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.

Early immune response to the components of the type III system of Pseudomonas aeruginosa in children with cystic fibrosis.

The lungs of patients with cystic fibrosis (CF) are colonized initially by Pseudomonas aeruginosa, which is associated with progressive lung destruction and increased mortality. The pathogenicity of P. aeruginosa is caused by a number of virulence factors, including exotoxin A (ETA) and the type III cytotoxins (ExoS, ExoT, ExoU, and ExoY). P. aeruginosa contacts the plasma membrane to deliver type III cytotoxins through a channel formed by PopB, PopD, and PcrV; ETA enters mammalian cells via receptor-mediated endocytosis. The Wisconsin CF Neonatal Screening Project is a longitudinal investigation to assess the potential benefits and risks of newborn screening for CF; the project was the source of serum samples used in this study. Past studies evaluated the longitudinal appearance of antibodies to ETA and elastase and P. aeruginosa infections in patients with CF. The current study characterized the longitudinal appearance of antibodies to components of the type III system in children with CF. Western blot analyses showed that serum antibodies to PopB, PcrV, and ExoS were common. Longitudinal enzyme-linked immunosorbent assays determined that the first detection of antibodies to pooled ExoS/PopB occurred at a time similar to those of detection of antibodies to a P. aeruginosa cell lysate and the identification of oropharyngeal cultures positive for P. aeruginosa. This indicates that children with CF are colonized early with P. aeruginosa expressing the type III system, implicating it in early pathogenesis, and implies that surveillance of clinical symptoms, oropharyngeal cultures, and seroconversion to type III antigens may facilitate early detection of P. aeruginosa infections.

Acceleration of lung disease in children with cystic fibrosis after Pseudomonas aeruginosa acquisition.

As part of the ongoing Wisconsin Cystic Fibrosis (CF) Neonatal Screening Project, we had the unique opportunity to study the longitudinal relationship between Pseudomonas aeruginosa (Pa) acquisition and infection and developing lung disease in children with CF. The primary objective was to determine whether acquisition of Pa was associated with a measurable change in the progression of lung disease. Two outcome measures were used to study 56 patients who were diagnosed through newborn screening: 1) Wisconsin additive chest radiograph score (WCXR), based on the average of scores from a pulmonologist and a radiologist, and 2) the highest forced expired volume in 1 sec (FEV(1))/forced vital capacity (FVC) ratio. We used two measures of Pa acquisition: 1) time of first positive protocol-determined oropharyngeal (with cough) culture, and 2) the magnitude of antibody titer detected by ELISA assays, using as antigen a crude cell lysate, purified exotoxin A, or an elastase toxoid prepared from three Pa strains. Other predictor variables included age, pancreatic status, height-for age, and weight-for-age-percentiles. The best regression model for predicting changes in the WCXR included time to first positive culture and antibody titer for Pa elastase. Prior to Pa acquisition, WCXR worsened by 0.45 points/year (P > 0.25); after Pa acquisition, the rate of worsening increased significantly (P < 0.001) to 1.40 points/year. Each antibody titer level (log base 2) increased the score by 0.48 points (P < 0.001). The best regression model for predicting change in the FEV(1)/FVC included only time to first positive culture. Prior to Pa acquisition, the FEV(1)/FVC ratio declined by 1.29%/year; after Pa infection, the rate of decrease significantly accelerated to 1.81%/year (P = 0.001). Our data show that Pa acquisition is associated with declining pulmonary status in children with CF, and that this effect is probably gradual rather than precipitous. Because these patients were diagnosed and treated aggressively, our estimates of the effects of Pa acquisition may be conservative. We also conclude that the WCXR appears to be more sensitive than FEV(1)/FVC in detecting early changes in lung disease associated with CF.

Genetic counseling and neonatal screening for cystic fibrosis: an assessment of the communication process.

