Immunoreactive trypsinogen in healthy newborns and infants with cystic fibrosis.

OBJECTIVE: Newborn screening (NBS) for cystic fibrosis (CF) was introduced in Switzerland in 2011 based on an immunoreactive trypsinogen (IRT)-DNA-IRT protocol. CF diagnosis was confirmed by sweat test and/or genetics but remained inconclusive for some newborns (cystic fibrosis transmembrane conductance regulator related metabolic syndrome (CRMS)/CF screen positive, inconclusive diagnosis (CFSPID)). We aimed to (1) Describe IRT levels in healthy newborns in the first year of life and by gestational age (GA), and (2) Compare IRT at two time points between healthy newborns and newborns with CF and CRMS/CFSPID. DESIGN: Retrospective study. SETTING: National NBS database. PATIENTS: All children with an IRT measurement by heel prick test from 2011 to 2019. INTERVENTIONS: None. MAIN OUTCOME MEASURES: IRT values were extracted from the National NBS Laboratory, and clinical characteristics of positively screened children from the CF-NBS database. Second IRT assessment in positively screened children was usually performed after 18-24 days. We calculated internal IRT Z-Scores and multiples of the median to compare our results across different laboratory tools. RESULTS: Among 815 899 children; 232 were diagnosed with CF, of whom 36 had meconium ileus (MI); 27 had CRMS/CFSPID. Among all samples analysed, mean IRT Z-Scores were higher for newborns with GA <33 weeks and ≥43 weeks (all Z-Scores >0.11) compared with term babies (all Z-Scores ≤0.06). Repeated IRT Z-Scores after a median (IQR) of 19 (17-22) days remained high for infants with CF with or without MI but decreased for infants with CRMS/CFSPID. CONCLUSIONS: Measurement of a second IRT value can help distinguish between children with CRMS/CFSPID and CF, early in life.

Final results of the southwest German pilot study on cystic fibrosis newborn screening - Evaluation of an IRT/PAP protocol with IRT-dependent safety net.

BACKGROUND: Previous studies suggest that PAP-based CF protocols are suitable for newborn screening (NBS) for cystic fibrosis (CF) when newborns designated as CFSPID should not be detected. However, there are still discussions about the performance of IRT/PAP algorithms. We present the final results of a pilot study evaluating a IRT/PAP protocol with an IRT-dependent safety net (SN) conducted from 2008 to 2016 in southwestern Germany on nearly 500,000 newborns. METHODS: To achieve reliable data, all newborns were screened using both the PAP-based and a DNA-based CFNBS algorithm. PAP quantification and genetic analysis of the four most common CFTR mutations in Germany were performed in all newborns with IRT≥99.0 percentile. NBS was rated positive if either PAP was ≥1.6 µg/l and/or at least one CFTR mutation was detected. In addition, an IRT-dependent SN resulted in positive rating for both protocols if IRT was ≥99.9 percentile. To evaluate the IRT/PAP protocol, its performance was compared to that of the IRT/DNA protocol. RESULTS: The IRT/PAP protocol with IRT-based SN used in the study achieved a sensitivity of 94%, if false-negative detected neonates with meconium ileus and those designated as CFSPID were excluded from analysis. CF/CFSPID ratio was 92. However, PPV of the IRT/PAP+SN protocol was with 10.3% very low. CONCLUSIONS: PAP-based CFNBS protocols can be used, if less detection of CFSPID is desired. The IRT/PAP protocol with IRT-dependent SN evaluated here achieved adequate sensitivity but should probably be used in combination with a third-tier test to also achieve an acceptable PPV.

Improving outcomes for Colorado's IRT-IRT-DNA cystic fibrosis newborn screening algorithm by implementing floating cutoffs.

