Immunoreactive Trypsinogen Levels Research Articles

Neutrophil lymphocyte ratio, mean platelet volume, and immunoreactive trypsinogen as early inflammatory biomarkers for cystic fibrosis in infancy: A retrospective cohort study.

Airway inflammation starts in early life in cystic fibrosis (CF) and limited, objective markers are available to help identify infants with increased inflammation. We aimed to investigate neutrophil, lymphocyte ratio (NLR), mean platelet volume (MPV) and immunoreactive trypsinogen (IRT) to be a possible inflammatory biomarker for CF in infancy. This was a retrospective cohort study in three centers. Between January 2015 and December 2022, children with CF newborn screening (NBS) positivity and diagnosed as CF were included in the study. Correlation analysis were performed with NLR, MPV, IRT and follow-up parameters such as z-scores, modified Shwachman-Kulczycki score (mSKS) at the first, second, third and sixth ages and pulmonary function test (PFT) at the sixth age. A total of 92 children with CF included in the study and 47.8% of them were female. There were no correlations between NLR, MPV and weight and height z-scores for all ages (p > 0.05), a negative correlation was found between MPV and body mass indexes (BMI) z-score at the age of 6 (r = -0.443, p = 0.038). No correlation was found between NLR, MPV and PFT parameters and mSKS at all ages (p > 0.05). There was a negative correlation between first IRT and BMI z-score at 6 years of age (r = -0.381, p = 0.046) and negative correlations between second IRT and weight and BMI z-score at the age of 6 (r = -0.462, p = 0.010; r = -0.437, p = 0.016, respectively). Higher MPV and IRT levels during NBS period are associated with worse nutritional outcome which may reflect chronic inflammation. Children with higher MPV and IRT should be followed up closely in terms of chronic inflammation and nutritional status.

Outcomes of children with cystic fibrosis screen positive, inconclusive diagnosis/CFTR related metabolic syndrome.

Some infants undergoing newborn screening (NBS) tests have inconclusive sweat chloride test (SCT) results that lead to the designation of Cystic Fibrosis Screen Positive, Inconclusive Diagnosis/CFTR-related metabolic syndrome (CFSPID/CRMS). Some proportion of them transition to a CF diagnosis, but no predictive markers can stratify which are at risk for this transition. We report single-center outcomes of children with CRMS. We retrospectively identified all infants born in Alabama from 2008 through 2020 referred to our CF Center with an elevated immunoreactive trypsinogen level (IRT) associated with a cystic fibrosis transmembrane conductance regulator (CFTR) mutation (IRT+/DNA+) who had at least one SCT result documented. Infants were classified per established guidelines as Carrier, CRMS, or CF based on the IRT+/DNA+ and SCT results. The electronic health record was reviewed for follow-up visits until the children received a definitive diagnosis (to carrier or CF) according to current diagnostic guidelines for CF, or through the end of the 2020 year. Of the 1,346 infants with IRT+ and at least 1 CFTR mutation identified (IRT+/DNA+), 63 (4.7%) were designated as CRMS. Of these infants, 12 (19.1%) transitioned to Carrier status (CRMS-Carrier), 40 (63.5%) of them remained CRMS status (CRMS-Persistent) and 11 (17.5%) of them transitioned to a diagnosis of CF (CRMS-CF). Of the 11 children in the CRMS-CF group, 4 (36%) had an initial SCT 30-39 mmol/L, 4 (36%) had an initial SCT 40-49 mmol/L and 3 (27%) had an initial SCT 50-59 mmol/L. These children also had higher initial sweat tests and greater yearly increases in sweat chloride values than others with CRMS. We found that in comparison to children in the CRMS-P group, a greater proportion of children in the CRMS-CF group cultured bacteria like methicillin-resistant Staphylococcus aureus, Stenotrophomonas maltophilia, and Pseudomonas aeruginosa, had smaller weight-for-height percentiles and remained smaller over time despite slightly greater growth. Infants with an inconclusive diagnosis of CF should continue to receive annual care and management given their potential risk of transition to CF. Further research is needed to assess whether certain phenotypic patterns, clinical symptoms, diagnostic tests or biomarkers could better stratify these children.

