ABSTRACT
Background and Objective
Primary Ciliary Dyskinesia (PCD) is a genetic disorder associated with recurrent infections and irreversible airway damage. No single diagnostic test exists, necessitating use of a diagnostic algorithm that varies internationally. This retrospective study aimed to describe the clinical characteristics of patients, and algorithm used to diagnose PCD in New South Wales between 2014 and 2024.
Methods
A retrospective review of patients diagnosed with PCD at Concord Repatriation General Hospital (CRGH) from 2014 to 2024 was performed.
Results
This study included 52 patients with median age of diagnosis 7.0 years. The diagnostic algorithm consists of nasal nitric oxide (nNO) in patients > 5 years, and nasal brushings for high‐speed video microscopy (HSVMA), immunofluorescence (IF) and electron microscopy (EM). Whole exome sequencing is not routine and was performed in 33% of the cohort. The diagnosis was confirmed by a multidisciplinary team that considered the test results and clinical phenotype. Non‐diagnostic results occurred in 14% (nNO), 15% (HSVMA), 41% (IF) and 30% (EM) of patients eventually diagnosed with PCD or PCD “highly likely”. Cumulatively, 56% of patients had at least one non‐diagnostic result. Of the 17 patients who underwent whole exome sequencing with a PCD panel, 41% had diagnostic genetic results.
Conclusion
Ciliary studies continue to be the mainstay of PCD diagnosis at CRGH. Although genetic testing is not part of the CRGH diagnostic algorithm, the CRGH algorithm has similar diagnostic performance to the ERS and ATS guidelines.
Keywords: Australia, cilia, diagnosis, primary ciliary dyskinesia
1. Introduction
Primary Ciliary Dyskinesia (PCD) is an autosomal recessive disorder caused by a defect in any of the genes that determine the structure or function of motile cilia. Patients with PCD have impaired mucociliary clearance, resulting in a daily wet cough, recurrent respiratory infections and chronic inflammation, potentially leading to bronchiectasis. PCD was previously considered rare, with an estimated prevalence of 1 in 10,000 [1, 2]. However, a recent worldwide genetic database study showed that the prevalence is at least 1 in 7500 [3].
A combination of tests is used to diagnose PCD, including nasal nitric oxide (nNO), high‐speed video‐microscopy analysis (HSVMA) of ciliary beat frequency (CBF) and pattern (CBP), electron microscopy (EM), and immunofluorescence (IF). Although genetic testing is increasingly accessible, it remains expensive and commercial PCD panels do not include all potential pathogenic genes associated with PCD. The European Respiratory Society (ERS), in 2017, and the American Thoracic Society (ATS), in 2018, published diagnostic guidelines for PCD [2, 4]. These guidelines recommend different test combinations and sequences, creating conflicting diagnostic outcomes depending on which guideline is followed [5, 6]. In 2025, the ERS and ATS published unified diagnostic guidelines that, for the first time, formally evaluated nNO, HSVMA and IF using GRADE methodology and strongly recommended each as an adjunct to electron microscopy and/or genetics [7].
In New South Wales, PCD testing for all ages is undertaken at a single specialist centre, Concord Repatriation General Hospital (CRGH), using a combination of screening tests (clinical history and nNO) and ciliary studies (HSVMA, IF and EM). Clinical history is used to determine the PICADAR score, which predicts the probability that a patient will have PCD [5]. Outside of this specialist centre, access to PCD testing is limited to screening with nNO, which is available in some centres across the state.
Although international guidelines provide an important framework for the diagnosis of PCD, implementation must account for differences in healthcare settings, resource availability and geographic access. This paper provides an update on the presentation of patients with confirmed PCD in the years following the publication of the ERS and ATS guidelines, and how these guidelines have been adapted for use at a single testing centre in New South Wales, Australia.
This study aimed to describe the baseline clinical features of patients with confirmed PCD or PCD highly likely presenting to CRGH between 01/01/2014 and 30/06/2024, evaluate the rate of non‐diagnostic results across screening tests, ciliary studies and genetic testing, and compare the CRGH diagnostic algorithm with the ATS and ERS guidelines. It was hypothesised that baseline patient characteristics would remain similar to data published in 2014, despite improved availability of diagnostic tests and international guidelines. We also expected that many patients would have normal screening and ciliary studies results, and that genetic testing would not consistently yield diagnostic results. We also hypothesised that the CRGH multidisciplinary team (MDT) diagnostic algorithm would provide similar diagnostic outcomes as the ATS and ERS guidelines.
2. Materials and Methods
A retrospective review of all patients who were diagnosed with PCD by the CRGH PCD MDT following ciliary studies at CRGH between 2014 and 2024 was performed.
