Diagnostic yield of nasal scrape biopsies in primary ciliary dyskinesia: A multicenter experience

Abstract

Summary Examination of ciliary ultrastructure remains the cornerstone diagnostic test for primary ciliary dyskinesia (PCD), a disease of abnormal ciliary structure and/or function. Obtaining a biopsy with sufficient interpretable cilia and producing quality transmission electron micrographs (TEM) is challenging. Methods for processing tissues for optimal preservation of axonemal structures are not standardized. This study describes our experience using a standard operating procedure (SOP) for collecting nasal scrape biopsies and processing TEMs in a centralized laboratory. We enrolled patients with suspected PCD at research sites of the Genetic Disorders of Mucociliary Clearance Consortium. Biopsies were performed according to a SOP whereby curettes were used to scrape the inferior surface of the inferior turbinate, with samples placed in fixative. Specimens were shipped to a central laboratory where TEMs were prepared and blindly reviewed. 448 specimens were obtained from 107 young children (0–5 years), 189 older children (5–18 years), and 152 adults (> 18 years), and 88% were adequate for formal interpretation. The proportion of adequate specimens was higher in adults than in children. 50% of the adequate TEMs showed normal ciliary ultrastructure, 39% showed hallmark ultrastructural changes of PCD, and 11% had indeterminate findings. Among specimens without clearly normal ultrastructure, 72% had defects of the outer and/or inner dynein arms, while 7% had central apparatus defects with or without inner dynein arm defects. In summary, nasal scrape biopsies can be performed in the outpatient setting and yield interpretable samples, when performed by individuals with adequate training and experience according to an SOP.

Clinical Features of Childhood Primary Ciliary Dyskinesia by Genotype and Ultrastructural Phenotype

“…We expect that other genotype-phenotype relationships will be identified in PCD, which will more fully define the influence of specific genetic defects on lung disease. PCD has classically been difficult to diagnose because of technical challenges associated with electron microscopy and video microscopy; patients often have to be evaluated at specialty centers to confirm the diagnosis (41). Genetic testing offers the benefit of not only confirming diagnosis, but also, as demonstrated in this study may contribute to prognosis.…”

Primary Ciliary Dyskinesia. Recent Advances in Diagnostics, Genetics, and Characterization of Clinical Disease

“…A few patients are reported to have absence of cilia on multiple biopsies, suggesting ciliary aplasia, but this finding is difficult to prove, as no genetic etiology has been identified for these patients. Transmission EM testing of cilia has additional limitations, due to challenges in obtaining adequate specimens, technical factors in processing specimens, and interpretation of images (9,62). This perspective was highlighted by the experience in our rare disease consortium, where as many as 15-20% of the patients referred with a "confirmed" diagnosis of PCD (based on ciliary ultrastructure) had a false-positive diagnosis of PCD.…”

“…Many EM cross-sections (at least 30 sections containing .60 highquality cilia images is desirable) should be examined by experienced readers, and a quantitative approach to interpretation is critical, because ciliary EMs from normal subjects may have only seven or eight visible ODAs, and only three visible IDAs, per cilium (9,63). EM analysis is more feasible in biopsies from adults versus children, likely due to the technical challenges of obtaining adequate "scrape" biopsies from narrow airways (10,62). Acquired (secondary) ciliary defects result from airway damage from recurrent infections, and can sometimes be difficult to differentiate from PCD.…”

Clinical Features and Associated Likelihood of Primary Ciliary Dyskinesia in Children and Adolescents

“…Ciliated epithelial cells were collected from the inferior surface of the inferior nasal turbinates and processed for transmission electron microscopy, as previously described (4,6,18). Three reviewers evaluated transmission electron micrographs in a blinded fashion for PCD-specific ciliary defects, specifically (1) absent or truncated outer dynein arms alone, (2) absent outer and inner dynein arms, (3) absent inner dynein arms with microtubular disorganization, and (4) central apparatus or radial spoke defects with absent or off-center central pair associated with transpositions of peripheral doublet.…”