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The Standardisation Committee of the European Cystic Fibrosis Society Clinical Trial work has undertaken the evaluation of clinical end-points for therapeutic interventions regarding their use in multicentre clinical trials in cystic fibrosis (CF). This review of biomarkers in bronchoalveolar lavage (BAL) is part of the group’s work. The aims of this project were: 1) to review the literature on reliability, validity and responsiveness of BAL in patients with CF; 2) to gain consensus of the group on the feasibility of BAL; and 3) to gain consensus on answers to key questions regarding the promotion of BAL to surrogate end-point status. Assessment of BAL inflammatory markers in the literature indicates that their reliability, validity and responsiveness are adequate for clinical trials. After discussion of the practical characteristics it was concluded that BAL has an attractive validity profile, albeit with limited feasibility. It is particularly applicable to multicentre trials in preschool children with CF and early or mild lung disease. This is the first article to collate the literature in this manner. This provides a rationale to support the use of BAL in early clinical trials in preschool children with CF. Introduction The European Cystic Fibrosis Society Clinical Trial work (ECFS-CTN) Standardisation Committee is undertaking a rigorous evaluation of outcome measures used in clinical trials in cystic fibrosis (CF). The committee is composed of six groups consisting of researchers with expertise in specific outcome measures: CF transmembrane conductance regulator biomarkers [1], respiratory function, inflammatory markers, anthropometrics, microbiology definitions and chest imaging. This article summarises the work of the inflammatory markers group on inflammatory markers obtained via bronchoalveolar lavage (BAL) and is one of a series of documents from the six groups. Outcome measures can be classified as clinical end-points, surrogate end-points or biomarkers. Clinical end-points reflect how a patient feels, functions or survives and detect a tangible benefit for the patient [2, 3]. A surrogate end-point is a laboratory measurement used to predict the efficacy of therapy [2, 3] when direct measurement of clinical effect is not feasible or practical. Surrogate end-points may shorten the period of follow-up required; however the link between the surrogate end-point and long-term prognosis must be proven. Forced expiratory volume in 1 s (FEV1) is still the only accepted surrogate outcome for the European Medicines Agency and the US Food and Drug Administration. With regard to their use as outcome measures, inflammatory markers obtained via BAL are currently considered to be “biomarkers”. A biomarker is defined as “a characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes or pharmacologic response to a therapeutic intervention” [2, 3]. Biomarkers are mainly used to explore proof-of-concept for a specific compound. Some are currently being considered for “promotion” to the status of surrogate end-point. A full description of the classification of outcome measures is provided in the first document in the series of articles from the ECFS-CTN Standardisation Committee [1]. Methods An exhaustive literature search was conducted in MEDLI, Allied and Complementary Medicine (AMED) and Embase using a combination of keywords: “bronchoalveolar lavage” or “pulmonary inflammation” or “airway inflammation” or “lung inflammation” or “neutrophil” or “polymorphonuclear” or “PMN” or “interleukin” or “IL-6” or “IL-8” or “cytokine” or “epithelial lining fluid” or “inflammatory marker”, and “cystic fibrosis”. The search was limited to full text articles in the English language, with no limits on year of publication. A bibliography search was also conducted of all included articles and other relevant literature such as reviews and editorials. For clinimetric properties, data were extracted and tabulated for reliability, validity, correlation with other outcome measures, responsiveness and reference values. Definitions are given in table 1. To evaluate feasibility, data were extracted and tabulated on the proportion of attempts that were successful and reasons for excluding tests. An expert panel also discussed the following topics at several face-to-face meetings (Venice, Italy: November 17 and 18, 2017; Hamburg, Germany: June 9, 2017; Rotterdam, the herlands: March 23 and 24, 2017) and reached consensus on each: risk involved, cost, ease of performance, ease of administration, time to administer, equipment and space needed, and applicable age group. Specific advantages and limitations of BAL were also discussed. Narrative answers to four key questions were prepared, discussed and agreed by the group. 1) Do BAL inflammatory markers have the potential to become surrogate outcome measures? 2) For what kind of therapeutic trial are BAL inflammatory markers appropriate? (Therapeutic aim, phase of trial, target population, number of patients involved and number of sites involved.) 3) Within what timeline can change be expected and what treatment effect can be considered clinically significant? 