OBJECTIVE: To assess the effectiveness of communication between health care providers (physicians, nurses, genetic counselors) in Wisconsin and parents of children identified as heterozygote carriers for cystic fibrosis (CF) in the routine Wisconsin Newborn Screening Program that was implemented using trypsinogen/DNA testing. METHODS: Routine CF neonatal screening, implemented in July 1994, involved a statewide system that recommended but did not mandate follow-up sweat tests at 1 of the Wisconsin's 2 certified CF centers. The Wisconsin Division of Health sent requests to participate to the parents of 483 infants identified as CF carriers between July 1994 and December 1997. Of the 483 parents, 183 agreed to participate and were asked to complete a questionnaire assessing their CF newborn screening experiences and their knowledge of CF genetics and any changes they made in their reproductive behavior as a result of this knowledge. Follow-up telephone interviews by a genetic counselor were attempted within 1 year for those completing the questionnaire. RESULTS: Within 4 months after the mailing, 138 of 183 (75%) parents completed the questionnaire. Subsequently, 123 of the 138 responders (89%) were contacted and interviewed by telephone. We learned that 67.6% of parents recalled receiving genetic counseling, but 32.4% of parents apparently did not participate in a risk communication session. When asked, "Who performed the genetic counseling?" parents indicated that their communication was with physicians in 8% of cases, nurses in 12.4%, and certified genetic counselors in 32.8% of cases; 17.5% of parents did not recall who performed the genetic counseling and 29.2% of parents indicated they did not receive genetic counseling. Based on the 138 responses, it was found that 88.3% of parents understood that their child was a carrier for CF, but 15.4% of parents were unsure whether being a carrier could cause illness. In addition, 12.4% of parents were unsure whether at least 1 of them (parents) was a carrier of the CF gene. Only 57% of parents knew there was a 1 in 4 chance that their child could have a child with CF if he or she reproduced with another carrier of the CF gene. Statistically significant differences were noted when comparing the frequency of correct responses between parents who received genetic counseling and parents who had not. The frequency of accurate responses did not depend on which health care professional provided the genetic counseling. Comparing responses of parents who were seen at a certified CF center with parents seen at other community hospitals and clinics revealed significant differences in the frequency of correct responses, with the former group showing a higher percentage of correct responses. Telephone interviews revealed that 11.4% of parents were unaware that their child was a carrier for CF and that 54.5% wished they had more information made available to them at the time of the initial positive newborn screen result, before the definitive sweat test. Also, 13.8% of parents recommended that community physicians be better informed of the details and implications of positive screening results for CF. CONCLUSION: Genetic counseling is imperative for the success of newborn screening for CF and other congenital diseases. With the completion of the Human Genome Project, more molecular screening for childhood disease is bound to enter the clinical arena. Based on our findings, efforts must be made to ensure that newborn screening programs have the means and the methods to communicate newborn screening results effectively to families. In addition, both the general public and community health providers must be better informed of the implications of all newborn screening results. Additional research is needed to determine whether there are communication styles and approaches that are better suited to counseling parents regarding newborn screening results.

Early diagnosis of cystic fibrosis through neonatal screening prevents severe malnutrition and improves long-term growth. Wisconsin Cystic Fibrosis Neonatal Screening Study Group.