At CRGH, nNO is measured using the ECO Medics CLD 88 Exhilizer during exhalation against resistance as per the ATS and ERS guidelines [2, 4]. Nasal epithelial cells were collected using a cytology brush for ciliary studies. On EM, Class 1 defects are structural defects that are diagnostic for PCD and include absence of the outer dynein arm (ODA), absence of both the ODA and inner dynein arm (IDA), or absence of the IDA with microtubular disorganisation. Other defects such as central complex defects, mislocalisation of basal bodies, and microtubular disorganisation alone are Class 2 defects that are suggestive of PCD in patients with a strong clinical phenotype but are not diagnostic since these defects have been found in healthy control patients [8, 9].
The CRGH PCD MDT defines PCD positive as patients with typical symptoms of PCD and either a diagnostic Class 1 defect on EM, or biallelic pathogenic or likely pathogenic variants on genetic testing. Patients without a Class 1 defect but typical symptoms of PCD and a combination of other suggestive results, such as a low nNO level, abnormal HSVMA, abnormal IF and/or a Class 2 defect on EM are defined as PCD highly likely [2, 4, 9]. Patients who were deemed PCD positive or PCD highly likely by the CRGH PCD MDT are considered to have a diagnosis of PCD and were included in this study. Patients who were considered PCD highly unlikely (low clinical suspicion and normal ciliary studies) or PCD inconclusive (reasonable clinical suspicion of PCD but inconclusive diagnostic test results) were excluded.
Only patients with available data were included in each component of the analysis. Since nNO has not been validated in patients < 5 years old, these patients had their nNO results excluded from analysis [10]. Sputum or bronchoalveolar lavage (BAL) results collected within 6 months of diagnosis were used to identify organisms present at diagnosis. Whole exome sequencing (WES) results, where available, were included in the genetic analysis. WES data were analyzed using a PCD gene panel.
Spirometry data were adjusted using the ERS Global Lung Index (GLI) Calculator [11]. Ethnicity was not included as a variable.
Data were collected from medical records and ciliary study reports and managed using REDcap electronic data capture tools [12, 13]. Data collected included demographic information, clinical symptoms, screening test and ciliary studies results, imaging, microbiology results and documented treatments. Bronchiectasis was determined using High‐Resolution Computed Tomography (HRCT) scan results [14].
Statistics were performed using IBM SPSS Statistics 27 [15]. Figures were made using GraphPad Prism version 10.3.1 for Windows. Results are presented as median (range) unless otherwise stated.
Ethics for this study were approved by the Sydney Local Health District Human Research Ethics Committee (Reference no. 2019/STE09224). The project was conducted according to the principles of the NHMRC National Statement on Ethical Conduct in Human Research [16], which aligns with recognised international guidelines such as the Declaration of Helsinki. All participants in this study provided informed consent for their de‐identified data to be used for research purposes.
3. Results
3.1. Cohort Description
From 2014 to 2024, 52 patients (43 paediatric, 9 adults) were diagnosed with PCD at CRGH and included in this study. Twenty‐nine (56%) were PCD positive (27 paediatric, 2 adult) and 23 (44%) were PCD highly likely (16 paediatric, 7 adult). Six pairs of siblings were identified, with 3 pairs being children of consanguineous parents. In total, 20/52 patients (38%) had a family history of PCD and 9/35 patients (26%) had a history of consanguinity.
The median age of referral was 6.8 years (0.2–43.7 years) and median age of diagnosis was 7.0 years (0.2–43.7 years) (Figure 1a). The clinical features of the cohort are summarised in Table 1. The most common symptom was a chronic wet cough (100%), followed by chronic sputum production (98%) and chronic nasal symptoms (95%). Self‐reported hearing impairment was documented for 45% of patients. Bronchiectasis was confirmed on HRCT for 15/52 patients (29%). Only 25/43 children had a HRCT scan at diagnosis and of these children, 9/25 children (36%) had confirmed bronchiectasis.
Figure 1.
(a) Age at diagnosis of PCD for the study cohort. (b) PICADAR scores for the study cohort. (c) PICADAR score compared to age of diagnosis for the study cohort. PCD = primary ciliary dyskinesia. [Color figure can be viewed at wileyonlinelibrary.com]
Table 1.
Clinical history and features of the study cohort at diagnosis.
