a study was done about non-participation during phase iii of the international study of asthma and allergy in childhood (isaac iii) in valencia to determine whether the non-response rate significantly affected the results obtained in valencia. of the schools selected to participate in isaac iii, 13.3% denied not to, the main reason being they were already participated in a similar study. the is...

The design of occupational epidemiology studies should be based on the need to minimise random and systematic error. The latter is the focus of this paper, and includes selection bias, information bias and confounding. Selection bias can be minimised by obtaining a high response rate (and by appropriate selection of the control group in a case-control study). In general, it is important to ensu...

Methods Many studies have been conducted on the epidemiology of in-patient violence by use of standardized scales such as the SOAS-R. Much research on patient and environment characteristics has been compromised by methodological flaws such as sample selection bias. Epidemiological data on the use of coercive measures is scarcely available in most countries, and different ways of reporting rend...

1. Snoep JD, Morabia A, Hernandez-Diaz S, Hernan MA, Vandenbroucke JP. A structural approach to Berkson’s fallacy: and a guide to a history of opinions about it. Int J Epidemiol 2014;43:515–21. 2. Berkson J. Limitations of the application of fourfold table analysis to hospital data. Biometrics Bull 1946;2:47–53. Reprinted Int J Epidemiol 2014;43:511–15. 3. Rothman KJ, Greenland S, Lash TL. Vali...

the Epidemiology of normal pregnancies with unknown last menstrual period (LMP) was studied in 1192 singleton  pregnancies.the LMP was unknown in 240(20.3%) pregnancies.unknown LMP is associated with high rates of low birth weight and all low socio-economic and socio-demographic status.such characteristics are also associated with a high rate of preterm deliveries.any possible bias introduced i...

The concept of meta-epidemiology has been introduced with considering the methodological limitations of systematic review for intervention trials. The paradigm of meta-epidemiology has shifted from a statistical method into a new methodology to close gaps between evidence and practice. Main interest of meta-epidemiology is to control potential biases in previous quantitative systematic reviews ...

This review article aims to anatomize sources of the healthy worker effect (HWE) and to summarize advantages and limitations of several approaches frequently proposed to eliminate the HWE. Although the HWE is frequently addressed in the context of selection bias, our review suggests that the selection of occupational cohorts with advantageous health status would preferably be addressed as a sou...