OBJECTIVE: Despite its relative frequency among autosomal recessive diseases and the availability of the sweat test, cystic fibrosis (CF) has been difficult to diagnose in early childhood, and delays can lead to severe malnutrition, lung disease, or even death. The Wisconsin CF Neonatal Screening Project was designed as a randomized clinical trial to assess the benefits and risks of early diagnosis through screening. In addition, the incidence of CF was determined, and the validity of our randomization method assessed by comparing 16 demographic variables. METHODOLOGY: Immunoreactive trypsinogen analysis was applied to dried newborn blood specimens for recognition of CF risk from 1985 to 1991 and was coupled to DNA-based detection of the DeltaF508 mutation from 1991 to 1994. Randomization of 650 341 newborns occurred when their blood specimens reached the Wisconsin screening laboratory. This created 2 groups-an early diagnosis, screened cohort and a standard diagnosis or control group. To avoid selection bias, we devised a unique unblinding method with a surveillance program to completely identify the control subjects. Because sequential analysis of nutritional outcome measures revealed significantly better growth in screened patients during 1996, we accelerated the unblinding and completely identified the control group by April 1998. Having each member of this cohort enrolled and evaluated for at least 1 year and having completed a comprehensive surveillance program, we performed another statistical analysis of anthropometric evaluated indices that includes all CF patients without meconium ileus. RESULTS: The incidence of classical CF, ie, patients diagnosed in this trial with a sweat chloride of 60 mEq/L greater, was 1:4189. By incorporating other CF patients born during the randomization period, including 2 autopsy diagnosed patients and 8 probable patients, we calculate a maximum incidence of 1:3938 (95% confidence interval: 3402-4611). Although there were group differences in the proportion of patients with DeltaF508 genotypes and with pancreatic insufficiency, validity of the randomization plan was demonstrated by analyzing 16 demographic variables and finding no significant difference after adjustment for multiple comparisons. Focusing on patients without meconium ileus, we found a marked difference in the mean +/- standard deviation age of diagnosis for screened patients (13 +/- 37 weeks), compared with the standard diagnosis group (100 +/- 117). Anthropometric indices of nutritional status were significantly higher at diagnosis in the screened group, including length/height, weight, and head circumference. During 13 years of study, despite similar nutritional therapy and the inherently better pancreatic status of the control group, analysis of nutritional outcomes revealed significantly greater growth associated with early diagnosis. Most impressively, the screened group had a much lower proportion of patients with weight and height data below the 10th percentile throughout childhood. CONCLUSIONS: Although the screened group had a higher proportion of patients with pancreatic insufficiency, their growth indices were significantly better than those of the control group during the 13-year follow-up evaluation and, therefore, this randomized clinical trial of early CF diagnosis must be interpreted as unequivocally positive. Our conclusions did not change when the height and weight data before 4 years of age for the controls detected by unblinding were included in the analysis. Also, comparison of growth outcomes after 4 years of age in all subjects showed persistence of the significant differences. Therefore, selection bias has been eliminated as a potential explanation. In addition, the results show that severe malnutrition persists after delayed diagnosis of CF and that catch-up may not be possible. We conclude that early diagnosis of CF through neonatal screening combined with aggressive nutritional therapy can result

Wisconsin cystic fibrosis chest radiograph scoring system: validation and standardization for application to longitudinal studies.

This study was designed to achieve a final modeling, validation, and standardization plan for the Wisconsin cystic fibrosis (CF) chest radiographic scoring system. Sixty chest radiographs were selected to reflect a range of severity of lung pathology in children with CF. Seven experienced volunteer raters (three radiologists and four pediatric pulmonologists) from five institutions were recruited to evaluate and score the films. Analysis of scores revealed that the subcomponents of the Wisconsin system showed considerable variation from rater to rater, but reliability assessment indicated satisfactory Cronbach's alpha coefficients (0.83-0.90) among the seven raters. It was found that an additive method of total score computation is significantly more reliable (P < 0.05) than either the original multiplicative model or the traditional Brasfield scoring system. Comparison of radiologists and pulmonologists revealed a marked, systematic difference in scoring with the former group being more conservative in interpretation of abnormalities than the pulmonologists, and some of the raters showing very limited sensitivity. Quantitative chest radiology applied to children with cystic fibrosis studied long-term in longitudinal research projects requires the careful use of sensitive scoring methods and careful selection and training of multiple raters. This is particularly important since pulmonologists and radiologists can differ systematically in interpreting/scoring abnormalities.

Nutritional status of patients with cystic fibrosis with meconium ileus: a comparison with patients without meconium ileus and diagnosed early through neonatal screening.

OBJECTIVE: This study was pursued as an extension of a randomized clinical investigation of neonatal screening for cystic fibrosis (CF). The objective was to determine if CF patients with meconium ileus (MI) were more likely to be malnourished compared with those without MI who were diagnosed during early infancy through neonatal screening. METHODOLOGY: Nutritional status was evaluated from early infancy to 13 years of age based on anthropometric, biochemical, and dietary assessments. RESULTS: MI patients (n = 32) were smaller at birth (3117 g compared with 3413 g) and were shorter (22nd percentile compared with 48th percentile) and thinner (24th percentile compared with 49th percentile) compared with non-MI early diagnosed patients (n = 50) up to 13 years of age. Poor growth was particularly evident in 26 MI patients who required surgery for MI (height and weight at the 20th percentile), whereas those treated without surgery (n = 6) showed better height (45th percentile) and weight (37th percentile). Abnormal essential fatty acid profiles were significantly more prevalent in MI compared with non-MI early-diagnosed patients before 3 years of age. Daily intakes of calorie (130% compared with 111% recommended dietary allowances) and protein (339% compared with 279% recommended dietary allowances) were higher but the percentage of fat (37% compared with 38%) and linoleic acid (4.5% compared with 4.7%) in the diet were similar between the two groups. CONCLUSIONS: These results demonstrated a clear association of MI with malnutrition in CF. The observed poor growth among our MI patients was not because of poor dietary intakes, but was related to surgical treatment for MI and poor essential fatty acid status. These findings present new challenges regarding the optimal medical treatment and nutritional intervention for CF patients with MI.

