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• W2022351730 abstract "The collection of exhaled breath condensate (EBC) is simple and non-invasive, however, there are few data on the methodological aspects affecting concentrations of compounds in EBC. The aim of this study was to investigate methodological issues for measuring nitric oxide metabolites (NOx) in EBC.Twenty-five healthy adults (12 females, age range 23–55 years) and 22 children (11 females, age range 7–6 years) were recruited for studies investigating inter- and intra-day repeatability, repeatability with controlled expiratory flows and temperature, flow dependence, and analytical variability of EBC NOx.Both intra- and inter-day repeatability was poor with a coefficient of repeatability of 103.4% of the mean difference between intra-day (15min) measures and 118.6% of inter-day (24h) differences. Repeatability was not improved when expiratory flow and temperature of the collection device were controlled. However, some of the variability (approximately 50%) may be accounted for by variability in the analytical technique (analytical variability) and this may result from difficulties in controlling for contamination. NOx levels were not affected by different expiratory flows in either adults or children but there was still significant variation within individuals.Levels of NOx in EBC seem to be highly variable and this needs to be considered if EBC NOx is to be used in clinical studies. The collection of exhaled breath condensate (EBC) is simple and non-invasive, however, there are few data on the methodological aspects affecting concentrations of compounds in EBC. The aim of this study was to investigate methodological issues for measuring nitric oxide metabolites (NOx) in EBC. Twenty-five healthy adults (12 females, age range 23–55 years) and 22 children (11 females, age range 7–6 years) were recruited for studies investigating inter- and intra-day repeatability, repeatability with controlled expiratory flows and temperature, flow dependence, and analytical variability of EBC NOx. Both intra- and inter-day repeatability was poor with a coefficient of repeatability of 103.4% of the mean difference between intra-day (15min) measures and 118.6% of inter-day (24h) differences. Repeatability was not improved when expiratory flow and temperature of the collection device were controlled. However, some of the variability (approximately 50%) may be accounted for by variability in the analytical technique (analytical variability) and this may result from difficulties in controlling for contamination. NOx levels were not affected by different expiratory flows in either adults or children but there was still significant variation within individuals. Levels of NOx in EBC seem to be highly variable and this needs to be considered if EBC NOx is to be used in clinical studies. The measurement of constituents of exhaled breath condensates (EBC) is a potential non-invasive method for monitoring patho-physiologic processes in the airways.1Hunt J. Exhaled breath condensate: an evolving tool for noninvasive evaluation of lung disease.J Allergy Clin Immunol. 2002; 110: 28-34Abstract Full Text Full Text PDF PubMed Scopus (269) Google Scholar This is a growing area of research and a large number of volatile and non-volatile compounds have been measured. Included among these are the metabolites of nitric oxide (NOx), such as nitrite, nitrate, nitrotyrosine and nitrosothiols. Nitric oxide metabolites in EBC have been found to be elevated in patients with inflammatory airways diseases such as asthma,2Corradi M. Montuschi P. Donnelly L.E. Pesci A. Kharitonov S.A. Barnes P.J. Increased nitrosothiols in exhaled breath condensate in inflammatory airway diseases.Am J Resp Crit Care Med. 2001; 163: 854-858Crossref PubMed Scopus (190) Google Scholar, 3Formanek W. Inci D. Lauener R.P. Wildhaber J.H. Frey U. Hall G.L. Elevated nitrite in breath condensates of children with respiratory disease.Eur Resp J. 2001; 19: 487-491Crossref Scopus (90) Google Scholar, 4Ganas K. Loukides S. Papatheodorou G. Panagou P. Kalogeropoulos