English 
Italian Sviluppo e validazione di un metodo analitico per la misurazione in neonati dell’ormone della crescita in campioni eluiti da carte filtro
Development and validation of a method for the measurement of growth hormone in newborns on dried blood spots
AUTORI
1 UOC Patologia Clinica, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milano
2 UOC Endocrinologia, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milano
3 Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, Milan
ABSTRACT
Development and validation of a method for the measurement of growth hormone in newborns on dried blood spots.
Introduction: severe deficiency of Growth Hormone (GHD) of the newborn is a rare but potentially life-threatening disease. GH can be measured during the first week of life when levels are physiologically higher. Aim of the study was to validate a method to measure GH in newborns from dried blood spots (DBS) for reference interval estimation. Methods: whole EDTA-blood and serum were collected from patients attending the Endocrinology Unit. 50 µL of EDTA-blood was spotted onto Guthrie cards (LTA Srl) which were air dried at room temperature (RT) for 4 hours and processed or stored at -20°C up to 8 months. Three disks (5.5 mm) were punched out into a 2 mL polypropylene tube and 250 µL of PBS1x were added. Samples were incubated at RT for 16 hours and then centrifuged at 12 500 rpm for 1 min. GH in supernatants or undiluted sera was determined by Immulite 2000 (Siemens Healthineers) and a calibration curve was built. Results: linearity was verified (R2 >0.99) up to 50 µg/L. At 1 µg/L, considered the Limit of Quantification (LOQ), CV% resulted to be 11%. Repeatability at 8 concentrations (from 1.5 to 50 µg/L) ranged from 2.4% to 11.1%. At 7 µg/L, the cut-off previously reported by literature for GHD, CV% was 3.7%. Within-laboratory imprecision, evaluated in a period of 8 months at two different concentrations (3.4 µg/L and 10.1 µg/L) was 13% and 5.9%, respectively. Conclusions. The new method displayed good analytical performances, suggesting it can be used to measure GH in newborns using DBS for reference interval estimation.