Prevalence of cystic fibrosis mutations in Israeli Jews

A comprehensive review of cystic fibrosis in Africa and Asia

Cystic fibrosis (CF) was earlier thought to be a disease prevalent in the West among Caucasians. However, quite a number of recent studies have uncovered CF cases outside of this region, and reported hundreds of unique and novel variant forms of CFTR. Here, we discuss the evidence of CF in parts of the world earlier considered to be rare; Africa, and Asia. This review also highlighted the CFTR mutation variations and new mutations discovered in these regions. This discovery implies that the CF data from these regions were earlier underestimated. The inadequate awareness of the disease in these regions might have contributed towards the poor diagnostic facilities, under-diagnosis or/and under-reporting, and the lack of CF associated health policies. Overall, these regions have a high rate of infant, childhood and early adulthood mortality due to CF. Therefore, there is a need for a thorough investigation of CF prevalence and to identify unique and novel variant mutations within these regions in order to formulate intervention plans, create awareness, develop mutation specific screening kits and therapies to keep CF mortality at bay.

Ivacaftor in People with Cystic Fibrosis and a 3849+10kb C→T or D1152H Residual Function Mutation

Rationale: Ivacaftor’s clinical effects in the residual function mutations 3849 + 10kb C→T and D1152H warrant further characterization.

Objectives: To evaluate ivacaftor’s effect in people with cystic fibrosis aged ≥6 years with 3849 + 10kb C→T or D1152H residual function mutations and to explore the correlation between ivacaftor-induced organoid-based cystic fibrosis transmembrane conductance regulator function measurements and clinical response to ivacaftor.

Methods: Participants were randomized (1:1) in this placebo-controlled crossover study; each treatment sequence included two 8-week treatments with an 8-week washout period. The primary endpoint was absolute change in lung clearance index_2.5 from baseline through Week 8. Additional endpoints included lung function, patient-reported outcomes, and in vitro intestinal organoid–based measurements of ivacaftor-induced cystic fibrosis transmembrane conductance regulator function.

Results: Of 38 participants, 37 completed the study. The primary endpoint was met; the Bayesian posterior probability of improvement in lung clearance index_2.5 with ivacaftor versus placebo was >99%. Additional endpoints improved with ivacaftor. Safety findings were consistent with ivacaftor’s known safety profile. Dose-dependent swelling was observed in 23 of 25 viable organoid cultures with ivacaftor treatment. Correlations between ivacaftor-induced organoid swelling and clinical endpoints were negligible to low.

Conclusions: In people with cystic fibrosis aged ≥6 years with a 3849 + 10kb C→T or D1152H mutation, ivacaftor treatment improved clinical endpoints compared with placebo; however, there was no correlation between organoid swelling and change in clinical endpoints. The organoid assay may assist in identification of ivacaftor-responsive mutations but in this study did not predict magnitude of clinical benefit for individual people with cystic fibrosis with these two mutations.

Clinical trial registered with ClinicalTrials.gov (NCT03068312).

Next generation sequencing to determine the cystic fibrosis mutation spectrum in Palestinian population

An extensive molecular analysis of the CF transmembrane regulator (CFTR) gene was performed to establish the CFTR mutation spectrum and frequencies in the Palestinian population, which can be considered as an understudied population. We used a targeted Next Generation Sequencing approach to sequence the entire coding region and the adjacent sequences of the CFTR gene combined with MLPA analysis of 60 unrelated CF patients. Eighteen different CF-causing mutations, including one previously undescribed mutation p.(Gly1265Arg), were identified. The overall detection rate is up to 67%, and when we consider only CF patients with sweat chloride concentrations >70 mEq/L, we even have a pickup rate of 92%. Whereas p.(Phe508del) is the most frequent allele (35% of the positive cases), 3 other mutations c.2988+1Kbdel8.6Kb, c.1393-1G>A, and p.(Gly85Glu) showed frequencies higher than 5% and a total of 9 mutations account for 84% of the mutations. This limited spectrum of CF mutations is in agreement with the homozygous ethnic origin of the Palestinian population. The relative large portion of patients without a mutation is most likely due to clinical misdiagnosis. Our results will be important in the development of an adequate molecular diagnostic test for CF in Palestine.

The D1152H cystic fibrosis mutation in prenatal carrier screening, patients and prenatal diagnosis

OBJECTIVE

To assess the frequency of the D1152H mutation in the CFTR gene in normal individuals, in cystic fibrosis (CF) patients and in the setting of prenatal diagnosis.

