A systematic screening for potential study subjects will be made by the research coordinators based on key computer searches fields throughout four different softwares. Through these databases, researchers will be able to perform a preliminary selection of any of the eligible subjects by identifying hospitalized patients that will ultimately be treated. The pharmacists responsible for validation of tinzaparin prescriptions at the pharmacy department will work with the research team at the initial screening by identifying eligible candidates. Since the choice of prescribed agents is to the prescriber's discretion, the recruitment procedures will be triggered mainly as soon as a prescription of tinzaparin at thromboprophylaxic dose is written.Subjects who meet the inclusion criteria and do not meet any exclusion criteria will be considered eligible candidates and additional baseline information will be collected at that point, such as ethnicity and sex. The eligible participant will be addressed directly by a member of the research team. Informed consent will be sought and documented through the Information Form and Informed Consent (FIC) already approved by the ethics committee the hospital.