CYFRA 21-1 measures fragments of cytokeratin 19, a structural protein from epithelial cells, that are released into the bloodstream when those cells are damaged or die; the test quantifies the serum concentration of these soluble cytokeratin 19 fragments (commonly reported in ng/mL).

Clinically, CYFRA 21-1 is used as a tumor marker—most often in non–small cell lung cancer (particularly squamous cell carcinoma)—to help assess tumor burden, prognosis, and response to therapy or recurrence; because levels can also rise with other malignancies and some benign conditions and sensitivity/specificity are limited, it is interpreted alongside imaging and other clinical information rather than as a standalone screening test.

A CYFRA 21‑1 test is performed on a small blood sample taken by venipuncture (a standard blood draw, usually from a vein in the arm) by a trained phlebotomist. The blood is collected into the tube type specified by the laboratory (commonly a serum separator tube; some labs use plasma tubes), and no special preparation or fasting is typically required unless your provider or the laboratory gives different instructions.

After collection the sample is processed to separate serum or plasma (allow clotting if required, then centrifuge) and is tested or stored per the lab’s protocol; samples should be handled promptly and kept cool to avoid hemolysis or degradation. Your laboratory or healthcare provider will report the measured CYFRA 21‑1 level and explain next steps as needed.

CYFRA 21‑1 measures fragments of a structural protein (cytokeratin 19) released into the blood when cells break down. In a personal context, a normal CYFRA 21‑1 result makes it less likely that you have a tumor that sheds this marker, but it does not rule out cancer — many cancers do not raise CYFRA 21‑1 and early disease can still give normal values. A raised result increases the likelihood that a cancer that releases CYFRA 21‑1 (most commonly some lung cancers) or certain noncancerous conditions is present, and higher values generally correlate with larger tumor burden or more aggressive disease.

CYFRA 21‑1 is not diagnostic on its own: false positives and false negatives occur, cutoffs vary by laboratory, and levels can be affected by noncancer illnesses. Its greatest clinical value for an individual is in combination with imaging, biopsy and your doctor’s assessment — and in serial measurements where rising or falling levels help monitor treatment response or detect recurrence. Discuss your specific result and the next steps with the clinician who ordered the test so it can be interpreted in your full medical context.

CYFRA 21-1 (a cytokeratin‑19 fragment) can be a useful tumor marker—commonly elevated in non‑small cell lung cancer, especially squamous histology—but its sensitivity is only moderate while specificity is higher. Because it can miss cancers (false negatives) and can be raised by some noncancer conditions, CYFRA 21-1 is not reliable as a standalone screening or diagnostic test; it’s most valuable for monitoring treatment response, detecting recurrence, and providing prognostic information when combined with clinical assessment.

Test accuracy is affected by the assay used, the cut‑off chosen, cancer stage, and nonmalignant causes of elevation (for example renal or hepatic dysfunction and inflammation). Interpreting CYFRA 21-1 results together with imaging, other tumor markers, and clinical findings improves reliability, and decisions should be made by the treating clinician in context.

Testing frequency for CYFRA 21-1 is individualized but commonly follows a pattern: obtain a baseline at diagnosis, monitor more frequently during active therapy (often every treatment cycle or about every 3–6 weeks) to assess response, and use regular surveillance after completion of treatment (commonly every 2–3 months in the first 1–2 years, then every 4–6 months up to around 5 years, and less often thereafter). Your treating clinician will tailor the exact schedule based on cancer type, stage, treatment plan and risk of recurrence.

Interpret results in the context of symptoms, physical exam and imaging—small fluctuations can reflect assay variability or noncancer causes—so decisions are made combining marker trends with clinical findings and radiology rather than a single isolated value. Follow your oncologist’s specific recommendations for timing and action thresholds.

No — CYFRA 21-1 test results highlight patterns of imbalance or resilience, not medical diagnoses. Elevated or changed CYFRA 21-1 levels can indicate an abnormal signal or risk pattern but are not definitive proof of cancer on their own.

Results must be interpreted alongside symptoms, clinical examination, medical history, imaging, and other laboratory or biomarker data by a qualified clinician to determine their significance and whether further diagnostic testing is needed.

CYFRA 21‑1 reflects tumor cell burden, so the most effective way to lower it is to treat the underlying cancer—appropriate therapy (surgery, chemotherapy, targeted agents, immunotherapy or radiotherapy as recommended by your oncology team) and monitoring will usually reduce levels if the cancer responds. Clinicians interpret CYFRA trends together with imaging and symptoms; a single result rarely tells the whole story, and benign lung disease or impaired renal function can also raise CYFRA.

Supportive steps that may help overall care include adhering to your prescribed treatment plan, quitting smoking, promptly treating infections or inflammation, managing comorbidities (especially kidney disease), and maintaining nutrition and activity as tolerated. Do not alter or stop therapy based on one marker value—discuss any rising or persistent CYFRA 21‑1 results with your oncologist so they can recommend further testing, treatment changes, or referrals.