SETTING

A database analysis of sequential screening results seen at the Sheba Medical Center, Israel, between 2001 and 2010.

METHODS

We retrospectively analyzed the frequency of D1152H in a large cohort of healthy individuals who were screened as part of a routine prenatal care programme, in individuals referred due to CF-related symptoms and in the setting of prenatal diagnosis.

RESULTS

We found one asymptomatic homozygous female and 195 D1152H carriers among 49,940 healthy individuals screened, establishing a carrier rate of 1:255 for this mutation. We detected D1152H in nine of 103 individuals referred due to CF-related symptoms. Four suffered from respiratory symptoms and five from congenital bilateral absence of the vas deferens (CBAVD). During this period D1152H was detected in three pregnancies, two of which were aborted.

CONCLUSION

The increased frequency of D1152H in individuals referred due to CF-related symptoms compared with healthy individuals included in the CF carrier screening programme (P < 0.001) clearly indicates that it is a disease-causing mutation.

Compressed Genotyping

Over the past three decades we have steadily increased our knowledge on the genetic basis of many severe disorders. Nevertheless, there are still great challenges in applying this knowledge routinely in the clinic, mainly due to the relatively tedious and expensive process of genotyping. Since the genetic variations that underlie the disorders are relatively rare in the population, they can be thought of as a sparse signal. Using methods and ideas from compressed sensing and group testing, we have developed a cost-effective genotyping protocol to detect carriers for severe genetic disorders. In particular, we have adapted our scheme to a recently developed class of high throughput DNA sequencing technologies. The mathematical framework presented here has some important distinctions from the 'traditional' compressed sensing and group testing frameworks in order to address biological and technical constraints of our setting.

DNA Sudoku--harnessing high-throughput sequencing for multiplexed specimen analysis

Next-generation sequencers have sufficient power to analyze simultaneously DNAs from many different specimens, a practice known as multiplexing. Such schemes rely on the ability to associate each sequence read with the specimen from which it was derived. The current practice of appending molecular barcodes prior to pooling is practical for parallel analysis of up to many dozen samples. Here, we report a strategy that permits simultaneous analysis of tens of thousands of specimens. Our approach relies on the use of combinatorial pooling strategies in which pools rather than individual specimens are assigned barcodes. Thus, the identity of each specimen is encoded within the pooling pattern rather than by its association with a particular sequence tag. Decoding the pattern allows the sequence of an original specimen to be inferred with high confidence. We verified the ability of our encoding and decoding strategies to accurately report the sequence of individual samples within a large number of mixed specimens in two ways. First, we simulated data both from a clone library and from a human population in which a sequence variant associated with cystic fibrosis was present. Second, we actually pooled, sequenced, and decoded identities within two sets of 40,000 bacterial clones comprising approximately 20,000 different artificial microRNAs targeting Arabidopsis or human genes. We achieved greater than 97% accuracy in these trials. The strategies reported here can be applied to a wide variety of biological problems, including the determination of genotypic variation within large populations of individuals.

Dynamic modification strategy of the Israeli carrier screening protocol: inclusion of the Oriental Jewish Group to the cystic fibrosis panel

PURPOSE

A retrospective population study was conducted to determine the carrier frequencies of recently identified mutations in Oriental Jewish cystic fibrosis patients.

METHODS

Data were collected from 10 medical centers that screened the following mutations: two splice site mutations-3121-1G>A and 2751 + 1insT-and one nonsense mutation-the Y1092X in Iraqi Jews. One missense mutation, I1234V, was screened in Yemenite Jews.

RESULTS

A total of 2499 Iraqi Jews were tested for one, two, or all three mutations. The 3121-1G>A, Y1092X, and 2751 + 1insT mutations had a carrier frequency of 1:68.5, 1:435, and 0, respectively. In 1435 Yemenite Jews screened, I1234V had a carrier frequency of 1:130.

CONCLUSION

The 0.84% allele frequency of the three Iraqi founder mutations falls within the Israeli Society of Medical Geneticists' inclusion criteria for screening of 1:60 carrier frequency; hence, Iraqi Jews were added to the carrier screening policy with a panel including the three Iraqi founder mutations in addition to the five Ashkenazi mutations previously detected in Eastern Jews. 2751 + 1insT that was detected in patients only was included in the screening panel to increase the detection rate. I1234V does not meet the inclusion criteria but is now offered on a diagnostic basis and can be added to the screening panel for individuals whose mixed origin includes Yemenite, in addition to protocol-recommended origins. This study demonstrates the dynamic modifications of the Israeli carrier cystic fibrosis screening protocol based on newly detected founder mutations in a large cohort, taking into account mutation impact and intercommunal admixture.