N. Total nitrite/nitrate in expired breath condensate of patients with asthma.Resp Med. 2001; 95: 649-654Abstract Full Text PDF PubMed Scopus (123) Google Scholar cystic fibrosis2Corradi M. Montuschi P. Donnelly L.E. Pesci A. Kharitonov S.A. Barnes P.J. Increased nitrosothiols in exhaled breath condensate in inflammatory airway diseases.Am J Resp Crit Care Med. 2001; 163: 854-858Crossref PubMed Scopus (190) Google Scholar, 3Formanek W. Inci D. Lauener R.P. Wildhaber J.H. Frey U. Hall G.L. Elevated nitrite in breath condensates of children with respiratory disease.Eur Resp J. 2001; 19: 487-491Crossref Scopus (90) Google Scholar, 5Balint B. Kharitonov S.A. Hanazawa T. et al.Increased nitrotyrosine in exhaled breath condensate in cystic fibrosis.Eur Respir J. 2001; 17: 1201-1207Crossref PubMed Scopus (102) Google Scholar, 6Cunningham S. McColm J.R. Ho L.P. Greening A.P. Marshall T.G. Measurement of inflammatory markers in the breath condensate of children with cystic fibrosis.Eur Respir J. 2000; 15: 955-957Crossref PubMed Scopus (71) Google Scholar, 7Ho L.P. Innes J.A. Greening A.P. Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide.Thorax. 1998; 53: 680-684Crossref PubMed Scopus (133) Google Scholar, 8Tate S. MacGregor G. Davis M. Innes J.A. Greening A.P. Airways in cystic fibrosis are acidified: detection by exhaled breath condensate.Thorax. 2002; 57: 926-929Crossref PubMed Scopus (186) Google Scholar and chronic obstructive pulmonary disease.2Corradi M. Montuschi P. Donnelly L.E. Pesci A. Kharitonov S.A. Barnes P.J. Increased nitrosothiols in exhaled breath condensate in inflammatory airway diseases.Am J Resp Crit Care Med. 2001; 163: 854-858Crossref PubMed Scopus (190) Google Scholar The collection of EBC is simple, in most cases requiring a subject to breathe tidally through a cooling apparatus via a mouthpiece. Indeed, EBC using oral tidal breathing has been successfully collected in children as young as 3 years old.3Formanek W. Inci D. Lauener R.P. Wildhaber J.H. Frey U. Hall G.L. Elevated nitrite in breath condensates of children with respiratory disease.Eur Resp J. 2001; 19: 487-491Crossref Scopus (90) Google Scholar However, there have been very few published methodological studies regarding the collection and analyses of EBC and there remain a number of unresolved issues. These include breathing patterns, reproducibility and dilution of compounds. The aim of this study was to investigate the repeatability and flow dependence of NOx in EBC. Twenty-five healthy adults (12 females, age range 23–55 years) and 22 children (11 females, age range 7–16 years) were recruited to participate in various methodological studies (see below). Of the 22 children, 10 had cystic fibrosis (CF), 4 had asthma and 8 had no respiratory disease. The studies were approved by the King Edward Memorial and Princess Margaret Hospitals Human Ethics Committee. Written consent was obtained from all adults and parents of the children. The collection device was custom made and based on a method described previously.3Formanek W. Inci D. Lauener R.P. Wildhaber J.H. Frey U. Hall G.L. Elevated nitrite in breath condensates of children with respiratory disease.Eur Resp J. 2001; 19: 487-491Crossref Scopus (90) Google Scholar Briefly, subjects were asked to breathe via a mouthpiece, which included a saliva trap and one-way valve, through a straight piece of Teflon tubing (length 55cm, ID 1cm). The Teflon tubing was encased in polypropylene pipe. Commercially available icepacks were wrapped around the tube and held in place by the pipe. Subjects breathed through the apparatus for between 5 and 10min. The condensate was collected directly into a 1.5mL microfuge tube and stored at −80°C until analysis. Total NOx were measured using the Sievers nitric oxide analyzer (NOA 280, Liquid System, Boulder, USA). Concentration of NOx was expressed in μmol/L. Briefly, using a micro-syringe aliquots of 20 or 50μL of the condensate were instilled into a heated reaction-cylinder which contained a saturated solution of Vanadium (III) chloride (VCl3) in 1M HCl. The NO3 was reduced by the VCl3 to