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Elevated IRT/no mutations

IRT is elevated in CF newborns, even those with pancreatic sufficiency (approx. 10-15% of CF patients) Damaged pancreatic acinar cells leak this enzyme precursor into bloodstream Nonspecific elevation can occur with perinatal stress DNA: CFTR mutations ELEVATED IMMUNOREACTIVE TRYPSINOGEN / CFTR IRT ≥ 170 ng/mL and no mutations found on CFTR Quantity not sufficient for sweat chlride CFTR mutation panel testing Sweat chloride mormal No further action Sweat chloride is ≥ 30 and ≤59mEq/L Repeat sweat chloride test at 1-

Infants with at least one CFTR mutation or very high IRT and no mutations (VHIRT) are referred for sweat testing High IRT, No Mutations Page 2 of 2 Version 2.0 December 2009 What happens next? Another blood sample needs to be taken from your baby's heel when your baby is 3 weeks (21 days) old. This sample is tested to see if your baby's IRT level is still increased. This second IRT level is a better indicator of C The bulk of screen-positive African-American infants were in the top 0.2% (IRT) group, with no CF mutations isolated. Repeat IRT testing at 2-3 weeks of age may represent a suitable approach to decrease the false-positive rate in this population

Newborn screening for Cystic Fibrosis (CF) began in New York in October, 2002 using immunoreactive trypsinogen (IRT)/DNA methodology. Infants with at least one CFTR mutation or very high IRT and no mutations (VHIRT) are referred for sweat testing. In a preliminary analysis, we noted a very low positive predictive value (PPV) and preponderance of Hispanic infants in the group of infants with CF. value. If no mutations are identified, the elevated IRT value is reported along with a comment that no mutations were identified. If the IRT concentration is greater than 128 ng/ml blood and no mutations are identified, the specimen is sent to the Emory Genetics Laboratory (EGL) for analysis for 16 additional rare CFTR mutations Flowchart depicting IRT/IRT1↑/DNA screening algorithm and failsafe algorithm to identify infants with 2 extremely elevated IRT levels and no CF mutations. Recommended sweat chloride reference values in infancy are in concordance with current diagnostic guidelines. 18. Linking of First and Second Specimens. A new laboratory information system. All 50 states perform newborn screening for cystic fibrosis. IRT is normally found in small levels in the body. In people who have CF, IRT levels tend to be high but IRT levels can also be high if a baby is premature, had a stressful delivery, or other reasons. Some states only test IRT levels on the first blood test

If the IRT level is not elevated, then it is likely that the newborn does not have CF. However, if suspicion of CF is high and the infant has signs and symptoms consistent with CF, other testing for cystic fibrosis, such as sweat chloride and/or CF gene mutation testing, should be considered Objective: to report the immunoreactive trypsinogen (IRT) values above the usual 99th percentile laboratory cut-off and determine the value of offering further testing to those infants with a markedly elevated IRT but no cystic fibrosis transmembrane regulator (CFTR) gene mutation identified by the screening program Infants with an elevated IRT (>99th centile of results) have cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation analysis for the commonest mutation, ΔF508, from the same card. 2 Other centres with NBS for CF screen with additional mutations, depending on the frequency of these mutations in their community. 3 Infants with two CFTR mutations have CF while infants with one copy of the common CFTR mutation are referred for a sweat test IRT-DNA testing will not only show your baby's IRT levels but also indicate whether the baby may be a carrier of the CF gene (which means he or she has only one CF gene mutation). If you have questions about newborn screening or genetic testing for CF, please contact a CF Foundation-accredited care center or talk with your doctor

