Immunoreactive Trypsinogen Concentrations Research Articles

Cystic Fibrosis Newborn Screening in Austria Using PAP and the Numeric Product of PAP and IRT Concentrations as Second-Tier Parameters.

In Austria, newborns have been screened for cystic fibrosis (CF) by analyzing immunoreactive trypsinogen (IRT) from dried blood spots (DBS)s for nearly 20 years. Recently, pancreatitis-associated protein (PAP) analysis was introduced as a second-tier test with the aim of reducing recalls for second DBS cards while keeping sensitivity high. For 28 months, when IRT was elevated (65–130 ng/mL), PAP was measured from the first DBS (n = 198,927) with a two-step cut-off applied. For the last 12 months of the observation period (n = 85,421), an additional IRT×PAP cut-off was introduced. If PAP or IRT×PAP were above cut-off, a second card was analyzed for IRT and in case of elevated values identified as screen-positive. Above 130 ng/mL IRT in the first DBS, newborns were classified as screen-positive. IRT analysis of first DBS resulted in 1961 (1%) tests for PAP. In the first 16 months, 26 of 93 screen-positive were confirmed to have CF. Two false-negatives have been reported (sensitivity = 92.8%). Importantly, less than 30% of families compared to the previous IRT-IRT screening scheme had to be contacted causing distress. Adding IRT×PAP caused a marginally increased number of second cards and sweat tests to be requested during this period (15 and 3, respectively) compared to the initial IRT-PAP scheme. One case of confirmed CF was found due to IRT×PAP, demonstrating an increase in sensitivity. Thus, the relatively simple and economical algorithm presented here performs effectively and may be a useful model for inclusion of CF into NBS panels or modification of existing schemes.

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.

Safety, pharmacokinetics, and pharmacodynamics of lumacaftor and ivacaftor combination therapy in children aged 2–5 years with cystic fibrosis homozygous for F508del-CFTR: an open-label phase 3 study

The efficacy, safety, and tolerability of lumacaftor and ivacaftor are established in patients aged 6 years and older with cystic fibrosis, homozygous for the F508del-CFTR mutation. We assessed the safety, pharmacokinetics, pharmacodynamics, and efficacy of lumacaftor and ivacaftor in children aged 2-5 years. In this multicentre, phase 3, open-label, two-part study, we enrolled children aged 2-5 years, weighing at least 8 kg at enrolment, with a confirmed diagnosis of cystic fibrosis who were homozygous for the F508del-CFTR mutation. Children received lumacaftor 100 mg and ivacaftor 125 mg (bodyweight <14 kg) or lumacaftor 150 mg and ivacaftor 188 mg (bodyweight ≥14 kg) orally every 12 h for 15 days in part A (to assess pharmacokinetics and safety) and for 24 weeks in part B (to assess safety, pharmacokinetics, pharmacodynamics, and efficacy). Children could participate in part A, part B, or both. Children were enrolled into part A at five sites in the USA and into part B at 20 sites in North America (USA, 17 sites; Canada, three sites). The primary endpoints of the study were the pharmacokinetics (part A) and safety (part B) of lumacaftor and ivacaftor; all analyses were done in children who received at least one dose of lumacaftor and ivacaftor. Secondary endpoints in part A were safety and pharmacokinetics of the metabolites of lumacaftor and ivacaftor, and in part B included pharmacokinetics in children who received at least one dose of lumacaftor and ivacaftor and absolute changes from baseline in sweat chloride concentration, growth parameters, and markers of pancreatic function. This study is registered with ClinicalTrials.gov, number NCT02797132. The study was done from May 13, 2016, to Sept 8, 2017. 12 children enrolled in part A, 11 of whom completed the 15-day treatment period and enrolled in part B. 60 children enrolled in part B, 56 of whom completed the 24-week treatment period. Safety and pharmacokinetics were consistent with the well characterised safety profile of lumacaftor and ivacaftor. In part B, most children (59 [98%] of 60 children) had one or more treatment-emergent adverse events; most events were mild to moderate in severity. The most common adverse events were cough (38 [63%] of 60), vomiting (17 [28%]), pyrexia (17 [28%]), and rhinorrhoea (15 [25%]). Serious adverse events occurred in four children: infective pulmonary exacerbation of cystic fibrosis (n=2), gastroenteritis viral (n=1), and constipation (n=1). Three (5%) of 60 children discontinued treatment because of elevated serum aminotransferase concentrations. Mean sweat chloride concentrations decreased by 31·7 mmol/L, biomarkers of pancreatic function improved (fecal elastase-1 concentrations increased and serum immunoreactive trypsinogen concentrations decreased), and growth parameters increased at week 24. Lumacaftor and ivacaftor were generally safe and well tolerated in children aged 2-5 years with cystic fibrosis for 24 weeks. Efficacy findings also suggest that early intervention with lumacaftor and ivacaftor has the potential to modify the course of disease. Vertex Pharmaceuticals Incorporated.