Immunoreactive Trypsinogen Levels in Infants Born to Women with Cystic Fibrosis Taking Elexacaftor-Tezacaftor-Ivacaftor

Background/Objective:Cystic Fibrosis (CF) is a lethal autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene affecting people of every race and ethnicity in the US. Highly effective modulator therapies (HEMT), such as elexacaftor-tezacaftor-ivacaftor (ETI), correct misfolding and/or improve functioning of the abnormal CFTR protein to lessen disease severity. Most people with CF are diagnosed following abnormal newborn screening (NBS), which involves measuring levels of immunoreactive trypsinogen (IRT). There have been case reports of falsely low IRT levels among infants with CF exposed to ETI in utero, but an overall assessment of IRT levels among these infants has not been conducted. We hypothesize that infants born to mothers with CF taking ETI (ETI-exposed) may have lower IRT levels than newborns with CF, CFTR-related metabolic syndrome (CRMS), or CF carriers.Methods:NBS data from infants born between 2020-22 in Indiana with at least one CFTR mutation were collected and compared to infants born to mothers with CF taking ETI followed at Indiana University, regardless of CFTR mutation status. Infants were categorized as: CF, CRMS, Carrier, ETI-exposed, and Unknown (i.e., diagnosis not determined). An ANOVA test was performed on log-transformed data, with p-values adjusted for Dunnett’s to compare IRT levels of infant groups to ETI-exposed group.Results:There were 51 children with CF, 21 with CRMS, 489 CF carriers, and 19 ETI-exposed infants. Compared to other groups, ETI-exposed infants had a lower median IRT value and IQR (p<0.0001). To our knowledge, there are no CF diagnoses among ETI-exposed infants.Conclusion:IRT levels for ETI-exposed infants, who are obligate CF carriers, were lower than for other infants with CF-related diagnoses, raising the likelihood of false normal NBS results. ETI-exposed infants should have CFTR mutation analysis performed to correctly categorize them as CF, CRMS, or CF carriers.

Missed Cystic Fibrosis Newborn Screening Cases due to Immunoreactive Trypsinogen Levels below Program Cutoffs: A National Survey of Risk Factors.

Testing immunoreactive trypsinogen (IRT) is the first step in cystic fibrosis (CF) newborn screening. While high IRT is associated with CF, some cases are missed. This survey aimed to find factors associated with missed CF cases due to IRT levels below program cutoffs. Twenty-nine states responded to a U.S-wide survey and 13 supplied program-related data for low IRT false screen negative cases (CFFN) and CF true screen positive cases (CFTP) for analysis. Rates of missed CF cases and odds ratios were derived for each factor in CFFNs, and two CFFN subgroups, IRT above ("high") and below ("low") the CFFN median (39 ng/mL) compared to CFTPs for this entire sample set. Factors associated with "high" CFFN subgroup were Black race, higher IRT cutoff, fixed IRT cutoff, genotypes without two known CF-causing variants, and meconium ileus. Factors associated with "low" CFFN subgroup were older age at specimen collection, Saturday birth, hotter season of newborn dried blood spot collection, maximum ≥ 3 days laboratories could be closed, preterm birth, and formula feeding newborns. Lowering IRT cutoffs may reduce "high" IRT CFFNs. Addressing hospital and laboratory factors (like training staff in collection of blood spots, using insulated containers during transport and reducing consecutive days screening laboratories are closed) may reduce "low" IRT CFFNs.

Immunoreactive trypsinogen in healthy newborns and infants with cystic fibrosis

ObjectiveNewborn 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...

Клинические особенности патогенного варианта нуклеотидной последовательности L138ins в гене CFTR при муковисцидозе

In this study, we analyzed phenotypic manifestations and clinical course of cystic fibrosis (CF) in patients with the pathogenic variant L138ins of the CFTR gene. The L138ins variant is rarely detected in CF patients worldwide, but is quite common in different regions of the Russian Federation, particularly in the Middle Urals. Before the neonatal screening implementation, the majority of CF patients with the L138ins variant were diagnosed late because of the mild disease course and dubious results of sweat tests. Such patients usually have elevated levels of immunoreactive trypsinogen (IRT) in the neonatal period, which enables early diagnosis; however, false-negative results in CF patients have also been reported. There were cases of male infertility among CF patients with the L138ins variant, while women had their reproductive function preserved. There were also cases of asymptomatic pancreatic hyperenzymemia in children. Respiratory infections caused by Pseudomonas aeruginosa are not very common in this group of patients. However, adult patients have more severe respiratory manifestations (even with a fatal outcome) than children. Thus, despite the mild disease phenotype in patients with the L138ins variant, the residual function of the protein is not sufficient to ensure normal functioning of lungs. Key words: cystic fibrosis, pathogenic CFTR variants, L138ins