Utility of a very high IRT/No mutation referral category

• CF is caused by mutations in the CFTR gene (chromosome 7) • Kalydeco is a drug therapy now available for some CF patients • NBS algorithms used to detect CF IRT/IRT (no molecular component) IRT/DNA & IRT/IRT/DNA: elevated IRT CFTR mutation(s) IRT/DNA/EGA (elevated IRT CFTR mutations gene sequencing whe Table 3 Mutations detected in 62 newborns with elevated IRT and elevated sweat chlorides Full size table There were 35 newborns with elevated IRT who had borderline sweat chloride results ( Table 4 ) CFTR Mutation Elevated 0 Mutations Detected No further evaluation necessary unless clinically indicated. Immunoreactive Trypsinogen (IRT) Elevated. None of the CFTR variants in the DSHS panel were detected. However, there is a minimal risk for Cystic Fibrosis due to variants not included in the panel Table 2 2 shows the relatively poor PPV of elevated IRT in the absence of a CFTR mutation compared to a PPV of 1 in 8 based on an elevated IRT and one CFTR mutation (table 3 3).). On this basis, there is no indication to recall the infants with an elevated IRT, but no CFTR mutation, for further testing, no matter how high the IRT An elevated serum trypsinogen level is an indirect indication of pancreatic injury, which is present in most newborns affected with CF. In most programs, newborns demonstrating an abnormally high level of immunoreactive trypsinogen (IRT) are flagged for complementary genetic mutation analysis using a tailored local screen

Elevated IRT levels in African-American infants

Normal IRT 6 Elevated IRT no p.F508del CFTR mutation 12* p.F508del/other, negative sweat test 595 Carrier frequency 1 in 13 Expected overall number of CF 354 *Data provided by Dr. Veronica Wiley NSW Newborn Screening Programme Description Number Identified. Neonatal Screening for CF. IRT/DNA (multi-mutation panel) IRT analysis of the initial specimen, with positive specimens subsequently tested for a panel of common mutations May not be required * IRT refers to the immunoreactive trypsin test, a blood test for elevated levels of trypsinogen Persons with CF have mutations in the gene encoding the Cystic Fibrosis Transmembran High IRT, No Mutations Page 2 of 2 What happens next? Another blood sample needs to be taken from your baby's heel when your baby is 3 weeks (21 days) old. This sample is tested to see if your baby's IRT level is still increased. This second IRT level is a better indicator of CF than the one done at 24-48 hours of age. Yo Those newborns with a positive screening test (i.e., elevated IRT test and >1 detected mutation) are usually referred to a diagnostic center for a sweat chloride test to make a definitive diagnosis, although children with two disease-causing mutations are considered to have CF, regardless of the results of the sweat test (37). The program in.

The IRT level is elevated even a infant with CF is pancreatic sufficient. In Maryland, if the IRT is elevated in two tests then the infant will be referred for a sweat test. Some states test only for elevated IRT levels in the blood while other states also test for the presence of CFTR gene mutations. In these states, if the IRT is high, then. No CFTR mutations detected in the 39 mutation panel IRT slightly elevated. CF is not likely. No further evaluation necessary unless clinically indicated. Age at collection: > 7 days < 50 < 50 Normal result No further action required ≥ 50 < 50 Abnormal Result - CF mutation testing performed. 1 or 2 CFTR mutations detected in the 39 mutation panel An IRT level can be high due to the baby being jaundice (like the article said about elevated bilirubin), traumatic delivery, and even oxytocin (pitocin) being given to the mother during labor. It is actually not necessarily a small number of mutations missing from the basic panel

A New Cystic Fibrosis Newborn Screening Algorithm: IRT

IRT values are often elevated in certain disease states such as GI disease in the postnatal period. Recommendations: • IRT Negative: Reassure parents that CF is highly unlikely. DNA testing and sweat test is not indicated. • IRT Positive / DNA Testing Negative (no mutations are identified): Reassure parents that CF is highly unlikely This test is a DNA test, and looks for mutations or changes within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. If the laboratory finds any mutations, the next step is to perform a sweat chloride test, which is a diagnostic test for cystic fibrosis. If the IRT result is extremely high, with no DNA mutations, a swea Specimens with no mutations and IRT ≤175 ng/mL are considered normal. If 1 or 2 CFTR mutations are identified, the patient is referred for sweat chloride testing at a certified CF center. If the initial IRT value is >175 ng/mL, the patient is automatically referred for sweat chloride testing, regardless of DNA findings Elevated IRT's reflex to check for the most common mutation associated with CF, ΔF508. If no copies of ΔF508 are found but the IRT is greater than 130, a repeat specimen will be requested. If one copy of the ΔF508 is present with an elevated IRT, a 36-mutation panel is done on the initia Elevated results (above the 99.5th centile) undergo mutation analysis (panel of 4 common mutations). If no mutations are identified yet the initial IRT is above the 99.9th centile, a second sample is collected on day 21, for repeat IRT analysis. If one mutation is identified, a larger panel of mutations is tested