NO2 which was further reduced to gaseous NO. The NO was then measured by a rapid response NO-Analyzer (Sievers, Boulder, USA). The reaction chamber was cleaned with UHPW before each analysis. Total NOx levels were calculated from a calibration curve which ranged from 0.625 to 10μmol/L. The calibration curve was linear and considered acceptable if the r2 was ⩾0.99. Nitric oxides are found in nearly all environments, including air, water and lab benches. To determine if environmental NOx could contaminate the collection device, known concentrations of NO3 were nebulised through the tubing. The tubing was always washed using ultra-high pure water before these tests, however, 3 of the tubes were allowed to drip dry while 4 were wiped clean after cleaning and just prior to use. Considerable contamination was evident if the tubes were left to drip dry. Average NOx were 9.4μmol/L in the solution prior to nebulisation, 14.5μmol/L in the solution after nebulisation and 31.4μmol/L in the solution collected through the tube. When the tubes were wiped with a clean cloth prior to collection there was no evidence of contamination from the tubing. Average NO3 levels were 5.4, 3.9 and 5.0μmol/L prior to nebulisation, post-nebulisation and in the collected condensate, respectively. For all methodology studies we used a clean cloth to wipe the inside of the tubing prior to collection. Three repeatability studies were conducted. Uncontrolled flow: Repeatability was assessed for both back-to back (15min apart) and 24h measurements. Condensate was collected from 10 adults for 15min repeatability and 20 adults for 24h repeatability. Condensate was collected during normal, uncontrolled tidal breathing. Controlled tidal flow: Condensate was collected from 9 adults on 2 occasions 15min apart using controlled tidal flows. Subjects were asked to maintain a square wave tidal pattern with a maximal expiratory flow during tidal breathing of either 250 or 500mL/s for both collections (whichever was the most comfortable). Expiratory flow was measured by inserting a pneumotachograph (No. 3719, Hans Rudolp Inc., Kansas City, MO) between the mouthpiece and the collection apparatus and visual feedback was provided via custom designed software (Anadat, RHT-Infodat, Montreal Canada). Controlled flow and temperature: Two collections were made from 5 adults 15min apart using controlled tidal flow, as presented above, and ensuring the internal temperature of the cooling apparatus was consistent at the start of each collection. Temperature of the collection tube was measured using a thermocouple attached to a digital thermometer. The temperature of the collection tube was between −12 and −11°C at the start of the collection and between −2 and −4°C after 10min of breathing. Variability in NOx may be due to the analytical procedure. To test the analytical variability, EBC was collected from 9 adults during normal, uncontrolled tidal breathing. Each sample of EBC was divided into 2 aliquots, stored at −80°C and then analysed separately, in a random order, on the same day. The effect of expiratory flow on EBC NOx was measured in both adults (n=18) and children (n=23). Three different expiratory flows were used for each of the adult subjects and two flows for each of the children. All subjects were asked to maintain a consistent breathing pattern with a set maximum expiratory flow. For adults the 3 flows were 250, 500, and 750mL/s. For children the expiratory flows were 250 and 500mL/s. To achieve this subjects maintained a square breathing pattern at the desired flow, and real-time feedback was provided using a computer monitor. For both adults and children the order of the maximum expiratory flow was randomised, with 15min between collections in the same subject. For both children and adults NOx levels were log-normally distributed. Data for repeatability and analytical variability were analysed using Bland and Altmann plots.9Bland J.M.D.G.A. Statistical methods for assessing agreement between two methods of clinical measurement.Lancet. 