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 20h. The useful rank of the curve is 0-500ng/mL, and the lowest detectable concentration is 4.8ng/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 12.8ng/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.

EPS01.5 Immunoreactive trypsinogen (IRT) and pancreatitis-associated protein (PAP) concentrations depend on age at blood collection

ePS01.5 Immunoreactive trypsinogen (IRT) and pancreatitis-associated protein (PAP) concentrations depend on age at blood collection

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.

Prospective and parallel assessments of cystic fibrosis newborn screening protocols in the Czech Republic: IRT/DNA/IRT versus IRT/PAP and IRT/PAP/DNA

Cystic fibrosis (CF) is a life-threatening disease for which early diagnosis following newborn screening (NBS) improves the prognosis. We performed a prospective assessment of the immunoreactive trypsinogen (IRT)/DNA/IRT protocol currently in use nationwide, versus the IRT/pancreatitis-associated protein (PAP) and IRT/PAP/DNA CF NBS protocols. Dried blood spots (DBS) from 106,522 Czech newborns were examined for IRT concentrations. In the IRT/DNA/IRT protocol, DNA-testing was performed for IRT ≥ 65 ng/mL. Newborns with IRT ≥ 200 ng/mL and no detected cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations were recalled for a repeat IRT. In the same group of newborns, for both parallel protocols, PAP was measured in DBS with IRT ≥ 50 ng/mL. In PAP-positive newborns (i.e., ≥1.8 if IRT 50-99.9 or ≥1.0 if IRT ≥ 100, all in ng/mL), DNA-testing followed as part of the IRT/PAP/DNA protocol. Newborns with at least one CFTR mutation in the IRT/DNA/IRT and IRT/PAP/DNA protocols; a positive PAP in IRT/PAP; or a high repeat IRT in IRT/DNA/IRT were referred for sweat testing. the combined results of the utilized protocols led to the detection of 21 CF patients, 19 of which were identified using the IRT/DNA/IRT protocol, 16 using IRT/PAP, and 15 using IRT/PAP/DNA. Decreased cut-offs for PAP within the IRT/PAP protocol would lead to higher sensitivity but would increase false positives. Within the IRT/PAP/DNA protocol, decreased PAP cut-offs would result in high sensitivity, an acceptable number of false positives, and would reduce the number of DNA analyses. Thus, we concluded that the IRT/PAP/DNA protocol would represent the most suitable protocol in our conditions.

23 Differences in blood immunoreactive trypsinogen concentrations and genotype in hypertrypsinaemic neonates

23 Differences in blood immunoreactive trypsinogen concentrations and genotype in hypertrypsinaemic neonates

Variation in immunoreactive trypsinogen concentrations among michigan newborns and implications for cystic fibrosis newborn screening

To investigate variation in immunoreactive trypsinogen (IRT) concentrations by race, sex, birth weight, and gestational age and their implications for the use of percentile-based cutoffs for cystic fibrosis (CF) newborn screening (NBS) programs. This cross-sectional population-based study of resident infants screened in Michigan investigates associations between demographic and perinatal variables and IRT concentrations after controlling for covariates. This study also analyzed how 96th and 99.8th IRT concentration percentiles values calculated by Michigan NBS vary by demographic and perinatal factors. Characteristics of infants having high (≥99.8th percentile) IRT concentrations and negative DNA tests are also explored. IRT mean concentrations and percentiles vary significantly by race, birth weight, gestational age, and to a lesser degree by sex. The greatest variation in mean IRT concentrations was observed among racial categories; black infants had an adjusted mean concentration of 36 ng/ml and Asian/Pacific Islander infants had a mean concentration of 25 ng/ml compared to an average concentration of 28 ng/ml in white infants and infants of other races. Variation in IRT concentrations resulted in the over-representation of certain groups referred for secondary testing, particularly referrals for sweat testing based on very high (≥99.8th percentile) concentrations alone, which is no longer recommended in Michigan. Further research may be warranted to evaluate initial IRT cutoffs used for CF NBS.

