ICD codes serve critical clinical and administrative functions across the healthcare system. Clinicians use them to order specific laboratory tests and prescribe targeted treatments, which laboratories then use to identify required diagnostic tests. Healthcare managers use these codes to verify the appropriateness of treatments, medical coders use them to assign codes for procedures, and medical billers use them to process insurance reimbursement claims. Additionally, they are used by vital-records keepers to document causes of death on death certificates, and by epidemiologists to calculate disease morbidity and mortality statistics.