of Interest: The subjects recruited for the case study were exposed to trihalomethane, a by-product produced during the chlorination of water, which is done for the purpose of disinfection.
Patients who were histologically confirmed to have primary bladder cancer were recruited as the case population for the study and they were identified with the help of urologic services. The other inclusion criteria’s for the recruitment of the case population were: age group between 20 and 80 years and they must reside within the geographical area surrounding the hospital.
The study was a multi-center case-control study conducted in Spain and the subjects were recruited from 18 participating hospitals located at five different geographic regions in and around Spain. The cases were recruited through regular reviews of the discharge and pathology records in hospitals at by the research staffs who were involved in the study.
The number of cases who participated in the study was 338 out of the 1,457 eligible cases who were interviewed. However the article does not provide any information about the eligible subjects who were not part of the subjects. The reason for their non-participation has not been mentioned.
The control population was chosen from the same hospitals where the case subjects were recruited. The control group included patients who suffered from problems like hernias, orthopedic problems, circulatory disorders, and who were admitted to the hospital. Those who had problems that were related to the study were not chosen as controls. About 582 controls from 1,465 eligible controls were selected. Signed informed consents were obtained from both the case and control participants before onset of the study.
During the initial interview demographic information and familial, medical, including smoking history, and occupational history of all the eligible participants were collected using computer assisted software. The short listed case and control population were