Summary of Class 1 and Class 2 defects for the ultrastructural diagnosis of PCD

Class 1 defects are diagnostic of PCD in a patient with clinical symptoms of PCD. Class 2 defects can indicate a diagnosis of PCD in a patient with clinical symptoms of the condition, if consistent across more than one sample and if consistent with other results (such as those from immunofluorescence, high speed video microscopy, or genetic analysis). Class 2 defects may require assessment of more ciliary axonemes than Class 1 defects. Care should be taken to assess cross sections from several cells and both proximal (in the region of the microvilli) and distal regions of the axoneme.