Pilot study for cystic fibrosis neonatal screening: the Cuban experience

Background In Cuba, no screening program for cystic fibrosis (CF) has been implemented yet. The ultramicro enzyme-linked immunosorbent assay (UMELISA)® TIR NEONATAL has been developed for the measurement of immunoreactive trypsin (IRT) in dried blood spots on filter paper. The analytical performance of the kit was evaluated in the national network of laboratories. Methods Newborn dried blood samples (DBS) were evaluated in 16 laboratories. An IRT/IRT/DNA protocol was followed using a cut-off value of 50 ng/mL. The mean, median and percentiles of the distribution were calculated and a two-sample t-test with unequal variance was used for statistical analysis. Influence of perinatal factors on IRT levels was analyzed. Results From January to June 2018, 6470 newborns were studied, obtaining a mean IRT value of 12.09 ng/mL (ranging 0-358 ng/mL) and a median of 8.99 ng/mL. Fifty-two samples (0.78%) were above the cut-off level and 16 samples (0.24%) were elevated in the re-screening process. One of them was confirmed positive by molecular biology (phe508del/c.3120 + 1G > A), constituting the first newborn screened and diagnosed early in Cuba. Second DBS samples were collected on average at 14 days and processed in the laboratory at 16 days of birth. Significant differences were observed (p < 0.05) when evaluating the influence of gender, birth weight (BW) and gestational age (GA) on the IRT values. Lower IRT concentrations were found in samples processed after 10 days of collection. Conclusions The performance of UMELISA® TIR NEONATAL in the laboratories has been satisfactory; hence CF newborn screening (NBS) was extended throughout the country from January 2019.

Evaluation of UMELISA® T4 NEONATAL and UMELISA® T4 using polystyrene plates coated with anti-thyroxine (T4) monoclonal antibodies

Congenital hypothyroidism is one of the most common preventable causes of mental retardation. The Center of Immunoassay has developed the UMELISA® T4 NEONATAL and UMELISA® T4 to determine neonatal T4 levels in dried blood and serum samples. Both reagent kits use the same polystyrene plates coated with anti-thyroxine (T4) polyclonal antibodies as solid phase. This work shows the re-standardization of the UMELISA® T4 NEONATAL and UMELISA® T4 using plates coated with anti-T4 monoclonal antibodies (T4Mabs). Polystyrene plates of the modified assays were firstly coated with polyclonal IgG sheep-anti-mouse IgG for 18 hours. T4Mabs were added to the plates and incubated for 2 hours at room temperature. Different performance parameters were evaluated and correlation studies with the commercial kits done. Using polystyrene plates coated with T4Mabs increases the slope of the calibration curve in the clinical interest zone. The assay conjugates work twice diluted in respect to the ones of the commercial kits. Recovery percentages (90.8-110.7 for UMELISA® T4 NEONATAL and 92.1-109.3 for UMELISA® T4) and intra (7.2-7.6 for UMELISA® T4 NEONATAL and 6.9-7.2 for UMELISA® T4) and inter (7.4-8.5 for UMELISA® T4 NEONATAL and 7.1-8.5 for UMELISA® T4) coefficients of variation were similar to the ones described for the commercial kits. Limits of detection and quantification were 9.0 and 21.1 nmol/L for UMELISA® T4 NEONATAL, and 8.9 and 20.5 nmol/L for UMELISA® T4, respectively. The results also showed high overall concordance between assays (n = 244, r = 0.92, ρc = 0.91 for UMELISA® T4 NEONATAL and n = 492, r = 0.92, ρc = 0.9 for UMELISA® T4). The analytical sensibility of UMELISA® T4 NEONATAL and UMELISA® T4 is improved by using polystyrene plates coated with T4Mabs, without affecting the precision and accuracy of the results.

ABBREVIATIONS

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

Newborn screening for congenital adrenal hyperplasia in Cuba: six years of experience

BACKGROUND

Since 2005, a newborn screening program for congenital adrenal hyperplasia (CAH) by measuring 17-alpha-hydroxyprogesterone (17OHP) in dried blood spots was introduced in Cuba.

METHODS

The hormone was measured by the 17OHP Neonatal UMELISA method, in samples collected on the 5th day as average. Confirmatory test was performed to those neonates with 17OHP values above 55 nmol/l. Some perinatal factors that can influence on 17OHP levels were studied.

RESULTS

From January 2005 to December 2010, 621,303 newborns were screened and 39 CAH cases were detected. Coverage of the program reached 98%. The incidence of CAH in Cuba was 1:15,931, similar to that reported by other programs. A recall for suspected CAH was performed in 10,799 cases (1.74%). Therapy in classical CAH patients was started at the mean age of 22 days. 17OHP levels were significantly higher in newborns with lower birth-weight (BW) and/or gestational age (GA). In addition, 17OHP values were affected by the gender, twin status or mode of delivery.

CONCLUSIONS

In Cuba, the nationwide newborn screening program has allowed the early detection of CAH. The use of an optimized cut-off level for BW or GA could lead to a reduction in the percentage of recalled babies.

Quantitative ultramicrotest for newborn screening of galactosemia in Cuba

BACKGROUND

To describe a simple, rapid, quantitative ultramicrotest (UMTEST) based on the fluorometric method introduced by Fujimura et al. adapted to an Ultra Micro Analytic System (SUMA) for the detection of total galactose (GAL) in dried blood specimens.

