Title: Accuracy of high-speed video microscopy analysis to diagnose primary ciliary dyskinesia
Funder: Department of Health and Social Care

Abstract: Primary ciliary dyskinesia (PCD) is a rare heterogeneous genetic disorder characterised by impaired mucociliary clearance due to abnormal ciliary function. It affects upper and lower airways, paranasal sinuses, ears and reproductive tract. Motile embryonic nodal cilia establish right-left symmetry, with approximately 50% of PCD patients having situs inversus with or without associated complex congenital cardiac defects. Prevalence is estimated to be 1:10,000, reflecting a significant burden for approximately 6,400 UK citizens. Recurrent lung and middle ear infections can lead to bronchiectasis, significant decline in lung function and permanent hearing loss. Studies suggest that early diagnosis and initiation of treatment can limit disease progression, particularly in infants and young children who are susceptible to irreversible lung damage after a single episode of lower tract respiratory infection. There is no single gold standard diagnostic test for PCD. NHS England commissioned three highly specialised PCD Diagnostic Centres that follow consensus guidelines on PCD diagnostics, using a combination of diagnostic tests. Of these, high-speed video microscopy analysis (HSVMA) is the only diagnostic test to examine ciliary function, which is impaired in all PCD patients. It is done on the day the patients attend clinics and results are readily available. In the absence of evidence that HSVMA is accurate and has good intra-observer reliability, the current diagnostic pathway requires additional tests to be performed before initiation of treatment. Transmission electron microscopy (TEM), one of the recommended tests, requires specialised technicians and is time-consuming, with test results taking up to 3 months to become available. Additionally, TEM assesses ultrastructural ciliary defects, which recent studies have suggested to be normal in 20-30% of patients with PCD. There is limited data available on the accuracy of HSVMA to diagnose PCD. A systematic review conducted by the European Respiratory Society Task Force on PCD diagnostic testing identified two studies that evaluated HSVMA, both of which reported high sensitivity (96-100%) and specificity (93-95%). However, both had risk of bias because of unblinded analyses and small samples sizes. We aim to conduct a systematic, blinded and powered study to determine the accuracy of HSVMA to diagnose PCD. Scientists blinded to clinical information, previous test results, and diagnostic outcome will assess and classify archived video-images from HSVMA from anonymised samples of patients seen at the three UK PCD specialist diagnostic centres. Patients have provided consent to the use of their data for research purposes. Experienced HSV-scientists will classify study samples as positive, negative or inconclusive. We will compare these study outcomes to the original outcomes from multidisciplinary team meetings, which were based on clinical information and combination testing. We will then calculate the sensitivity and specificity for each scientist s assessment. If HSVMA was sufficiently accurate (i.e. >90% sensitive and specific), we will recommend its use by experienced HSV-scientists as a stand-alone test to guide early initiation of treatment. This study can provide the necessary evidence-base to immediately amend the current NHS diagnostic pathway for PCD, with a direct impact in patient care. If found to be sufficiently accurate, HSVMA results can guide early diagnosis and initiation of treatment. Immediate implementation of findings is possible and highly likely as all three UK PCD Diagnostic Centres will participate in this study and already use HSVMA on a daily basis, demonstrating a clear pathway to impact.

Lay abstract: Primary ciliary dyskinesia (PCD) is an inherited disease, affecting approximately 1 in 10,000 people. Tiny hair-like structures called cilia move in a sweeping motion in the airways to remove mucus and bacteria. In people with PCD the cilia do not move normally leading to frequent chest, ear and sinus infections from birth. If diagnosed late, patients can develop permanent lung damage and hearing loss. The NHS PCD diagnostic service investigates over 750 patients annually. A combination of specialised tests are required to diagnose PCD and results can take up to 3 months. However, results of a test called high-speed video microscopy analysis (HSVMA) are available on the day the patient attends clinic. This test records movement of the cilia and is done routinely in PCD centres for all patients suspected of having PCD. The problem is that we do not know how accurately this test can diagnose PCD on its own so additional tests are done to confirm the diagnosis, which can delay the patient getting appropriate treatment. Focus groups and surveys with PCD representatives have prioritised research for earlier and accurate diagnosis, to help patients obtain the correct treatment as soon as possible as well as removing the worry of having to wait for the diagnosis. In this study, scientists will independently review video images previously recorded from patients seen at PCD Diagnostic Centres and determine whether the patient has PCD. We will compare the diagnosis by scientists to the original diagnosis (originally based on a combination of tests available at the time) and calculate the accuracy of HSVMA (i.e. how well it performed). If we can demonstrate that HSVMA can correctly identify patients with PCD with no additional tests then treatment can start on the same day. This will potentially shorten the time to diagnosis by 3 months.

Research activity codes: 4.2 EVALUATION OF MARKERS AND TECHNOLOGIES
Health categories: CONGENITAL DISORDERS