| Clinical Features | Paediatric | Adult | Total cohort |
|---|---|---|---|
| Age at referral | 3.4 (0.2–17.7) | 30.8 (20.0–43.7) | 6.8 (0.2–43.7) |
| Age at diagnosis | 3.6 (0.2–17.8) | 31.1 (20.0–43.7) | 7.0 (0.2–43.7) |
| Symptoms | |||
| Wet cough | 41/41 (100%) | 9/9 (100%) | 50/50 (100%) |
| Chronic nasal symptoms | 33/35 (94%) | 9/9 (100%) | 42/44 (95%) |
| Sputum production | 34/35 (97%) | 9/9 (100%) | 43/44 (98%) |
| Wheeze | 12/18 (67%) | 4/4 (100%) | 16/22 (73%) |
| Bronchiectasis | |||
| All patients | 9/43 (21%) | 6/9 (67%) | 15/52 (29%) |
| Patients with CT scan at diagnosis | 9/25 (36%) | 6/9 (67%) | 15/34 (44%) |
| Hearing impairment | 17/38 (45%) | 3/6 (50%) | 20/44 (45%) |
| Cardiovascular malformation | 2/37 (5%) | 1/8 (13%) | 3/45 (7%) |
| Fertility issues | — | 3/9 (33%) | 3/9 (33%) |
| Situs abnormality | 17/43 (40%) | 2/9 (22%) | 19/52 (37%) |
| Situs inversus totalis | 13/43 (30%) | 2/9 (22%) | 15/52 (29%) |
| Situs ambiguous | 2/43 (5%) | 0/9 (0%) | 2/52 (4%) |
| Isolated dextrocardia | 2/43 (5%) | 0/9 (0%) | 2/52 (4%) |
| Neonatal history | |||
| Neonatal respiratory distress | 27/40 (68%) | 6/7 (86%) | 33/47 (70%) |
| Admission to neonatal unit | 28/37 (76%) | 2/3 (67%) | 30/40 (75%) |
Note: Values are reported as median (range) or median (%). The denominator represents the number of patients with documented information or results available.
Abbreviation: PCD = primary ciliary dyskinesia.
Examination revealed abnormal auscultation in 17/45 patients (38%). All adult patients had either crackles or wheeze present, whereas 10/39 (26%) paediatric patients had crackles present, 1/39 (3%) had rhonchi, and 3/39 paediatric patients (8%) had wheeze.
Spirometry was performed in 22/29 patients (76%) within 3 months of diagnosis. Many of the paediatric patients were too young to undergo spirometry. In the paediatric cohort, median FEV1 z‐score was −1.22 and FEV1/FVC z‐score was 1.09. In the adult cohort, median FEV1 z‐score was −1.53 and median FEV1/FVC z‐score was −1.75.
A recent respiratory culture was available for 21/43 paediatric patients (49%) and 7/9 adult patients (78%). For the paediatric cohort, 18/21 (86%) were sputum samples, 2/21 (10%) were bronchoalveolar lavage samples and 1/21 (5%) was an oropharyngeal swab. Seven adult patients had sputum samples analysed. The most common pathogen was Haemophilus influenzae identified in 8/28 (29%) [6/21 paediatric (29%), 2/7 adult (29%)] followed by Pseudomonas aeruginosa in 4/28 patients (14%) [2/21 paediatric (10%), 2/7 adult (29%)].
Inhaled bronchodilators were used in 13/49 patients (27%) [7/40 paediatric (18%), 6/9 adult (67%)] and inhaled corticosteroids were used in 13/49 patients (27%) [9/40 paediatric (23%), 4/9 (44%) adult]. Nasal corticosteroids were used by 8/49 patients (16%) [5/40 paediatric (13%), 3/9 adult (33%)]. Physiotherapy was recommended for 44/48 patients with a documented physiotherapy consult (92%), with positive expiratory pressure devices prescribed most frequently for children, whereas active cycle of breathing was most common for adults. Macrolide antibiotics were the most frequently prescribed long‐term antibiotic class, whereas β‐lactams were most prescribed for acute exacerbations. Further detail is available in the supporting information.
3.2. PICADAR Score
All patients with a persistent cough had their PICADAR score calculated [1] (Figure 1b). The median score was 8 which corresponds to a pre‐test probability of 44.1% [1]. Scores ranged from 3 to 12. In this cohort, 5/52 patients (10%) had a score ≤ 5, 31/52 (60%) had a score 6–9, and 16/52 (31%) had a score ≥ 10. In total, 47/52 (90%) of patients had a PICADAR score above the recommended cut‐off score of 5 [1] (Figure 1c). This proportion increases to 39/43 (91%) in the paediatric cohort.
3.3. Nasal Nitric Oxide
Twenty‐nine patients underwent nNO using an ECO Medics CLD 88 Exhilizer. A cut‐off of 233 ppb on this device is equivalent to 77 nL/min recommended on alternative devices [17]. The median nNO was 90 ppb (8–400 ppb). Low nNO was detected in 25/29 patients (86%). Normal nNO (> 233 ppb) was detected in 4/29 patients (14%), 2 of whom were later deemed PCD positive (Figure 2).
Figure 2.
Nasal nitric oxide results at initial ciliary studies appointment for the study cohort. The dotted line reflects the normal reference range (> 233ppb). nNO = nasal nitric oxide, PCD = primary ciliary dyskinesia.
