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One of the main perceived advantages of using a case-cohort design compared with a nested case-control design in an epidemiologic study is the ability to evaluate with the same subcohort outcomes other than the primary outcome of ...
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One of the main perceived advantages of using a case-cohort design compared with a nested case-control design in an epidemiologic study is the ability to evaluate with the same subcohort outcomes other than the primary outcome of interest. In this paper, we show that valid inferences about secondary outcomes can also be achieved in nested case-control studies by using the inclusion probability weighting method in combination with an approximate jackknife standard error that can be computed using existing software. Simulation studies demonstrate that when the sample size is sufficient, this approach yields valid type 1 error and coverage rates for the analysis of secondary outcomes in nested case-control designs. Interestingly, the statistical power of the nested case-control design was comparable with that of the case-cohort design when the primary and secondary outcomes were positively correlated. The proposed method is illustrated with the data from a cohort in Cardiovascular Health Study to study the association of C-reactive protein levels and the incidence of congestive heart failure.
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Background: The concurrent sampling design was developed for case-control studies of recurrent events. It involves matching for time. Standard conditional logistic-regression (CLR) analysis ignores the dependence among recurrent e...
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Background: The concurrent sampling design was developed for case-control studies of recurrent events. It involves matching for time. Standard conditional logistic-regression (CLR) analysis ignores the dependence among recurrent events. Existing methods for clustered observations for CLR do not fit the complex data structure arising from the concurrent sampling design.
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Background: Previous simulation studies of the case-control study design using incidence density sampling, which required individual matching for time, showed biased estimates of association from conditional logistic regression (C...
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Background: Previous simulation studies of the case-control study design using incidence density sampling, which required individual matching for time, showed biased estimates of association from conditional logistic regression (CLR) analysis; however, the reason for this is unknown. Separately, in the analysis of case-control studies using the exclusive sampling design, it has been shown that unconditional logistic regression (ULR) with adjustment for an individually matched binary factor can give unbiased estimates. The validity of this analytic approach in incidence density sampling needs evaluation.
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Thyroid hormones, which influence body metabolism and development, could be affected by persistent organic pollutants. We sought to examine the relationship between polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PC...
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Thyroid hormones, which influence body metabolism and development, could be affected by persistent organic pollutants. We sought to examine the relationship between polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) and thyroid disease. We employed incidence density sampling to perform a nested case control analysts of the Michigan Long-Term PBB Cohort. Cohort members (n = 3333) were exposed to PBBs through contaminated cattle feed in 1973-1974 and to PCBs through daily life. Those with detectable serum PBB and PCB concentrations at enrollment were categorized into tertiles of PBB and PCB exposure. Case-patients were cohort members answering "Yes" to "Has a healthcare provider ever told you that you had a thyroid problem?" during follow-up interviews; control-patients were cohort members answering "No". We used odds ratios (OR) with 95% confidence intervals (CI) to compare odds of thyroid disease by PBB and PCB exposure and by various risk factors. Total cumulative thyroid disease incidence after 33 years was 13.9% among women and 2.6% among men. After adjusting for body mass index, we found no statistically significant differences in odds of any type of thyroid disease among women or men with elevated PBB or PCB exposure. Compared to control-patients, women with thyroid disease had increased odds of being overweight/obese (OR-2.82, 95% Cl: 1.94-4.11) and developing infertility (OR- 1.71, 95% CI: 1.08-2.69), diabetes (OR- 1.61, 95% CI: 1.04-2.51), or arthritis (OR =1.71, 95% CI: 1.18-2.50) during follow-up. Additional research should explore potential associations between PBBs/PCBs and thyroid disease among children exposed in utero.
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Background Hypernatremia is a major electrolyte disorder associated with death among critically ill patients. Glucocorticoid therapy may cause hypernatremia in refractory septic shock patients, but the association between glucocor...
