Lack of sensitivity and specificity for PCD diagnosis when ciliary videomicroscopy is performed at room temperature - 17/02/23

Primary ciliary dyskinesia (PCD) is a heterogenic inherited ciliopathy in which respiratory cilia are stationary or dyskinetic. Digital high-speed videomicroscopy (DHSV) is highly sensitive and specific for PCD diagnosis, but lacks standardization. Various laboratories perform DHSV using different temperature,which may influence ciliary functional analysis (CFA), including ciliary beat frequency (CBF) and beat pattern (CBP). Recent data suggest that CBF increases with temperature, but the relationship between CBP and temperature has not been extensively studied. However, CBF should not be used without CBP assessment in diagnosing PCD, given its lack of sensitivity and specificity. The aim of this study is to evaluate the effect of temperature during DHSV on CFA.

Ciliated epithelial samples were obtained by nasal brushing from 14 patients referred to our PCD diagnosis center (7 with a confirmed PCD diagnosis (PCD), and 7 with an excluded PCD diagnosis (non-PCD) and from 5 healthy volunteers, to establish our laboratory normal values. Beating cilia were recorded using DHSV at 37°C and at room temperature(25°C) within 9hours after sampling. CFA was assessed by CBF and the percentage of abnormal CBP.

When DHSV is performed at 37°C, our result show a 100% sensitivity and specificity of the percentage of abnormal CBP to diagnose PCD, with a result above normal values for all PCD patients, and within or under normal values for all non-PCD patients.

However, when the percentage of abnormal CBP is measured at 25°C, a PCD diagnosis might be missed in 1 PCD patient with a borderline value and might lead to a wrong PCD diagnosis in 3 non-PCD patients.

CBF measured at 37°C is abnormal in all PCD patients, but also abnormal or borderline in 6 non PCD patients. CBF measured at 25°C is abnormal or borderline in 6 PCD patients, and in 6 non-PCD patients (Table 1).

DSHV might lead to lack a diagnosis in PCD patients or to overdiagnosis some non-PCD referred to a PCD diagnosis center:

– if CBF is used without CBP evaluation. Indeed, our results confirm that the evaluation of CBP is required for PCD diagnosis, as stated in international recommendation;

– if DHSV is performed at room temperature. Indeed, this pilot study confirms that some PCD variants present a temperature sensitive ciliary beating as suggested previously.

Given the heterogeneity of PCD, these preliminary data have to be confirmed in larger studies.