Elevated newborn serum immunoreactive trypsinogen associated with a congenital pancreatic cyst

Congenital abdominal cysts have a broad differential diagnosis. Pancreatic cysts are rare lesions that offer a diagnostic and surgical challenge to surgeons. We report on a case of a large left upper quadrant cyst detected in utero , which remained of unclear etiology despite cross-sectional imaging at birth. Intraoperative findings confirmed its pancreatic origin. In hindsight, a pre-operative elevated immunoreactive trypsinogen, performed as part of universal cystic fibrosis (CF) newborn screening, may have suggested the diagnosis. False-positive CF screening tests may be unnoticed by a surgical team assessing infants with an abdominal mass. As universal testing for cystic fibrosis increases in Canada and worldwide, physicians should review a patient's CF screening history. Elevated immunoreactive trypsinogen levels with normal sweat chloride and cystic fibrosis transmembrane conductance regulator (CFTR) detection tests may orient towards a pancreatic etiology when assessing a patient with a congenital abdominal cyst of unclear etiology. • Investigate false-positive cystic fibrosis screening tests when assessing patients with a congenital abdominal cyst. • High immunoreactive trypsinogen levels on cystic fibrosis screening tests may be a marker of congenital pancreatic cysts. • Negative sweat chloride test and genetic testing were not enough to rule out a pancreatic etiology in our case.

Fecal elastase levels in children diagnosed with functional abdominal pain-not otherwise specified.

Although the exact pathophysiology of functional gastrointestinal diseases remains unclear, numerous etiologies have been blamed, including visceral hypersensitivity, gastrointestinal motility disorders, psychological factors, intestinal mucosal inflammation, intestinal microbiota, and post-infectious syndromes. In the present study, we aimed to evaluate pancreatic insufficient patients diagnosed with functional abdominal pain-not otherwise specified (FAP-NOS) according to Rome IV criteria. The study included a total of 110 patients aged 4-17 years who were diagnosed with FAP-NOS according to Rome IV criteria. The control group consisted of 80 patients with no gastrointestinal disorders and chronic diseases. Glucose, amylase, lipase, pancreatic amylase, immunoreactive trypsinogen (IRT) and fecal elastase (FE-1) levels were examined for each patient. No significant difference was found between the two groups with regard to lipase, pancreatic amylase, IRT, and serum glucose levels. However, the amylase levels were significantly higher and the FE-1 levels were significantly lower in the study group compared to the control group (p=0.007 and p < 0.001). The cut-off value detected in in ROC analysis for the diagnostic value of FE-1 in predicting FAP-NOS was found to be 140.107 μg/g. Based on this value, the sensitivity, specificity, PPV, and NPV of FE-1 were 82.1%, 66.2%, 77%, 73%, respectively. Accordingly, the likelihood of FE-1 in providing a positive value in patients with FAP-NOS was almost 9 times higher than in individuals without FAP-NOS. FE-1 levels were significantly lower in children diagnosed with FAP-NOS and we consider that this difference could be attributed to malabsorption secondary to dysbiosis as there is not enough data.

P014 Are lower respiratory tract symptoms different in children with high immunoreactive trypsinogen levels?

P014 Are lower respiratory tract symptoms different in children with high immunoreactive trypsinogen levels?

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.