3.4. Ciliary Studies
Ciliary studies results, including HSVMA, IF and EM, are summarised in Table 2. All patients who were seen at CRGH after 2017 had IF performed. In total, 48 patients had samples sent for IF. For 23 patients, the IF panel included antibodies targeting DNAH5, DNALI1, GAS8 and RSPH4 only, and 20 patients had the addition of DNAH11, RSPH1, and RSPH9 to this panel based on the availability of these antibodies at the time of testing. The remaining five patients had insufficient samples with no ciliated cells present and therefore, the IF panel that was used was not documented. For 5/48 patients (10%), there was a normal staining pattern on IF, but a Class 1 defect was detected on EM. Conversely, 3/48 (6%) had IF staining patterns suggestive of an ultrastructural abnormality that would correlate with a Class 1 defect on EM but did not have a Class 1 defect identified on EM. Normal ciliary ultrastructure was seen on EM for 1/29 (3%) PCD‐positive patients.
Table 2.
Ciliary studies results for the study cohort.
| High‐speed video microscopy analysis | ||||
|---|---|---|---|---|
| Paediatric (n = 43) | Adult (n = 9) | Total (n = 52) | ||
| Ciliary Beat Frequency | ||||
| Median (Hz) | 1.4 | 3.0 | 1.8 | |
| Range (Hz) | 0.0−18.1 | 0.0−6.3 | 0.0−18.1 | |
| Reduced (<7 Hz) | 34 (79%) | 9 (100%) | 43 (83%) | |
| Increased (>10 Hz) | 2 (5%) | 0 (0%) | 2 (4%) | |
| Normal (7–10 Hz) | 7 (16%) | 0 (0%) | 7 (13%) | |
| Ciliary Beat Pattern | ||||
| Immotile | 20 (47%) | 3 (33%) | 23 (44%) | |
| Stiff | 6 (14%) | 2 (22%) | 8 (15%) | |
| Strongly reduced activity | 10 (23%) | 2 (22%) | 12 (23%) | |
| Uncoordinated beating | 1 (2%) | 0 (0%) | 1 (2%) | |
| Hyperkinetic | 1 (2%) | 0 (0%) | 1 (2%) | |
| Rotating | 0 (0%) | 1 (11%) | 1 (2%) | |
| Other | 3 (7%) | 1 (11%) | 4 (8%) | |
| Normal | 3 (7%) | 0 (0%) | 3 (6%) | |
| Immunofluorescence Results | ||||
|---|---|---|---|---|
| Target Structure | Absent antibody stain | Paediatric | Adult | Total (n = 48) |
| ODA | DNAH5 | 15/33 (45%) | 3/9 (33%) | 18/42 (43%) |
| DNAH11 | 3/9 (33%) | 1/2 (50%) | 4/11 (36%) | |
| IDA | DNALI1 | 3/33 (9%) (+ 1 patient with partial staining) | 0/9 (0%) | 3/42 (7%) (+ 1 patient with partial staining) |
| N‐DRC | GAS8 | 1/34 (3%) (+ 2 patients with partial staining) | 1/9 (11%) | 2/43 (5%) (+ 2 patients with partial staining) |
| RS | RSPH1 | 1/13 (8%) | 1/3 (33%) | 2/16 (13%) |
| RSPH4 | 0/34 (0%) | 1/7 (14%) | 1/41 (2%) | |
| RSPH9 | 0/13 (0%) | 1/4 (25%) | 1/17 (6%) | |
| Insufficient sample | 12/39 (31%) | 2/9 (22%) | 14/48 (29%) | |
| Normal staining pattern | 11/39 (28%) | 3/9 (33%) | 14/48 (29%) | |
| Electron Microscopy Results | ||||
|---|---|---|---|---|
| Paediatric (n = 43) | Adult (n = 9) | Total (n = 52) | ||
| Class 1 defects | ODA defect | 14 (33%) | 1 (11%) | 15 (29%) |
| ODA + IDA defect | 6 (14%) | 1 (11%) | 7 (13%) | |
| IDA defect + microtubular disorganisation | 1 (2%) | 0 (0%) | 1 (2%) | |
| Class 2 defects | Central complex defect | 0 (0%) | 2 (22%) | 2 (4%) |
| Microtubular disorganisation + central complex abnormalities | 1 (2%) | 1 (11%) | 2 (4%) | |
| Partial ODA defect | 1 (2%) | 0 (0%) | 1 (2%) | |
| Insufficient sample | 10 (23%) | 2 (22%) | 12 (23%) | |
| Normal ciliary ultrastructure | 10 (23%) | 2 (22%) | 12 (23%) | |
Abbreviations: Hz = hertz; ODA = outer dynein arm; IDA = inner dynein arm; N‐DRC = nexin–dynein regulatory complex; RS = radial spokes
3.5. Genetic Testing
All patients who had genetic testing performed were in the paediatric age range. Of the 23 patients who had genetic testing performed, 17 underwent whole exome sequencing that was analysed using a PCD gene panel and were included in the genetics analysis. Patients who underwent alternative genetic testing modalities were excluded from this analysis, including one patient who underwent Sanger sequencing, one patient who had a chromosome microarray and four patients whose type of genetic testing was undocumented. Table 3 summarises the genetic testing results.
Table 3.
