Differences in immunoreactive trypsin values between type of feeding and ethnicity in neonatal cystic fibrosis screening: a cross-sectional study

Factors Influencing Creatine Kinase-MM Concentrations in Newborns and Implications for Newborn Screening for Duchenne Muscular Dystrophy

INTRODUCTION

Newborn screening for Duchenne muscular dystrophy can be performed via a first-tier creatine kinase-MM measurement followed by reflex testing to second-tier molecular analysis of the DMD gene. In order to establish appropriate cut-offs for the creatine kinase-MM screen, factors that influence creatine kinase-MM in newborns were investigated.

MATERIALS AND METHODS

Creatine kinase-MM data from a consented pilot study in New York State were collected over a two-year period and combined with de-identified validation data and analyzed. Univariate analysis and multiple linear regression analysis were performed.

RESULTS

The analysis indicated that age of newborn at specimen collection, gestational age and birth weight were significant influencers of CK-MM levels in newborns. In addition, to a lesser extent, sex, race/ethnicity and seasonal temperature also affect CK-MM levels in newborns.

CONCLUSIONS

To reduce false positive and false negative cases, newborn screening programs should be cognizant of factors that influence CK-MM when determining cut-offs for the assay. Variability based on age at specimen collection and birth weight are primarily observed within the first week of life. Therefore, particularly during this time period, multi-tiered cut-offs based on age of collection and lower cut-offs for premature and low birth weight babies are recommended. Other cut-off determinants may include sex, race/ethnicity and seasonal temperature.

Generation and characterization of murine monoclonal antibodies against immunoreactive trypsinogen for newborn screening of cystic fibrosis

Cystic fibrosis (CF) is a multisystem disorder that reduces quality of life and survival in affected individuals. In newborns, the release of pancreatic enzymes into the blood raises the levels of immunoreactive trypsinogen (IRT), the main marker for CF screening, which is detected in dried blood samples on filter paper by immunoenzymatic assays. In Cuba, CF has an estimated incidence of 1/9862 live births and should be included in the national basic newborn screening (NBS) panel given its benefits in terms of nutrition, lung function and survival. The Immunoassay Center develops and produces diagnostic kits allowing the establishment of large-scale NBS programs for inherited metabolic disorders in Cuba and other Latin American countries. IRT-specific monoclonal antibodies (MAbs) obtained at the Immunoassay Center are essential for developing an affordable immunoassay for IRT to support CF NBS in our low-income country. An immunization scheme with trypsinogen-1 originated two IgG1-producing murine hybridomas. 4C9C9 and 4C9E11 MAbs recognized different determinants on both trypsin-1 and trypsin-2 molecules. Both antibodies identified conformational epitopes on the molecule of trypsin-1 and of its zymogen. As 4C9E11 MAb cross-reacted with proteins structurally and functionally related to trypsinogen, it was used as revealing antibody in a sandwich-type UMELISA® assay for IRT determination with 4C9C9 MAb for capture. This combination, aside from detecting several commercially available trypsins, adequately quantified IRT from dried blood samples on filter paper of newborns. The evaluation of the assay's accuracy yielded percentage recoveries ranging 93.3-109.2% for commercial controls. The properties of the studied MAbs demonstrate their suitability for being used in a sandwich-type UMELISA® assay for the CF NBS in Cuba.

Factors associated with moderate neonatal hyperthyrotropinemia

BACKGROUND

Maternal iodine deficiency is related to high neonatal thyroid-stimulating hormone (TSH) values, with the threshold of 5 mIU/L recommended as an indicator of iodine nutrition status. The objective of this study was to analyse possible risk factors for increased TSH that could distort its validity as a marker of iodine status. The clinical relevance of this research question is that if the factors associated with iodine deficiency are known, iodine supplementation can be introduced in risk groups, both during pregnancy and in newborns.

METHODS

A case-control study was carried out in a sample of 46,622 newborns in 2002-2015 in Spain. Of these, 45,326 had a neonatal TSH value ≥5 mIU/L. The main variable was having TSH ≥5 mIU/L and the secondary variables were: sex, gestational age, day of sample extraction and maternal origin. Associated factors were analysed through a logistic regression model, calculating the odds ratio (OR).

