Role of sweat ion ratios in diagnosing cystic fibrosis.

Sweat chloride (Cl- ) concentration is the gold standard for diagnosing cystic fibrosis (CF). This is, however, challenging among patients with borderline values. Previous studies have reported that the sweat Cl- /Na+ ratio may be useful for diagnosing CF; however, little is known about Cl- /K+ and (Cl- + Na+ )/K+ ratios. This study aimed to retrospectively define the most appropriate outcome of the sweat test. Samples of sweat were collected using the Gibson and Cooke method. Cl- , Na+ , and K+ were further quantified in 2084 participants-1283 CF and 801 non-CF-based on clinical diagnosis. Among those with borderline sweat Cl- values (n = 502), 34.8% had CF. In the receiver operating characteristic curve analysis, the area under the curve was calculated to evaluate the diagnostic value of the ion ratios. In the overall population, all the ratios significantly discriminated CF from non-CF, whereas in the borderline group, only Cl- /Na+ significantly discriminated CF and non-CF subjects, regardless of age.

Optical Measurements of Sweat for in Vivo Quantification of CFTR Function in Individual Sweat Glands.

Optical measurement of CFTR-dependent sweat secretion stimulated by a beta-adrenergic cocktail (C-phase) vs. CFTR-independent sweat secretion induced by methacholine (M-phase) can discriminate cystic fibrosis (CF) patientts from controls and healthy carriers by the ratio of sweat rate in the C-phase vs. the M-phase (C/M ratio). However, image analysis is experimentally demanding and time-consuming. Here, sweat droplet number (SDN) in the C-phase, corresponding to the number of sweat-secreting glands, was a statistically significant predictor for detecting the effects of CFTR-targeted therapy. We show that in 44 non-CF subjects and 110 CF patients, SDN in the C-phase provides a linear readout of CFTR function that is more sensitive than that using the C/M ratio. In CF patients, increased SDN in the C-phase during treatment with (LUMA/IVA) was associated with a trend toward improved lung function (FEV1). Our method is suitable for multicenter monitoring of the effects of CFTR modulators.

Genotypic and phenotypic relatedness of Pseudomonas aeruginosa isolates among the major cystic fibrosis patient cohort in Italy.

BACKGROUND: Pseudomonas aeruginosa is the predominant pathogen associated with the decline of pulmonary function in cystic fibrosis (CF) patients. Both environment-to-host acquisition and patient-to-patient transmission have been described for P. aeruginosa infection. Epidemic clones and bacterial phenotypic adaptation to the CF lung have been recognised as independent risk factors for disease progression. So far, there is no established link between genotypic prevalence and phenotypic traits. Here, we look at the major CF patient cohort in Italy to identify shared P. aeruginosa clones and associated common phenotypic traits. RESULTS: A comprehensive analysis of P. aeruginosa genotypes to determine the presence of high-risk shared clones and their association to specific phenotypic traits has been performed in a major Italian CF centre. Pulsed-field gel electrophoresis (PFGE) of P. aeruginosa isolates from 338 CF subjects identified 43 profiles shared by two or more patients and 214 profiles exclusive to individual patients. There was no evidence of a P. aeruginosa outbreak, but four most prevalent pulsotypes were detected. Common phenotypic traits were recorded intra-pulsotypes, but we detected heterogeneity inter-pulsotypes. Two of the four major pulsotypes included P. aeruginosa isolates with hallmarks of adaptation to the CF airways, including loss of motility, low production of siderophore, pyocyanin and proteases, and antibiotic resistance. One of these pulsotypes grouped a high percentage of hypermutable isolates. No clear correlation between epidemiological and clinical data was found. CONCLUSIONS: We conclude that CF patients of this cohort shared common pulsotypes, but their phenotypic heterogeneity indicates an absence of specific traits associated to P. aeruginosa genotypic prevalence.

Impact of polymorphism of Multidrug Resistance-associated Protein 1 (ABCC1) gene on the severity of cystic fibrosis.

A 5'FR/G-260C (NCBI reference: 010393.16:g.15983174C>G) functional polymorphism of Multidrug Resistance-associated Protein 1 (ABCC1) promoter has been reported which influences ABCC1 expression including inflammatory related events. We aimed at investigating the impact of this polymorphism on the severity of CF disease. In this multicentric study, key clinical features of 203 CF patients homozygous for the F508del mutation were recorded. Kaplan-Meier analysis showed that patients with the rare CC genotype were chronically colonized by PA around 6 years earlier (mean ± SD: 11.2 year ± 7.8, 95% CI for the mean: 5.7-16.8) than those with the GG or the CG alleles (p<=0.01) and a FEV1 <60% predicted was first observed earlier in this group (p<0.05). Concordant trends to better nutritional status and FEV1 were observed in the slightly older GG subgroup. The potential role of ABCC1 promoter as a modifier gene deserves further study.

Growth and long-term lung function in cystic fibrosis: a longitudinal study of patients diagnosed by neonatal screening.

OBJECTIVE: So far there is no long-term analysis relating the achievement of growth milestones (such as prepubertal and pubertal take-off and peak velocity) to the course of respiratory function from childhood to adulthood in cystic fibrosis. This study was designed to evaluate linear growth and severity of lung disease, find a correlation between growth and disease severity throughout childhood. PATIENTS: One hundred sixty-three patients from one center were selected according to: diagnosis by neonatal screening, complete follow-up available (four height measurements/year) until the age of 20, respiratory tests available from the age of 5-6 years until adulthood, lung transplantation, or death. Disease was classified as mild or severe according to FEV(1) (group 1 and group 2). A third group of patients (group 3) consisted of those who died or underwent lung transplantation before the age of 18. METHODS: Individual growth profiles were fitted with a seven-constant nonlinear growth function. A multivariate linear model was fitted, with gender and severity of disease as covariates, and age, height, and height velocity at growth milestones as dependent variables. Data were compared with those of the normal Italian population. RESULTS: Lung disease severity correlates with delayed prepubertal and pubertal growth milestones. Peak height velocities were significantly reduced in relation to the severity of the disease. CONCLUSIONS: Patients with severe forms of cystic fibrosis exhibit reduced growth velocity values at an early age, before a clear decline in pulmonary function.

Epidemiology and survival analysis of cystic fibrosis in an area of intense neonatal screening over 30 years.

This population-based study was conducted in Veneto and Trentino (northwestern Italy, population 5 million). In this area, neonatal screening for cystic fibrosis started in 1973 and has been virtually universal since the early 1980s. During this study, the estimated incidence of cystic fibrosis in this region was 1/2,650 livebirths per year. The authors analyzed data on 593 patients born in 1938-2000 and living in the region who were followed by a single referral center. Median time from birth to confirmation of diagnosis after screening was 32 days (range, 0-1,531). For patients whose disease was recognized after symptoms occurred, median age at diagnosis was always less than 1 year. Median survival age was 37.7 years. Long-term survival (to age 20-30 years) was not significantly influenced by mode of diagnosis (screened or unscreened), sex, or age at diagnosis for unscreened patients (<1, 1-5, >5 years). Current survival analysis of three consecutive decades showed that improving survival tended to vanish in the last years of the study. The authors concluded that a regional neonatal screening program allows very early recognition of cystic fibrosis. They could not conclude that neonatal screening improves long-term survival if compared with diagnosis by symptoms in early infancy.