title: Characteristics and clinical validity of two immunoassays for ProGRP.
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.
authors.affiliation: Department of Medical Biochemistry, Oslo University Hospital, Radiumhospitalet, Oslo, Norway. marianne.sparby.nordlund@radiumhospitalet.no
authors.forename: Marianne S
authors.initials: MS
authors.lastname: Nordlund
authors.forename: Petra
authors.initials: P
authors.lastname: Stieber
authors.forename: Odd Terje
authors.initials: OT
authors.lastname: Brustugun
authors.forename: David J
authors.initials: DJ
authors.lastname: Warren
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Paus
mesh_terms: D000595:Amino Acid Sequence; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis / Q000378:metabolism; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D015200:Fluoroimmunoassay / Q000379:methods*; D006801:Humans; D008168:Lung / Q000737:chemistry* / Q000473:pathology; D008171:Lung Diseases / Q000175:diagnosis / Q000378:metabolism; D008175:Lung Neoplasms / Q000175:diagnosis / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis*; D011379:Prognosis; D011994:Recombinant Proteins / Q000032:analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055752:Small Cell Lung Carcinoma / Q000175:diagnosis / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D011994:Recombinant Proteins; C087079:pro-gastrin-releasing peptide (31-98)