Comprehensive analysis of risk factors for acquisition of Pseudomonas aeruginosa in young children with cystic fibrosis.

The objective of this study was to identify risk factors of significance for acquisition of Pseudomonas aeruginosa by children with cystic fibrosis (CF). Our working hypothesis is that exposure of infants and young children with CF to older, infected patients increases their risk for acquiring this organism. A special opportunity arose to study this question in detail, as we have been performing a randomized clinical trial of neonatal screening for CF throughout the state of Wisconsin during the period of 1985-1994. Patients were selected for this study based on either early identification through screening or diagnosis by standard methods. A longitudinal protocol employed at Wisconsin's two CF Centers includes routine cultures of respiratory secretions and collection of clinical, demographic, and activity information on patients and their families. Previous observations in our trial revealed that one center at an old hospital in an urban location showed a significantly shorter time to acquisition of P. aeruginosa for CF patients followed there. To study the center effect further, we performed statistical analyses using survival curves and stepwise regression analysis of all life history covariates available. The results of these analyses showed that the statistically significant correlations involve the following risk factors: 1) center and old hospital (r=0.42); 2) center and original physician (r=0.61); 3) center and exposure to pseudomonas-positive patients (r=0.29); and 4) population density and urban location (r=0.49). The final statistical model demonstrated that increased risk due to aerosol use (odds ratio=3.45, P=0.014) and a protective effect associated with education of the mother (odds ratio=0.81, P=0.024) were the most significant factors for acquisition of P. aeruginosa. The previously observed center effect was confined to the 1985-1990 interval at the old hospital (odds ratio=4.43, P < 0.001). We conclude that multiple factors are involved in increasing the risk of young children with CF to acquire P. aeruginosa, and that the observed center effect can best be explained by a combination of factors. These results suggest that facilities and methods used to care for young children with CF can significantly influence their likelihood of acquiring pseudomonas in the respiratory tract.

Cystic fibrosis newborn screening: impact on reproductive behavior and implications for genetic counseling.

OBJECTIVE: To evaluate the impact of newborn screening for cystic fibrosis (CF) on the reproductive knowledge and behavior of CF families and to determine if heterozygote detection with the immunoreactive trypsinogen (IRT) method in conjunction with DNA analysis (IRT/DNA) influences knowledge and attitudes about reproduction in false-positive families. METHODS: The Wisconsin CF Neonatal Screening Project investigated 650 340 infants from 1985 to 1994 in a comprehensive randomized controlled trial to study both benefits and risks of newborn screening and to determine if early diagnosis would improve the prognosis of children with CF. Assessments of reproductive knowledge, attitudes, and behaviors of 135 families of children diagnosed as having CF in both the early treatment group and control groups were made 3 months after diagnosis using a questionnaire which was completed by 100 families. The same questionnaire was administered 1 year later to evaluate retention of information. It was completed by 71 families. A follow-up assessment tool was also administered in 1994 and responses obtained from 73 families. Knowledge, attitudes, and behavior among false-positive families were also assessed at the time of the sweat test in 206 families who experienced IRT screening and 109 families tested with the IRT/DNA method. Follow-up assessments were completed 1 year later in 106 IRT families and 63 IRT/DNA families. RESULTS: In families with a CF child, 95% initially understood that there was a 1 in 4 risk in subsequent pregnancies, and there was good retention of this information 1 year later. At the 1994 assessment, 52% of families had not yet conceived more children, but 74% of these already had children. In the couples in whom CF was diagnosed in the first child, 70% (95% confidence interval = 54% to 85%) conceived more children. There were 43 subsequent pregnancies in 31 families. Prenatal diagnosis was used by 26% of the families (8/31) for 21% of the pregnancies (9/43). There were 3 pregnancies with CF detected, all of which were carried to term. In the false-positive groups, >95% of families initially understood that their child definitely did not have CF. There was no difference between false-positive IRT and IRT/DNA groups, and the information was retained at 1 year. Follow-up assessment 1 year after negative sweat tests revealed that 7% of the IRT and 10% of the IRT/DNA families still thought about the results often or constantly. When asked whether the experience of screening affected feelings about having more children, an affirmative response was obtained in 4% of IRT families but in 17% of IRT/DNA families. One year later, more than half of the false-positive IRT/DNA families did not understand that they were at increased risk of having a child with CF. CONCLUSIONS: We conclude that CF neonatal screening does not have a significant impact on the reproductive behavior of most families and that prenatal diagnosis is not used by the majority of CF families. IRT/DNA testing experiences seem to affect attitudes about having more children, and some parents are confused about the implications of the results, even with genetic counseling. However, persistent concerns about the sweat test result are limited. Questions raised by this study confirm the need for more research regarding the process of genetic counseling and its impact on reproductive attitudes and behavior in the newborn screening setting.