The Colorado Newborn Screening Program (CO-NBS) screens for cystic fibrosis (CF) by measuring immunoreactive trypsinogen (IRT) from two screens coupled with DNA analysis (IRT/IRT/DNA). The Colorado CF Care Center identified 8 missed CF cases among 358,187 infants screened by the CO-NSP since 2016. Retrospective analysis of CO-NSP IRT data shows that a 96th percentile floating IRT cutoff with a 50 ng/mL fixed cutoff on the first screen, and second screen 50 ng/mL fixed cutoff would have identified 7 of the 8 missed cases. These efforts demonstrate the importance of continuous quality improvement in order to increase sensitivity and reduce missed cases.

Phenotype of children with inconclusive cystic fibrosis diagnosis after newborn screening.

OBJECTIVE: To characterize the phenotypic expression of children with conductance regulator-related metabolic syndrome (CRMS)/cystic fibrosis screen positive inconclusive diagnosis (CFSPID) designation after positive newborn screening, reassign labeling if applicable and better define these children's prognosis. METHODS: A multicenter cohort with CRMS/CFSPID designation was matched with cystic fibrosis (CF)-diagnosed cohort. Cohorts were prospectively compared on baseline characteristics, cumulative data and when they reached 6 to 7 years at endpoint assessment. RESULTS: Compared to infants with CF (n = 63), the CRMS/CFSPID cohort (n = 63) had initially lower immunoreactive trypsinogen (IRT) and sweat chloride (SC) values, delayed visits, less symptoms, and better nutritional status; during follow-up, they had fewer hospitalizations, Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus identification, CF comorbidities, and treatment burden. At endpoint assessment, they presented a milder pulmonary phenotype on Brody computed tomography scores (0.0[0.0; 2.0] vs 13[2.0; 31.0]; P < .0001, respectively), Wisconsin and Brasfield chest radiograph scores, pulmonary function tests, and improved nutritional status. Among the inconclusive CF diagnosis cohort, 28 cases (44%) converted to CF diagnosis based on genotype (44%), SC (28%) or both (28%); yet, comparing those with or without final CF diagnosis, we found no differences, possibly related to their young age and mild degree of lung disease. In the total cohort, we found significant associations between Brody scores and IRT, SC values, genotype, Wisconsin and Brasfield score and spirometry. CONCLUSIONS: The matched CRMS/CFSPID and CF cohorts showed differences in outcomes. By a mean age of 7.6 years, a high proportion of the CRMS/CFSPID cohort converted to CF. Our results highlight that monitoring at CF clinics until at least 6 years is needed as well as further studies.

Maximizing Selective Cleavages at Aspartic Acid and Proline Residues for the Identification of Intact Proteins.

A new approach for the identification of intact proteins has been developed that relies on the generation of relatively few abundant products from specific cleavage sites. This strategy is intended to complement standard approaches that seek to generate many fragments relatively non-selectively. Specifically, this strategy seeks to maximize selective cleavage at aspartic acid and proline residues via collisional activation of precursor ions formed via electrospray ionization (ESI) under denaturing conditions. A statistical analysis of the SWISS-PROT database was used to predict the number of arginine residues for a given intact protein mass and predict a m/z range where the protein carries a similar charge to the number of arginine residues thereby enhancing cleavage at aspartic acid residues by limiting proton mobility. Cleavage at aspartic acid residues is predicted to be most favorable in the m/z range of 1500-2500, a range higher than that normally generated by ESI at low pH. Gas-phase proton transfer ion/ion reactions are therefore used for precursor ion concentration from relatively high charge states followed by ion isolation and subsequent generation of precursor ions within the optimal m/z range via a second proton transfer reaction step. It is shown that the majority of product ion abundance is concentrated into cleavages C-terminal to aspartic acid residues and N-terminal to proline residues for ions generated by this process. Implementation of a scoring system that weights both ion fragment type and ion fragment area demonstrated identification of standard proteins, ranging in mass from 8.5 to 29.0 kDa. Graphical Abstract ᅟ.