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Background Hypernatremia is a major electrolyte disorder associated with death among critically ill patients. Glucocorticoid therapy may cause hypernatremia in refractory septic shock patients, but the association between glucocorticoid and intensive care unit (ICU)-acquired hypernatremia (IAH) remains unclear. The aim of this study was to clarify whether glucocorticoid administration was associated with IAH. Methods This was a nested case-control study using data from an established cohort including 121 IAH cases identified from 1756 patients who were admitted to ICU in a tertiary care facility in Japan. We included patients who were admitted with a normal range of serum sodium concentrations (130-149 mEq/L) from January 1, 2013 to December 31, 2015 and remained in ICU for >= 2 days. Hypernatremia was defined as serum sodium concentration >= 150 mEq/L. Each case was matched to one control. Results Multivariable conditional logistic regression revealed high-dose glucocorticoid {odds ratio (OR), 4.15 [95% confidence interval (CI) 1.29-13.4]}, acute kidney injury (AKI) [OR, 2.72 (95% CI 1.31-5.62)], and osmotic diuretics [OR, 3.44 (95% CI 1.41-8.39)] to be significantly associated with IAH. The contents and amounts of fluid infusion were not significantly associated with IAH. There were also significant duration-response effects between duration of glucocorticoid use and IAH; however, pulse glucocorticoid administration was not associated with IAH. Conclusion In this nested case-control study, we demonstrated a significant association between IAH and high-dose glucocorticoid with significant duration-response effects. Serum sodium concentrations should be monitored carefully in critically ill patients administered prolonged high-dose glucocorticoid.
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Similarities in population parameters among aphid species led us to investigate the potential for a single set of parameters that can be used to develop a 'generic' sampling plan for multiple small grain aphid species. A weighted ...
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Similarities in population parameters among aphid species led us to investigate the potential for a single set of parameters that can be used to develop a 'generic' sampling plan for multiple small grain aphid species. A weighted average for the slope and intercept used to relate the proportion of infested tillers to the number of aphids per tiller was determined from the data in 15 published reports. These average parameter estimates were used to predict the number of aphids per tiller in 48 wheat fields sampled for four aphid species. The predicted estimates were regressed on the observed estimates with neither slopes nor intercepts differing significantly from one or zero, respectively. Therefore, it appears the single model is adequate for predicting aphid density for the aphid species tested.
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Risk factors for nosocomial COVID-19 outbreaks continue to evolve. The aim of this study was to investigate a multi-ward nosocomial outbreak of COVID-19 between 1st September and 15th November 2020, occurring in a setting without ...
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Risk factors for nosocomial COVID-19 outbreaks continue to evolve. The aim of this study was to investigate a multi-ward nosocomial outbreak of COVID-19 between 1st September and 15th November 2020, occurring in a setting without vaccination for any healthcare workers or patients.Outbreak report and retrospective, matched case–control study using incidence density sampling in three cardiac wards in an 1100-bed tertiary teaching hospital in Calgary, Alberta, Canada. Patients were confirmed/probable COVID-19 cases and contemporaneous control patients without COVID-19. COVID-19 outbreak definitions were based on Public Health guidelines. Clinical and environmental specimens were tested by RT-PCR and as applicable quantitative viral cultures and whole genome sequencing were conducted. Controls were inpatients on the cardiac wards during the study period confirmed to be without COVID-19, matched to outbreak cases by time of symptom onset dates, age within ± 15 years and were admitted in hospital for at least 2 days. Demographics, Braden Score, baseline medications, laboratory measures, co-morbidities, and hospitalization characteristics were collected on cases and controls. Univariate and multivariate conditional logistical regression was used to identify independent risk factors for nosocomial COVID-19.The outbreak involved 42 healthcare workers and 39 patients. The strongest independent risk factor for nosocomial COVID-19 (IRR 3.21, 95% CI 1.47–7.02) was exposure in a multi-bedded room. Of 45 strains successfully sequenced, 44 (97.8%) were B.1.128 and differed from the most common circulating community lineages. SARS-CoV-2 positive cultures were detected in 56.7% (34/60) of clinical and environmental specimens. The multidisciplinary outbreak team observed eleven contributing events to transmission during the outbreak.Transmission routes of SARS-CoV-2 in hospital outbreaks are complex; however multi-bedded rooms play a significant role in the transmission of SARS-CoV-2.
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Laser-induced breakdown spectroscopy of CuO plasma in the presence and absence of magnetic field has been investigated. The plasma was generated by employing Nd: YAG laser (532 nm, 9 ns) at various pulse laser energy ranging from ...
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Laser-induced breakdown spectroscopy of CuO plasma in the presence and absence of magnetic field has been investigated. The plasma was generated by employing Nd: YAG laser (532 nm, 9 ns) at various pulse laser energy ranging from 100 to 400 mj in a vacuum. The increasing of pulse laser energy in the presence and absence of the magnetic field had shown increasing in electron density while the electron temperature was decreases. The presence of the magnetic field cause to a rising the electron density but it reduces the electron temperature comparison with the case of absence of the magnetic field. According to theβ value distribution along the target, the results shows in the central region of the target the plasma plump that produced by laser is in a good confinement in this region in contrasted with edge region of the target region.
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