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Refereed/Peer-reviewed Nasal nitric oxide (nNO) is extremely low in most people with primary ciliary dyskinesia (PCD) and its measurement is an important contributor to making the diagnosis. Existing guidelines and technical standards focus on nNO measurements in older, cooperative children using chemiluminescence analysers. However, measurements of nNO in pre-school-age children (age 2–5 years) may facilitate early diagnosis and electrochemical rather than chemiluminescence analysers are widely used. Pre-schoolers often need different methods to be employed when measuring nNO. Hence, a European Respiratory Society Task Force has developed this technical standard as the first step towards standardising sampling, analysis and reporting of nNO measured as part of the diagnostic testing for PCD in all age groups, including pre-school-age children. Furthermore, we considered both chemiluminescence and electrochemical analysers that are in use worldwide. There was a paucity of quality evidence for electrochemical analysers and sampling methods used in young children, and the Task Force proposes future research priorities to allow updates of this technical standard.

Primary ciliary dyskinesia (PCD) symptoms are non-specific and tools to aid patient selection for referral are needed. Objectives: To assess accuracy of a validated symptom score (PICADAR) [Behan, ERJ, 2016], in combination with nasal nitric oxide (nNO) to identify patients needing full diagnostics. Methods: Prospective data from 142 consecutive referrals for PCD diagnostics (33 PCD positive, 111 negative). Sensitivity/specifity calculated using either PICADAR score >5 or nNO below threshold (30, 77 or 100nl/min) as a positive test compared to final diagnosis of PCD. Results: PICADAR alone had sensitivity 0.88 and specificity 0.95. nNO+PICADAR improved identification of PCD positive patients. Accuracy was dependent on nNO threshold; sensitivities/specificities were 0.94/0.89, 0.94/0.78 and 1.0/0.73 using 30, 77 and 100nl/min. Conclusion: PICADAR effectively selects patients for referral to PCD diagnostics but some cases are missed. Addition of nNO provides a highly sensitive patient selection; 100nl/min nNO threshold gives a sensitivity and negative predictive value of 100%.

Background: Nasal nitric oxide (nNO) is usually low in primary ciliary dyskinesia (PCD) and measurement is part of a complex diagnostic work-up. Previous research has failed to define the accuracy of nNO testing in differing patient populations. Aims: Use accuracy data of nNO testing in patients referred to a UK national diagnostic service to calculate the predictive value of nNO testing in children with persistent wet cough (estimated 5% PCD prevalence) and in the general population (1:10,000 prevalence). Methods: From June 2006 to January 2014, 282 consecutive referrals (aged 6-79 years) had nNO measured by breath hold technique on the chemiluminescent NIOX Flex analyser. PCD was diagnosed by high resolution video microscopy and quantitative electron microscopy. Sensitivity and specificity was calculated and used to derive positive and negative predictive values (PPV & NPV) for each population. Results: 31 patients were PCD positive. Using a published cut-off of 77 nl/min (256 parts per billion on NIOX Flex), sensitivity was 93.6% (95% CI 78.5-99.0) and specificity 84.1% (95% CI 78.9-88.4). PPV was 42% (30.2-54.5%) and NPV 99.1% (96.6-99.9%) for referrals (prevalence of PCD 11%). PPV was 23.6% for persistent wet cough and Conclusion: PPV is poor and diminishes rapidly with lower PCD prevalence therefore screening should be targeted at those with high clinical suspicion of PCD. Whilst NPV is excellent, it must be interpreted alongside clinical history given published cases of PCD with normal nNO. These findings highlight the importance of using clinical features to select those who undergo nNO testing.

Background Patients with primary ciliary dyskinesia (PCD) have abnormal ciliary function and low nasal nitric oxide (nNO) and fractional exhaled NO (FeNO). Nitric oxide (NO) biosynthesis is dependent on nitric oxide synthases (NOS). Cilia line the bronchial but not the alveolar epithelium. It has been hypothesised that NOS function relies on normal ciliary function and that in PCD bronchial (JNO) but not alveolar (CalvNO) NO might therefore be reduced. The aim of this study was to compare JNO and CalvNO in children with PCD, cystic fibrosis (CF), asthma and healthy subjects.