1986; 1: 307-310Abstract PubMed Scopus (37015) Google Scholar Differences in NOx levels collected at the 3 different flows for adults were analysed using one-way analysis of variance (ANOVA) with repeated measures. Child flow NOx data were analysed using a paired t-test. Repeatability (co-efficient of repeatability—COR) was determined using the method described by Chinn.10Chinn S. Statistics in respiratory medicine. 2. Repeatability and method comparison.Thorax. 1991; 46: 454-456Crossref PubMed Scopus (308) Google Scholar All statistics were done using SPSS 11.5 (SPSS Science, Inc., Chicago, USA), where appropriate total NOx data are presented as geometric mean (GM) with 95% confidence intervals (95%CI). For all repeatability measures the mean difference between any 2 sets of results are expressed as both raw data and as percentage difference from the mean in order to allow comparison between the different tests (Table 1).Table 1NOx levels for repeat measurements from different methodology studies.Measure 1 (μmol/L)Measure 2 (μmol/L)Difference (%) (μmol/L)COR (%) (μmol/L)Uncontrolled flow 15min1.821.810.01 (5.5)1.99 (103.4)Uncontrolled flow 24h1.721.680.04 (6.8)1.71 (118.4)Flow controlled4.113.930.18 (7.4)5.30 (116.9)Flow and temp controlled4.443.870.57 (22.4)2.21 (105.0)Analytical variability4.584.370.21 (5.9)3.01 (58.5)COR, co-efficient of repeatability. Open table in a new tab COR, co-efficient of repeatability. Uncontrolled flow: Separate Bland and Altmann plots were generated for the 15min and 24h repeatability. The mean difference between 0 and 15min was 0.01μmol/L (5.5%) with a COR of 1.71μmol/L (103.4%) (Table 1). For 24h measurements the mean difference was 0.04μmol/L (6.8%) and COR of 1.99μmol/L (118.4%) (Fig. 1, Table 1). Controlled flow: Repeatability was not improved using controlled flows. The difference between levels collected 15min apart 7.4% with a COR of 116.9% (Table 1). Controlled flow and temperature: When both flow and temperature were controlled for repeat measures the mean difference was 0.57μmol/L (22.4%) and the COR was 2.21μmol/L (105.0%) (Table 1). Two aliquots from the same EBC sample were collected from 9 subjects, stored and then analysed on the same day. The group mean difference between the two aliquots was 0.21μmol/L (5.9%) with a COR of 3.01μmol/L (58.5%) (Table 1). Agreement was very good for 7 of the 9 repeat injections (Fig. 2). Adults: Geometric mean (95%CI) NOx levels for the 3 different flows were 1.80μmol/L (1.35–2.41μmol/L), 1.54μmol/L (1.14–2.07μmol/L) and 1.57μmol/L (1.04–2.36μmol/L) for 250, 500 and 750mL/s, respectively (Fig. 3). There was no significant difference between levels measured for the three flows (P=0.69). However, in some cases, there was considerable variation between NOx levels measured at different flows (Fig. 3). The mean coefficient of variation of levels measured at the 3 different flows for all subjects was 36.5% and ranged from 1.4% to 73.2%. Children: There was no difference in the NOx levels using 2 separate flows for children (Fig. 4). Geometric mean levels were 2.92μmol/L (2.57–3.31μmol/L) for expiratory flows of 250mL/s and 2.81μmol/L (2.46–3.18μmol/L) for 500mL/s (P=0.76). Again, in some cases, there was marked variability in levels measured at the different flows with up to 2.5 times difference between levels. We investigated if there was greater variability in the CF compared with the healthy group and, although numbers in each group were small, this was not the case. In these series of studies we investigated a number of methodological issues regarding the collection and analyses of nitric oxide metabolites in exhaled breath condensates. We have found in EBC collected during tidal breathing, that there was reasonably poor short-term (15min and 24h) repeatability in NOx levels and this was not improved if expiratory flow was controlled and temperature of the collection device, at the start of collection, kept constant. About half of this variability may be explained by variability in the analytical technique for measuring NOx. We did not find any significant differences in NOx levels in either adults or children when EBC was collected