No abstract

Cystic fibrosis (CF) is a severe autosomal recessive disorder. It is caused by mutations in the CF transmembrane conductance regulator gene. Early diagnosis of CF can be carried out by determining high immunoreactive trypsinogen (IRT) blood values in newborns. A simple sandwich-type ultramicroELISA assay (UMELISA®) has been developed for the measurement of IRT in dried blood spots on filter paper. Strips coated with a high affinity monoclonal antibody directed against IRT are used as solid phase, to ensure the specificity of the assay. The assay is carried out within 20 h. The useful rank of the curve is 0-500 ng/mL, and the lowest detectable concentration is 4.8 ng/mL. Intra- and inter-assay coefficients of variation were lower than 10%. The recovery mean value was 100.3 ± 11.2%. Cross-reactivity with proteins structurally related to IRT (α2-macroglobulin, α1-antitrypsin, and human chymotrypsin) was lower than the detection limit of the assay. Four thousand four hundred six newborn samples from the Cuban Newborn Screening Program were analyzed, and the mean IRT concentration was 12.8 ng/mL. Higher IRT values were obtained when samples were eluted overnight. Regression analysis showed a good correlation with the commercially available AutoDELFIA® Neonatal IRT kit (n = 3948, r = 0.885, ƙ = 0.976, p < 0.01). The analytical performance characteristics of our UMELISA® TIR Neonatal suggest that it can be used for the neonatal screening of CF.

The analytical performance characteristics of this assay is suitable for mass newborn screening of galactosemia in Cuba.

T4: L-Thyroxine; ELISA: Enzyme-linked immunosorbent assay; SUMA: Ultra Micro Analytic System; UMELISA: Ultramicro enzyme-linked immunosorbent assay; TSH: Thyroid-stimulating hormone.

The ultramicroanalytic system (SUMA), created in the 1980s, is a complete system of reagents and instrumentation to perform ultramicroassays combining the sensitivity of the micro-enzyme-linked immunosorbent assay (ELISA) tests with the use of ultramicrovolumes. This technology permitted establishing large-scale newborn screening programs (NSPs) for metabolic and endocrine disorders in Cuba. This article summarizes the main results of the implementation during the 30 years of SUMA technology in NSP for 5 inherited metabolic diseases, using ultramicroassays developed at the Department of Newborn Screening at the Immunoassay Center. Since 1986, SUMA technology has been used in the Cuban NSP for congenital hypothyroidism, initially studying thyroid hormone in cord serum samples. In 2000, a decentralized program for the detection of hyperphenylalaninemias using heel dried blood samples was initiated. These successful experiences permitted including protocols for screening congenital adrenal hyperplasia, galactosemia, and biotinidase deficiency in 2005. A program for the newborn screening of CH using the thyroid-stimulating hormone Neonatal ultramicro-ELISA was fully implemented in 2010. Nowadays, the NSP is supported by a network of 175 SUMA laboratories. After 30 years, more than 3.8 million Cuban newborns have been screened, and 1002 affected children have been detected. Moreover, SUMA technology has been presented in Latin America for over 2 decades and has contributed to screen around 17 million newborns. These results prove that developing countries can develop appropriate diagnostic technologies for making health care accessible to all.