Newborn screening for cystic fibrosis in Wisconsin: comparison of biochemical and molecular methods.

OBJECTIVES: To evaluate neonatal screening for cystic fibrosis (CF), including study of the screening procedures and characteristics of false-positive infants, over the past 10 years in Wisconsin. An important objective evolving from the original design has been to compare use of a single-tier immunoreactive trypsinogen (IRT) screening method with that of a two-tier method using IRT and analyses of samples for the most common cystic fibrosis transmembrane regulator (CFTR) (DeltaF508) mutation. We also examined the benefit of including up to 10 additional CFTR mutations in the screening protocol. METHODS: From 1985 to 1994, using either the IRT or IRT/DNA protocol, 220 862 and 104 308 neonates, respectively, were screened for CF. For the IRT protocol, neonates with an IRT >/=180 ng/mL were considered positive, and the standard sweat chloride test was administered to determine CF status. For the IRT/DNA protocol, samples from the original dried-blood specimen on the Guthrie card of neonates with an IRT >/=110 ng/mL were tested for the presence of the DeltaF508 CFTR allele, and if the DNA test revealed one or two DeltaF508 alleles, a sweat test was obtained. RESULTS: Both screening procedures had very high specificity. The sensitivity tended to be higher with the IRT/DNA protocol, but the differences were not statistically significant. The positive predictive value of the IRT/DNA screening protocol was 15.2% compared with 6.4% if the same samples had been screened by the IRT method. Assessment of the false-positive IRT/DNA population revealed that the two-tier method eliminates the disproportionate number of infants with low Apgar scores and also the high prevalence of African-Americans identified previously in our study of newborns with high IRT levels. We found that 55% of DNA-positive CF infants were homozygous for DeltaF508 and 40% had one DeltaF508 allele. Adding analyses for 10 more CFTR mutations has only a small effect on the sensitivity but is likely to add significantly to the cost of screening. CONCLUSIONS: Advantages of the IRT/DNA protocol over IRT analysis include improved positive predictive value, reduction of false-positive infants, and more rapid diagnosis with elimination of recall specimens.

Acquisition of Pseudomonas aeruginosa in children with cystic fibrosis.

OBJECTIVE: This study was pursued as an extension of a randomized clinical investigation of neonatal screening for cystic fibrosis (CF). The project included assessment of respiratory secretion cultures for pathogens associated with CF. The objective was to determine whether patients diagnosed through neonatal screening and treated in early infancy were more likely to become colonized with Pseudomonas aeruginosa compared with those identified by standard diagnostic methods. METHODOLOGY: The design involved prospective cultures of respiratory secretions obtained generally by oropharyngeal swabs at least every 6 months and more often if clinically indicated. Patients were managed with a standardized evaluation and treatment protocol at the two Wisconsin certified CF centers; however, there were community and environmental variations associated with the follow-up period as described below. RESULTS: Overall, there were no differences in acquisition of respiratory pathogens between the screened and the control (standard diagnosis) groups. Evaluation of the data between and within the two centers, however, revealed significant differences with earlier acquisition of P aeruginosa in the center with the following distinguishing characteristics: urban location; following patients with the standard US approach in which newly diagnosed, young children were interspersed with older CF patients; and where there were more opportunities for social interactions with other CF patients. The differences were confined to the screened group followed in the urban center in which the median pseudomonas-free survival period was 52 weeks contrasted with 289 weeks in the other center. In addition, assessment of data for the entire CF populations followed at the two centers revealed that the urban center showed a significantly higher prevalence of P aeruginosa colonization in patients between the ages of 3 and 9 years. CONCLUSIONS: These results present questions and generate hypotheses on risk factors for acquisition of P aeruginosa in CF and suggest that clinic exposures and/or social interactions may predispose such patients to pseudomonas infections.

