Background and objectives: The 14-3-3 test shows a high efficiency for the diagnosis of Creutzfeldt-Jakob disease (CJD), as long as an appropriate clinical setting exists. We analyze the evolution of the use and the validity of this test in Spain.
Patients and method: From January 1997 to June 2001, 1,092 samples were tested in our laboratory; 674 samples were selected for the study. Diagnoses were obtained by the referring physicians and the national CJD surveillance system according to standard criteria (results of the test were not included).
Results: The number of samples analyzed (% of follow-up) was: 75 (96%) in 1997, 138 (82.3%) in 1998, 197 (73%) in 1999 and 264 (59%) in 2000. The negative predictive value, sensitivity and specificity for a diagnosis of prion disease revealed stable values (95, 86 and 86%, respectively). The positive predictive value (PPV) decreased from 77% in 1997 to 51% in 2000 because of an increase of false-positive (FP) results. Up to 25% of FP might have been excluded through neuroimaging or CSF characteristics.
Conclusions: The observed increase of the demand suggests that the test is used as a screening technique. In this setting, the PPV of the test decreases due to an increase of false-positive results.