Abstract
A fragment of cytokeratin 19, CYFRA 21-1, has been reported to be a sensitive tumor marker for non-small cell lung cancer (NSCLC). We describe analytical performance characteristics of a novel CYFRA 21-1 assay and hypothesize that CYFRA 21-1 complements the clinical sensitivity of carcinoembryonic antigen (CEA) and squamous cell carcinoma antigen (SCCa).
Performance characteristics of a CYFRA 21-1 immunochemiluminescent assay included analytical sensitivity, imprecision, linearity, analyte stability, and reference interval determination. Ninety-two pretreatment NSCLC serum samples were tested for CYFRA 21-1, CEA, and SCCa. Sensitivity was determined for each marker individually and in combination, with regard to tumor stage and histology.
The analytical sensitivity was 0.01
ng/mL. Total imprecision ranged from 4.0 to 6.3% at 4.9 to 28.4
ng/mL, respectively. The assay was linear from 0.9 to 71.4
ng/mL (slope
=
0.995, intercept
=
−
0.60,
r
2
=
0.999). CYFRA 21-1 was stable for 48
h at ambient temperature and 14
days at 4
°C. The 97.5th percentile of a reference population was 1.9
ng/mL. Across disease stage, the sensitivities of CYFRA 21-1, CEA, and SCCa were 17–81%, 30–52%, and 24–39%, respectively. CYFRA 21-1 combined with CEA or SCCa increased sensitivity above that of any single marker.
An immunochemiluminescent assay for CYFRA 21-1 had favorable performance characteristics. CYFRA 21-1 was complementary to CEA and SCCa and increased clinical sensitivity in patients with NSCLC.