4) What are the most needed studies to further define BAL inflammatory markers in patients with CF and to explore their potential as a surrogate outcome measures? The consensus of the group is presented in the current article. Results Why use BAL inflammatory markers in clinical trials in CF? Flexible bronchoscopy with BAL provides a regional measurement of lung inflammation and infection within the respiratory tract, including the small airways and alveoli [8]. Inflammation has been shown to be present early in CF lung disease before changes are detected by traditional pulmonary function techniques such as spirometry [9]. The ability to identify early airway inflammation and infection in these “silent years” is of great importance for investigating new therapies in infants and young children. Being the most direct measurement of infection and inflammation of the lower airways and distal lung, BAL has greatly contributed to the understanding of the pathophysiological process in CF, especially in infants and young children. Lung secretions from patients with CF contain large concentrations of TNF-α and interleukins/chemokines (IL-8, IL-6, IL-1, etc.) [5]. All of these cytokines share a common characteristic: their synthesis is promoted by nuclear factor-κB, which is activated by cellular interaction with bacteria, bacterial products and proinflammatory cytokines. IL-8 is a chemoattractant of PMN cells and its mRNA increases with osmotic stress, which is a part of the pathogenesis of CF [10, 11]. Cell counts and mediators reflect endobronchial inflammation. PMN cell infiltration induces the release of oxidants and proteases, leading to lung tissue degradation. CF lungs may be primed for inflammation, and bacterial and/or viral infection may potentiate such inflammation [12]. Inflammation with increased numbers of PMN cells is seen in BAL from the first few weeks of life, independent of clinical signs and symptoms. In early disease, BAL changes represent a preclinical indicator of possible underlying (but clinically silent) inflammation [13–15]. A substantial proportion of infants diagnosed with CF after detection by newborn screening have active pulmonary inflammation, 30% have detectable activity, 20% have pulmonary infection and 80% have evidence of structural lung disease on chest computed tomography (CT) at 3 months of age [9]. Together with chest CT, BAL inflammatory markers have been used as clinical end-points in pathophysiological studies (Australian Respiratory Early Surveillance Team for CF) [9], in clinical trials of tobramycin inhaled solution [16–18] and in clinical trials of recombinant human (rh)DNase [19–21]. It has also been used to direct therapy against Pseudomonas aeruginosa infection (Australasian CF Bronchoalveolar Lavage) [22]. However, no soluble marker of inflammation has been studied in a comprehensive, longitudinal manner so as to be validated as a “gold standard” for assessing the inflammatory response [23, 24]. Reliability To the best of our knowledge, short-term reproducibility has not been studied in CF. One study of 60 BAL samples from intubated non-CF children in the intensive care unit showed satisfactory short-term reproducibility of cell counts in blind nonbronchoscopic BAL, except for lymphocytes [25] (table E1). In noninfected infants with CF, some insight regarding long-term reproducibility has been provided by repeat BAL conducted 6–18 months apart, indicating a certain degree of variability related to an ongoing inflammatory process [26]. Similarly, PAUL et al. [19] showed that the PMN cell percentage and in pooled BAL samples significantly increased over time (up to 36 months) in children with CF not treated by rhDNase. Although considered the gold standard for sampling lower respiratory secretions, BAL may produce variable results due to regional heterogeneity of inflammation [23, 27]. PMN cell count and percentage and activity are generally greater in upper-lobe BAL fluid (BALF) in adults [27]. Upper- versus lower-lobe differences were more pronounced in subjects with better preservation of lung function [27]. Concurrent validity Due to the localised nature of enhanced inflammation in CF, respiratory secretions from the lower airways are considered by many researchers to be the optimal source of inflammatory cells and soluble mediators [5]. BAL is considered the best method for obtaining samples from the lower respiratory tract (especially in very young children who are too young to successfully undergo sputum induction with hypertonic saline), thus yielding the most accurate measure of the infectious and/or inflammatory process in the CF airway lumen [24]. However, it has been shown that the inflammatory patterns and responses to infective stimuli in the airway lumen and the airway wall of children with CF are distinct and compartmentalised, and thus BAL and endobronchial biopsy provide different but complementary information [28]. In contrast to the neutrophil dominated inflammation present in the airway lumen, the bronchial mucosa is characterised by the recruitment and accumulation of lymphocytes [28]. Convergent validity In young pre-adolescent children, there is a good correlation (r>0.55) between BAL PMN cell count/percentage and IL-8 (five out of five studies [13, 29–32]) or neutrophil elastase (one study) [13]. The correlation was not a constant finding in older patients and adults (three out of four studies) [27, 33–35] (table E2). One study ed good correlation (r2=0.48, p=0.036) between the inflammatory response (IL-8 and PMN cells) in the upper airway, sampled by nasal washes, and the lower airways, sampled by BAL [36]. The correlation between inflammatory markers obtained via BAL and other sampling methods is variable. Two studies showed no correlation between BAL and induced sputum [6, 34], while one study showed excellent agreement between IL-8 recovered from BALF and spontaneously expectorated sputum (r=0.967, p=0.007) [37]. In contrast to induced sputum, which originates from the airways, BAL samples the bronchial or terminal airways and air spaces (alveoli), according to the fractions analysed (the latter aliquots more likely representing the alveolar region). Induced sputum and BAL thus provide different but complementary data. 网站原创范文除特殊说明外一切图文作品权归所有；未经官方授权谢绝任何用途转载或刊发于媒体。如发生侵犯作品权现象，英语论文网站，英语论文，保留一切法学追诉权。() |
