All ART patients aged 18 and above who came to receive ART at one of the 11 health centers during the day of the visit by the study interviewer team were asked to participate in face-to-face interviews.
First, transcripts were coded independently by the study interviewer and the principal investigator, and compared for consistency.
The questionnaire was always administered by the study interviewer immediately after postpartum and included sociodemographic characteristics (parents' age, parents' birth country, social class defined by parents' occupation using the UK Registrar General's 1990 classification which categorizes people with similar levels of occupational skills).
Family doctors should provide preventive and curative healthcare services, according to womens' individual health needs, and send the candidates to the waiting room where they will be interviewed by study interviewers, who will explain the purpose and content of the study, and obtain the signed informed consent from those women who agree to participate.
Data were collected by trained study interviewers from the Valencia Institute of Public Health (IVESP) who were unaware of cataract status and the hypotheses under study.
Cases and controls were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other major risk factors.
In the subsequent 10 years post-trial, subjects were contacted monthly, either by village health workers or by study interviewers, and cancer diagnoses were verified by senior Chinese diagnosticians from Beijing.
One hundred and seven potential participants changed their mind or could not be contacted, resulting in 839 (64.5%) individuals - 576 women and 263 men - who were interviewed face-to-face by trained study interviewers between February 2001 and March 2002.
After obtaining written consent, an in-person interview was conducted at the hospital either before or after delivery by trained study interviewers using a standardized and structured questionnaire.
The external appearance of the block the respondent lived on and five housing conditions were rated by study interviewers.