Genetic testing results for the study cohort. biallelic variants reflect patients who had genetic testing results consistent with a diagnosis of PCD.
| Genetics Results | Number of Patients (n = 17) | % of patients |
|---|---|---|
| Biallelic variants ‐ diagnostic of PCD | 7 | 41% |
| Homozygous variants | 5 | 29% |
| CCNO | 4 | 23% |
| CCDC103 | 1 | 6% |
| Compound heterozygous variants | 2 | 12% |
| CCDC40 | 1 | 6% |
| DNAH5 | 1 | 6% |
| Other variants | 8 | 47% |
| Pathogenic or likely pathogenic variant and VOUS | 5 | 29% |
| DNAH5 | 3 | 18% |
| DNAAF1 | 1 | 6% |
| LRRC56 | 1 | 6% |
| Biallelic VOUS | 1 | 6% |
| DNAH11 | 1 | 6% |
| Single heterozygous variant | 2 | 18% |
| GAS8 | 1 | 6% |
| SPAG1 | 1 | 6% |
| No pathogenic variants | 2 | 12% |
Abbreviation: VOUS = variant of unknown significance.
3.6. Rate of Non‐Diagnostic Test Results
Although all 52 patients in this cohort are considered to have confirmed PCD, no test yielded diagnostic results in every instance it was performed. The tests with the lowest rates of non‐diagnostic test results were nNO and HSVMA and were considered better performing. Normal nNO (nNO > 233 ppb) was detected in only 4/29 patients (14%) and normal CBF or CBP was seen in 8/52 patients (15%). In contrast, 28/48 patients (58%) had inconclusive IF and 24/52 patients (46%) had inconclusive EM. However, half of these inconclusive results for IF and EM were due to insufficient sampling. Excluding patients with insufficient sampling, IF yielded the highest rate of non‐diagnostic test results of all tests conducted at CRGH at 14/34 (41%), followed by EM at 12/40 (30%). Genetic testing did not detect diagnostic biallelic pathogenic variants for 10/17 patients (59%). A pathogenic variant and a VOUS or biallelic VOUS were detected for 6/17 patients (35%). In total, 29/52 patients (56%) had at least one non‐diagnostic test result.
4. Diagnostic Algorithm
The diagnostic algorithm at CRGH starts with screening tests, with the clinical history scored using the PICADAR score, and nNO performed in patients > 5 years. Patients then undergo ciliary brushing for HSVMA, IF and EM. Test results are discussed during an MDT meeting involving clinicians and pathologists where the patient's diagnostic status is determined.
Genetic testing is not a routine part of the CRGH diagnostic algorithm. Genetic testing was completed prior to ciliary studies or after an inconclusive ciliary studies result, depending on the discretion of the treating clinician and the availability of testing. Genetic testing was performed prior to ciliary studies for 12 patients, of whom 4/12 (33%) had diagnostic biallelic pathogenic variants, and 5/12 (42%) had a pathogenic variant and a VOUS. Of the remaining 3 patients who had inconclusive genetic testing results, 2 remained as PCD highly likely following ciliary studies, whereas 1 patient had a Class 1 defect identified on EM and was confirmed as PCD positive. Of the 5 patients who had genetic testing after ciliary studies, 2 had been confirmed as PCD positive from their ciliary studies, 2 had insufficient sampling for ciliary studies, and 1 had a Class 2 defect on EM. Genetic testing allowed for a diagnosis of PCD positive to be made for 2/3 patients with inconclusive EM results, both of whom had mutations in the CCNO gene. Genetic testing confirmed the diagnosis for 1 patient with diagnostic ciliary studies. In total, for the group who had genetic testing after ciliary studies, 3/5 had diagnostic genetic testing results, 1/5 was compound heterozygous with a VOUS, and 1/5 had a single heterozygous variant. Combining both groups, 7/17 (41%) of patients who underwent WES with a PCD gene panel had a diagnostic genetic result: 4/12 (33%) of those tested prior to ciliary studies and 3/5 (60%) of those tested after ciliary studies.
All patients deemed PCD positive using the CRGH algorithm are also considered PCD positive when using the ATS and ERS guidelines (Table 4). Using the ATS guidelines, an additional 15/23 (65%) PCD highly likely patients would be classified as PCD positive instead of PCD highly likely, deeming 44/52 patients in the CRGH cohort (85%) PCD positive. The remaining 8/52 (15%) would be classified PCD “still possible” [4]. Under the ERS guidelines, 7/23 (30%) PCD highly likely patients would be recommended to have further testing such as radioaerosol mucociliary clearance [2], and so for the purposes of this analysis are termed PCD uncertain. Since patients who are classified as PCD positive or PCD highly likely are considered to have a PCD diagnosis, a total of 45/52 patients (87%) would be diagnosed with PCD using the ERS guidelines.
Table 4.
