Medical diagnostics integrates laboratory testing, imaging, and tissue sampling to identify or exclude disease. This overview explains when to use blood tests, X-ray, ultrasound, CT scan, MRI, and biopsy, and how results inform a differential diagnosis guided by clinical guidelines.

Accurate diagnosis starts with a clinical question and proceeds through a systematic process. Clinicians synthesize history and examination findings with blood tests, imaging, and sometimes tissue sampling to confirm or rule out conditions. Interpreting results in context—and comparing them with clinical guidelines—helps prioritize next steps and avoid unnecessary procedures.

Imaging is often the first window into anatomy and function. For bones and chest evaluations, an X-ray offers speed and low cost; for soft tissues and pregnancy, ultrasound provides real-time, radiation-free views. When cross-sectional detail is needed quickly, a CT scan maps anatomy in fine slices, whereas MRI excels at high-contrast visualization of brain, spine, joints, and many organs.

Laboratory data extend beyond routine blood tests to include biomarkers, cultures, and genetic assays that refine probability estimates. When microscopic confirmation is necessary, a biopsy can characterize inflammation, infection, or malignancy and guide targeted therapy. Integrating these findings narrows the differential diagnosis rather than chasing a single result in isolation.

Choice of tests balances diagnostic yield, risks, and patient values. Radiation exposure, contrast allergies, cost, and timing all matter, and clinicians aim to order the right test at the right time according to clinical guidelines and local pathways. Patients can ask why each test is recommended, what the results might change, and what alternatives exist, ensuring care remains evidence based and personalized.