Nordlund MS, Stieber P, Brustugun OT, Warren DJ, Paus E. Characteristics and clinical validity of two immunoassays for ProGRP.
Tumour Biol 2012;
33:1105-13. [PMID:
22399443 DOI:
10.1007/s13277-012-0351-1]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 02/08/2012] [Indexed: 10/28/2022] Open
Abstract
Progastrin-releasing peptide (proGRP) is a promising serum tumor marker for small cell lung cancer (SCLC). We have tested assay specificity and performed a correlation study between a recently developed time-resolved immunofluorometric assay (TR-IFMA) for proGRP and the established Advanced Life Science Institute (ALSI) ELISA method. Between-method correlation and comparison of clinical performance were studied in 481 individuals, among them, 178 lung cancers, 84 benign diseases of the lung, and 219 healthy controls. Follow-up time >6 years was observed for 89 patients with SCLC. The two assays had quite different epitope specificities where the TR-IFMA recognized a considerable smaller proGRP fragment than the ALSI ELISA. However, the correlation between the two methods for elevated proGRP values (>85 ng/l) was good (ρ = 0.948). Both assays displayed good discrimination between benign lung diseases and SCLC. The cut-off values for positive classification of SCLC versus non-small cell lung cancers and benign lung diseases at >95% specificity were 85 ng/l for the TR-IFMA and 42 ng/l for the ALSI ELISA. Both proGRP assays showed good clinical validity. However, due to differences in the recommended cut-off values, switching methods is not recommended. There was a significant difference in survival of patients with TR-IFMA proGRP values over the cut-off (85 ng/l) compared with patients with values under the cut-off, p = 0.0002. In contrast, the ALSI ELISA assay failed to provide statistically significant prognostic information, p = 0.066.
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