Comparison of the diagnostic outcomes when using the 2024 CRGH PCD diagnostic algorithm and the ATS or ERS diagnostic guidelines.
| CRGH algorithm | Total | |||
|---|---|---|---|---|
| PCD positive | PCD highly likely | |||
| ATS guidelines | PCD positive | 29 | 15 | 44 |
| PCD still possible | 0 | 8 | 8 | |
| Total | 29 | 23 | 52 | |
| ERS guidelines | PCD positive | 29 | 0 | 29 |
| PCD highly likely | 0 | 16 | 16 | |
| PCD uncertain | 0 | 7 | 7 | |
| Total | 29 | 23 | 52 | |
Abbreviations: ATS = American Thoracic Society, CRGH = Concord Repatriation General Hospital, ERS = European Respiratory Society, PCD = Primary Ciliary Dyskinesia.
5. Discussion
Diagnosing PCD remains a significant challenge since the condition is rare, presents with non‐specific symptoms and diagnosis requires access to highly specialised testing that demands technical expertise and interpretative experience. Appropriate screening tests should be performed prior to referral to avoid overwhelming the limited resources of specialised centres providing this service. Despite a high clinical suspicion of PCD in this cohort, who were screened with the PICADAR score prior to undergoing testing, 44% of patients still could not be definitively diagnosed as PCD positive.
With increasing awareness of PCD and the availability of diagnostic guidelines, the median age of referral and of diagnosis in the paediatric cohort has fallen since 2014 from 5.5 to 3.4 years, and from 6.4 to 3.6 years, respectively [18]. Despite this earlier recognition, 36% of children who had a baseline HRCT still had radiographically confirmed bronchiectasis at diagnosis. In patients diagnosed in adulthood, 67% had bronchiectasis at diagnosis, emphasising the importance of early diagnosis in childhood for early intervention and prevention of complications.
The CRGH algorithm had similar diagnostic performance as the ERS and ATS guidelines, with 87% and 85% of this cohort diagnosed with PCD under the ERS and ATS guidelines, respectively. The CRGH MDT approach of interpreting nNO, ciliary studies and genetic testing against clinical pre‐test probability is consistent with the 2025 unified guideline, emphasising that no single test can confirm or exclude PCD and that pre‐test probability should guide interpretation [7]. Incorporating pre‐test probability in the diagnostic pathway ensures that resource‐intensive investigations are reserved for those who will most likely benefit to ensure equitable access to specialised testing.
The PICADAR score serves as an effective tool to triage patients. In this cohort, 90% of patients had a PICADAR score > 5, which is consistent with data that shows a PICADAR score > 5 has 90% sensitivity and 75% specificity for PCD‐positive patients [1]. Given that CRGH is the only PCD testing facility in New South Wales, the PICADAR score is a simple and cost‐effective tool for clinicians outside of specialist centres that can identify patients with a high pre‐test probability of PCD and facilitate earlier diagnosis and intervention.
In this cohort, nNO and HSVMA had the lowest rates of non‐diagnostic results. Only 14% of patients had a normal nNO, supporting the use of nNO as a first‐line screening test in patients with a strong clinical phenotype in centres where nNO is accessible [7]. Using nNO as an initial screening tool can lead to a more resource‐efficient diagnostic pathway to ensure that patients with a low nNO result can be prioritised for further investigation. The 2025 unified ERS/ATS guideline now gives a strong recommendation (high certainty of evidence) for IF as an adjunct diagnostic test [7], consistent with our practice at CRGH of using IF because it is cheaper and faster than EM [19]. In this cohort, IF identified absent staining in 6% of patients who had inconclusive EM results, allowing them to be classified as PCD‐highly likely. However, IF was normal in 41% of patients who were PCD highly likely or PCD positive and had adequate sampling, which is higher than the previously reported rate of 31% [20]. This is likely due to differences in the panels of antibodies used and panel availability between centres.
The ATS guidelines suggest using genetic testing rather than EM in patients with a strong clinical phenotype, whereas the ERS guidelines strongly recommend including EM as part of the diagnostic process [2, 4]. In the CRGH cohort, 46% of patients had inconclusive EM results. Genetic testing provided diagnostic results for 2/3 patients who had inconclusive ciliary studies. Both patients had mutations in the CCNO gene and available literature indicates that CCNO may play a key role in ciliogenesis [21], which may account for the difficulties in obtaining sufficient samples for ciliary studies in these patients, consistent with prior reports [22]. This highlights the importance of using a combination of tests during the diagnostic process for PCD. When only considering adequate sampling, 30% of patients had normal EM results, consistent with reports that up to 30% of patients with PCD will have no significant ciliary ultrastructural defect [18], and confirming that EM should not be used as a standalone diagnostic test.
