Sample sizes for clinical trials with time-to-event endpoints and competing risks.

We consider clinical trials where the time to occurrence of events in the presence of competing risks is the primary endpoint for treatment evaluation. The number of events with regard to the defined primary endpoint required to ensure the specified power can be calculated according to Schoenfeld's formula like in classical survival studies. However, determination of the number of patients that have to be recruited to observe the calculated number of events requires specification of the length of the accrual period, the trial duration and assumptions about the event-specific hazard functions.

Nosocomial pneumonia: a cost-of-illness analysis.

Background: We investigated incremental cost of nosocomial pneumonia (NP) from the perspective of a hospital and health insurance funds.

Patients And Methods: The incremental cost was determined by calculating total costs for pneumonia patients and controls using prospective and retrospective matched-pairs analysis with 29 and 37 matched pairs, respectively.

Results: Compared to controls, patients who developed pneumonia had to be on artificial ventilation 5 days longer, needed markedly more intensive care with 6.

Identifying outliers of antibiotic usage in prevalence studies on nosocomial infections.

Objective: To investigate whether the correlation between patients' antibiotic treatment (yes/no) and patients' infections (yes/no) in each hospital department, described by Pearson's correlation coefficient (p) for binary data as a measure for adequate use of antibiotics, is an appropriate quality indicator.

Design: Comparison of the results of repeated prevalence studies in different hospitals with the data of a national prevalence study, comparing the hospital (p) and reference (pNIDEP[Nosokomiale Infektionen in Deutschland: Erfassung und Pravention]) correlation coefficients for "use of antibiotics/ presence of infections."

Setting: The data of 5,377 surgical patients were separated from the total data of a national prevalence study in 72 representative hospitals to create a reference correlation coefficient (rhoNIDEP) with a reference range.

Estimation of extra hospital stay attributable to nosocomial infections: heterogeneity and timing of events.

Infections acquired in hospital are likely to affect the duration of hospitalization. Suitable statistical methods for estimating the extra days spent in hospital due to nosocomial infections should allow modeling of the heterogeneity of the patient population and the timing of events, as failure to account for important covariates and failure to model adequately the timing of events may lead to biased results. Three approaches have been used in the past to estimate the extra stay: a comparison of duration of stay of infected and uninfected patients, matching of infected and uninfected patients with respect to potentially important determinants of the length of hospital stay, and matching for time-to-infection in addition to the other factors.

Low alpha-linolenic acid content of adipose breast tissue is associated with an increased risk of breast cancer.

Data derived from experimental studies suggest that alpha-linolenic acid may have a protective effect in breast cancer. Observations obtained from epidemiological studies have not allowed conclusions to be drawn about a potential protective effect of dietary alpha-linolenic acid on breast cancer, possibly because of methodological issues. This case-control study conducted in an homogeneous population from a central area in France was designed to explore the hypothesis that alpha-linolenic acid inhibits breast cancer, using fatty acid levels in adipose breast tissue as a biomarker of past qualitative dietary intake of fatty acids.