Resultados del programa de screening neonatal de fibrosis quística en Andalucía tras 5 años de su implantación / Results of the Andalusian Cystic Fibrosis Neonatal Screening Program, 5 Years After Implementation

Introducción: Andalucía dispone de screening neonatal de fibrosis quística (SNFQ) desde mayo 2011, basado en doble determinación de tripsinógeno inmunorreactivo ([TIR] [TIR1/TIR2]). Si el screening es positivo realizamos un test del sudor y si es positivo o dudoso solicitamos genética. Objetivo: Analizar el SNFQ, basado en los resultados de los primeros 4,5 años. Material y método: Estudio descriptivo prospectivo de los neonatos sometidos a SNFQ. Se recogen los niveles de TIR, cloruro en sudor, mutaciones. Mediante SPSS12.0 se realizó análisis estadístico. Resultados: Desde mayo 2011 a diciembre 2016, 474.953 neonatos fueron sometidos a SNFQ. Mil ochenta y siete (0,23%) presentaron TIR2 elevado. Desde la implantación del SNFQ se diagnosticaron 73 casos con fibrosis quística; 60 de ellos fueron diagnosticados mediante un SNFQ positivo, mientras que 13 no. Concretamente un paciente comenzó con clínica clásica de fibrosis quística y se comprobó que no se había realizado el SNFQ por decisión paterna; los 12 restantes tuvieron un SNFQ negativo (falsos negativos). De estos, un paciente fue diagnosticado presintomáticamente al tener su hermano gemelo con SNFQ positivo; otro con cloruro en el límite alto de la normalidad se diagnosticó presintomáticamente mediante genética; 10 pacientes comenzaron clínicamente. Excluyendo los pacientes con íleo meconial, la sensibilidad y especificidad del programa de SNFQ asciende al 85,71 y 99,78% respectivamente. La incidencia de la enfermedad en Andalucía es de 1/6.506 recién nacidos vivos. Conclusión: Los presentes resultados nos permiten reflexionar sobre posibles áreas de mejoras adicionales del algoritmo del SNFQ, que debe pasar por la introducción de estudios genéticos para así aumentar la sensibilidad y disminuir los falsos positivos

Introduction: Cystic fibrosis neonatal screening (CFNS), based on double determination of immunoreactive trypsinogen ([IRT] [IRT1/IRT2]), has been available in Andalusia since May 2011. If screening is positive, a sweat test is performed, and if that is positive or inconclusive, genetic testing is requested. Objective: To analyze CFNS, based on results from the first 4.5 years of the program. Materials and methods: Prospective descriptive study of neonates undergoing CFNS. IRT levels, sweat chloride, and mutations were recorded. Statistical analysis was performed using SPSS 12.0. Results: Between May 2011 and December 2016, 474,953 neonates underwent CFNS. Of these, 1,087 (0.23%) had elevated IRT2. Since CFNS was introduced, 73 cases of cystic fibrosis were diagnosed; 60 were diagnosed by positive CFNS, and 13 were diagnosed by other means. In one case, the patient developed a typical clinical picture of cystic fibrosis, but had not undergone CFNS at the decision of the parents; the remaining 12 had a negative CFNS (false negatives). Of these, one patient was diagnosed before symptoms developed, as his twin brother had a positive CFNS result; another had chloride at the upper limit of normal, and was subsequently diagnosed with genetic testing before symptoms appeared; and 10 patients developed clinical signs and symptoms. Excluding patients with meconium ileus, sensitivity and specificity of the CFNS program were 85.71% and 99.78%, respectively. The incidence of the disease in Andalusia is 1/6,506 live births. Conclusion: These results are a basis for reflection on possible areas for improvement of the CFNS algorithm, and thought may be given to the introduction of genetic studies to increase sensitivity and reduce false positives

An Enzyme Immunoassay for Determining Immunoreactive Trypsinogen (IRT) in Dried Blood Spots on Filter Paper Using an Ultra-Microanalytical System.