Nutritional benefits of neonatal screening for cystic fibrosis. Wisconsin Cystic Fibrosis Neonatal Screening Study Group.

BACKGROUND: Many patients with cystic fibrosis are malnourished at the time of diagnosis. Whether newborn screening and early treatment may prevent the development of a nutritional deficiency is not known. METHODS: We compared the nutritional status of patients with cystic fibrosis identified by neonatal screening or by standard diagnostic methods. A total of 650,341 newborn infants were screened by measuring immunoreactive trypsinogen on dried blood spots (from April 1985 through June 1991) or by combining the trypsinogen test with DNA analysis (from July 1991 through June 1994). Of 325,171 infants assigned to an early-diagnosis group, cystic fibrosis was diagnosed in 74 infants, including 5 with negative screening tests. Excluding infants with meconium ileus, we evaluated nutritional status for up to 10 years by anthropometric and biochemical methods in 56 of the infants who received an early diagnosis and in 40 of the infants in whom the diagnosis was made by standard methods (the control group). Pancreatic insufficiency was managed with nutritional interventions that included high-calorie diets, pancreatic-enzyme therapy, and fat-soluble vitamin supplements. RESULTS: The diagnosis of cystic fibrosis was confirmed by a positive sweat test at a younger age in the early-diagnosis group than in the control group (mean age, 12 vs. 72 weeks). At the time of diagnosis, the early-diagnosis group had significantly higher height and weight percentiles and a higher head-circumference percentile (52nd, vs. 32nd in the control group; P=0.003). The early-diagnosis group also had significantly higher anthropometric indexes during the follow-up period, especially the children with pancreatic insufficiency and those who were homozygous for the deltaF508 mutation. CONCLUSIONS: Neonatal screening provides the opportunity to prevent malnutrition in infants with cystic fibrosis.

Effect of linoleic acid intake on growth of infants with cystic fibrosis.

Essential fatty acid deficiency as a result of inadequate linoleic acid impairs growth in healthy infants and is common in infants with malabsorption due to cystic fibrosis (CF). We investigated the effect of dietary linoleic acid intake on the growth of infants with CF. In this study, predigested formula preparations A and B, with linoleic acid contents of 12% and 7% of energy, respectively, were fed before and after 1989 to infants enrolled in the evaluation and treatment protocol of the Wisconsin CF Neonatal Screening Project. Outcome was assessed from height-for-age (HAZ) and weight-for-age (WAZ) Z scores on follow-up exams during the first year. Baseline characteristics did not differ significantly between groups A (n = 43) and B (n = 33). At diagnosis, 53% of the enrolled infants (n = 76) showed low plasma linoleic acid concentrations and 22% had a high ratio of triene to tetraene. After correcting for the effect of potentially confounding variables, we found that HAZ (by .27, P < 0.05) and WAZ (by 0.26, P = 0.081) were higher in group A than in group B. This occurred despite a significantly higher energy intake in group B. This difference was most pronounced between 6 and 9 mo of age. Our results suggest that a high linoleic acid content in formula benefits infants with CF because it optimizes nutrition, growth, and feeding efficiency.

Severe hemolytic anemia associated with vitamin E deficiency in infants with cystic fibrosis. Implications for neonatal screening.

Three infants are described with cystic fibrosis (CF) and malnutrition leading to severe anemia beginning as early as 6 weeks of age. Laboratory studies demonstrated high reticulocyte counts, negative Coombs' tests, abnormal peroxide hemolysis test results, and biochemical evidence of vitamin E deficiency. Oral administration of alpha-tocopherol resulted in rapid correction of the in vitro hemolysis and improvement of in vivo hematologic indices. Investigation of these patients supports the conclusion that the hemolytic anemia of infancy in CF is caused by vitamin E deficiency and should be treated promptly with 50 IU/day of vitamin E. Because two of the three patients were identified in a CF screening/surveillance program, we can estimate that the frequency of clinically significant anemia in CF infants is 4%. Our observations demonstrate a potential advantage of CF neonatal screening for individual patients susceptible to vitamin E-deficient hemolytic anemia and suggest that confirmatory follow-up diagnostic studies, such as sweat tests, should be performed by 4 to 6 weeks of age.