However, a second IRT is measured at 3-4 weeks in babies with one mutation and a first IRT elevated above the 99.5th centile and in babies with no mutation but a first IRT extremely elevated above the 99.9th centile. Confirmatory sweat tests are done on those with an elevated second IRT IRT/IRT protocol: includes a second measurement of IRT between 25 and 40 days post birth, and if this second test is positive, genetic testing is performed. IRT/DNA protocol: after detection of elevated IRT levels, genetic testing is performed in the same heel prick capillary blood sample, analysing the variants that are most prevalent locally IRT testing is only useful for screening - it is not diagnostic. There is a substantial rate of false positives due to diseases other than CF and pancreatic dysfunction. An elevated level must be followed with other testing to establish a diagnosis. This may include CF gene mutation testing and/or sweat chloride testing Babies with an IRT greater than a pre-defined cut-off (Australian centres use the 99 th percentile of values) for that batch have CFTR mutation analysis from the same filter paper sample. 10, 43 Infants with two CFTR mutations are considered to have CF while those with one CFTR mutation are referred for sweat testing to determine whether they. If a second IRT level is elevated, the patient's DNA is tested for CFTR mutation analysis. 12 The newer IRT/IRT1/DNA algorithm has a sensitivity of more than 99.5%, according to Sontag and colleagues. 13 Genotyping is commonly performed when patients have an elevated IRT or a positive chloride sweat test. Initial analysis consists of about 100.

Newborn Screening for CF CF Foundatio

One baby had an elevated IRT of 144 μg/L (greater than the 99.9 percentile), but no mutation was detected and, thus, was reported as a negative screen. This baby was subsequently diagnosed with CF at six months of age. The baby suffered from failure to thrive and was referred to a gastroenterologist who ordered CFTR full screening If no mutations are identified, but the baby has two very high IRT levels, they will be classified as having a positive screening test and will automatically be referred to the CF team for further assessment, which may include a sweat test or further mutation testing. This scenario may be the case for non-Caucasian babies If the IRT is in the top 4% of the day or qualifies as an ultra-high IRT of ⩾170 ng/mL, second tier DNA mutation analysis for a panel of 74 CFTR mutations is performed. 6 A positive CF NBS is defined as (1) an elevated IRT and the presence of one or two CFTR mutations, or (2) an ultra-high IRT level with no mutations. 7 Positive screens must. the top 4% of the day or qualifies as an ultra-high IRT of ⩾170ng/mL, second tier DNA mutation analysis for a panel of 74 CFTR mutations is performed.6 A positive CF NBS is defined as (1) an elevated IRT and the presence of one or two CFTR mutations, or (2) an ultra-high IRT level with no mutations.7 Positive screens must be followed by For the new IRT/DNA protocol, we predicted that, with 75% prevalence of the common mutation in persons with CF, we would achieve early diagnosis in 94%-95% of all case-patients (accounting for patients at high risk, negative IRT results, and negative DNA results). Results of our study have been consistent with our hypotheses

The second tier is either a limited CFTR mutation analysis or a repeat measurement of the IRT concentration at the age of 4-6 weeks.3 Protocols using IRT alone or IRT/IRT have a high false-positive rate.4 The major drawback of using CFTR mutation analysis is the high number of identified healthy carriers and cases with an equivocal diagnosis.1 The number of babies referred fell from 2007 to 2011 (Table 2) because the algorithm was changed in March 2010 such that specimens with high IRT but without mutations collected within 24 h of birth were no longer referred immediately (instead, a repeat specimen was requested) and specimens with elevated IRT and in the top 0.1 % for IRT were. an immunoreactive trypsinogen (IRT) assay as the 1st tier screen for CF. Specimens with elevated IRT (≥96th daily percentile) then move to the 2nd tier of testing and are screened for CF gene mutations. The recall involves only the 2nd tier molecular test used for about 4% of infants screene IRT-repeat IRT. Test second specimen for IRT. Exceeds cutoff. Refer to sweat test. IRT-DNA (ΔF508) DNA assay for ΔF508 alleles. One to two mutations detected. Refer to sweat test. No mutation.

