St Kitts Eye Study Grand Rounds, Artes 2009)

The St Kitts Eye Study Grand Rounds, January 2009

Content

Background of Project Screening Protocol of the St Kitts Eye Study What we have learned so far Where do we go from here

Federation of St Kitts and Nevis

St Kitts 5 km

168 sq.km 35,000 inhabitants (2001 census)

St Kitts and Halifax: Connections

St Kitts and Halifax: Connections 1991: Eye Centre of Joseph N France Hospital established, with help from Halifax 2001: first proposal for screening project 2003: funds from industry Alcon, Allergan, Merck, Pfizer 2005: it nearly happened 2007: it nearly happened (again) 2008: it really happened.

Glaucoma and black ancestry

Survey of Ophthalmology (2003)

St Lucia Study Ophthalmology (1989) Baltimore Eye Survey Am J Epidem (1991) The Barbados Eye Study Arch Ophth 1994)

Glaucoma and black ancestry

Survey of Ophthalmology (2003)

prevalence 3 - 6× higher than in Caucasians earlier onset & more rapid progression 5× larger prevalence of ocular hypertension (OHT) ↑ risk of progression from OHT to glaucoma ↑ rates of glaucoma-related blindness

Glaucoma in the Caribbean St Lucia Study Ophthalmology, 1989 Sep;96(9):1363-8 1679 individuals, aged 30+ years VA, IOP, C/D ratio 1/3 had supra-threshold screening fields on HFA positives underwent definitive exam, including threshold fields

Prevalence of 8.8% in the 30+y population.

What is Screening? Identify people who probably have a disease from those that probably do not.

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? The condition sought should be an important health problem. There should be an accepted treatment. The natural history of the disease should be well understood. There should be a latent or early symptomatic stage. There should be a suitable and acceptable screening test. Facilities for diagnosis and treatment should be available. There should be an agreed policy on whom to treat as patients. Early treatment should be of benefit. The cost should be economically balanced. Case finding should be a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile? S Hatt, R Wormald, J Burr

Cochrane Database of Systematic Reviews 2008 Screening for prevention of optic nerve damage due to chronic open angle glaucoma Main results

“As no trials were identified, no formal analysis was performed.”

Glaucoma screening: worthwhile? S Hatt, R Wormald, J Burr

Cochrane Database of Systematic Reviews 2008 Screening for prevention of optic nerve damage due to chronic open angle glaucoma Main results

“As no trials were identified, no formal analysis was performed.”

The Bottom Line •

Screening can be cost-effective in highrisk populations.

•

Most economic evaluations compare to current model of routine case-finding by optometrists, which does not exist in Caribbean.

•

Screening tests need very high specificity to be workable.

A good screening program… simple, cheap, and accessible in peripheral health centres rely on local expertise (nurses, assistants)

good sensitivity, and very high specificity false-positive rate <2% more false-positive cases – negative impact

Likelihood ratios sensitivity / (1 – specificity)

Likelihood ratios sensitivity / (1 – specificity)

Fagan Nomogram

Likelihood ratios sensitivity / (1 – specificity)

Fagan Nomogram

Likelihood ratios sensitivity / (1 – specificity) Example: Moorfields Regression Analysis of HRT Sensitivity = 65%, Specificity = 95% Likelihood ratio = 0.65 / 0.05 = 13

Fagan Nomogram

Brain Teaser Sensitivity = 50% Specificity = 95% Prevalence = 0.3%

Brain Teaser Sensitivity = 50% Specificity = 95% Prevalence = 0.3% What is the probability that a patient with a positive test has the disease?

Fagan Nomogram

Fagan Nomogram

5% Doctors with an average of 14 yrs experience Answers ranged from 1% to 99% half of them estimating the probability as 50% Gigerenzer, BMJ 2003;327:741-744

Aim - St Kitts Eye Study

help establish a robust and effective screening program for St Kitts and wider Caribbean region

Questions - St Kitts Eye Study Which tests provide high specificity and good sensitivity, in a Caribbean population? Which combination of tests provides the best trade-off between performance and effort? Can new technologies (eg HRT imaging) improve on the current standard of care?

Objectives – St Kitts Eye Study Examine a representative sample of 200 individuals >50 yrs with screening tests as well as “gold standard” protocol. Establish combination of screening tests that provides specificity >98%. Establish criteria for referral to Eye Centre.

Design – St Kitts Eye Study random sample of St Kitts residents (n=370) drawn from Social Security list. invited to participate by letter from Ministry of Health complete protocol of tests, including screening- and “gold standard” tests

Visual Fields Frequency Doubling (“Matrix”) Perimetry Moorfields Motion Displacement Perimetry Suprathreshold (white-on-white) Perimetry (all screening tests on one eye only)

Humphrey 24-2 Sita-Standard (both eyes)

Tonometry

EasyEye NCT (Keeler) Tonopen (Reichert) Goldmann Applanation Tonometry (GAT)

Imaging Heidelberg Retina Tomograph (HRT2) Nidek AFC 230 Stereo Fundus Camera Dilated Fundus Examination (Volk 90D)

Consent, Interview, Visual Acuity

SKES: Protocol

Humphrey Matrix 1% supra-threshold test

HFA 24-2 SITA Std Threshold Visual Fields

Gonioscopy

Moorfields Motion Displacement Perimetry

Keeler EasyEye Non-Contact Tonometry

Fundus Photography

HFA 76 point 3-zone supra-threshold test

Tonopen

Dilated exam of Anterior & Posterior Segments

Heidelberg Retina Tomograph 2

Goldmann Applanation Tonometry Clinical Decision & Referral (if appropriate)

Initial Findings Invited: 373 individuals (169 women, 204 men) age range 50 – 87 yrs Participated: 172 individuals (46%) of those invited 44 individuals (opportunistic) 208 (96%) completed entire program

Initial Findings Prevalence of glaucoma 18/172 = 10.5% 8 previously unknown (44%) Prevalence of Ocular Hypertension 15/172 = 9% 12 previously unknown (80%)

Initial Findings* Other conditions Pterygium: almost universal Significant cataract: ~25% Diabetic Retinopathy: ?? AMD: very few * No formal analysis conducted as yet

Initial Findings* Visual Fields High rate of unreliable results with threshold perimetry. Moorfields Motion Displacement test – easy to explain and well accepted. Matrix Frequency Doubling: high rate of abnormal test results * No formal analysis conducted as yet

Initial Findings* Imaging Optic disc size distribution different from caucasians (larger number of large discs?) Fundus photography: significant number of nerve fibre layer defects as isolated finding.

* No formal analysis conducted as yet

Initial Findings* Tonometry Non-contact tonometry surprisingly well tolerated (but needs practice). Impression: NCT appears more accurate & precise compared to Tonopen.

* No formal analysis conducted as yet

Where do we go from here? Formal analysis of test performance, compared to “gold standard” of clinical examination. Report to Ministry of Health, St Kitts and Nevis, with suggested paradigm and cost estimates.

Younes Agoumi, Carol Beattie, Beulah & Terrela Byron, Balwantray Chauhan, Anthony Crouse, Stacey Durling, Marcelo Nicolela, Glen Sharpe