Splicing modulation as a modifier of the CFTR function

A significant fraction of CF-causing mutations affects pre-mRNA splicing. These mutations can generate both aberrant and correct transcripts, the level of which varies among different patients. An inverse correlation was found between this level and disease severity, suggesting a role for splicing regulation as a genetic modifier. Subsequent studies showed that overexpression of splicing factors modulated the level of correctly spliced RNA, transcribed from minigenes carrying CF-causing splicing mutations. Overexpression of splicing factors also modulated the level of normal CFTR transcripts, transcribed from the endogenous CFTR allele carrying splicing mutations, in CF-derived epithelial cells. Several of the factors promoted higher level of correct CFTR transcripts. The increased level of normal transcripts led to activation of the CFTR channel and restoration of its function. Restoration was also obtained by sodium butyrate, a histone deacetylase inhibitor, known to up-regulate the expression of splicing factors. These results highlight the role of the splicing machinery as a modifier of disease severity in patients carrying splicing mutations and shed a new light on the therapeutic potential of splicing modulation for genetic diseases caused by splicing mutations.

Cystic fibrosis mutations with widely variable phenotype: the D1152H example

D1152H is a type IV cystic fibrosis transmembrane regulator (CFTR) mutation associated with abnormal chloride gating. Although comprising 5-6% of mutations on genetic screening, clinical reports of cystic fibrosis (CF) are rare, suggesting that the disease is mild, atypical, or even absent. We describe our experience, which contrasts with this assumption, in a retrospective case series encompassing 91 CF patients (74 Jewish) aged 8 months to 56 years, from 2000-2005. Nine patients of varied Jewish ethnic origins were homozygous (2 patients) or compound heterozygous for D1152H with 11 of 182 potential alleles (6%). Five were diagnosed at age 33-49 years. Of 4 infants, 1 was diagnosed by prenatal screening, 1 had a prenatal dilated bowel, and 1 had pulmonary symptoms. Sweat chloride was 28-120 meq/l. Three adults had chronic mucoid Pseudomonas aeruginosa in sputum, and a forced expired volume in 1 sec (FEV1) of 20-55%. One was on bilevel positive airway pressure (BIPAP) ventilation. The infants had pulmonary symptoms that responded well to therapy. All 9 patients had good nutrition, 6 were pancreatic-sufficient, and 3 adults had subclinical pancreatic insufficiency. Three adults had recurrent pancreatitis. None had a bowel obstruction. Two of 3 adult males were fertile. Although asymptomatic at times, the D1152H mutation is associated with a broad clinical spectrum. This information is crucial for genetic counseling. Lung disease may be evident from infancy, and is severe in some adults, although all have outlived the median life expectancy of CF. Hopefully, with early diagnosis and therapy, prognosis can be good. A multicenter study of this mutation is warranted.

Mutation spectrum in Jewish cystic fibrosis patients in Israel: implication to carrier screening

We have tested 144 unrelated Jewish patients suffering from the classical form of cystic fibrosis. The patients were screened for a panel of 12 mutations including the six Ashkenazi founder mutations (DeltaF508, W1282X, N1303K, G542X, 3849 + 10 kb C-->T, 1717-1G > A) and six mutations that were found in non-Ashkenazi Jewish patients (S549R (T-->G), G85E, 405 + 1G-->A, W1089X, Y1092, and D1152H). Patients of Georgian origin were tested also for the Q359K/T360K mutation. In addition, all the patients were tested for the IVS-8 variant (9T/7T/5T). Of all the cystic fibrosis (CF)-bearing chromosomes, 94% (264/281) were accounted for by one of the known mutations, and none of the patients had the 5T allele of the IVS-8 variant. Single strand conformation polymorphism (SSCP) analysis of the coding sequence of the CFTR gene followed by sequencing showed eight mutations on ten CF chromosomes, leaving seven chromosomes (2.5%) with unknown mutations. We identified three mutations in two or more CF chromosomes, 2571 + 1insT in Jews from Iraq, 3121-1G > A in patients from Kurdistan and I1234V in Yemenite Jewish patients. The other five mutations appeared on a single allele and are considered "private mutations." In this study we have identified 99% of CF alleles in Ashkenazi Jewish patients, 91% in Jews of North African origin and 75% in Jewish patients from Iraq. The significance of these findings to the population screening in Israel is discussed.