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.

Optimization of the French cystic fibrosis newborn screening programme by a centralized tracking process.

Objectives To evaluate the French cystic fibrosis newborn screening algorithm, based on data tracked by a centralized monitoring process, from 2002 to 2014. The programme aimed to attain European Standards in terms of positive predictive value, sensitivity, the ratio of screen positive patients diagnosed with cystic fibrosis to infants who screen positive but with inconclusive diagnosis (CFSPID), and time to diagnosis. Methods Retrospective analysis of programme performance, compliance with the algorithm, and changes in screening strategy. Results Modifications in the flow chart protocol improved the positive predictive value to 0.31 while maintaining the sensitivity at 0.95. Among infants diagnosed with cystic fibrosis, or identified as CFSPID, sweat test results were obtained for 94%, and two mutations were identified after exhaustive screening for the gene, when applicable, in 99.6%. The rate of pending diagnosis was very low (0.5%). The ratio of infants with cystic fibrosis:CFSPID was 6.3:1. Age at initial visit at the CF centre was ≤ 35 days, respectively, in 53%/26%. Conclusion Performances were in agreement with European standards, but timeliness of initial visit needed improvement. Our data complement an accumulating body of evidence demonstrating that attention must be paid to such ethical considerations as limiting carrier detection and inconclusive diagnosis. Newborn screening programmes should have a rigorous centralized monitoring process to warrant adjustments for improving performance to attain consensus guidelines.

A product of immunoreactive trypsinogen and pancreatitis-associated protein as second-tier strategy in cystic fibrosis newborn screening.

BACKGROUND: In cystic fibrosis newborn screening (CFNBS), immunoreactive trypsinogen (IRT) and pancreatitis-associated protein (PAP) can be used as screening parameters. We evaluated the IRT×PAP product as second-tier parameter in CFNBS in newborns with elevated IRT. METHODS: Data on 410,111 screened newborns including 78 patients with classical cystic fibrosis (CF) from two European centers were retrospectively analyzed by discrimination analysis to identify a screening protocol with optimal cutoffs. We also studied differences in PAP measurement methods and the association of IRT and PAP with age. RESULTS: PAP values differed systematically between fluorometric and photometric assays. The IRT×PAP product showed better discrimination for classical CF than PAP only as second-tier screening parameter (p<0.001). In CF patients, IRT decreased while PAP values remained high over years. In newborns without CF, IRT decreased after birth over weeks while PAP increased within days. CONCLUSIONS: The IRT×PAP product performs well as second-tier cutoff parameter for CFNBS. Screening quality parameters depend on the analytic method and on age at blood collection.

A false positive newborn screening result due to a complex allele carrying two frequent CF-causing variants.

The detection of two frequent CFTR disease-causing variations in the context of a newborn screening program (NBS) usually leads to the diagnosis of cystic fibrosis (CF) and a relevant genetic counseling in the family. In the present study, CF-causing variants p.Phe508del (F508del) and c.3140-26A>G (3272-26A>G) were identified on a neonate with positive ImmunoReactive Trypsinogen test by the Elucigene™ CF30 kit. The CF diagnosis initially suggested, despite three inconclusive Sweat Chloride Tests (SCT), was finally ruled out after the familial segregation study combined with a negative SCT. Haplotype studies, based on the comparison of 80 p.Phe508del haplotypes, suggested a probable de novo occurrence of c.3140-26A>G on the p.Phe508del ancestral allele in this family. This false positive case emphasizes the importance of SCT in the NBS strategy. Moreover, it raises the need for familial segregation studies in CF and in overall molecular diagnosis strategy of autosomal recessive diseases.

Measurement of fecal elastase improves performance of newborn screening for cystic fibrosis.

