Accuracy of a Self-monitoring Test for Identification and Monitoring of Age-related Macular Degeneration: A Diagnostic Case-control Study
Martin K. Schmid2, Livia Faes1, *, Lucas M. Bachmann1, Michael A. Thiel2
1 Eye Clinic, Cantonal Hospital of Lucerne, Lucerne, Switzerland
2 Medignition Inc, Research Consultants, Zurich, Switzerland
To evaluate diagnostic accuracy of a new self-monitoring device using a Vernier hyperacuity alignment task.
A total of 11 wet Age-Related Macular Degeneration (AMD) patients and 9 controls contributing 37 eyes were consecutively enrolled into this prospective diagnostic case-control study at the retina centre of the Cantonal Hospital Lucerne, Switzerland. Vernier acuity testing (index test) and Optical Coherence Tomography (OCT, reference test) were performed in all participants. OCT scans were evaluated and graded by a retinal specialist masked to diagnosis and index test results. Candidate parameters of the index test to be used as the diagnostic statistic were identified using a bootstrap procedure. Ten parameters remaining were further assessed in univariate analyses. The overall Standard Deviation (SD) of absolute distances across all four axes of the Vernier acuity test provided the highest area under the Receiver Operating Characteristics (ROC) curve and was therefore selected.
Mean age of patients with wet AMD was 81.2 years (SD 4.99), mean numbers of letters were 67.4 (SD 14.1). The proportion of women was similar in both groups (controls: 88%, wet AMD: 72%). The area under the ROC curve was 0.87 (95% confidence interval CI: 0.75- 0.99) indicating excellent discrimination. Best accuracy was reached at a cut-off value of 0.64 with a sensitivity of 75% and a specificity of 94%.
This diagnostic case-control study of a new screening device for AMD shows acceptable diagnostic accuracy. The promising preliminary data of this study call for further upstream evaluations in reasonably sized clinical studies.
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* Address correspondence to this author at the Eye Clinic, Cantonal Hospital of Lucerne, Livia Faes, Cantonal Hospital Lucerne, Spitalstrasse, 6000 Luzern 16, Switzerland; Tel: +4141 205 33 09; E-mail: firstname.lastname@example.org