Imperial Collage Healthcare

CYFRA 21-1

Test Background
CYFRA 21-1, a cytokeratin 19 (CK19) fragment, is an acid-type cytoplasmic protein with a molecular weight of 40 kDa that belongs to the intermediate filament group of proteins. Cytokeratins are sub-grouped into acidic type I (40-56.5 kDa) and basic type II (53-67 kDa). Cytokeratins 8, 18 and 19 are the most abundant types present in epithelial cells. Due to their release during cell proliferation or apoptosis, cytokeratins provide useful markers for epithelial malignancies.
Serum levels of CYFRA 21-1 are frequently elevated in lung cancer, particularly in non-small cell lung cancer patients (NSCLC). CYFRA 21-1 levels are particularly high in patients with squamous cell carcinoma. However, elevated levels of cytokeratin 19 fragments are also seen in other cancers, eg. bladder cancer. Elevated levels of CYFRA 21-1 may also be found in subjects with non-malignant disease including: acute pneumonia, tuberculosis, liver diseases and renal failure.

Clinical Indications
Lung cancer

  • Diagnosis: due to limited sensitivity and specificity, single measurements of CYFRA 21-1 are not recommended for screening purposes. CYFRA 21-1 in combination with other tumour markers is useful in the differential diagnosis of lung cancer, particularly in patients who are difficult to biopsy. The pattern of serological tumour marker elevation correlates histological subtype: CEA elevation correlates adenocarcinoma; CYFRA 21-1 and SCC elevation squamous cell carcinoma; CYFRA 21-1 and NSE elevation large cell cancer and NSE elevation small cell lung cancer.
  • Prognosis and staging: several multivariate studies and a recent multicentre study demonstrate CYFRA 21-1 to be an independent prognostic factor in NSCLC.
  • Treatment monitoring: in advanced NSCLC, trends in serum CYFRA 21-1 levels during initial chemotherapy predict responsiveness to subsequent therapy.
  • Surveillance: CYFRA is helpful for the detection of recurrent disease after primary therapy, particularly in squamous cell lung cancer.

Reference Range

<3.3 ng/mL

Sample Required
Serum (red top) preferred, SST (gold top) acceptable

Sample Volume
0.5 mL

Turnaround Time
4 weeks

Brahms Kryptor assay

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