title: Accuracy of combined GDx-VCC and matrix FDT in a glaucoma screening trial.
abstract: OBJECTIVE
  To assess the advantage in glaucoma screening of the use of scanning laser polarimetry with customized cornea compensation (GDx-VCC) combined with Matrix Frequency Doubling Technology (M-FDT) testing.
  
  
  METHODS
  In a nonpopulation-based prepublicized trial, self-recruited white participants were screened for glaucoma with GDx-VCC, with M-FDT, and by independent clinical examination. Cases with possible glaucoma as found with any of the screening methods underwent a detailed clinical investigation to verify or exclude glaucoma. Sensitivity, specificity, accuracy, likelihood ratios, and predictive values were calculated using different threshold criteria for GDx-VCC alone, M-FDT alone, and for various combinations.
  
  
  RESULTS
  Of the 233 attendees, 181 participants (345 eyes) successfully underwent the GDx-VCC and M-FDT measurements. Thirty-nine eyes of 24 participants had glaucoma (11.3% prevalence among eyes tested successfully). All but 2 of the glaucomatous eyes had only early damage. Evaluated separately, the criterion GDx-VCC NFI (normal threshold < or =30) performed best, with 97.0% specificity, 88.8% accuracy, and 25.6% sensitivity; but with only 8.5 positive likelihood ratio (PLR). For paired criteria, the best combination of GDx-VCC-screening test with M-FDT-screening test provided 99.6% specificity, 91.3% accuracy, and 28.6 PLR. For NFI combined with GDx-VCC nerve fiber bundle defect criterion, specificity was 99.0%, accuracy 89.6%, and PLR 18.0. However, the sensitivities in the 2 cases fell to 12.0% and 18.0%. For a triple combination of M-FDT-screening test with the latter pair of criteria, sensitivity increased to 41.7% and PLR (13.6) still remained clinically useful.
  
  
  CONCLUSIONS
  In a self-recruited white population with relatively high risk for mild glaucomatous damage, a combination of GDx-VCC together with M-FDT could usefully be employed for mass glaucoma screening.
authors: Department of Ophthalmology, Semmelweis University, Budapest, Hungary.
authors: Márta
authors: M
authors: Tóth
authors: Péter
authors: P
authors: Kóthy
authors: Péter
authors: P
authors: Vargha
authors: Gábor
authors: G
authors: Holló
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003941:Diagnostic Techniques, Ophthalmological; D005189:False Positive Reactions; D005260:Female; D005901:Glaucoma / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D007429:Intraocular Pressure; D007834:Lasers; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012680:Sensitivity and Specificity