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Abstract
Design: diagnostic test accuracy cohort study to estimate the sensitivity and specificity of home monitoring tests to detect active nAMD in patients previously diagnosed with nAMD. Participants will be followed for >=12 months,accruing on average 6 clinic attendances at which home monitoring and reference test results can be compared. Setting: Homes of patients being monitored by HES for nAMD in 5 NHS hospitals (Belfast,Moorfields,Southampton,Liverpool and Great Yarmouth). Target population: Patients being monitored by HES for nAMD, stratified by time since starting treatment (6-17 months; 18-29 months; 30-41 months) to ensure test performance is estimated across this range of duration of nAMD. Eligibility criteria:patients diagnosed with active nAMD (>=6 months earlier) and currently being treated with an anti-VEGF drug or monitored (i.e.with active or inactive nAMD) by the HES will be eligible. Exclusions are: vision in the eye being monitored limited by another eye condition;surgery in the study eye in the previous 6 months; refractive error >-6D; choroidal neovascularization not due to nAMD; inability to do one or more of the proposed tests during ‘training’; unable to understand English; home circumstances cannot support internet access. Health technologies being assessed: 3 home-monitoring tests spanning low to moderate cost and complexity (KSJ, adapted for UK use; MBT app* and mVT app).Participants will carry out these tests weekly. The KSJ is a booklet of near vision tests including a modified Amsler test, with results recorded in the booklet(booklets collected at the next clinic visit). The mVT and MBT apps are display visual stimuli on an iPod Touch, capture participant responses and transmit data by the internet (by home wi-fi or mobile broadband). Reference standard: Classification of eyes being monitored by the HES as active/inactive nAMD based on colour fundus photographs (CF),optical coherence tomography(OCT) fluorescein angiography (FFA) or other investigations carried out as part of usual care at the HES clinic attendance (‘blind’ to home monitoring results). Qualitative study: We will observe test completion and conduct one-to-one interviews during home visits (n=~75 across 3 sites). Carers will be interviewed separately via telephone or e-interview mode (n=~60). Transcripts will be analysed using established qualitative research methods. Sample size: Assumptions: reference standard will be ‘active’ for 30% of monitoring visits; correlations between tests and reference standard will be 0.6 for both active and inactive lesions[1]. We will recruit >=400 participants with test and reference data for about 2300 clinic visits (average 6 visits/participant, 5% attrition). Multiple visits per participant are not independent and measurement error will dilute power to discriminate test performance, so we have assumed an effective sample size of 1200 visits, giving 90% (80%) power to detect a difference of 0.06(0.05) in the area under the receiver operating characteristic curves (AUROC) for 2 tests if the AUROC is 0.75[1]. Projected timetable:Total duration,42 mths: set up sites, mths 1-6; recruit, mths 7-24; follow-up mths 8-36; analyses/draft study report, mths 37-42. Assuming that each centre has >500 patients being actively monitored (at varying times since diagnosis), that 60% will be eligible and >25% of eligible patients will consent, we estimate that sites will each recruit ~80 participants in 18 months.