IGF-I Levels in Children on rhGH Treatment Is Strongly Dependent of IGF-I Assay: the Effect of Sample Pretreatment

M.E. RODRÍGUEZ; M.G. BALLERINI; D. BRASLAVSKY; H.M. DOMENÉ; A. MARTÍNEZ; A. KESELMAN; I. BERGADÁ; M.G. ROPELATO; H.G. JASPER

Cartagena de Indias

Congreso; XXII Annual Meeting of the Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP); 2011

Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP)

IGF-I Levels in Children on rhGH Treatment Is Strongly Dependent of IGF-I Assay: the Effect of Sample Pretreatment M.E. Rodriguez, M.G. Ballerini, D. Braslavsky, H.M. Domené, A. Martinez, A. Keselman, I. Bergadá, M.G. Ropelato, H.G. Jasper Hospital de Niños R Gutiérrez, Division Endocrinologia, Buenos Aires, Argentina Introduction: It has been suggested that monitoring IGF-I after rhGH treatment could be useful to ascertain both compliance and safety. Hence, its measurements must prove reliable. Aim: To compare two IGF-I assay’s performance in monitoring rhGH treatment in children. Methods: IGF-I concentration by extracted in house RIA and by ICMA (IMMULITE 2000, Siemens) was measured in 134 serum samples from children after 0.5 to 3 years on rhGH. In addition, 63/134 samples were also measured after alcohol-acid extraction (followed by cryoprecipitation) by ICMA (eICMA). Results: Unextracted ICMA results were positively biased compared to RIA (y = 1.608x-8.2, r = 0.96) and showed higher divergences at higher IGF-I-RIA values. However, in 63 samples eICMA results were similar to those obtained by RIA (y = 1.036x-16.4, r = 0.88), with recovery >90%. Considering a theoretical IGF-I optimal target on rhGH treatment between 0 to +2.0 SDS, 17 samples by RIA were within –2.0 to 0 SDS, but by ICMA 7/17 (41%) showed IGF-SDS >0. Thirty six samples by RIA were within 0 to +2.0 SDS, but by ICMA 11/36 (31%) showed IGFSDS >+2.0. Overall ICMA without extraction misinterpreted 18/53 samples (34%). Conclusion: Our findings stress the need of extraction procedures prior to ICMA measurement in GH treated children to properly interpret IGF-I results