In order to ensure the representativeness of the cases, the samples were selected across different business sectors ranging from service (such as IT, consulting, entertainment, and housekeeping), education, and trading to food and manufacturing.
To assess the representativeness of the case-patients whose specimens were tested for antiviral susceptibility and to identify any potential selection bias, our control group was compared with pandemic (H1N1) 2009 patients who were recorded in the hospital database as not having been tested for antiviral susceptibility.
Selection (4 items): adequacy of case definition; representativeness of the cases; selection of controls; and definition of controls.
For case-control studies, we also removed the item "representativeness of the cases".
In short, the scoring method was based on the following five aspects: whether the diagnosis of cancer was clear; numbers of the cases; representativeness of the cases collected; judgment criteria of FOXM1; and the data sources of HR (95% CI).
The limitations of the studies of cases and controls are related to the representativeness of the cases selected for the study with respect to the whole population of cases.
The methodological quality of the included studies was evaluated based on the Newcastle Ottawa Scale (NOS) [ 22], by appraising the following characteristics (an example for case control and cross-sectional studies): Selection (4 items): adequacy of case definition; representativeness of the cases; selection of controls; and definition of controls.
However, such analyses should be viewed as multiple-site studies, with all the concerns of individual site studies as well as issues of diagnostic consistency across sites, type and amount of data recorded, as well as representativeness of the cases to the base populations.
Although such studies are susceptible to confounding and to bias due to differential ascertainment of cases, investigators can mitigate the impact of these biases by standardizing measures of key variables, achieving near complete case ascertainment, and evaluating the representativeness of the included cases.
Key data collected on all admissions, such as age, residence in catchment area, and admission diagnosis from existing hospital sources (eg, admission registers), will help assess the representativeness of the enrolled cases.
To determine the representativeness of the selected cases vis-à-vis the entire patient population, we compared the 88 patients' risk for PUs, age, sex, and BMI to the non-included patients in round three of the project using ANOVA at baseline.