Application of DNA analysis in a population-screening program for neonatal diagnosis of cystic fibrosis (CF): comparison of screening protocols.

We compare two protocols for newborn screening for cystic fibrosis (CF). The first uses the immunoreactive trypsinogen (IRT) assay with a cutoff of > or = 180 ng/ml and a sweat test to identify CF patients. The second uses the IRT assay with a 100 ng/ml cutoff in conjunction with direct analysis for the delta F508 CF transmembrane conductance regulator (CFTR) mutation in a two-tiered (i.e., IRT/DNA) protocol, followed by a sweat test. We screened 220,865 newborns from Wisconsin for CF, using the IRT protocol identifying 369 infants with an elevated IRT, of whom 46 were found to have CF. Another 7 CF patients were identified who had a false-negative IRT level. The CF incidence in the white population was 1 in 3,431 (carrier incidence of 1 in 30). The IRT protocol had a sensitivity of 87% and a positive predictive value of 12.5%. We subsequently used the IRT/DNA protocol to screen 21,258 infants. Of 518 infants with an IRT level > or = 100 ng/ml, 24 carried at least one copy of the delta F508 CFTR mutation, and 4 of these infants were found to have CF, yielding a positive predictive value for this protocol of 16.7%. Direct comparison of the positive predictive value of the two protocols is not valid, because of the different populations screened. However, had the IRT protocol been used on the IRT/DNA cohort, 50 infants, including the 4 with CF, would have received sweat tests, yielding a positive predictive value of 8%. Because of the small sample size, this positive predictive value is not significantly different from that obtained for the IRT/DNA test. However, from a practical point of view the IRT/DNA approach does decrease considerably the number of sweat tests that must be undertaken. The number of false positives for the IRT protocol (46 in 21,258) is increased significantly compared with that for the IRT/DNA approach (20 in 21,258; P < .001). The incidence of delta F508 carriers detected in cohorts with an elevated IRT level was increased compared with the incidence in the general population. The direct costs for the IRT/DNA approach (100 ng/ml) were $11,374 per CF patient detected, compared with $10,187 per CF patient detected for the IRT protocol. Therefore, we conclude that the IRT/DNA approach to CF newborn screening decreases the number of false-positive subjects contacted, without a significant increase in cost.

Nutritional status of infants with cystic fibrosis associated with early diagnosis and intervention.

The purpose of this study was to characterize the nutritional status of infants diagnosed with cystic fibrosis (CF) through neonatal screening and to determine if they would achieve normal nutrition when managed with early intervention. In addition, nutrient intake was assessed to determine energy and macronutrient-consumption patterns. Evaluation of growth revealed that normal patterns could be achieved with mean energy intake values at ages 6 and 12 mo of 481 and 426 kJ/kg body wt (115 and 102 kcal/kg body wt), respectively. Biochemical assessment demonstrated low alpha-tocopherol and linoleic acid values at diagnosis in the majority of infants whereas one-third had abnormal indices of protein nutriture. Essential fatty acid deficiency was also demonstrated at diagnosis by abnormal triene-tetraene ratio values in 27% of screened infants. With predigested formula and dietary supplementation, there was improvement in all indices of nutritional status and only a low percentage of patients showed mild biochemical abnormalities at age 12 mo.

Nutritional assessment of infants with cystic fibrosis diagnosed through screening.

Presymptomatic infants diagnosed through neonatal screening for cystic fibrosis can have biochemical evidence of malnutrition. With aggressive dietary management and treatment with pancreatic enzymes, normal biochemical indices of nutrition can be achieved at 12 months of life in most cases. Males with cystic fibrosis appear to be more at risk than females for abnormal growth and biochemical indices of nutrition in the first year of life. This may be related to the observed decrease in fat intake when compared to females. Males, especially, should be carefully observed for development of nutritional abnormalities based on this data. Careful attention should be paid to vitamin E and essential fatty acid status in all CF infants. The numbers in this study are small and the long-term consequences of early nutritional intervention await the conclusion of the randomized, controlled study on-going in Wisconsin.