METHODS

The assay uses 3 mm discs of dried blood on Whatman 903 filter paper and small volumes of each reagent. A methanol/acetone/water solution is used for deproteination, and a specially designed 96-well polystyrene opaque ultramicroplates, with a maximum capacity of 30 μL per well, are used for the reading.

RESULTS

The UMTEST GAL is completed in 2 h, with measuring range of 0.28-3.92 mmol/L. The intra- and inter-assay coefficients of variation were 2.3%-8.9% and 6.8%-11.1%, respectively, depending on the total GAL concentrations. Percentage recovery ranged from 97.7% to 103%. Limit of detection and limit of quantitation were 0.06 and 0.16 mmol/L, respectively. The mean GAL concentration, in 2510 dried blood samples from the National Neonatal Screening Program was 0.23 mmol/L. Our assay showed high concordance correlations with the commercially available ICN Immuno-Chem™ GAL-MW EA kit.

CONCLUSIONS

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

Qualitative colorimetric ultramicroassay for the detection of biotinidase deficiency in newborns

BACKGROUND

We describe a simple qualitative visual ultramicroassay based on the colorimetric method introduced by Heard et al. for the detection of biotinidase deficiency in dried blood samples spotted on filter paper.

METHODS

The assay uses 3-mm discs of dried blood on Schleicher and Schuell 903 filter paper and ultramicrovolumes of each reagent. Ten thousand newborn samples from the National Screening Program for the Detection of Phenylketonuria were evaluated.

RESULTS

The ultramicroassay shows a good reproducibility. The lower detection limit is around 2% of the mean normal activity. We found one sample with the absence of enzymatic activity, another that was between 10% and 30%, and 10 with activity levels <40%. There was coincidence of our results with those obtained by the conventional colorimetric method that uses B-PAB as substrate.

CONCLUSIONS

The qualitative colorimetric ultramicroassay does not require special laboratory equipment and it is suitable for the neonatal screening of biotinidase deficiency.

Monoclonal antibody against human trypsin: production, characterization, and use for diagnosis

A monoclonal antibody (MAb) directed against human immunoaffinity purified trypsinogen has been produced by hybridization of myeloma cells with spleen cells of BALB/c immunized mice. Antibodies were screened by ultramicro-enzyme-linked immunosorbent assay (UMELISA). The MAb was purified by affinity chromatography on protein A-sepharose, and MAb had a high affinity for trypsinogen with the affinity constant equal 2.06 x 10(9) L/mol. Specificity was studied by UMELISA using cross-reactant proteins; MAb gave a positive reaction with native trypsinogen-1 but did not react with the same protein after reduction. The antibody seem to be directed against conformational epitope. The MAb obtained was characterized immunologically and used to develop UMELISA for detection Trypsin. This monoclonal assay enabled the detection of 2.8 ng/mL.

Specific monoclonal antibody against human trypsin

A monoclonal antibody (MAb) directed against human trypsin-1 has been produced by hybridization of myeloma cells with spleen cells of BALB/c immunized mice. Antibodies were screened by ultramicro enzymelinked immunosorbent assay (UMELISA). MAb was purified by affinity chromatography on protein A-Sepharose, and MAb had a high affinity for trypsin-1 with the affinity constant equal 1.79 x 10(9) L/mol. Specificity was studied by UMELISA using cross-reactant proteins; MAb gave a positive reaction with native trypsinogen-1 and with the same protein after reduction. Antibody appeared to be directed against sequential epitope. One-step purification is described. The method evolved the adsorption of the enzyme onto a Sepharose-MAb(3H9) affinity column. The collected fraction was characterized and is available for immunization of BALB/c mice and for the preparation of a standard for immunoenzymatic assay.

[Determination of total phenylalanine and galactose from a sample of dry blood on paper filter: its application on neonatal screening]

Neonatal screening programs for metabolic disorders are recommended especially for phenylketonuria and congenital hypothyroidism. The present study was designed to adapt, develop and evaluate a SUMA method for total galactose (Gal) and phenylalanine (Phe) measurement on filter paper blood specimens. A single 5 mm disk with blood was deproteinized with methanol-acetone and eluted with distilled water. Ten microliters of the extract was transferred to one well of a ultramicroELISA plate, and the reaction solution was added to determine Phe level. The remaining extract was used for the GAL determinations. The method showed good linearity in a 0-50 mg/dl concentration range for Phe and 0-60 mg/dl for Gal. The detection limit was 0.14 mg/dl for Phe and 0.9 mg/dl for Gal. Reproducibility was assessed with filter paper blood specimens containing Gal and Phe at low, middle and high levels. Intraassay coefficients of variation were 10%, 7.5%, 6.22%, and 8.5%, 7%, 5%, respectively, whereas interassay coefficients of variation were 9.54%, 6%, 7% and 6%, 4.6%, 5.6%, respectively. In 1,000 samples from newborns, four samples of Phe and two samples of Gal showed a concentration below the threshold set for each assay. This method provides a rapid means to survey for a low incidence disease (i.e., galactosaemia: incidence, 1/30,000), in existing phenylketonuria analysis programs, where an incidence of 1/10,000), easily justifies the cost of mass screening.