TY - JOUR T1 - The sensitivity and specificity of <em>pseudomonas aeruginosa</em> detection using hydrogen cyanide concentration in exhaled breath – The SPACE study JF - European Respiratory Journal JO - Eur Respir J VL - 44 IS - Suppl 58 SP - 3444 AU - Francis Gilchrist AU - Andrew Jones AU - Kevin Webb AU - David Smith AU - Warren Lenney Y1 - 2014/09/01 UR - http://erj.ersjournals.com/content/44/Suppl_58/3444.abstract N2 - IntroductionHydrogen cyanide (HCN) is an in-vitro marker of Pseudomonas aeruginosa (PA). This is the first in-vivo study to investigate if HCN is an early marker of PA infection in children with cystic fibrosis (CF).MethodsChildren who had not grown PA in the last year were recruited from 8 CF centres. At each CF appointment for the next 2 years they provided an exhaled breath sample and completed a questionnaire about symptoms and antibiotic use. The HCN concentration of the breath sample was analysed using selected ion flow tube mass spectrometry. At study completion the results of the routine microbiology samples were compared to the HCN concentrations.Results233 children were recruited, median (IQR) age: 8 (5.0-12.2) years. The median duration of follow-up was 2.0 (1.7-2.3) years with a total of 2086 clinic visits and 2072 breath samples. The median number of breath samples per child was 9 (6-12). There were 71 new PA isolates with an incidence of 0.19 cases per patient year. A study visit (with proforma and breath sample) had been completed within 7 days (+/-) of the culture result for 57 of the new PA isolates. 24/57 (42%) children were asymptomatic at the time of the PA isolate. An elevated HCN concentration (&gt;5ppb) was present in 28/57 breath samples (sensitivity 49%). In 5 children the elevated HCN concentration preceded the PA culture by &gt; 2 months. 8 children who did not isolate PA had an elevated HCN at some point (specificity 95%).ConclusionsIn children with CF, an elevated HCN concentration in exhaled breath is a specific marker of PA infection. Further studies are required to investigate if the sensitivity can be improved. ER -