Immunoreactive Trypsinogen (IRT) Lab Tests Onlin

  1. imal risk for Cystic Fibrosis (CF) in the absence of detected mutations, a very elevated immunoreactive trypsinogen (IRT) result may be indicative of CF due to mutations not included in the 40-mutation panel. Recommend referral fo
  2. In IRT/IRT method, a second specimen is not obtained and there is no follow-up 8. In IRT/IRT method, the second IRT result is not above the cutoff value 9. In IRT/DNA method, uncommon mutation(s) is/are present and not identified 10. Lab errors (e.g., errors measuring IRT, or DNA mutation analysis) 11
  3. that the IRT was elevated and DNA analysis resulted in 1 of 3 possible outcomes. 21 CF Results Mutant Heterozygote Ultra-high IRT >175ng/mL with no mutations. 8 22 Report Format (Laboratory Results) RESULTS for IRT and DNA with mutation(s) listed INTERPRETATION-carrier, disease RECOMMENDATION-sweat test at accredited CF center. 23 What should.
  4. IRT concentrations particularly impacts the demographic distribution of infants having IRT concentrations 99.8th percentile and no identified CF mutation. Specifically, the proportions of infants born very preterm or very low birth weight that undergo sweat chloride testing based on IRT alone are more than 15 times greater than their respectiv
  5. either replacing the existing 39-mutation panel, or as a third-tier in which infants with high IRT and less than two mutations on the InPlex panel could be reflex tested using the 139-VA. MaterialsandMethods Procedures for CF screening in NYS using an IRT-DNA al-gorithm have been described [Kay et al., 2015]. Briefly, the Im
  6. No CFTR mutation detected but very high (≥ 99.9th centile) first IRT and raised second IRT - CF suspected For babies with this screening result, follow the guidance in part 1 and advice below

positive if: [1] IRT exceeded the site-specific cut-off, in addition to at least one CFTR mutation (and/or raised meconium lactase in Verona, Italy); or, [2] IRT exceeded the 99.9th centile when no mutations were identified. All infants who were identified as NBS-positive were then referred to their local CF centre for sweat testing an Since the late 1970s when the potential of the immunoreactive trypsinogen assay for early identification of infants with cystic fibrosis was first recognised, the performance of newborn blood spot screening (NBS) has been continually assessed and its use has gradually expanded. NBS for cystic fibrosis is a cost-effective strategy and, if standards of care are fully implemented and robust. An elevated IRT with two CFTR mutations is primarily associated with: • Cystic ˜ brosis — Incidence of 1 in 3,500 Other (less likely) disorder to consider: • CFTR-related metabolic syndrome (CRMS) Clinical Summary CF is an autosomal recessive disorder caused by mutations in the cystic ˜ brosis transmembrane conductance regulator (CFTR.

Markedly elevated neonatal immunoreactive trypsinogen

mutation is found (often indicating a heterozygote carrier); in some regions, a very high IRT concentration is considered a positive screen - ing test. Elevated sweat chloride is a robust indicator of the loss of CFTR function that is independent of the type of mutation (15) and remains the gold standard for diagnosis of CF. As a result, quantita Measurement of immunoreactive trypsinogen (IRT) in blood of newborn babies is an assay in rapidly increasing use as a screening test for cystic fibrosis (CF).. In CF, there is poor release from pancreatic ducts. Trypsinogen is a pancreatic enzyme precursor found in the blood that is elevated in most of those with CF at birth, regardless of whether their mutation is pancreatic sufficient or. Referral to Specialty Care Center for DxMost healthy single mutation carriers Normal IRT (bottom 95%)(top 5%) IRT (bottom 99.9%) Screen 2 Mut Screen Positive: Negative Most confirmed (30-40 referrals, 19-37 cases) 39 Mutation Panel (Hologic) IRT Assay 1 Mut VHIRT (top 0.1%) Elevated IRT 0 Mut NYS CF Newborn Screening Algorithm (2010-2013) 1 Mut.