BACKGROUND: The aim of newborn screening (NBS) for CF is to detect children with 'classic' CF where early treatment is possible and improves prognosis. Children with inconclusive CF diagnosis (CFSPID) should not be detected, as there is no evidence for improvement through early treatment. No algorithm in current NBS guidelines explains what to do when sweat test (ST) fails. This study compares the performance of three different algorithms for further diagnostic evaluations when first ST is unsuccessful, regarding the numbers of children detected with CF and CFSPID, and the time until a definite diagnosis. METHODS: In Switzerland, CF-NBS was introduced in January 2011 using an IRT-DNA-IRT algorithm followed by a ST. In children, in whom ST was not possible (no or insufficient sweat), 3 different protocols were applied between 2011 and 2014: in 2011, ST was repeated until it was successful (protocol A), in 2012 we proceeded directly to diagnostic DNA testing (protocol B), and 2013-2014, fecal elastase (FE) was measured in the stool, in order to determine a pancreas insufficiency needing immediate treatment (protocol C). RESULTS: The ratio CF:CFSPID was 7:1 (27/4) with protocol A, 2:1 (22/10) with protocol B, and 14:1 (54/4) with protocol C. The mean time to definite diagnosis was significantly shorter with protocol C (33days) compared to protocol A or B (42 and 40days; p=0.014 compared to A, and p=0.036 compared to B). CONCLUSIONS: The algorithm for the diagnostic part of the newborn screening used in the CF centers is important and affects the performance of a CF-NBS program with regard to the ratio CF:CFSPID and the time until definite diagnosis. Our results suggest to include FE after initial sweat test failure in the CF-NBS guidelines to keep the proportion of CFSPID low and the time until definite diagnosis short.

Online Hydrophobic Interaction Chromatography-Mass Spectrometry for Top-Down Proteomics.

Recent progress in top-down proteomics has led to a demand for mass spectrometry (MS)-compatible chromatography techniques to separate intact proteins using volatile mobile phases. Conventional hydrophobic interaction chromatography (HIC) provides high-resolution separation of proteins under nondenaturing conditions but requires high concentrations of nonvolatile salts. Herein, we introduce a series of more-hydrophobic HIC materials that can retain proteins using MS-compatible concentrations of ammonium acetate. The new HIC materials appear to function as a hybrid form of conventional HIC and reverse phase chromatography. The function of the salt seems to be preserving protein structure rather than promoting retention. Online HIC-MS is feasible for both qualitative and quantitative analysis. This is demonstrated with standard proteins and a complex cell lysate. The mass spectra of proteins from the online HIC-MS exhibit low charge-state distributions, consistent with those commonly observed in native MS. Furthermore, HIC-MS can chromatographically separate proteoforms differing by minor modifications. Hence, this new HIC-MS combination is promising for top-down proteomics.

Implementation of newborn screening for cystic fibrosis in Norway. Results from the first three years.

BACKGROUND: Norway introduced newborn screening for cystic fibrosis (CF) March 1, 2012. We present results from the first three years of the national newborn CF screening program. METHODS: Positive primary screening of immunoreactive trypsinogen (IRT) was followed by DNA testing of the Cystic fibrosis transmembrane conductance regulator (CFTR) gene. Infants with two CFTR mutations were reported for diagnostic follow-up. RESULTS: Of 181,859 infants tested, 1454 samples (0.80%) were assessed for CFTR mutations. Forty children (1:4546) had two CFTR mutations, of which only 21 (1:8660) were confirmed to have a CF diagnosis. The CFTR mutations differed from previously clinically diagnosed CF patients, and p.R117H outnumbered p.F508del as the most frequent mutation. One child with a negative IRT screening test was later clinically diagnosed with CF. CONCLUSIONS: The CF screening program identified fewer children with a conclusive CF diagnosis than expected. Our data suggest a revision of the IRT/DNA protocol.

Cost-effectiveness of newborn screening for cystic fibrosis determined with real-life data.

