A diagnostic biomarker is a biological indicator that helps identify the presence of a disease or condition in an individual. These markers can be found in various biological samples, such as blood, urine, or tissue, and can include proteins, genes, or metabolites. By analyzing these substances, healthcare professionals can make more accurate diagnoses and tailor treatment plans for patients. The use of diagnostic biomarkers is crucial in fields like oncology, where they can help detect specific types of cancer, such as breast cancer or lung cancer. Additionally, they can assist in monitoring disease progression and response to therapy, improving patient outcomes and personalized medicine approaches.