A test for Creutzfeldt-Jakob disease using nasal brushings

Abstract

Background: Definite diagnosis of sporadic Creutzfeldt-Jakob disease in living patients remains a challenge. A test that detects the specific marker for Creutzfeldt-Jakob disease, the prion protein (PrP(CJD)), by means of real-time quaking-induced conversion (RT-QuIC) testing of cerebrospinal fluid has a sensitivity of 80 to 90% for the diagnosis of sporadic Creutzfeldt-Jakob disease. We have assessed the accuracy of RT-QuIC analysis of nasal brushings from olfactory epithelium in diagnosing sporadic Creutzfeldt-Jakob disease in living patients.

Methods: We collected olfactory epithelium brushings and cerebrospinal fluid samples from patients with and patients without sporadic Creutzfeldt-Jakob disease and tested them using RT-QuIC, an ultrasensitive, multiwell plate-based fluorescence assay involving PrP(CJD)-seeded polymerization of recombinant PrP into amyloid fibrils.

Results: The RT-QuIC assays seeded with nasal brushings were positive in 30 of 31 patients with Creutzfeldt-Jakob disease (15 of 15 with definite sporadic Creutzfeldt-Jakob disease, 13 of 14 with probable sporadic Creutzfeldt-Jakob disease, and 2 of 2 with inherited Creutzfeldt-Jakob disease) but were negative in 43 of 43 patients without Creutzfeldt-Jakob disease, indicating a sensitivity of 97% (95% confidence interval [CI], 82 to 100) and specificity of 100% (95% CI, 90 to 100) for the detection of Creutzfeldt-Jakob disease. By comparison, testing of cerebrospinal fluid samples from the same group of patients had a sensitivity of 77% (95% CI, 57 to 89) and a specificity of 100% (95% CI, 90 to 100). Nasal brushings elicited stronger and faster RT-QuIC responses than cerebrospinal fluid (P<0.001 for the between-group comparison of strength of response). Individual brushings contained approximately 10(5) to 10(7) prion seeds, at concentrations several logs10 greater than in cerebrospinal fluid.

Conclusions: In this preliminary study, RT-QuIC testing of olfactory epithelium samples obtained from nasal brushings was accurate in diagnosing Creutzfeldt-Jakob disease and indicated substantial prion seeding activity lining the nasal vault. (Funded by the Intramural Research Program of the National Institute of Allergy and Infectious Diseases and others.).

Figure 1. Results of Real-Time Quaking-Induced Conversion (RT-QuIC) Assays of Olfactory Mucosa (OM) and Cerebrospinal Fluid (CSF) Samples

Panel A shows the average percent thioflavin T (ThT) fluorescence readings from four replicate reactions (normalized as described in the Methods section), determined in samples of OM and CSF from patients with possible, probable, or definite Creutzfeldt–Jakob disease and from controls without Creutzfeldt–Jakob disease. The means (thick lines) with standard deviations (thin lines) of those averages are shown as a function of RT-QuIC reaction time. Panel B shows the final average relative ThT fluorescence readings for each person with Creutzfeldt–Jakob disease (CJD) and for each control with either a neurologic disease other than Creutzfeldt–Jakob disease (other neurologic disease [OND]) or no neurologic disease (NND) at either 50 hours (OM samples) or 90 hours (CSF samples). Inherited CJD refers to patients with the E200K PRNP genetic mutation causing CJD. All OM and CSF samples obtained from patients with CJD and from controls are reflected in these data. The total number of CSF samples from patients with CJD (34) does not include a sample from one patient (Patient 31; CSF not tested) and includes results from two lumbar punctures each in four patients with CJD.