Immunoreactive trypsinogen levels in newborn screened infants with an inconclusive diagnosis of cystic fibrosis

BackgroundNewborn screening (NBS) for cystic fibrosis (CF) not only identifies infants with a diagnosis of CF, but also those with an uncertain diagnosis of cystic fibrosis (CF), i.e. CF transmembrane conductance regulator (CFTR)-related metabolic syndrome (CRMS) or CF screen positive inconclusive diagnosis (CFSPID). These infants have an uncertain long-term outcome and it is currently unclear around time of diagnosis, which infants are at higher risk of later fulfilling a CF diagnosis. In this study, we hypothesised that immunoreactive trypsinogen (IRT) levels, used in NBS as a marker of pancreatic disease and function, may reflect the degree of CFTR dysfunction in each individual and therefore would help to identify those with CRMS/CSPID who are later at risk for meeting the criteria of CF.MethodsIn this longitudinal, prospective study, infants with CRMS/CFSPID and CF were recruited and followed in 9 CF clinics (Canada and Italy). We compared NBS IRT levels between CF and CRMS/CFSPID, and between children with CRMS/CFSPID→CF and CRMS/CFSPID→CRMS/CFSPID during the period of June 2007 to April 2016.ResultsNinety eight CRMS/CFSPID and 120 CF subjects were enrolled. During the study period, 14 (14.3%) CRMS/CFSPID subjects fulfilled the diagnostic criteria for CF (CRMS/CFSPID→CF), while the diagnosis remained uncertain (CRMS/CFSPID→ CRMS/CFSPID) in 84 (85.7%) subjects. Significantly higher NBS IRT concentrations (ng/ml) were present in CF than CRMS/CFPSID (median (interquartile range): 143.8 (99.8–206.2) vs. 75.0 (61.0–105.9); P < 0.0001). Infants with CRMS/CFSPID→CF (n = 14) had significantly higher NBS IRT concentrations (ng/ml) than CRMS/CFSPID→ CRMS/CFSPID (n = 83) (median (interquartile range): 108.9 (72.3–126.8) vs. 73.7(60.0–96.0); P = 0.02).ConclusionsAmongst infants who tested positive on NBS for CF, there is a gradation of elevated NBS IRT concentrations. Infants with CF have higher NBS IRT levels than CRMS/CFPSID, and higher NBS IRT concentrations were present in infants with CRMS/CFSPID→CF than CRMS/CFSPID→ CRMS/CFSPID. NBS IRT concentrations, in concert with other factors, may have the potential to predict the likelihood of CF amongst infants with CRMS/CFSPID.

Secondhand Smoke Exposure and Serum Trypsinogen in Cystic Fibrosis Carriers.

The objective of this study was to determine if infants carrying 1 cystic fibrosis transmembrane receptor (CFTR) mutation demonstrate pancreatic inflammation in response to tobacco exposure. Cystic fibrosis carrier infants aged 4 to 16 weeks were prospectively enrolled. Tobacco exposure was assessed by survey and maternal hair nicotine analysis. Serum immunoreactive trypsinogen (IRT) levels at birth and at the time of recruitment were analyzed relative to the presence or absence of tobacco exposure. The effect of the severity of the CFTR mutation carried by the infant on the tobacco-IRT relationship was also analyzed. Forty-eight infants completed the study. Newborn screen and follow-up IRT levels were not different between exposed infants (19 by hair analysis) and nonexposed infants (29 by hair analysis). Follow-up IRT levels were lower in infants with more severe CFTR mutations (P = 0.005). There was no difference in follow-up IRT based on CFTR mutation severity in exposed infants. Nonexposed infants with milder CFTR mutations had higher median IRT values on follow-up testing than those with more severe CFTR mutations (P < 0.05). The pancreas of cystic fibrosis carrier infants is affected by tobacco exposure, and those carrying less severe CFTR mutations may be more susceptible to tobacco effects.

Later Diagnosis of Cystic Fibrosis with Negative Newborn Screen: Importance of the Clinical Picture

Cystic fibrosis (CF) is the most common inherited life-limiting disorder among Caucasians. The implementation of CF newborn screening has enabled early diagnosis and prompt treatment onset. However, several factors may affect circulating levels of immunoreactive trypsinogen leading to a normal CF newborn screen. This case aims to highlight the importance of taking clinical manifestations as a strong factor for the diagnosis of CF even in the presence of a negative newborn screen. This may allow early referral to a specialized CF center where the onset of appropriate treatment can be implemented, thereby positively impacting the course of the disease.