Pancreatitis among patients with cystic fibrosis: correlation with pancreatic status and genotype

OBJECTIVE

Pancreatitis is an infrequent complication among patients with cystic fibrosis (CF). It has mainly been reported for patients with pancreatic sufficiency (PS). Previous studies involved only a small number of patients because they contained data from single centers. The aim of this study was to evaluate the incidence of pancreatitis in a large heterogeneous CF population, to determine the relationship with pancreatic function, and to assess whether pancreatitis is associated with specific CFTR mutations.

METHODS

Physicians caring for patients with CF were approached through the CF Thematic Network or through the European Cystic Fibrosis Foundation newsletter. They were asked to provide data on their current patient cohort through a standardized questionnaire and to report how many patients they had ever diagnosed as having pancreatitis. A detailed questionnaire was then sent, to be filled out for all of their patients for whom pancreatitis had ever occurred. We defined pancreatitis as an episode of acute abdominal pain associated with serum amylase levels elevated above the ranges established by each participating center's laboratory. General clinical data included age, genotype, age at diagnosis of CF, sweat chloride concentrations, pancreatic status, biometric findings, and respiratory status. CFTR mutations were also reported according to the functional classification of classes I to V. Patients were categorized as having PS, pancreatic insufficiency (PI), or PI after an initial period of PS. PI was defined as a 72-hour stool fat loss of >7 g/day, fat absorption of <93%, or fecal elastase levels of <200 microg/g feces. Clinical data on pancreatitis included age at the first episode, amylase and lipase levels, possible triggers, and occurrence of relapses or complications.

RESULTS

A total of 10071 patients with CF, from 29 different countries, who were undergoing follow-up monitoring in 2002 were surveyed. Among this group, pancreatitis had ever been diagnosed for 125 patients (1.24%; 95% confidence interval [CI]: 1.02-1.46%). There was variability in the reported rates of pancreatitis for different countries. Twenty-six centers in 15 different countries sent detailed clinical data on their patients with pancreatitis and on their whole CF clinic. This involved 3306 patients with CF and 61 cases of pancreatitis, leading to a prevalence of 1.84% (95% CI: 1.39-2.30%). The mean age of the patients with pancreatitis ever was 24.4 years (SD: 10.8 years). The first episode of pancreatitis occurred at a mean age of 19.9 years (SD: 9.6 years). The median serum amylase level at the time of pancreatitis was 746 IU/L (interquartile range: 319-1630 IU/L), and the median lipase level was 577 IU/L (interquartile range: 229-1650 IU/L). The majority of patients had PS (34 of 61 patients, 56%; 95% CI: 43-68%). Pancreatitis occurred for 15 patients with PI (25%; 95% CI: 14-35%). Eight patients developed PI after initial PS. The occurrence of pancreatitis among patients with PS was 34 cases per 331 patients, ie, 10.27% (95% CI: 7.00-13.55%); the occurrence of pancreatitis among patients with PI was 15 cases per 2971 patients, ie, 0.5% (95% CI: 0.25-0.76%). The mean age (in 2002) of the CF cohort with pancreatitis did not differ between the PS and PI subgroups. The forced expiratory volume in 1 second was significantly lower among the patients with PI than among the patients with PS, ie, 65% (SEM: 7%) vs 79% (SEM: 4%). The mean age at the occurrence of pancreatitis and the amylase and lipase levels during pancreatitis were not different for patients with pancreatitis and PI versus PS. In the group with PS, 31 of 34 patients carried at least 1 class IV or V CFTR mutation. In the groups with PI and PI after PS, 5 of 15 patients and 3 of 8 patients, respectively, carried 2 class I, II, or III CFTR mutations. Relapses and/or evolution to chronic pancreatitis occurred for 42 patients. Pancreatitis preceded the diagnosis of CF in 18 of 61 cases. These patients were significantly older than the rest of the cohort, ie, age of 28.4 years (SEM: 3.4 years) vs 22.7 years (SEM: 1.3 years). Their median age at the diagnosis of CF was also significantly greater, ie, 21.5 years (interquartile range: 11.9-31 years) vs 7.6 years (interquartile range: 0.4-17.0 years). However, the ages at the occurrence of pancreatitis were similar, ie, 21.0 years (SEM: 3.0 years) vs 19.5 years (SEM: 1.2 years).

