02547nas a2200229 4500008004100000022001400041245016500055210006900220260001300289300000900302490000700311520179200318100002502110700002702135700002102162700001402183700001702197700002002214700002502234700002202259856003602281 2016 eng d a1532-223800aAgreement between circulating IGF-I, IGFBP-1 and IGFBP-3 levels measured by current assays versus unavailable assays previously used in epidemiological studies.0 aAgreement between circulating IGFI IGFBP1 and IGFBP3 levels meas c2016 Feb a11-60 v263 a

OBJECTIVE: Levels of insulin-like growth factor (IGF) proteins are associated with the risk of cancer and mortality. IGF assays produced by Diagnostic Systems Laboratories (DSL) were widely used in epidemiological studies, were not calibrated against recommended standards and are no longer commercially available.

DESIGN: In a split sample study among 1471 adults participating in the Cardiovascular Health Study, we compared values obtained using DSL assays with alternative assays for serum IGF-I (Immunodiagnostic Systems, IDS), IGFBP-1 (American Laboratory Products Company, ALPCO) and IGFBP-3 (IDS).

RESULTS: Results were compared using kernel density estimation plots, quartile analysis with weighted kappa statistics and linear regression models to assess the concordance of data from the different assays. Participants had a mean age of 77years. Results between alternative assays were strongly correlated (IGF-I, r=0.93 for DSL versus IDS; log-IGFBP-1, r=0.90 for DSL versus ALPCO; IGFBP-3, r=0.92 for DSL versus IDS). Cross tabulations showed that participants were usually in the same quartile categories regardless of the assay used (overall agreement, 74% for IGF-I, 64% for IGFBP-1, 71% for IGFBP-3). Weighted kappa also showed substantial agreement between assays (kw, 0.78 for IGF-I, 0.69 for IGFBP-1, 0.76 for IGFBP-3). Regressions of levels obtained with DSL assays (denoted X) to alternative assays were, IGF-I: 0.52X+15.2ng/ml, log-IGFBP-1: 1.01X-1.73ng/ml IGFBP-3: 0.87X+791.1ng/ml. Serum values of IGF-I, IGFBP-1 and IGFBP-3 measured using alternative assays are moderately correlated.

CONCLUSIONS: Care is needed in the interpretation of data sets involving IGF analytes if assay methodologies are not uniform.

1 aAneke-Nash, Chino, S1 aDominguez-Islas, Clara1 aBůzková, Petra1 aQi, Qibin1 aXue, XiaoNan1 aPollak, Michael1 aStrickler, Howard, D1 aKaplan, Robert, C uhttps://chs-nhlbi.org/node/6952