Predictors of insufficient sweat production during confirmatory testing for cystic fibrosis

Michigan's Newborn Screening (NBS) Program began statewide screening for cystic fibrosis (CF) in October 2007. Confirmatory sweat testing is performed in infants having initial immunoreactive trypsinogen concentrations ≥ 99.8th percentile or ≥ 96 th percentile and at least one CF mutation identified by DNA analysis. Some infants fail to produce a sufficient quantity of sweat (QNS-quantity not sufficient) to test for CF, meaning disease confirmation is delayed and sweat testing is later repeated. In this study, we evaluate predictors of QNS results. Information from the linked birth certificates and NBS diagnostic confirmation data were used. The study population was resident infants born in Michigan in 2008 who underwent a sweat test. Bivariate analyses revealed that preterm birth, low birth weight, CF care center, and race were significantly associated with QNS sweat testing results. Adjusted analyses indicated that preterm infants were 2.4 times more likely to have QNS results (95% CI 0.9, 6.4). When age at time of test, accounting for gestational age (gestational age at delivery plus postdelivery age of life=corrected age), was used in the multivariable model, infants <39 weeks were 7.4 times more likely to have QNS results (95% CI 2.5, 21.8). Waiting to sweat test until an infant is aged 39 weeks or more (corrected age) would likely reduce the rate of QNS results, thereby reducing the burden of repeat sweat testing on families and healthcare providers. Further research is necessary to understand the impact of potential delays in diagnosis/treatment relative to postponing sweat testing.

Clarification of Laboratory and Clinical Variables That Influence Cystic Fibrosis Newborn Screening With Initial Analysis of Immunoreactive Trypsinogen

To ensure that each newborn receives an equitable test of the highest possible sensitivity, we recognized the necessity to reassess immunoreactive trypsinogen and DNA issues in cystic fibrosis newborn screening algorithms. Our objectives included clarification of various factors that influence immunoreactive trypsinogen concentrations and resolution of long-standing questions about variations in immunoreactive trypsinogen levels among newborns. Immunoreactive trypsinogen data on 660443 newborns who were born between July 1, 1994, and June 30, 2004, were abstracted from the Wisconsin State Laboratory of Hygiene databases and deidentified for analysis. Using a compiled data set, we analyzed various demographic characteristics to determine their role, if any, in immunoreactive trypsinogen variation. Specifically, season of birth, reagent lot, and birth weight were examined. Sensitivities of the most common cystic fibrosis newborn screening protocols, namely immunoreactive trypsinogen/immunoreactive trypsinogen and immunoreactive trypsinogen/DNA, were also investigated. Mean and 95th percentile immunoreactive trypsinogen levels were shown to vary by both season and reagent lot number and affect sensitivity of the assay. Low birth weight infants had significantly higher immunoreactive trypsinogen values than normal birth weight infants. Sensitivities were also found to vary on the basis of the algorithm used, with the highest sensitivity of 96.2% calculated for an immunoreactive trypsinogen/DNA protocol with 23 cystic fibrosis transmembrane conductance regulator mutation analyses compared with 80.2% with the immunoreactive trypsinogen/immunoreactive trypsinogen method used in 9 states. Floating, rather than fixed, cutoff values for the initial immunoreactive trypsinogen portion of any cystic fibrosis newborn screening protocol are generally necessary on the basis of the seasonal and reagent lot variations observed. Because of its lower sensitivity, immunoreactive trypsinogen/immunoreactive trypsinogen does not optimize detection of patients with cystic fibrosis.

Population quantile‐quantile plots for monitoring assay performance in newborn screening

Immunoreactive trypsinogen (IRT) used in screening for cystic fibrosis is heterogeneous, poorly characterized, and displays marked matrix effects when incorporated into blood spots, making long-term control of assay calibration difficult. The cut-off required to select a fixed proportion of samples (0.5% for the UK protocol) for second-tier mutation analysis varies over time, partly owing to slight differences in calibration of individual lots of assay kit. To investigate this and possible inter-laboratory differences in analytical performance, we developed a monitoring system based on the distribution of measured IRT concentrations in the screened samples. Results were collected fortnightly from five UK screening laboratories in the form of numbers of samples in histogram 'bins' of IRT concentration. These data were converted to cumulative percentages and the IRT concentrations at fixed centiles then approximated by triangulation. The quantile-quantile plot of any subset (by laboratory or by kit lot) of these data using pooled results (all-laboratories all-kit-lots, approximately 270,000 samples) as the reference distribution is analogous to a calibration curve and gives a measure of bias in terms of sensitivity (slope) and baseline (y-intercept). This allows a revised 99.5th centile cut-off for each subset to be calculated directly. A similar approach has allowed inter-laboratory comparison of tandem-mass spectrometric assays for free carnitine (with emphasis on low values) and phenylalanine and has demonstrated that apparently trivial differences in instrumentation and procedures have resulted in marked variation in resultant assay performance.

