A primary cilia dyskinesia (PCD) diagnosis can only be confirmed by genetic testing or transmission electron microscopy (TEM), but ideally multiple adjunct tests should also be used, new international guidelines state.
The joint guidelines from the European Respiratory Society (ERS) and American Thoracic Society (ATS) replace separate guidelines from each organisation and were presented at the ERS 2025 Congress in Amsterdam.
They strongly recommend using nasal nitric oxide, immunofluorescence staining and high-speed video microscopy (HSVM) to assess patients with suspected PCD, but emphasise that none of these tests alone is sufficient to confirm or exclude a diagnosis.
“No single test has 100% specificity and sensitivity, which necessitates the use of multiple tests in the diagnostic approach,” wrote the guideline authors, including Professor Amelia Shoemark, Asthma Lung UK Chair of Respiratory Research at the University of Dundee.
The guidelines, published in the European Respiratory Journal [link here], were developed by an international taskforce chaired by Prof Shoemark and Dr Amjad Horani, Associate Professor at Washington University, USA, who presented the guidelines at the ERS congress, following a comprehensive literature review with TEM and genetic testing as the reference tests.
The taskforce strongly recommended use of nasal nitric oxide testing during velum closure, based on moderate certainty evidence of high test accuracy and given that an accurate diagnosis outweighs the risk of any side effects.
Nasal nitric oxide testing during tidal breathing was conditionally recommended, as the taskforce found it to have lower accuracy and greater variability. However, it can still be informative, particularly in younger patients who are unable to achieve velum closure, they stressed.
The guidelines also strongly recommend ciliary beat pattern assessment using HSVM, although the taskforce only identified very low certainty evidence.
This was based on the observation that PCD diagnoses could be missed in the cases when nasal nitric oxide is normal or cannot be completed (e.g. in younger patients) and TEM and genetics are normal or incomplete.
“This scenario has been described repeatedly in the literature during the previous years of gene discovery (DNAH11, HYDIN, RSPH1),” the authors noted.
“Despite the very low certainty of evidence about the test performance, HSVM is the only diagnostic test in which ciliary dyskinesia can be directly visualised and the primary nature determined by reproducibility of an abnormal finding after culture in vitro,” they added.
Post-culture HSVM should be used when possible, due to its superiority to pre-culture analysis, and testing should only be performed in specialist centres.
The guidelines also strongly recommend using immunofluorescence staining, based on high certainty evidence, but again note that it should only be performed by experienced laboratories, due to batch-to-batch variability between antibodies and the importance of the choice and quality of the antibodies.
The authors also highlight that immunofluorescence can be particularly useful for patients with genetic variants of unknown significance, especially those associated with normal (or near normal) TEM results, such as pathogenic variants in DNAH11 or HYDIN.
“In the case of HYDIN, TEM may appear near normal while genetic analysis is often confounded by the pseudogene HYDIN2 [therefore, immunofluorescence] can show absent localisation of SPEF2 and aid in the diagnosis of PCD caused by pathogenic variants in HYDIN,” they note.
As such, immunofluorescence can enable clinicians to establish a precise genetic cause of disease and determine whether patients may be eligible for future precision therapies.
When to refer for diagonsis
The guidelines also discuss the clinical manifestations of PCD at various life stages that would warrant diagnostic testing, including bronchiectasis, infertility and congenital heart disease.
“It’s important to know that not every PCD patient will have all these symptoms, but if there is a constellation of symptoms in a patient then those patients should be referred for a diagnosis,” said Dr Horani, when presenting the guidelines at the ERS Congress.
“One can use the PICADAR [PrImary CiliARy DyskinesiA Rule] score or the ATS Leigh’s criteria to help decide which patients to send for diagnosis,” he added.
Additionally, the guidelines address other testing techniques that may be used in the future, as well as strategies for overcoming diagnostic challenges in resource-limited settings.
“The taskforce used a stringent methodological approach to put forth an international guideline which will allow a united diagnosis of PCD wherever in the world the patient presents,” the authors wrote.
“This will aid access to care and inclusion for future clinical trials,” they concluded.