BACKGROUND: Previous cost-effectiveness studies using data from the literature showed that newborn screening for cystic fibrosis (NBSCF) is a good economic option with positive health effects and longer survival. METHODS: We used primary data to compare cost-effectiveness of four screening strategies for NBSCF, i.e. immunoreactive trypsinogen-testing followed by pancreatitis-associated protein-testing (IRT-PAP), IRT-DNA, IRT-DNA-sequencing, and IRT-PAP-DNA-sequencing, each compared to no-screening. A previously developed decision analysis model for NBSCF was fed with model parameters mainly based on a study evaluating two novel screening strategies among 145,499 newborns in The Netherlands. RESULTS: The four screening strategies had cost-effectiveness ratios varying from €23,600 to €29,200 per life-year gained. IRT-PAP had the most favourable cost-effectiveness ratio. Additional life-years can be gained by IRT-DNA but against higher costs. When treatment costs reduce with 5% due to early diagnosis, screening will lead to financial savings. CONCLUSION: NBSCF is as an economically justifiable public health initiative. Of the four strategies tested IRT-PAP is the most economic and this finding should be included in any decision making model, when considering implementation of newborn screening for CF.

Comparison of different IRT-PAP protocols to screen newborns for cystic fibrosis in three central European populations.

BACKGROUND: In recent years different IRT/PAP protocols have been evaluated, but the individual performance remains unclear. To optimize the IRT/PAP strategy we compared protocols from three regional CF newborn screening centers (Heidelberg, Dresden, and Prague). METHODS: We evaluated the effect of elevating the IRT-cut-off from 50 to 65 µg/l (~97.5th to ~99.0th percentile), the need of a failsafe protocol (FS, IRT ≥ 99.9th percentile) and the relative performance using either two IRT-dependent PAP-cut-offs or one PAP-cut-off. FINDINGS: Elevation of the IRT cut-off to 65 µg/l (~99.0th percentile) increased the PPV significantly (Dresden: 0.065 vs. 0.080, p < 0.0001, Prague: 0.052 vs. 0.074, p < 0.0001) without reducing sensitivity. All three IRT/PAP protocols showed a trend towards a higher sensitivity with FS than without and when using one PAP-cut-off instead of two IRT-dependent PAP-cut-offs. CONCLUSIONS: For best performance we suggest an IRT/PAP protocol with an IRT-cut-off close to the 99.0th percentile, FS, and a single PAP-cut-off.

Low trypsinogen-1 expression in pediatric ulcerative colitis patients who undergo surgery.

AIM: To investigate whether matrix metalloproteinases-9 (MMP-9) or trypsinogens could serve as histological markers for an aggressive disease course in pediatric ulcerative colitis (UC). METHODS: We identified 24 patients with pediatric onset (≤ 16 years) UC who had undergone surgery during childhood/adolescence a median of 2.1 years (range 0.1-7.4 years) after the diagnosis (between 1990 and 2008) in Children's Hospital, Helsinki, Finland. We also identified 27 conservatively treated UC patients and matched them based on their age at the time of diagnosis and follow-up at a median of 6 years (range 3-11 years) to serve as disease controls. Twenty children for whom inflammatory bowel disease (IBD) had been excluded as a result of endoscopy served as non-IBD controls. Colon biopsies taken by diagnostic endoscopy before the onset of therapy were stained using immunohistochemistry to study the expression of MMP-9, trypsinogen-1 (Tryp-1), Tryp-2, and a trypsin inhibitor (TATI). The profiles of these proteases and inhibitor at diagnosis were compared between the surgery group, the conservatively treated UC patients and the non-IBD controls. RESULTS: The proportions of Tryp-1 and Tryp-2 positive samples in the colon epithelium and in the inflammatory cells of the colon stroma were comparable between the studied groups at diagnosis. Interestingly, the immunopositivity of Tryp-1 (median 1; range 0-3) was significantly lower in the epithelium of the colon in the pediatric UC patients undergoing surgery when compared to that of the conservatively treated UC patients (median 2; range 0-3; P = 0.03) and non-IBD controls (median 2; range 0-3; P = 0.04). For Tryp-2, there was no such difference. In the inflammatory cells of the colon stroma, the immunopositivities of Tryp-1 and Tryp-2 were comparable between the studied groups at diagnosis. Also, the proportion of samples positive for TATI, as well as the immunopositivity, was comparable between the studied groups in the colon epithelium. In the stromal inflammatory cells of the colon, TATI was not detected. In UC patients, there were significantly more MMP-9 positive samples and a higher immunopositivity in the stromal inflammatory cells of the colon when compared to the samples from the non-IBD patients (P = 0.006 and P = 0.002, respectively); the immunopositivity correlated with the histological grade of inflammation (95%CI: 0.22-0.62; P = 0.0002), but not with the other markers of active disease. There were no differences in the immunopositivity or in the proportions of MMP-9 positive samples when examined by epithelial staining. The staining profiles in the ileal biopsies were comparable between the studied groups for all of the studied markers. CONCLUSION: For pediatric UC patients who require surgery, the immunopositivity of Tryp-1 at diagnosis is lower when compared to that of patients with a more benign disease course.