363 Monthly variation in newborn screening immunoreactive trypsinogen concentrations [IRT

363 Monthly variation in newborn screening immunoreactive trypsinogen concentrations [IRT

Cystic fibrosis carriers have higher neonatal immunoreactive trypsinogen values than non‐carriers

Following cystic fibrosis (CF) neonatal screening implementation, a high frequency of heterozygotes has been reported among neonates with elevated immunoreactive trypsinogen (IRT) and normal sweat chloride levels. We studied the relationship between normal IRT values and CF heterozygosity: 10,000 neonates were screened for CF by IRT measurement and tested for 40 CF mutations; the 294 carriers detected were coupled with newborns negative to the same genetic testing, and the two groups' IRT levels compared. Heterozygotes had higher IRT levels than their controls (mean 35.32 vs. 27.58 microg/L, P<0.001). Even within normal trypsinogen range, the probability of being a CF carrier increases with neonatal IRT concentration.

Blood immunoreactive trypsinogen concentrations are genetically determined in healthy and cystic fibrosis newborns

Newborns with cystic fibrosis (CF) have increased blood immunoreactive trypsinogen concentrations. When screening for CF in the newborn by immunoreactive trypsinogen measurement, an abnormally high proportion of healthy ΔF508 carriers is found among false‐positive neonates, suggesting that a relationship could exist between immunoreactive trypsinogen concentration at birth and the genetic status. Therefore, this study analysed the possible relationships between neonatal blood immunoreactive trypsinogen concentrations and genotype in 1842 healthy newborns and 111 CF patients detected by a neonatal screening programme. A close correlation was found between immunoreactive trypsinogen and ΔF508: the probability of a healthy newborn being a carrier of this mutation increased regularly with the neonatal immunoreactive trypsinogen concentration. In CF patients, there was a significant difference between ΔF508 homozygotes and ΔF508/X (X = other mutation) compound heterozygotes with respect to the mean neonatal blood immunoreactive trypsinogen concentration. CF neonates with two mutations affecting the nucleotide binding domains of the cystic fibrosis transmembrane conductance regulator protein had significantly higher mean immunoreactive trypsinogen concentrations than patients with one mutation affecting a membrane‐spanning domain. The data strongly suggest that the neonatal immunoreactive trypsinogen concentration is, in part, genetically determined, with a wide range of variations, similar to the features which have been shown for the relations between the genotype and clinical phenotypes of CF patients.

Blood immunoreactive trypsinogen concentrations are genetically determined in healthy and cystic fibrosis newborns.

Newborns with cystic fibrosis (CF) have increased blood immunoreactive trypsinogen concentrations. When screening for CF in the newborn by immunoreactive trypsinogen measurement, an abnormally high proportion of healthy deltaF508 carriers is found among false-positive neonates, suggesting that a relationship could exist between immunoreactive trypsinogen concentration at birth and the genetic status. Therefore, this study analysed the possible relationships between neonatal blood immunoreactive trypsinogen concentrations and genotype in 1842 healthy newborns and 111 CF patients detected by a neonatal screening programme. A close correlation was found between immunoreactive trypsinogen and deltaF508: the probability of a healthy newborn being a carrier of this mutation increased regularly with the neonatal immunoreactive trypsinogen concentration. In CF patients, there was a significant difference between deltaF508 homozygotes and deltaF508/X (X = other mutation) compound heterozygotes with respect to the mean neonatal blood immunoreactive trypsinogen concentration. CF neonates with two mutations affecting the nucleotide binding domains of the cystic fibrosis transmembrane conductance regulator protein had significantly higher mean immunoreactive trypsinogen concentrations than patients with one mutation affecting a membrane-spanning domain. The data strongly suggest that the neonatal immunoreactive trypsinogen concentration is, in part, genetically determined, with a wide range of variations, similar to the features which have been shown for the relations between the genotype and clinical phenotypes of CF patients.

Malnutrition, gastroenteritis and trypsinogen concentration in hospitalised Aboriginal children.

