ISO (the International Organization for Standardization) is a worldwide federation of national standard bodies (ISO member bodies). The work of preparing international standards is normally carried out through ISO technical committees. ISO 15189 was prepared by Technical Committee ISO/TC 212, clinical laboratory testing, and in vitro diagnostic test systems. This third edition replaces the second edition (ISO 15189:2007), which was technically revised. Medical laboratory services are essential for patient care and, therefore, have to be available to meet the needs of all patients and the clinical personnel responsible for the care of those patients.