CONTEXT: IGF-1 measurements are used for screening and monitoring GH deficiency (GHD) and acromegaly. OBJECTIVE: Our objective was to study whether the introduction of the IDS-iSYS IGF-1 assay would lead to different clinical interpretations in GHD and acromegaly. DESIGN: In 106 GHD subjects and in 15 acromegalic subjects visiting our university hospital, total IGF-1 levels were measured before and during therapy by using the Immulite (IM) assay and IDS-iSYS (ID) assay. Z-scores were calculated by using assay-specific age-specific normative range values. All treatment decisions were based upon results obtained by the IM assay. RESULTS: In GHD subjects, absolute IGF-1 concentrations differed significantly between both IGF-1 assays before treatment (P < .001) but not during GH treatment (P = .32), and mean Z-scores for IGF-1 differed significantly before starting (IM, -2.23, vs ID, -1.43; P < .001) and during GH treatment (IM, -0.60, vs ID, +0.21; P < .001). In acromegalic subjects, absolute IGF-1 concentrations did not differ between both IGF-1 assays before treatment (P = .18) but were significantly different during treatment (P = 0.009), and mean Z-scores for IGF-1 were not different before starting (IM, 10.93, vs ID, 10.78; P = .41) or during treatment (IM, 3.60, vs ID, 3.18; P = .23). CONCLUSIONS: In GHD subjects, mean IGF-1 Z-scores significantly differed when measured by the IM assay compared with the ID assay irrespective of treatment. In contrast, in acromegaly, mean IGF-1 Z-scores did not differ significantly between both assays. Our study suggests that replacement of the IM assay by the ID assay may have far-reaching consequences for the clinical diagnosis and treatment of GHD.
CONTEXT: IGF-1 measurements are used for screening and monitoring GH deficiency (GHD) and acromegaly. OBJECTIVE: Our objective was to study whether the introduction of the IDS-iSYS IGF-1 assay would lead to different clinical interpretations in GHD and acromegaly. DESIGN: In 106 GHD subjects and in 15 acromegalic subjects visiting our university hospital, total IGF-1 levels were measured before and during therapy by using the Immulite (IM) assay and IDS-iSYS (ID) assay. Z-scores were calculated by using assay-specific age-specific normative range values. All treatment decisions were based upon results obtained by the IM assay. RESULTS: In GHD subjects, absolute IGF-1 concentrations differed significantly between both IGF-1 assays before treatment (P < .001) but not during GH treatment (P = .32), and mean Z-scores for IGF-1 differed significantly before starting (IM, -2.23, vs ID, -1.43; P < .001) and during GH treatment (IM, -0.60, vs ID, +0.21; P < .001). In acromegalic subjects, absolute IGF-1 concentrations did not differ between both IGF-1 assays before treatment (P = .18) but were significantly different during treatment (P = 0.009), and mean Z-scores for IGF-1 were not different before starting (IM, 10.93, vs ID, 10.78; P = .41) or during treatment (IM, 3.60, vs ID, 3.18; P = .23). CONCLUSIONS: In GHD subjects, mean IGF-1 Z-scores significantly differed when measured by the IM assay compared with the ID assay irrespective of treatment. In contrast, in acromegaly, mean IGF-1 Z-scores did not differ significantly between both assays. Our study suggests that replacement of the IM assay by the ID assay may have far-reaching consequences for the clinical diagnosis and treatment of GHD.
Authors: Vivien Bonert; John Carmichael; Zengru Wu; James Mirocha; Daniel A Perez; Nigel J Clarke; Richard E Reitz; Michael J McPhaul; Adam Mamelak Journal: Pituitary Date: 2018-02 Impact factor: 4.107
Authors: Selveta S van Santen; Peter Wolf; Natalia Kremenevski; Cesar L Boguszewski; Hannes Beiglböck; Marta Fiocco; Mark Wijnen; Ville R Wallenius; Marry M van den Heuvel-Eibrink; Aart J van der Lely; Gudmundur Johannsson; Anton Luger; Michael Krebs; Michael Buchfelder; Patric J D Delhanty; Sebastian J C M M Neggers; Daniel S Olsson Journal: J Clin Endocrinol Metab Date: 2021-10-21 Impact factor: 5.958