Diagnostic tests are medical procedures used to determine the presence or absence of a disease or condition. These tests can include blood tests, imaging studies like X-rays or MRIs, and biopsies. They help healthcare providers gather important information about a patient's health, guiding treatment decisions. The results of diagnostic tests can reveal vital information about how the body is functioning. For example, a blood test can indicate levels of certain substances, while an ultrasound can visualize internal organs. Accurate diagnosis is crucial for effective treatment and management of health issues.