at different expiratory flows, although there was considerable within-subject variability. Nitric oxide metabolites are raised in EBC of various patient groups.2Corradi M. Montuschi P. Donnelly L.E. Pesci A. Kharitonov S.A. Barnes P.J. Increased nitrosothiols in exhaled breath condensate in inflammatory airway diseases.Am J Resp Crit Care Med. 2001; 163: 854-858Crossref PubMed Scopus (190) Google Scholar, 3Formanek W. Inci D. Lauener R.P. Wildhaber J.H. Frey U. Hall G.L. Elevated nitrite in breath condensates of children with respiratory disease.Eur Resp J. 2001; 19: 487-491Crossref Scopus (90) Google Scholar, 4Ganas K. Loukides S. Papatheodorou G. Panagou P. Kalogeropoulos N. Total nitrite/nitrate in expired breath condensate of patients with asthma.Resp Med. 2001; 95: 649-654Abstract Full Text PDF PubMed Scopus (123) Google Scholar, 5Balint B. Kharitonov S.A. Hanazawa T. et al.Increased nitrotyrosine in exhaled breath condensate in cystic fibrosis.Eur Respir J. 2001; 17: 1201-1207Crossref PubMed Scopus (102) Google Scholar, 6Cunningham S. McColm J.R. Ho L.P. Greening A.P. Marshall T.G. Measurement of inflammatory markers in the breath condensate of children with cystic fibrosis.Eur Respir J. 2000; 15: 955-957Crossref PubMed Scopus (71) Google Scholar, 7Ho L.P. Innes J.A. Greening A.P. Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide.Thorax. 1998; 53: 680-684Crossref PubMed Scopus (133) Google Scholar, 8Tate S. MacGregor G. Davis M. Innes J.A. Greening A.P. Airways in cystic fibrosis are acidified: detection by exhaled breath condensate.Thorax. 2002; 57: 926-929Crossref PubMed Scopus (186) Google Scholar Differences are at least 1-fold higher in disease groups and often greater than this, although significant overlap is evident between patients and healthy subjects. Further, significant reductions in NO metabolites have been demonstrated in asthmatics after both treatment with inhaled steroids11Kharitonov S.A. Donnelly L.E. Montuschi P. Corradi M. Collins J.V. Barnes P.J. Dose-dependent onset and cessation of action of inhaled budesonide on exhaled nitric oxide and symptoms in mild asthma.Thorax. 2002; 57: 889-896Crossref PubMed Scopus (192) Google Scholar and high-altitude climate therapy.12Straub D.A. Ehmann R. Hall G.L. et al.Correlation of nitrites in breath condensates and lung function in asthmatic children.Pediatr Allergy Immunol. 2004; 15: 20-25Crossref PubMed Scopus (23) Google Scholar However, very few studies have reported the repeatability of NO metabolites in EBC, an important consideration for the use of these compounds for intervention studies. Ho et al.7Ho L.P. Innes J.A. Greening A.P. Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide.Thorax. 1998; 53: 680-684Crossref PubMed Scopus (133) Google Scholar measured nitrites in 7 healthy subjects on two occasions 3–8 days apart and reported a 95% confidence interval for the intra-subject variability of ±1.12μmol/L. It is not clear how this related to mean or median levels measured in this group, however, median nitrite levels for a larger group of healthy subjects was only 0.36μmol/L. Ganas et al.4Ganas K. Loukides S. Papatheodorou G. Panagou P. Kalogeropoulos N. Total nitrite/nitrate in expired breath condensate of patients with asthma.Resp Med. 2001; 95: 649-654Abstract Full Text PDF PubMed Scopus (123) Google Scholar measured total NOx on consecutive days in healthy and asthmatic subjects. The mean difference (and standard deviation) for the asthmatics was 0.07μmol/L (0.04) and 0.03μmol/L (0.02) for the healthy subjects. Again, it was unclear how this related to the mean values. In our series of repeatability studies the mean differences between repeat measures were small—usually less than 10%—however, there was considerable intra-subject variability with differences between measures ranging up to 125%. This variability may not affect differences between healthy subjects and patients with respiratory disease if group differences are large, however, it is an important consideration for intervention studies when changes in NOx levels may be relatively small, e.g. less than 