CONCLUSIONS

This study of 10071 patients with CF from 29 different countries revealed an estimated overall occurrence of pancreatitis among patients with CF of 1.24% (95% CI: 1.02-1.46%). The incidence of pancreatitis was much higher among patients with PS. However, pancreatitis was also reported for 15 patients with PI from 11 centers in 9 different countries. A correct diagnosis of pancreatitis for the reported patients with PI was supported by amylase and lipase levels increased above 500 IU/L, similar to those for patients with PS and pancreatitis. A correct diagnosis of PI for these patients with pancreatitis was supported by the adequacy of the methods used. We chose the cutoff values used to distinguish between patients with PI and control subjects without gastrointestinal disease. For one half of the patients, the diagnosis of PI was established on the basis of low levels of stool elastase (mean: 97 mug/g stool). With a cutoff value of 200 microg/g stool, this noninvasive test has high sensitivity (>95%) and high specificity (>90%) to differentiate patients with PI from control subjects with normal pancreatic function. For the other one half of the patients with PI in the cohort, the pancreatic status was determined on the basis of the 3-day fecal fat balance, with the widely used cutoff value of >7 g of fat loss per day. The most likely reason for pancreatitis occurring among patients with PI is that some residual pancreatic tissue is present among these patients. Pancreatitis is a rare complication among patients with CF. It occurred for 1.24% (95% CI: 1.02-1.46%) of a large CF cohort. Pancreatitis occurs mainly during adolescence and young adulthood. It is much more common among patients with CF and PS (10.3%), but it can occur among patients with PI (0.5%). Pancreatitis can be the first manifestation of CF. Pancreatitis was reported for patients carrying a wide range of mutations.

Clinical sensitivity of prenatal screening for cystic fibrosis via CFTR carrier testing in a United States panethnic population

PURPOSE

To estimate CFTR mutation frequencies, clinical sensitivities (proportions of carrier couples or affected fetuses detected), and birth prevalence estimates for broad racial/ethnic groups and for a panethnic U.S. population.

METHODS

Published sources of information were identified, corrected when appropriate, and summarized. Combining racial/ethnic-specific mutation frequencies and birth prevalence estimates allowed the computation of panethnic estimates.

RESULTS

Two of the 25 recommended mutations do not meet the 0.1% threshold in a panethnic population set by the American College of Medical Genetics. The clinical sensitivities are estimated to be 71.9%, 51.7%, 41.6%, 88.6%, and 23.4% for non-Hispanic Caucasians, Hispanic Caucasian, African American, Ashkenazi Jewish Caucasian, and Asian American couples, respectively. Birth prevalence estimates are 1:2,500, 1:13,500, 1:15,100, 1:2,270, and 1:35,100, whereas the number of couples needed to screen to detect an affected fetus are about 3,200, 26,120; 36,040; 2,600, and 129,600, respectively, for the same racial/ethnic groups.

CONCLUSIONS

Overall, the panethnic estimates for CFTR mutation frequencies are similar to those for non-Hispanic Caucasians. However, large differences in both clinical sensitivity and birth prevalence exist between the broad racial/ethnic groups examined. Whether and how the differences in the numbers of couples needed to screen to detect an affected fetus are to be included in prenatal screening for cystic fibrosis needs to be more explicitly addressed.

Premarital and prenatal screening for cystic fibrosis: experience in the Ashkenazi Jewish population

PURPOSE

Since the early 1990s, Dor Yeshorim (DY) and the Mount Sinai School of Medicine (MSSM) have conducted premarital and prenatal carrier screening for cystic fibrosis (CF) in the Ashkenazi Jewish (AJ) population as part of their genetic testing programs, respectively. Together, over 170,000 screenees have been tested. In this study, we report the CF mutation frequencies in over 110,000 screenees who reportedly were of 100% AJ descent from the DY program and MSSM. In addition, the CF mutation frequencies in a group of > 7,000 screenees for AJ diseases who were of < 100% AJ descent are reported.

METHODS

Testing for CF mutations was performed by either PCR and restriction digestion or ASO hybridization analyses at MSSM or sent to various academic and commercial laboratories by DY.

RESULTS

The overall (and individual) carrier frequency for the five common AJ mutations, W1282X (0.020), DeltaF508 (0.012), G542X (0.0024), 3849+10kb C>T (0.0020), and N1303K (0.0016), among screenees who were 100% AJ was 1 in 26; when D1152H and the rare 1717-1G>A were included, the overall carrier frequency increased to approximately 1 in 23. In four families with D1152H, five compound heterozygotes for D1152H and W1282X (n = 2), DeltaF508 (1) or 3849+10kb C>T (1) were identified. In contrast, the carrier frequency for screenees reporting < 100% AJ descent was approximately 1 in 30 for the seven mutations.

