Ciliary beating remains stable 9 hours after brushing, but is modified by storage temperature

Introduction Primary ciliary dyskinesia is a rare inherited heterogeneous motile ciliopathy in which respiratory cilia are stationary, or beat in a slow or dyskinetic manner, leading to impaired mucociliary clearance and significant otosinopulmonary disease. Ciliary beating can be evaluated using digital high-speed videomicroscopy (DHSV). However, given the lack of standard operating procedures, and as minor variations in DHSV protocols might influence ciliary beating, varying normal reference ranges are described between centers. We aimed to evaluate whether the delay after sampling, and the temperature for conservation of respiratory ciliated samples before videomicroscopy, might modify ciliary beating. Methods In all, 37 healthy nasal brushing samples of respiratory ciliated epithelium were collected. Video sequences were recorded immediately using DHSV at 37°C. For each subject, the samples were divided equally, and conserved either at 4°C or at room temperature (RT). Video sequences of ciliated beating edges conserved at 4°C and at RT were recorded 3hours (H3), then 9hours (H9) after sampling. Ciliary beating was assessed manually by ciliary beat frequency (CBF) and by the percentage of abnormal ciliary beat pattern (CBP). The evolution of each parameter with the storage time and the storage temperature was assessed using a linear mixed model. Results Of the 37 nasal brushing samples collected, 26 samples allowed a manual ciliary beating evaluation at H0, then after storage at both 4°C and at RT, at H3 and at H9 after sampling. The linear mixed model showed that, up to 9hours after sampling, CBF and the percentage of abnormal CBP were not significantly affected by the storage duration (P=0.54 and P=0.70) during 9hours after brushing, and that there was no interaction between the time and the storage temperature (CBF: P=0.44; the percentage of abnormal CBP: P=0.58).However, CBF was significantly higher when evaluated using samples stored at RT than in the fridge (P=0.041), but the percentage of abnormal CBP was not affected by the storage temperature (P=0.59). Conclusion Ciliary beating can be evaluated at 37°C within the first 9hours after nasal brushing. The storage temperature modifies ciliary beating, and this has to be considered when establishing normal reference values in a laboratory.