pregnancy in reported counts of maternal deaths for most of the causal categories we considered.
We studied the association of GSTM1 and GSTT1 and GSTP1 Ile105-Val105 polymorphism with the duration of intoxication, polyorgan failure, and severity of drug poisoning in children. The combination of GSTM1 and GSTT1 zero genotypes is a favorable sign for the duration of intoxication and severity of the disease.
BACKGROUND: This is the first systematic review and meta-analysis of the large body of data describing the Swedish adjustable gastric band (SAGB) and Lap-Band (LB). METHODS: A systematic review was performed that included screening of studies published in any language (January 1, 1998 through April 30, 2006) identified through MEDLINE, Current Contents, or the Cochrane Library. Studies with > or =10 SAGB or LB patients reporting > or =30-day efficacy or safety outcomes were eligible for review; the data were extracted from the accepted studies. A weighted means analysis and random-effects meta-analysis of efficacy outcomes of interest were conducted. RESULTS: A total of 4592 bariatric surgery studies met the initial criteria. Of these studies, 129 (28,980 patients) were accepted (33 SAGB and 104 LB studies); most had a retrospective single-center design. For 4273 patients (36 treatment groups) in 33 SAGB studies and 24,707 patients (111 groups) in 104 LB studies, the mean baseline age (39.1-40.2 yr), body mass index (43.8-45.3 kg/m2), and gender (women 79.2-82.5%) were similar. A laparoscopic technique was used in > or =88% and a pars flaccida technique in > or =41% of both groups. Early mortality was equivalent for SAGB/LB (
Increasing the use of biofuels influences atmospheric greenhouse gas concentrations. Although widely recognized, uncertainties related to the particular impacts are typically ignored or only partly considered. In this paper, various sources of uncertainty related to the GHG emission savings of biofuels are considered comprehensively and transparently through scenario analysis and stochastic simulation. Technology and feedstock production chain-specific factors, market-mediated factors and climate policy time frame issues are reflected using as a case study Fischer-Tropsch diesel derived from boreal forest biomass in Finland. This case study shows that the GHG emission savings may be positive or negative in many of the cases studied, and are subject to significant uncertainties, which are mainly determined by market-mediated factors related to fossil diesel substitution. Regardless of the considerable uncertainties, some robust conclusions could be drawn; it was likely of achieving some sort of but unlikely of achieving significant savings in the GHG emissions within the 100 year time frame in many cases. Logging residues (branches) performed better than stumps and living stem wood in terms of the GHG emission savings, which could be increased mainly by blocking carbon leakage. Forest carbon stock changes also significantly contributed to the GHG emission savings.
Mandatory helmet legislation for cyclists is the subject of much debate. Opponents of helmet legislation suggest that making riders wear helmets will reduce ridership, thus having a negative overall impact on health. Mandatory bicycle helmet legislation for children was introduced in Ontario, Canada in October 1995. The objective of our study was to examine trends in children's cycling rates before and after helmet legislation in one health district.
Child cyclists were observed at 111 preselected sites (schools, parks, residential streets, and major intersections) in the late spring and summer of 1993-97 and in 1999, in a defined urban community.
Trained observers counted the number of child cyclists. The number of children observed in each area was divided by the number of observation hours, resulting in the calculation of cyclists per hour.
A general linear model, using Tukey's method, compared the mean number of cyclists per hour for each year, and for each type of site.
Although the number of child cyclists per hour was significantly different in different years, these differences could not be attributed to legislation. In 1996, the year after legislation came into effect, average cycling levels were higher (6.84 cyclists per hour) than in 1995, the year before legislation (4.33 cyclists per hour).
Contrary to the findings in Australia, the introduction of helmet legislation did not have a significant negative impact on child cycling in this community.