CONCLUSIONS

The carrier frequency for five common CF mutations in a large 100% AJ sample increased from 1 in 26 to 1 in 23 when D1152H was included in the panel. Addition of D1152H to mutation panels when screening the AJ population should be considered because compound heterozygosity is associated with a variable disease phenotype. Further studies to delineate the phenotype of CF patients with this mutation are needed.

Prenatal screening for cystic fibrosis

This article focuses on essential components related to prenatal screening for cystic fibrosis, including the clinical disease, inheritance, prognosis and treatment, birth prevalence, and ethnic variability. The molecular basis of this disease is presented, including a discussion of the gene, mutations, and genotype/phenotype correlations. The models that have been used for delivering prenatal screening services in pilot trials are described, along with lessons learned, expected screening performance, and relevant ELSI considerations. A realistic view of laboratory issues is considered, including current standards of performance, guidelines and oversight, and quality assurance. Examples of current laboratory technologies for cystic fibrosis testing are displayed.

Standards and guidelines for CFTR mutation testing

One mission of the ACMG Laboratory Quality Assurance (QA) Committee is to develop standards and guidelines for clinical genetics laboratories, including cytogenetics, biochemical, and molecular genetics specialties. This document was developed under the auspices of the Molecular Subcommittee of the Laboratory QA Committee by the Cystic Fibrosis (CF) Working Group. It was placed on the "fast track" to address the preanalytical, analytical, and postanalytical quality assurance practices of laboratories currently providing testing for CF. Due to the anticipated impact of the ACMG recommendation statement endorsing carrier testing of reproductive couples, it was viewed that CF testing would increase in volume and that the number of laboratories offering CF testing would also likely increase. Therefore, this document was drafted with the premise of providing useful information gained by experienced laboratory directors who have provided such testing for many years. In many instances, "tips" are given. However, these guidelines are not to be interpreted as restrictive or the only approach but to provide a helpful guide. Certainly, appropriately trained and credentialed laboratory directors have flexibility to utilize various testing platforms and design testing strategies with considerable latitude. We felt that it was essential to include technique-specific guidelines of several current technologies commonly used in laboratories providing CF testing, since three of the four technologies discussed are available commercially and are widely utilized. We take the view that these technologies will change, and thus this document will change with future review.

Cystic fibrosis: a worldwide analysis of CFTR mutations--correlation with incidence data and application to screening

Although there have been numerous reports from around the world of mutations in the gene of chromosome 7 known as CFTR (cystic fibrosis transmembrane conductance regulator), little attention has been given to integrating these mutant alleles into a global understanding of the population molecular genetics associated with cystic fibrosis (CF). We determined the distribution of CFTR mutations in as many regions throughout the world as possible in an effort designed to: 1) increase our understanding of ancestry-genotype relationships, 2) compare mutational arrays with disease incidence, and 3) gain insight for decisions regarding screening program enhancement through CFTR multi-mutational analyses. Information on all mutations that have been published since the identification and cloning of the CFTR gene's most common allele, DeltaF508 (or F508del), was reviewed and integrated into a centralized database. The data were then sorted and regional CFTR arrays were determined using mutations that appeared in a given region with a frequency of 0.5% or greater. Final analyses were based on 72,431 CF chromosomes, using data compiled from over 100 original papers, and over 80 regions from around the world, including all nations where CF has been studied using analytical molecular genetics. Initial results confirmed wide mutational heterogeneity throughout the world; however, characterization of the most common mutations across most populations was possible. We also examined CF incidence, DeltaF508 frequency, and regional mutational heterogeneity in a subset of populations. Data for these analyses were filtered for reliability and methodological strength before being incorporated into the final analysis. Statistical assessment of these variables revealed that there is a significant positive correlation between DeltaF508 frequency and the CF incidence levels of regional populations. Regional analyses were also performed to search for trends in the distribution of CFTR mutations across migrant and related populations; this led to clarification of ancestry-genotype patterns that can be used to design CFTR multi-mutation panels for CF screening programs. From comprehensive assessment of these data, we offer recommendations that multiple CFTR alleles should eventually be included to increase the sensitivity of newborn screening programs employing two-tier testing with trypsinogen and DNA analysis.