Letter to the editor April 01, 2015 April 01, 2015

Current reliability of the Immulite^® assay for measurement of serum IGF-1 in the Brazilian adult population

DOI: 10.1590/2359-3997000000035

DEAR EDITOR,

The Immulite^® assay, the test most commonly used for IGF-1 measurement by clinical laboratories in Brazil, recently had supply problems () and temporarily ceased to be used. Earlier, the assay had been reported to overestimate IGF-1 concentrations (-). Many laboratories are now returning to use the Immulite^® assay for IGF-1 measurement. This test will therefore continue to be used in Brazil, at least in the short and medium term, although it does not meet the current recommendation of calibration against the World Health Organization (WHO) International Standard (IS) 02/254 (). Another assay (Liaison^®), calibrated against IS 02/254, is available in Brazil. However, IGF-1 reference values obtained with this assay have not been established in studies including a sufficient number of individuals and following current recommendations (). With the return of the Immulite^® assay, it is necessary to confirm that the current lots no longer overestimate IGF-1. This confirmation is necessary since the information was only provided by the manufacturer (), but so far there are no published data that prove this. Furthermore, the causes of the problem and the respective technical adjustments to solve it were not clarified ().

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