1-fold difference. One factor that may affect the variability of EBC constituents is expiratory flow. Breath condensates are often collected during normal tidal breathing and expiratory flow is generally not controlled. However, non-volatile substances, such as NO2 and NO3, are transported to the condensate in respiratory droplets14Effros R.M. Biller J. Foss B. et al.A simple method for estimating respiratory solute dilution in exhaled breath condensates.Am J Respir Crit Care Med. 2003; 168: 1500-1505Crossref PubMed Scopus (159) Google Scholar and the amount of aerosol formed in the respiratory tract depends on the velocity of the passing air as well as the surface tension of the extracellular surface fluid layer.13Mutlu G.M. Garey K.W. Robbins R.A. Danziger L.H. Rubinstein I. Collection and analysis of exhaled breath condensate in humans.Am J Respir Crit Care Med. 2001; 164: 731-737Crossref PubMed Scopus (256) Google Scholar Therefore, expiratory flow may be an important determinant of EBC constituents and variability in concentrations may be due to breath to breath variations in the size and number of respiratory droplets generated. In this study, however, short-term repeatability of NOx levels was not improved by controlling tidal flow. We also found that there was no difference in NOx levels, in either adults or children, when EBC was collected at different flows. Other studies have investigated the effect of flow on both volatile15Schleiss M.B. Holz O. Behnke M. Richter K. Magnussen H. Jorres R.A. The concentration of hydrogen peroxide in exhaled air depends on expiratory flow rate.Eur Respir J. 2000; 16: 1115-1118Crossref PubMed Scopus (101) Google Scholar and non-volatile16Corradi M. Folesani G. Andreoli R. et al.Aldehydes and glutathione in exhaled breath condensate of children with asthma exacerbation.Am J Respir Crit Care Med. 2003; 167: 395-399Crossref PubMed Scopus (145) Google Scholar, 17Corradi M. Rubinstein I. Andreoli R. et al.Aldehydes in exhaled breath condensate of patients with chronic obstructive pulmonary disease.Am J Respir Crit Care Med. 2003; 167: 1380-1386Crossref PubMed Scopus (176) Google Scholar constituents of EBC with conflicting results. Schleiss et al.15Schleiss M.B. Holz O. Behnke M. Richter K. Magnussen H. Jorres R.A. The concentration of hydrogen peroxide in exhaled air depends on expiratory flow rate.Eur Respir J. 2000; 16: 1115-1118Crossref PubMed Scopus (101) Google Scholar reported a significant flow dependence for H2O2 concentrations during full exhalations ranging from 48 to 140mLs−1, while variations in flow had no effect on aldehyde levels in either adults17Corradi M. Rubinstein I. Andreoli R. et al.Aldehydes in exhaled breath condensate of patients with chronic obstructive pulmonary disease.Am J Respir Crit Care Med. 2003; 167: 1380-1386Crossref PubMed Scopus (176) Google Scholar or children.16Corradi M. Folesani G. Andreoli R. et al.Aldehydes and glutathione in exhaled breath condensate of children with asthma exacerbation.Am J Respir Crit Care Med. 2003; 167: 395-399Crossref PubMed Scopus (145) Google Scholar Despite the lack of significant difference in mean NOx levels measured using different expiratory flows there was considerable variability with regard to the effect of flow in individuals. The reasons for this observation are unclear but might be due to variable dilution of airway condensate. Effros et al.14Effros R.M. Biller J. Foss B. et al.A simple method for estimating respiratory solute dilution in exhaled breath condensates.Am J Respir Crit Care Med. 2003; 168: 1500-1505Crossref PubMed Scopus (159) Google Scholar suggest that ‘reference indicators’ are developed to control for the variable dilution of EBC constituents, although suitable candidates are yet to be established. A significant effect of collection temperature on NOx concentrations in EBC has been demonstrated.18Vaughan J.J. Hunt J. Exhaled breath condensate sampling: colder is not necessarily better.Eur Respir J. 2002; 20: 175sGoogle Scholar For this study, we used a custom built device that was designed to be light and portable and could