Riley Children’s Health has developed advanced capabilities for performing both high-speed video microscopy (HSVM) and immunofluorescence microscopy (IFM) to complement current technologies in diagnosing primary ciliary dyskinesia (PCD). A pulmonology research team at Riley Children’s is using these advanced diagnostic tools as part of a leading-edge research program in the United States to clinically validate other methods for diagnosing PCD.
Helping to achieve earlier and more accurate diagnoses, HSVM and IFM can augment the standard methods for PCD diagnosis such as genetic testing, which have limitations (particularly false negative tests). HSVM and IFM also help substantiate nasal nitric oxide measurement, widely used to diagnose PCD but not yet an approved test.
“In about one-third of patients where PCD has been proven through genetic testing, the electron microscopy is normal, and conversely, when electron microscopy is abnormal, PCD is ruled out through genetic testing in about a third of those cases as well,” said Benjamin Gaston, MD, pediatric pulmonologist at Riley Children’s and Billie Lou Wood Professor of Pediatrics at Indiana University School of Medicine.
While genetic diagnosis of PCD is becoming more common, it won’t be fully reliable until more genes and variants with ties to PCD are identified. Dr. Gaston said that while researchers have linked more than 50 proteins and the genes encoding them to primary ciliary dysfunction, there are likely many more that play a role.
“If genetic testing proves PCD, then you have a diagnosis,” Dr. Gaston explained. “However, we’re finding that in up to 30% of patients undergoing genetic testing for PCD, the testing is negative or ambiguous, and that can be where high-speed video microscopy is helpful.”
Using a specialized microscope, HSVM examines the entire ciliary beat waveform, focusing on how the cilia move. The instrument enables views of the cilia from different angles and by adjusting the video speed, clinicians can look for any dysfunctional properties as the cilia beat.
“The high-speed video allows us to analyze the ciliary motion, looking at how the cilia beat and measuring how fast,” said Michael Davis, PhD, RRT, associate research professor of pediatrics, who has trained with some of the world’s leading HSVM experts in the United Kingdom. “We may notice some dysfunction that causes only the top of the cilia to beat, or there’s swirling instead of a smooth beating motion—or even that the cilia appear to be structurally correct, but they’re not beating at all.”
Much like HSVM, IFM is a complementary method for diagnosing PCD. Using antibodies, IFM reveals proteins that are absent from the cilia’s axial filament. While not useful as a standalone test for diagnosing PCD, IFM contributes evidence to develop a more complete diagnostic picture of a patient’s condition.
The Gaston Laboratory at Riley Children’s and IU School of Medicine began using IFM in late 2022 and validated HSVM for some preliminary clinical applications in May 2023. In addition to analyzing ciliary motion with HSVM in real time through brush biopsy, the team extends its studies to cell culture. Headquartered at Riley Children’s, the Gaston lab’s multicenter Primary Human Airway Cell Culture Core has a higher than 80% success rate with PCD cell cultures.
In January 2024, Drs. Gaston and Davis presented some of their early results at the PCD On the Move International Scientific Conference in Puerto Rico. The potential for HSVM and IFM to contribute to more accurate PCD diagnoses has generated interest nationally, particularly since data published by Dr. Gaston in The Lancet Respiratory Medicine showed that PCD is more common than previously thought.
“The calculations are that we’re likely looking at thousands of patients nationwide for whom a PCD diagnosis has been missed or not thought of,” Dr. Gaston said. “With high-speed and immunofluorescence, it’s really about taking PCD care to the next level. We had the flexibility and resources to put this program in place at Riley, and we’re pleased to be able to offer it and to collaborate with other centers across the nation.”
Riley Children’s Health is a worldwide leader in PCD research and treatment. A regional referral center for PCD, Riley Children’s is a member of the PCD Foundation Clinical and Research Centers Network.