Since genetic testing is not routine at CRGH, diagnostic yield is difficult to interpret. Overall, 41% of patients who underwent WES with a PCD panel had diagnostic results. For the patients who had genetic testing as a first‐line investigation prior to ciliary studies, 33% had a diagnostic genetic test result of biallelic pathogenic variants. Among those testing after ciliary studies, 60% had diagnostic genetic studies. This may reflect clinical pre‐selection of patients who are known to have abnormal ciliary studies and therefore, considered highly likely to have PCD. A VOUS accounted for 35% of inconclusive genetic testing results. As further research into the underlying genetic variants that cause PCD is conducted, these patients’ VOUS have the potential to be reclassified as PCD‐causing variants. There may also be further PCD‐associated genes that are yet to be identified that were not included in the PCD gene panel, suggesting a potential for greater diagnostic yield of genetic testing in the future. Given the cost and limited access to genetic testing at CRGH, prioritising testing for patients with a positive screening result, such as a low nNO, in addition to a high clinical suspicion, may offer a more resource‐efficient pathway in future.
In summary, although PCD is being diagnosed earlier in life, it remains difficult to diagnose as individual tests are frequently normal in the setting of PCD. As more PCD‐causing genes are identified, genetic testing may play a greater role in diagnosis in the future, however, a combination of nNO, ciliary studies and genetic tests remain crucial to the diagnostic process. The CRGH algorithm is a local and cost‐effective adaptation of the ERS and ATS guidelines that provides similar diagnostic yield. Given the significant resources required to conduct ciliary studies, the PICADAR score has ongoing utility as an easily accessible screening test to identify patients who should be referred for PCD diagnostic services. Later diagnosis is associated with greater incidence of bronchiectasis and as such, clinicians should screen for and aim to diagnose PCD during early childhood.
Author Contributions
Michelle Cai: formal analysis, data curation, writing – original draft, writing – review and editing. Megan Frohlich: data curation, formal analysis, supervision, writing – review and editing, conceptualisation. Louisa Owens: writing – review and editing. Kate Hardaker: data curation, writing – review and editing. Dominic A Fitzgerald: writing – review and editing, conceptualisation. Raewyn Campbell: writing – review and editing. Bernadette Prentice: conceptualisation, supervision, writing – review and editing, formal analysis. Lucy Morgan: conceptualisation, supervision, writing – review and editing, formal analysis, data curation.
Ethics Statement
Ethics for this study were approved by the Sydney Local Health District Human Research Ethics Committee (Reference no. 2019/STE09224).
Conflicts of Interest
M.F. served as a board member for PCD Australia from 2022 to 2025. DF serves as the Editor‐in‐Chief of Paediatric Respiratory Reviews. L.M. has received consulting fees from GSK, Pfizer, reCODE Therapeutics, Sanofi, and Chiesi. L.M. has also received payment from Boehringer Ingelheim for education events and serves as the Chair of Lung Foundation Australia. All other authors have no conflicts of interest to report.
Supporting information
Supporting File 1
Supporting File 2
Acknowledgments
B.P. is funded by the Sydney Children's Hospitals Network Kids Research Clinician Researcher fellowship, funded by Sydney Children's Hospitals Foundation. Open access publishing facilitated by University of New South Wales, as part of the Wiley ‐ University of New South Wales agreement via the Council of Australasian University Librarians.
Cai M., Frohlich M., Owens L., et al., “Making the diagnosis of Primary Ciliary Dyskinesia in Australia,” Pediatric Pulmonology 61 (2026): e71863. 10.1002/ppul.71863.
Bernadette Prentice and Lucy Morgan contributed equally to this work.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
References
- 1. Behan L., Dimitrov B. D., Kuehni C. E., et al., “Picadar: A Diagnostic Predictive Tool for Primary Ciliary Dyskinesia,” European Respiratory Journal 47, no. 4 (2016): 1103–1112, 10.1183/13993003.01551-2015. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Lucas J. S., Barbato A., Collins S. A., et al., “European Respiratory Society Guidelines for the Diagnosis of Primary Ciliary Dyskinesia,” European Respiratory Journal 49, no. 1 (2017): 1601090, 10.1183/13993003.01090-2016. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Hannah W. B., Seifert B. A., Truty R., et al., “The Global Prevalence and Ethnic Heterogeneity of Primary Ciliary Dyskinesia Gene Variants: A Genetic Database Analysis,” Lancet Respiratory Medicine 10, no. 5 (2022): 459–468, 10.1016/S2213-2600(21)00453-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Shapiro A. J., Davis S. D., Polineni D., et al., “Diagnosis of Primary Ciliary Dyskinesia. An Official American Thoracic Society Clinical Practice Guideline,” American Journal of Respiratory and Critical Care Medicine 197, no. 12 (2018): e24–e39, 10.1164/rccm.201805-0819ST. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Nussbaumer M., Kieninger E., Tschanz S. A., et al., “Diagnosis of Primary Ciliary Dyskinesia: Discrepancy According to Different Algorithms,” ERJ Open Research 7, no. 4 (2021): 00353‐2021, 10.1183/23120541.00353-2021. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6. Shoemark A., Dell S., Shapiro A., and Lucas J. S., “Ers and Ats Diagnostic Guidelines for Primary Ciliary Dyskinesia: Similarities and Differences in Approach to Diagnosis,” European Respiratory Journal 54, no. 3 (2019): 1901066, 10.1183/13993003.01066-2019. [DOI] [PubMed] [Google Scholar]
