Purpose: To describe the baseline data of a large cohort of patients included for follow-up with perimetry using the frequency doubling technique (FDT) and w ith quantification of the retinal nerve fibre layer as assessed by GDx, and to c alculate the sensitivity and specificity of both devices from these baseline dat a. Methods: Regular visitors to our glaucoma service were included. All subjects were followed for at least 4 years with FDT in full-threshold mode, GDx and co nventional perimetry. Patients were classified as having either glaucoma or susp ect glaucoma, according to baseline perimetry results. In addition, a group of h ealthy subjects was recruited outside the hospital. Results: A total of 452 glau coma patients, 423 glaucoma suspects and 237 healthy subjects were incorporated into the analyses. Sensitivities for both FDT and GDx were fixed at 0.90. For th e group as a whole, the specificity was 0.81 for FDT, using number of depressed test-points p 1, and 0.78 for GDx, using the Number, with a cut-off point >29. The area u nder the receiver operating characteristic (ROC)curve was 0.92 for FDT and 0.94 for GDx. Of the subjects with suspect glaucoma, 75%showed normal FDT test resul ts and 52%showed normal GDx results. Unlike FDT, GDx failed to detect some mode rate/severe glaucoma cases. Conclusions: The performances of FDT and GDx are app roximately equivalent in terms of sensitivity, specificity and area under the RO C curve. In glaucoma suspects, GDx in particular yielded a rather high percentag e of positive test results. The majority of these positive test results are pres umably false-positive results rather than results indicating preperimetric glau coma.
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