To explore relationships between malnutrition and pancreatic damage in hospitalised aboriginal children. Immunoreactive trypsinogen (IRT) concentrations were measured in two populations of hospitalised aboriginal children in Australia: 472 children aged 0-3 years, in Alice Springs (Northern Territory); and 187 children aged 0-16 years in Mount Isa (Queensland). Correlation of whole blood IRT with height and weight z-scores, four-site skinfold thickness and upper arm circumference was sought. In Mount Isa, the geometric mean IRT concentration rose with decreasing weight z-score. The IRT concentration was otherwise unrelated to nutritional indices. Sixty percent of the 39 Mount Isa patients with gastroenteritis and 24.5% of the 358 Alice Springs patients with gastroenteritis had an IRT concentration in the upper quartile for their population, compared with 16% for patients with other diagnoses in both populations. A high IRT concentration in patients with low weight z-scores is a confounding effect of gastroenteritis, and may result from subclinical pancreatic disease in gastroenteritis.

Neonatal screening for cystic fibrosis using immunoreactive trypsinogen and direct gene analysis: four years' experience.

To assess the performance and impact of a two tier neonatal screening programme for cystic fibrosis based on an initial estimation of immunoreactive trypsinogen followed by direct gene analysis. Four year prospective study of two tier screening strategy. First tier: immunoreactive trypsinogen measured in dried blood spot samples from neonates aged 3-5 days. Second tier: direct gene analysis of cystic fibrosis mutations (delta F508, delta I506, G551D, G542X, and R553X) in samples with immunoreactive trypsinogen concentrations in highest 1% and in all neonates with meconium ileus or family history of cystic fibrosis. South Australian Neonatal Screening Programme, Adelaide. All 88,752 neonates born in South Australia between December 1989 and December 1993. Neonates with two identifiable mutations were referred directly for clinical assessment and confirmatory sweat test; infants with only one identifiable mutation were recalled for sweat test at age 3-4 weeks. Parents of neonates identified as carriers of cystic fibrosis mutation were counselled and offered genetic testing. Identification of all children with cystic fibrosis in the screened population. Of 1004 (1.13%) neonates with immunoreactive trypsinogen > or = 99th centile, 912 (90.8%) had no identifiable mutation. 23 neonates were homozygotes or compound heterozygotes; 69 carried one identifiable mutation, of whom six had positive sweat tests. Median age at clinical assessment for the 29 neonates with cystic fibrosis was 3 weeks; six had meconium ileus and two had affected siblings. 63 neonates were identified as carriers of a cystic fibrosis mutation. Extra laboratory costs for measuring immunoreactive trypsinogen and direct gene analysis were $A1.50 per neonate screened. This strategy results in early and accurate diagnosis of cystic fibrosis and performs better than screening strategies based on immunoreactive trypsinogen measurement alone.

Relationship of genotype to early pulmonary function in infants with cystic fibrosis identified through neonatal screening

To determine whether pulmonary function in infants with asymptomatic cystic fibrosis is related to genotype, we studied 18 infants with cystic fibrosis identified through neonatal screening and 18 healthy control infants. Infants with cystic fibrosis (mean age, 2.0 months; range, 1.0 to 4.6 months) were identified from June 1990 to September 1991 through a statewide screening program based on elevated immunoreactive trypsinogen concentrations. Pulmonary function testing was done before and after inhalation of albuterol. There were no differences in pulmonary function between the cystic fibrosis group and the control infants (mean age, 2.7 months; range, 0.9 to 4.5 months). However, infants homozygous for the delta F508 deletion (n = 10) differed from infants with other genotypic variants of cystic fibrosis and control infants with respect to respiratory system resistance (79.4 +/- 11.5 vs 52.0 +/- 3.8 vs 55.5 +/- 5.0 cm H2O/L per second, respectively; p = 0.04) and specific conductance (0.15 +/- 0.02 vs 0.21 +/- 0.02 vs 0.21 +/- 0.02 cm H2O-1 sec-1, respectively; p = 0.02). Infants homozygous for the delta F508 deletion, but not other infants, responded to albuterol with a decrease in respiratory system resistance. We conclude that infants with asymptomatic cystic fibrosis homozygous for the delta F508 deletion have early evidence of airways obstruction and may need early respiratory treatment.

Immunoreactive trypsinogen concentrations in infants with meconium ileus.

Immunoreactive trypsinogen concentrations in infants with meconium ileus.