- 7. Shoemark A., Goutaki M., Kinghorn B., et al., “European Respiratory Society and American Thoracic Society Guidelines for the Diagnosis of Primary Ciliary Dyskinesia,” European Respiratory Journal 66 (2025): 2500745, in press 10.1183/13993003.00745-2025. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8. Brennan S. K., Ferkol T. W., and Davis S. D., “Emerging Genotype‐Phenotype Relationships in Primary Ciliary Dyskinesia,” International Journal of Molecular Sciences 22, no. 15 (2021): 8272, 10.3390/ijms22158272. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9. Shoemark A., Boon M., Brochhausen C., et al., “International Consensus Guideline for Reporting Transmission Electron Microscopy Results in the Diagnosis of Primary Ciliary Dyskinesia (Beat PCD Tem Criteria),” European Respiratory Journal 55, no. 4 (2020): 1900725, 10.1183/13993003.00725-2019. [DOI] [PubMed] [Google Scholar]
- 10. Paternò S., Pisani L., Zanconato S., Ferraro V. A., and Carraro S., “Role of Nasal Nitric Oxide in Primary Ciliary Dyskinesia and Other Respiratory Conditions in Children,” International Journal of Molecular Sciences 24, no. 22 (2023): 16159, 10.3390/ijms242216159. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11. European Respiratory Society. Gli Lung Function Calculator. 2021. [Google Scholar]
- 12. Harris P. A., Taylor R., Minor B. L., et al., “The Redcap Consortium: Building An International Community of Software Platform Partners,” Journal of Biomedical Informatics 95 (2019): 103208, 10.1016/j.jbi.2019.103208. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13. Harris P. A., Taylor R., Thielke R., Payne J., Gonzalez N., and Conde J. G., “Research Electronic Data Capture (Redcap)—A Metadata‐Driven Methodology and Workflow Process for Providing Translational Research Informatics Support,” Journal of Biomedical Informatics 42, no. 2 (2009): 377–381, 10.1016/j.jbi.2008.08.010. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14. Choi H., McShane P. J., Aliberti S., and Chalmers J. D., “Bronchiectasis Management in Adults: State of the Art and Future Directions,” European Respiratory Journal 63, no. 6 (2024): 2400518, 10.1183/13993003.00518-2024. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Corp. I. IBM SPSS Statistics for Windows, version 27.0. Armonk, NY: IBM Corp. 2020.
- 16.National Health and Medical Research Council, Australian Research Council and Universities Australia. National Statement on Ethical Conduct in Human Research. National Health and Medical Research Council, editor.; 2023. [Google Scholar]
- 17. Collins S. A., Gove K., Walker W., and Lucas J. S. A., “Nasal Nitric Oxide Screening for Primary Ciliary Dyskinesia: Systematic Review and Meta‐Analysis,” European Respiratory Journal 44, no. 6 (2014): 1589–1599, 10.1183/09031936.00088614. [DOI] [PubMed] [Google Scholar]
- 18. Hosie P. H., Fitzgerald D. A., Jaffe A., Birman C. S., Rutland J., and Morgan L. C., “Presentation of Primary Ciliary Dyskinesia in Children: 30 Years’ Experience,” Journal of Paediatrics and Child Health 51, no. 7 (2015): 722–726, 10.1111/jpc.12791. [DOI] [PubMed] [Google Scholar]
- 19. Rumman N., Jackson C., Collins S., Goggin P., Coles J., and Lucas J. S., “Diagnosis of Primary Ciliary Dyskinesia: Potential Options for Resource‐Limited Countries,” European Respiratory Review 26, no. 143 (2017): 160058, 10.1183/16000617.0058-2016. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Baz‐Redón N., Rovira‐Amigo S., Camats‐Tarruella N., et al., “Papel De La Inmunofluorescencia y el Diagnóstico Molecular en la Caracterización de la Discinesia Ciliar Primaria,” Archivos de Bronconeumología 55, no. 8 (2019): 439–441, 10.1016/j.arbr.2019.01.007. [DOI] [PubMed] [Google Scholar]
- 21. Wang L., Gao L., Chen Y., and Xu B., “Transcriptional Regulation of CCNO During the Formation of Multiple Motile Cilia,” Biochemical and Biophysical Research Communications 735 (2024): 150428, 10.1016/j.bbrc.2024.150428. [DOI] [PubMed] [Google Scholar]
- 22. Henriques A. R., Constant C., Descalço A., et al., “Primary Ciliary Dyskinesia Due to Ccno Mutations—A Genotype‐Phenotype Correlation Contribution,” Pediatric Pulmonology 56, no. 8 (2021): 2776–2779, 10.1002/ppul.25440. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supporting File 1
Supporting File 2
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.