How Babies are Screened in IRT-Only vs

  1. mutations using the Tag-It TM Mutation Detection Kit CFTR 40+4 ® (Tin Bioscience Corporation, Toronto, Canada). Mutation analysis was performed on the top 8% of IRT specimens. All infants with one or two CF mutations detected or an IRT in the highest 0.1% were recalled for pilocarpine iontophoresis
  2. CRMS remained the diagnosis for 533 (71.9%) children; 47 (8.8%) of these children had a maximum SCT value in the intermediate range (40-59 mmol/L). A typical child with CRMS had a high IRT value, 1 panel mutation, and ≥1 mutation/variant from DNA sequencing in the trans phase and a maximum SCT result <60 mmol/L
  3. tected no mutations. When ST was performed the state of hydration of the patient was normal. Two days later her clinical conditions and laboratory parameters got worse, i.e., Hb 7.7g/dL, AST 521U/L. Thus, on the basis of vomiting, anorexia, failure to thrive, increased level of liver enzymes and unspecified anemia, CD was suspecte

Cystic fibrosis testing 8 years on: Lessons learned from

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR is a member of the adenosine triphosphate (ATP)-binding cassette superfamily of proteins and it functions as a chloride channel. CFTR largely controls the working of epithelial cells of the airways, the gastrointestinal tract, exocrine glands. Infants with at least one CFTR mutation or very high IRT and no mutations (VHIRT) are referred for sweat testing. In a preliminary analysis, we noted a very low positive predictive value (PPV) and preponderance of Hispanic infants in the group of infants with CF referred for VHIRT, which led to a decision to revise, but not eliminate, the VHIRT. Pancreatic function and extended mutation analysis in ΔF508 heterozygous infants with an elevated immunoreactive trypsinogen but normal sweat electrolyte levels. The Journal of Pediatrics, 2000 (IRT/DNA/IRT) in the Italian population. By R. Padoan. Recommendations for the classification of diseases as CFTR-related disorders A total of 110 of 112 CF-affected infants screened (negative predictive value: 99.99%) were detected with IRT/multiple-CFTR-mutation screening; 2 false-negative screens did not show elevated IRT. A total of 107 (97%) of the 110 had 1 or 2 mutations detected by the multiple- CFTR-mutation screen, and 3 had positive screens on the basis of the. All CF NBS programs begin with detection of an elevated immunoreactive trypsinogen (IRT) level in a dried blood specimen from the newborn [3, 5, 6]. A positive IRTscreen is triaged to second-tier testing, which is DNA mutation testing in many national screening programs, including Poland (IRT/DNA protocol) [3,4,5,6,7]

Immunoreactive Trypsinogen - an overview ScienceDirect

Prospective and parallel assessments of cystic fibrosis newborn screening protocols in the Czech Republic: IRT/DNA/IRT versus IRT/PAP and IRT/PAP/DNA. 9 Pages. Optimal DNA tier for the IRT/DNA algorithm determined by CFTR mutation results over 14years of newborn screening IRT levels also tend to be high in people who have CF. When high IRT levels are detected in the blood, the results of the newborn screening are said to be positive. In Michigan when the IRT is elevated a 60 mutation panel for CF causing mutations is done. If two mutations are found the child likely has CF, but this must be confirmed with a. No mutations IRT >99.9th centile Sweat test yes Elevated? no yes no Repeat genetic test and carry out sweat test DNA 4 mutations thcentile 1 mutation 2 mutations CF not suspected blood spot IRT at 21-28 days thcentile Sweat test Screen negative CF confirmed High chloride IRT >99.5

IRT-IRT-DNA algorithm • We have now decided to change our algorithm to IRT-IRT-DNA • By adding genetic testing for CFTR variants, can lower IRT cut-off • Increases sensitivity from ~96% to 98% without huge increase in carrier detection • Originally developed in CO; also used in TX and several other states • Start goal: May 15, 201 IRT is elevated in most people with CF due to abnormal pancreatic function. Even though this assay is designed to detect CF, newborns with CF-related metabolic syndrome (CRMS), congenital absence of the vas deferens (CAVD), and even carriers with no CF disease may also screen positive Neo IRT Results ELEVATED IRT ng/ml Attention: Due to the Hologic CF DNA test recall, the CF DNA test has not been performed by the NC State Laboratory of Public Health as of 4/1/16. Beginning 06/13/16 specimens with IRT values >96%tile will be sent to the Wisconsin State Laboratory of Hygiene (WSLH) for Cystic Fibrosis CFTR mutation (DNA. A child with a high initial IRT and 2 CF mutations A child with a high (>99.5th centile) initial IRT, one CF mutation identified and a high second IRT A child with a high (>99.9th centile) initial IRT, no CF mutations and a high second IRT The children in group 1 have cystic fibrosis (but will need a confirmatory test)