RESULTS

The factors associated with this outcome were: male sex (OR = 1.34, 95% CI: 1.20-1.50, p<0.001), originating from an Asian/Oceanic country (OR = 0.80, 95% CI: 0.54-1.20, p = 0.536) or Europe (OR = 0.80, 95% CI: 0.66-0.96, p = 0.285) (including Spain, OR = 1) [p<0.001 for America (OR = 0.54, 95% CI: 0.44-0.68) and p = 0.025 for Africa (OR = 0.78, 95% CI: 0.62-0.97)] and fewer days from birth to sampling (OR = 0.80, 95% CI: 0.77-0.82, p<0.001).

CONCLUSIONS

The risk of high neonatal TSH without congenital hypothyroidism is higher in males, decreases with a greater number of days from birth to extraction, and is dependent on maternal ethnicity but not on gestational age.

Newborn screening: a review of history, recent advancements, and future perspectives in the era of next generation sequencing

PURPOSE OF REVIEW

The purpose of this review is to summarize the development and recent advancements of newborn screening.

RECENT FINDINGS

Early initiation of medical care has modified the outcome for many disorders that were previously associated with high morbidity (such as cystic fibrosis, primary immune deficiencies, and inborn errors of metabolism) or with significant neurodevelopmental disabilities (such as phenylketonuria and congenital hypothyroidism). The new era of mass spectrometry and next generation sequencing enables the expansion of the newborn screen panel, and will help to address technical issues such as turnaround time, and decreasing false-positive and false-negative rates for the testing.

SUMMARY

The newborn screening program is a successful public health initiative that facilitates early diagnosis of treatable disorders to reduce long-term morbidity and mortality.

Screening for cystic fibrosis in New York State: considerations for algorithm improvements

Newborn screening for cystic fibrosis (CF), a chronic progressive disease affecting mucus viscosity, has been beneficial in both improving life expectancy and the quality of life for individuals with CF. In New York State from 2007 to 2012 screening for CF involved measuring immunoreactive trypsinogen (IRT) levels in dried blood spots from newborns using the IMMUCHEM(™) Blood Spot Trypsin-MW ELISA kit. Any specimen in the top 5% IRT level underwent DNA analysis using the InPlex(®) CF Molecular Test. Of the 1.48 million newborns screened during the 6-year time period, 7631 babies were referred for follow-up. CF was confirmed in 251 cases, and 94 cases were diagnosed with CF transmembrane conductance regulated-related metabolic syndrome or possible CF. Nine reports of false negatives were made to the program. Variation in daily average IRT was observed depending on the season (4-6 ng/ml) and kit lot (<3 ng/ml), supporting the use of a floating cutoff. The screening method had a sensitivity of 96.5%, specificity of 99.6%, positive predictive value of 4.5%, and negative predictive value of 99.5%.

CONCLUSION

Considerations for CF screening algorithms should include IRT variations resulting from age at specimen collection, sex, race/ethnicity, season, and manufacturer kit lots.

WHAT IS KNOWN

Measuring IRT level in dried blood spots is the first-tier screen for CF. Current algorithms for CF screening lead to substantial false-positive referral rates.

WHAT IS NEW

IRT values were affected by age of infant when specimen is collected, race/ethnicity and sex of infant, and changes in seasons and manufacturer kit lots The prevalence of CF in NYS is 1 in 4200 with the highest prevalence in White infants (1 in 2600) and the lowest in Black infants (1 in 15,400).

Highest Plasma Phenylalanine Levels in (Very) Premature Infants on Intravenous Feeding; A Need for Concern

OBJECTIVE

To analyse the association in newborns between blood levels of phenylalanine and feeding method and gestational age.

STUDY DESIGN

This observational, cross-sectional study included a sample of 11,829 infants between 2008 and 2013 in a Spanish region. Data were recorded on phenylalanine values, feeding method [breast, formula, mixed (breast plus formula), or partial or fully intravenous feeding], gestational age in weeks (<32, 32-37, ≥37), gender and days since birth at the moment of blood collection. Outcomes were [phenylalanine] and [phenylalanine] ≥95th percentile. Associations were analysed using multivariate models [linear (means difference) and logistic regression (adjusted odds ratios)].

RESULTS

Higher phenylalanine values were associated with lower gestational age (p<0.001) and with intravenous feeding (p<0.001).

CONCLUSION

The degree of prematurity and intravenous feeding influenced the plasma concentration of phenylalanine in the newborn. Caution should be taken in [phenylalanine] for newborns with intravenous feeding, monitoring them carefully. Very preterm infants given the recommended amount of amino acids should also be strictly monitored. These findings should be taken into consideration and call for adapting the amounts to the needs of the infant.