Commercially Bottled Purified Water as an Alternative Instrument Feed Water in Automated Time-Resolved Fluorescent Immunoassay for TSH, 17-OHP and IRT in Neonatal Screening

Objective. The study was undertaken to determine if commercially bottled purified water can be used as substitute instrument feed water for three (3) newborn screening immunoassays. Methdology. A total of 294 control samples and 300 patient samples were included in this study. Accuracy and precision studies using control samples, and parallel testing using patient samples, were done to compare the use of clinical laboratory reagent water (CLRW) and commercially bottled purified water (CBPW) in the performance of automated time-resolved fluorescent immunoassay of thyroid stimulating hormone (TSH), 17α-OH-progesterone (17-OHP) and immunoreactive trypsinogen (IRT). Results. The use of CBPW as instrument feed water for measurements of TSH, 17-OHP and IRT levels by automated time-resolved fluorescent immunoassay using AutoDELFIA (Perkin-Elmer) in NBS has an acceptable accuracy and precision compared to using CLRW. The parallel testing using patient samples showed that, overall, the performance of using CBPW in automated time-resolved fluorescent immunoassay for TSH, 17-OHP, and IRT is acceptable, compared with using CLRW as instrument feed water. Conclusion. Commercially bottled purified water can be used as substitute when setting up a laboratory water purification system is too expensive for a laboratory, or as back up to clinical laboratory reagent water when there is breakdown of the installed water purification system to be used as instrument feed water in automated time-resolved fluorescent immunoassay of TSH, 17-OHP and IRT in NBS using AutoDELFIA (Perkin-Elmer).

Diagnosis of Cystic Fibrosis: Consensus Guidelines from the Cystic Fibrosis Foundation

Cystic fibrosis (CF), caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, continues to present diagnostic challenges. Newborn screening and an evolving understanding of CF genetics have prompted a reconsideration of the diagnosis criteria. To improve diagnosis and achieve standardized definitions worldwide, the CF Foundation convened a committee of 32 experts in CF diagnosis from 9 countries to develop clear and actionable consensus guidelines on the diagnosis of CF and to clarify diagnostic criteria and terminology for other disorders associated with CFTR mutations. An a priori threshold of ≥80% affirmative votes was required for acceptance of each recommendation statement. After reviewing relevant literature, the committee convened to review evidence and cases. Following the conference, consensus statements were developed by an executive subcommittee. The entire consensus committee voted and approved 27 of 28 statements, 7 of which needed revisions and a second round of voting. It is recommended that diagnoses associated with CFTR mutations in all individuals, from newborn to adult, be established by evaluation of CFTR function with a sweat chloride test. The latest mutation classifications annotated in the Clinical and Functional Translation of CFTR project (http://www.cftr2.org/index.php) should be used to aid in diagnosis. Newborns with a high immunoreactive trypsinogen level and inconclusive CFTR functional and genetic testing may be designated CFTR-related metabolic syndrome or CF screen positive, inconclusive diagnosis; these terms are now merged and equivalent, and CFTR-related metabolic syndrome/CF screen positive, inconclusive diagnosis may be used. International Statistical Classification of Diseases and Related Health Problems, 10th Revision codes for use in diagnoses associated with CFTR mutations are included.

Refining the continuum of CFTR-associated disorders in the era of newborn screening.

Clinical heterogeneity in cystic fibrosis (CF) often causes diagnostic uncertainty in infants without symptoms and in older patients with milder phenotypes. We performed a cross-sectional evaluation of a comprehensive set of clinical and laboratory descriptors in a physician-defined cohort (N = 376; Children's Hospital of Wisconsin and the American Family Children's Hospital CF centers in Milwaukee and Madison, WI, USA) to determine the robustness of categorizing CF (N = 300), cystic fibrosis transmembrane conductance regulator (CFTR)-related disorder (N = 19), and CFTR-related (CRMS) metabolic syndrome (N = 57) according to current consensus guidelines. Outcome measures included patient demographics, clinical measures, sweat chloride levels, CFTR genotype, age at diagnosis, airway microbiology, pancreatic function, infection, and nutritional status. The CF cohort had a significantly higher median sweat chloride level (105 mmol/l) than CFTR-related disorder patients (43 mmol/l) and CFTR-related metabolic syndrome patients (35 mmol/l; p ≤ 0.001). Patient groups significantly differed in pancreatic sufficiency, immunoreactive trypsinogen levels, sweat chloride values, genotype, and positive Pseudomonas aeruginosa cultures (p ≤ 0.001). An automated classification algorithm using recursive partitioning demonstrated concordance between physician diagnoses and consensus guidelines. Our analysis suggests that integrating clinical information with sweat chloride levels, CFTR genotype, and pancreatic sufficiency provides a context for continued longitudinal monitoring of patients for personalized and effective treatment.