Thirty-years of screening for cystic fibrosis in East Anglia.

BACKGROUND: Newborn screening for cystic fibrosis (CF) relies on the measurement of immunoreactive trypsinogen (IRT) originating from the pancreas. The Norfolk, Suffolk and Cambridgeshire screening programme initially exploited the persistent increase in IRT seen in CF (IRT-IRT protocol) and later changed to include mutation analysis as a second tier test (IRT-DNA-IRT protocol). RESULTS: During a 30 year period 582 966 babies have been screened by IRT-IRT and 147 764 by IRT-DNA-IRT (total 730730), resulting in 296 screen positive cases of CF and 29 false negatives (including 10 false negatives with meconium ileus). Ten missed CF cases were pancreatic insufficient, however all were diagnosed before their first birthday, suggesting that a false negative result did not forestall appropriate clinical investigation. The IRT-DNA-IRT protocol had a much improved positive predictive value (PPV) of 85.9% compared to 67.3% for IRT-IRT, excluding CF babies with meconium ileus. The PPVs increased to 82.2% and 98.2% respectively if only well, term babies were considered. The main factor to account for this improvement in PPV has probably been the incorporation of DNA analysis in the second tier testing. CONCLUSIONS: The diagnosis of screen-positive babies proved difficult in a minority of cases with the classification of some patients changing with evolving phenotype. Our results illustrate the importance of collecting outcome data over a long time period for accurate assessment of the screening programme. This study provides evidence that newborn screening for CF is a valid undertaking that detects 95% of unsuspected CF cases presenting before 3 years of age.

Method for estimation of protein isoelectric point.

Adsorption of sample protein to Eu(3+) chelate-labeled nanoparticles is the basis of the developed noncompetitive and homogeneous method for the estimation of the protein isoelectric point (pI). The lanthanide ion of the nanoparticle surface-conjugated Eu(3+) chelate is dissociated at a low pH, therefore decreasing the luminescence signal. A nanoparticle-adsorbed sample protein prevents the dissociation of the chelate, leading to a high luminescence signal. The adsorption efficiency of the sample protein is reduced above the isoelectric point due to the decreased electrostatic attraction between the negatively charged protein and the negatively charged particle. Four proteins with isoelectric points ranging from ~5 to 9 were tested to show the performance of the method. These pI values measured with the developed method were close to the theoretical and experimental literature values. The method is sensitive and requires a low analyte concentration of submilligrams per liter, which is nearly 10000 times lower than the concentration required for the traditional isoelectric focusing. Moreover, the method is significantly faster and simpler than the existing methods, as a ready-to-go assay was prepared for the microtiter plate format. This mix-and-measure concept is a highly attractive alternative for routine laboratory work.