be used for collecting EBC outside the laboratory. Commercially available ice packs were used as the coolant and the temperature of these may vary depending on time in and out of the freezer. In a small number of subjects we found that controlling the initial temperature of the collection device did not improve the repeatability of NO metabolites in EBC but it is likely that the temperature range of the tubes had not varied greatly during the initial repeatability studies. Some of the variability in repeated measurements of EBC compounds may be due to variability in the assay. Indeed, Zacharasiewicz et al.19Zacharasiewicz A. Wilson N. Lex C. et al.Repeatability of sodium and chloride in exhaled breath condensates.Pediatr Pulmonol. 2004; 37: 273-275Crossref PubMed Scopus (42) Google Scholar recently reported that, for sodium and chloride concentrations in EBC, the analytical variability accounted for most of the within day variability. Further, Van Hoydonck et al.20Van Hoydonck P.G. Wuyts W.A. Vanaudenaerde B.M. Schouten E.G. Dupont L.J. Temme E.H. Quantitative analysis of 8-isoprostane and hydrogen peroxide in exhaled breath condensate.Eur Respir J. 2004; 23: 189-192Crossref PubMed Scopus (60) Google Scholar found that neither 8-isoprostane nor hydrogen peroxide levels could be reproducibly assessed due to low concentrations or poor sensitivity of the available assays. We investigated the analytical variability for NOx analyses using our collection device and analytical method. This seemed to account for about half of the variability we had observed although repeatability of 7 of the 9 paired samples was very good (i.e. varied by 20% or less). We did not observe such a high proportion of repeatable results in other methodology studies. Nitric oxides are found in most environments and there is considerable potential for contamination of the EBC during collection and analyses of samples. Indeed, we found that if the collection tubing was not cleaned (wiped) just prior to collection there was evidence of contamination in the sample. It is also possible that contamination can occur during the analyses in simple ways such as touching the injection needle with your hands. The injection needle was always flushed with ultra-high pure water and wiped clean between injections. For all studies the samples were injected 3 or 4 times but we only accepted the levels when at least 2 results varied by less than 5%. However, we did sometimes see 100% difference between repeat injections suggesting contamination could easily occur. Considerable care needs to be taken to reduce the risk of contamination in the collection and analyses of NOx. Our results suggest there is an inherent variability in the repeat measurement of EBC NOx that cannot be fully explained by the collection or analytical technique. Day-to-day variability, therefore, needs to be taken into consideration if EBC NOx is to be useful in tracking the progression of disease or effect of treatment in individual patients. Variability of other EBC constituents needs to be investigated fully before EBC can be used as a reliable clinical tool." @default.
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• W2022351730 title "Variability of nitric oxide metabolites in exhaled breath condensate" @default.
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• W2022351730 cites W2041208066 @default.
• W2022351730 cites W2046541211 @default.
• W2022351730 cites W2063696441 @default.
• W2022351730 cites W2090227927 @default.
• W2022351730 cites W2091833173 @default.
• W2022351730 cites W2108013032 @default.
• W2022351730 cites W2115218816 @default.
• W2022351730 cites W2123903646 @default.
• W2022351730 cites W2134976705 @default.
• W2022351730 cites W2139767534 @default.
• W2022351730 cites W2149040382 @default.
• W2022351730 cites W2151520766 @default.
• W2022351730 cites W2154056694 @default.
• W2022351730 cites W2156107878 @default.
• W2022351730 cites W2157786880 @default.
• W2022351730 cites W2166466675 @default.
• W2022351730 cites W2465692541 @default.
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