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J.J. O'Neill, G.J. McKay, D.A. Simpson, G. Silvestri; Retinitis Pigmentosa Assessment Severity Scale (RPASS) for Use in Scientific Analysis and Classification of Disease Progression . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1419.
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© ARVO (1962-2015); The Authors (2016-present)
Retinitis Pigmentosa (RP) is a group of genetic disorders exhibiting wide phenotypic expression which makes classification for scientific evaluation difficult. The aim of this study is to establish a clinical assessment scale to objectively evaluate the disease state of patients with RP in Northern Ireland and subsequently correlate disease severity and progression with genotype.
50 patients with a clinical diagnosis of RP, confirmed with ISCEV, were selected from the Northern Ireland Retinitis Pigmentosa Database. Each participant was assessed using LogMar distance acuity charts, Farnsworth Dichotomous test for colour blindness series D15 and Humphrey 24–2 for visual fields. The fundus was imaged using the Topcon TRC 50EX. A grading scale was constructed using a combination of subjective clinical findings such as optic disc pallor, extent of retinal pigmentary changes and vascular attenuation. Objective parameters such as visual acuity assessment, visual field loss and electrodiagnostics were also included. The clinical grading scale was then applied to the 50 selected patients and assessed for appropriateness in terms of reflecting clinical severity using the Statistical Package for Social Sciences.
34% of the participants had Autosomal Dominant RP, 34% had Autosomal Recessive RP, 4% had X–linked RP and 28% were sporadic. The fundus assessment scale demonstrated a strong correlation with the visual function scale of distance acuity and contrast sensitivity and when both scales were combined they correlated highly with disease duration. However the scale also illustrates the varying severity which exists between inheritance patterns when cross tabulated with genetic type. Higher mean assessment scores were recorded for patients who had X–linked RP in comparison to those who had similar disease durations with dominant, recessive or sporadic inheritance patterns.
Classification scales are difficult to apply to disorders such as RP because of the variety of manifestations of disease. However this method of applying a score to each clinical sign and objective test parameter, has allowed us to categorise this group of patients into a mild, moderate or severe set with reference to age and disease duration. This simplistic method of classifying RP can be used as a scale to assess disease progression over a period of time and could be used to inform genotypic–phenotypic studies. It is anticipated that this scale would form the basis of a phenotyping system that could be applied consistently by independent clinicians.
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