Cystic Fibrosis (CF) State Public Health Laboratory

screening strategy is IRT at day 3 with a fixed cutoff (aimed at 0·5% positive), followed by a DNA analysis (30 mutations covering 80% of allele detection), and an IRT safety net at 3 weeks, if parental written consent for DNA analysis was not obtained, or if no mutation was detected and a very high IRT level was noted at day 3 IRT = immunoreactive trypsinogen. na = no second sample required. * These babies had an elevated initial IRT level and were recalled for a second sample. † These babies were carriers of a CFTR gene mutation (elevated IRT level, one CFTR mutation, sweat chloride level < 60mmol/L, no CF symptoms) Delta F508 is the most common CF gene mutation, but upwards of 1000 mutations have Markedly elevated IRT (>99.9. th. centile) and NO . CFTR

those with very elevated IRT have recommended follow up even with no found mutations -- repeat NBS at 4 weeks, refer to CF center if IRT still elevated Basic timeline: at about 2 weeks of age, abnormal NBS results given to PCP and CF center, inform family, CF center schedules sweat test/diagnostic evaluation. at about 5 weeks. full term infant. Patients with elevated IRT levels should then be referred for a diagnostic sweat test (Farrell et al. J Pediatr. 2017). In 2018, newborn screening accounted for 61.5% of all new diagnoses and 86.6% of diagnoses under 6 months of age ( CFF Patient Registry 2018 Annual Data Report ) Five other children had no mutation identified at the first step but their IRT remained elevated at 3 weeks of life. The Necker-Enfants Malades Institutional Review Committee approved the protocol, and each parent provided written informed consent elevated IRT and the F508del homozygous genotype. RESULTS Phenotypic description of patients compound heterozygous for R117H and F508del Among 278 individuals carrying two CFTR mutations with R117H at least on one allele, 193 [R117H]+[F508del] individuals were identified: 121 were referred for diagnosis request o A baby with very elevated IRT levels will have a CF DNA study performed on the existing blood spot. If IRT levels are very elevated on both newborn screening tests, or if the IRT levels are high on two tests and a change in the DNA (mutation) is detected, the baby will need a sweat test to determine if the high IRT is due to CF

While an elevated IRT is strongly suggestive of CF, other conditions can trigger an increase, including premature birth. As such, it is not so much diagnostic of CF as it a red flag of the disease. If the IRT is high, a genetic test is then performed. If the test is positive, it means that the baby either has CF or is a carrier trypsinogen (IRT). • Normally, if IRT is high, then DNA analysis is done to look for 60 common CF gene mutations. • If IRT is normal, no DNA analysis is done and the test is marked negative for CF. • In an infant of a parent with CF, the blood is sent for DNA analysis of CF mutations, even if IRT is normal We use the Luminex 60 mutation panel, and the cost it says there. This is just approximate cost, including the reagents, equipment, the maintenance, and personnel. I think that's it for that, for this approximate number of cost, and elevated IRT actually gets reflects to DNA, and we have identified I think more than 30 CF cases this way The IRT level and # of mutations detected will be reported: Zero mutations, IRT: ≥57 ng/ml Infants with this result have approximately a 1% chance of having cystic fibrosis. Follow-up or sweat testing is recommended only if clinically indicated or if there is a family history of cystic fibrosis. One mutation, IRT: ≥57 ng/m (IRT-DNA-IRT) for Cystic Fibrosis, using a second IRT measurement at three weeks of age for all individuals with one mutation on CFTR testing or an initial IRT in the top 0.1% and no CFTR mutations, screening over 400,000 infants from 2010-2018 (Figure1)

In 200 of these the second IRT is normal and the family are notified that the baby is likely to be a carrier, in the remaining 50 the IRT is elevated and the baby is referred as 'CF suspected'. If the IRT is particularly high (>99.9th centile - approximately) a second sample is obtained even if no mutations have been identified, this is. His CF NBS showed serum IRT 139 ng/ml and was negative for the 40 gene mutations panel. At 1 month of age, he developed a wet cough without any other symptoms. He was followed by his primary care provider (PCP), and no treatment was given at the time. His symptoms continued on and off until 1 year of age There are two methods of following up on an elevated IRT level. In one method, a second IRT is done, which, if also elevated, is followed by a sweat test. In the other, more commonly used method, an elevated IRT level is followed by CFTR mutation testing, and, if 1 or 2 mutations are identified, then a sweat test is done