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

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

Assessing the improvements in the newborn screening strategy for cystic fibrosis in the Balearic Islands

ObjectivesNewborn screening strategies for cystic fibrosis (CF) are run worldwide, and aim at the early detection of the disorder to significantly improve the quality of life. Elevated levels of immunoreactive trypsinogen (IRT) represent a high likelihood for the screened child to be affected with CF. However, the specificity of IRT is low. The objective of this study was to assess the screening program in the Balearic Islands during the past 14years. Design & methodsWe evaluated all results of the screening program after 14years, by considering all changes in the protocol and assessing the number of positive samples, the mutations detected, the number of sweat tests performed, the incidence of CF and the presence of false-negative cases. ResultsDespite a great variability among the different Balearic Islands, the global incidence of CF was 1:6059 for the 14years assessed. The incidence in the smaller islands is about 5 times higher than in Majorca (1:2376 versus 1:10,613). After different changes in the protocol, an IRT cut-off value of 60ng/mL was established. The two most common mutations are ΔF508 and G542X, in accordance with other geographical regions. ConclusionsThe changes in the protocol helped reduce the number of sweat tests performed without any increase in the false-negative rate.

Newborn screening for cystic fibrosis in Serbia: A pilot study

We performed a pilot study of neonatal screening for cystic fibrosis (CF) in order to introduce it to the national screening program in Serbia. Immunoreactive trypsinogen (IRT) concentrations were analyzed in dried blood spot samples. Patients were recalled for repeated measurements in case of high IRT levels. Persisting high IRT levels resulted in DNA testing for the 29 most common mutations in the CF transmembrane regulator (CFTR) gene (IRT/IRT/DNA method). Sweat chloride measurements and clinical assessment were further performed for newly diagnosed patients. Of 1000 samples, three were initially positive and were further analyzed for the presence of the most common CFTR mutations in the Serbian population. DNA analysis revealed two patients being homozygous for F508del mutation. One sample was false positive, as the genetic test proved to be negative and associated with normal sweat chloride concentration and unremarkable clinical presentation. The results of our pilot study justified the expanding of the routine neonatal screening program in Serbia with CF. Data could be used in future in order to obtain accurate incidence of CF and carrier prevalence in our country.

Lessons learned from 20 years of newborn screening for cystic fibrosis

To compare three cystic fibrosis (CF) newborn screening strategies used in Victoria since 1989. Retrospective review of newborn screening and clinical records for people with CF born in Victoria between 1989and 2008to compare screening strategies: repeat immunoreactive trypsinogen (IRT) testing (IRT/IRT, 1989-1990), IRT and p.F508del mutation analysis (IRT/p.F508del, 1991-2006) and IRT with analysis of 12CFTR mutations (IRT/12mutations, 2007-2008). Total number of infants screened, people identified with CF (by screening or clinical diagnosis), number of CF-affected terminations of pregnancy, and number of carriers detected. There were 420people born with CF (live-birth prevalence, 1/3139; 95% CI, 1/2853-1/3462) and 78CF-affected pregnancy terminations (overall prevalence, 1/2647; 95% CI, 1/2425-1/2896). Of the babies born with CF, 283(67.4%) were detected by newborn screening alone, 61(14.5%) had meconium ileus, 33(7.9%) had a family history of CF, nine (2.1%) were diagnosed antenatally, and 34(8.1%) were missed by screening (17missed because IRT level was <99th percentile, two with repeat IRT level not elevated, 14without a screened CFTR mutation, and one with missing data). The sensitivities of the protocols were 86.6% for IRT/IRT, 89.9% for IRT/p.F508del, and 95.8% for IRT/12mutations. Including 12mutations in the analysis detected one patient who would otherwise have been missed and, had this protocol been implemented from 1989, it would have detected four others. Most babies with CF without meconium ileus, a family history or antenatal diagnosis are detected by newborn screening. Despite improved sensitivity with the 12-mutation analysis, most infants detected would have been diagnosed using the IRT/p.F508del protocol.