A diagnostic test is a medical procedure 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 information about a patient's health and make informed decisions regarding treatment. The results of diagnostic tests are crucial for diagnosing conditions such as diabetes, cancer, or heart disease. By analyzing the data obtained from these tests, doctors can identify the best course of action, monitor disease progression, and evaluate the effectiveness of treatments.