ESPE Abstracts (2015) 84 P-3-927

Comparison of Two IGF1 Assays in Patients Treated with GH

María Martíneza, Marta Murilloa, M Luisa Granadaa, Marta Aldeaa, Estefanía Guerrinib & Joan Bela

aGermans Trias i Pujol Hospital, Badalona, Spain; bFoundation Leo Messi, Badalona, Spain

Background: IGF1 measurements are used to diagnose and monitoring GH related disorders. GH dose is titrated against IGF1 concentrations which should be kept within the age-and sex-related normal range. However, IGF1 results vary widely depending on the immunoassay used. International guidelines advise to report IGF1 results as S.D. scores from an assay-specific age-related reference population.

Objective and hypotheses: Our objective was to assess whether the change in immunoassay lead to different clinical interpretation in prepubertal children, followed-up in our paediatric unit and treated with similar dose of GH.

Method: We collected 101 samples of 58 patients (23 girls and 35 boys) with tanner 1. IGF1 was measured by the Immulite 2000 (Siemens Diagnostics) immunoassay until February 2013 and by the Liaison (DiaSorin) from this date onwards. IGF1 data from 51 determinations were obtained with the Immulite (group A) and from 50 with the Liaison (group B).

Results: No differences were found in age (7.96±2.2 vs 8.38±2.2 age; P=N.S:), dose of GH (0.2165±0.031 vs 0.2096±0.034 mg/kg·week, P=N.S), absolute IGF1 concentrations (290.5±118 vs 281.9±78.3 ng/ml, P=N.S.), or SDS-IGF1 (1.22±1.04 vs 1.25±0.69, P=N.S.) between both groups. We took a subgroup of 16 children with determinations by both methods, where no significant differences in the levels of SDS-IGF1 were found.

Conclusion: In our group of prepubertal GHD patients treated with GH the change in the immunoassay for IGF1 was not associated to changes in clinical decisions. In both groups the same GH dose of GH was maintained as there were not significant changes in SDS-IGF1 regardless of the method used.

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