Participants in each neighborhood attended a structured training session at which they practiced data-collection activities.
In practice, data collection for the majority of surveys cannot be conducted on a single day, but the goal is still to represent the population as of that date.
Cases were "lost" for the purpose of this retrospective study at two points: at the general practice data collection stage and at the questionnaire stage.
Patients were censored on the earliest date from among: the date of first CVD presentation, date of death from other causes, date leaving the practice, or date of last practice data collection.
Couples were followed in the primary care record from the index date for their practice between 2005 and 2008 to their last practice data collection date up to September 2010.
All study cohort members were followed up for a mean of 5.6 years from the first day after their start date to the earliest of the following endpoints: first recorded diagnosis of uncomplicated PUD, cancer, alcohol abuse or alcohol-related disease; reaching the age of 85 years; date of the last practice data collection; death; or end of the study period (30 September 2011).
An exemplary case was provided to practice the data collection.
Answering these questions and overcoming the problems in sampling are central to good-practice in data collection and study design.
We agreed to pool resources and retrospectively audit our own data on ONS for CDH to help guide us on future clinical indications for ONS, identify areas for improved clinical practice, technical practice and data collection.
Follow-up information for each patient was based on data from the index date (inclusive) to the end of patient records (earliest date of patient transfer out of practice and practice last data collection date).
Patients left the study at the earliest date of death, leaving the practice, last data collection from the practice, renal replacement therapy (dialysis or kidney transplantation), or March 31 , 2011
