Cytokeratins are structural proteins forming the subunits of epithelial intermediary filaments. Twenty different cytokeratin polypeptides have so far been identified. Due to their specific distribution patterns they are eminently suitable for use as differentiation markers in tumor pathology. Intact cytokeratin polypeptides are poorly soluble, but soluble fragments can be detected in serum.
With the aid of two specific monoclonal antibodies (KS 19.1 and BM 19.21), CYFRA 21‑1 measures a fragment of cytokeratin 19 having a molecular weight of approximately 30000 daltons.
The main indication for CYFRA 21‑1 is monitoring the course of non‑small cell lung cancer (NSCLC). CYFRA 21‑1 is also suitable for course‑monitoring in myoinvasive cancer of the bladder. Good specificity is shown by CYFRA 21‑1 relative to benign lung diseases (pneumonia, sarcoidosis, tuberculosis, chronic bronchitis, bronchial asthma, emphysema).
Slightly elevated values (up to 10 ng/mL) are rarely found in marked benign liver diseases and renal failure. There is no correlation with sex, age or smoking. The values are also unaffected by pregnancy. The primary diagnosis of pulmonary carcinoma should be made on the basis of clinical symptomatology, imaging or endoscopic procedures and intraoperative findings. An unclear circular focus in the lung together with CYFRA 21‑1 values > 30 ng/mL indicate with high probability the existence of primary bronchial carcinoma. High CYFRA 21‑1 serum levels indicate an advanced tumor stage and a poor prognosis.A normal or only slightly elevated value does not rule out the presence of a tumor.
Successful therapy is documented by a rapid fall in the CYFRA 21‑1 serum level into the normal range. A constant CYFRA 21‑1 value or a slight or only slow decrease in the CYFRA 21‑1 value indicates incomplete removal of a tumor or the presence of multiple tumors with corresponding therapeutic and prognostic consequences. Progression of the disease is often shown earlier by increasing CYFRA 21‑1 values than by clinical symptomatology and imaging procedures
SI units Conversion Calculator. Convert CYFRA 21-1 level to ng/ml, µg/l, µg/dl, µg/100ml, µg%. Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for CYFRA 21-1 unit conversion to ng/ml, µg/l, µg/dl, µg/100ml, µg%.