To the Editor—Our article “A Practical Approach to Avoiding Iatrogenic Creutzfeldt-Jakob Disease (CJD) from Invasive Instruments”Reference Brown and Farrell ¹ included the recommendation that all patients with either cerebellar or mental abnormalites be tested for elevated levels of 14-3-3 protein in spinal fluid. Although this test has proved invaluable as a diagnostic aid for nearly 2 decades, the protein was from the start recognized as being a “marker protein” that was not causally related to CJD, and efforts to detect the pathogenetic prion protein in spinal fluid have continued. Two just published independent studiesReference Orru, Groveman, Hughson, Zanusso, Coulthart and Caughey ^{2 ,} Reference Cramm, Schmitz and Karch ³ of a newly modified prion protein amplification test named RT-QuIC (real-time quaking-induced conversion) now justify those efforts.

One study of 48 CJD and 39 control patients yielded a sensitivity of 96% and specificity of 100%Reference Orru, Groveman, Hughson, Zanusso, Coulthart and Caughey ² ; the second study of 110 patients with various forms of prion disease and 400 control patients yielded a sensitivity of 85% and specificity of 99%.Reference Cramm, Schmitz and Karch ³ Test results are available within 24 hours of specimen collection.

We regret that the timing of our diagnostic test recommendations just missed the pubication dates of these 2 new articles but are delighted to be able to add the RT-QuIC spinal fluid test as perhaps the easiest, fastest, most accurate, and practical premortem diagnostic test for prion disease.