improving the value of screening for macular oedema using surrogate photographic markers dr john...

Improving the Value of Screening For Macular

Oedema usingSurrogate Photographic

Markers

Dr John Olson

NHS Grampian

Improving The Economic Value Of Photographic Screening For Optical Coherence Tomography

Detectable Macular Oedema – A Prospective Multicentre, United Kingdom Study

• Olson J, Sharp P , Goatman K, Prescott G, Scotland G, Fleming A, Philip S, Santiago C, Borooah S, Broadbent D, Chong V, Dodson P, Harding S, Leese G, Styles C, Swa K, Wharton H

• Health Technol Assess, Vol 17,, May- June 2013, In Press

A Success Story?

• Systematic screening programme for diabetic retinopathy

Missing the target?

• The health-economic case is based on the detection of people with, or at risk of– proliferative diabetic

retinopathy– before they develop

complications• Vitreous haemorrhage• Traction retinal detachment

• But 90% of referrals are for ? diabetic macular oedema

Why?

• Retinal photographs are not discriminatory for proliferative retinopathy or its precursors

• Other things may be present– e.g. diabetic “maculopathy”– We have to manage these findings

How did we get there?

• Retinopathy grades based on ETDRS

• Maculopathy grades basedon

…(GOBSAT)

Different management

New Vessels Oedema

Definitive treatment Indefinite treatment

Management independent of visual acuity

Management depended on visual acuity

2 D red structure 3 D transparent elevation

Few false +ves Many false +ves

What did ISMO question?

• Can we do it better?

• What will it cost?

• What will it mean?

The Answers In Short- Can Grading Schemes do it better ?

• Computer says nah

The Answers In Short- Can OCT do it better ?

• Yes• Increases the

specificity of referrals• With no loss of

sensitivity

The Answers-What will it cost?

• Less• If you use OCT • Whatever grading

strategy you use• Saves you money

The Answers- What will it mean?

Study Highlights

© 2008 Google-Imagery © 2008 TerraMetrics

Aberdeen

Dundee

Edinburgh

Liverpool

Birmingham

Oxford

Study centres

Aberdeen

Birmingham

Dundee

Edinburgh

Glasgow

Liverpool

Oxford

Glasgow

Every day practice

Aberdeen

Dundee

Edinburgh

Liverpool

Birmingham

Oxford

Glasgow

3450 Subjects

• Photographic signs of diabetic retinopathy– exudates ≤ 2DDr– blot haemorrhages ≤ 1DDr– dot haemorrhages/microaneurysms ≤ 1DDr

• Each subject had photography and optical coherence tomography on both eyes, where possible.

Patient Characteristics

• Median age 60

• 60.7% male

• 85.4% Caucasian

• 77.4% type 2 diabetes

370 Excluded (10.5%)

• 6 years older

• Female

• Asian/ Black

• Zeiss Stratus

• Topcon OCT 1000

Lesion Distribution

Expected % Recruited %

Ma/dot only 69.8 40.3

Blot no exudate 8.6 8.4

Exudate 21.6 20.4

No Ma/dot/blot/exudate ≤ 1DDr

28.1

Definition of Macular Oedema

• Central ETDRS region thickness > 250µm

• OR any of 5 inner regions > 300µm

• AND visible intraretinal cyst/ area of subretinal fluid

Prevalence of oedema

• 7.7% of study population

• Prevalence differed greatly by centre– 3.7% to 12.2%

• Prevalence differed greatly by scanner– 4.5% to 11.8%

Relationship to Centre

• Aberdeen 12.0%• Birmingham 3.7%• Dundee 12.2%• Edinburgh 6.4%• Liverpool 2.9%• Dunfermline 4.4%• Oxford 7.7%

All scanners are equal, but some scanners are more equal than others

• Zeiss Stratus– 4.5%

• Topcon OCT1000– 6.5%

• Heidelberg Spectralis– 8.7%

• Zeiss Cirrus– 11.8%

Relationship to patient features

• Older age– 68yrs cf 60

• Caucasian– 8.4% cf 3-4%

• Type 2 diabetes– 8.7% cf 3.9%

• Poorer vision– 5x more likely– If VA ≤ 6/9

• BUT NOT– Sex, glitazone, amblyopia

Relationship to Lesions

R Eye % L Eye %

No lesions

0.8 0.6

Ma/dot only

2.2 2.3

Blot no Exudate

10.2 11.2

Exudate 12.5 11.2

Other 1.1 1.1

Can we do any better?

• Three Grading Strategies Examined– Manual grading

• Presence/ absence of features• SDRGS 2007

– Computer-assisted manual annotation• All individual lesions ≤ 2DDr

– Fully automated annotation grading• Three versions

– Automated image analysis– +VA

– +VA + Age+ Type DM + Sex

Manual Grading (features)

Manual Grading (features)

• Scotland– 59.5% sensitivity– 79.0% specificity

• England– 72.6% sensitivity– 66.8% specificity

• England plus– 73.3% sensitivity– 70.9% specificity

Computer Assisted, Manual Annotation, Grading• Best for sensitivity &

specificity• Time-consuming

procedure • Unlikely to be

considered for routine screening practice

In Years To Come

Marvin the Manically Depressed Autograder

""I think you ought to I think you ought to know…. I'm feeling know…. I'm feeling very very depressed ......noboddepressed ......nobody likes mey likes me""

DRS in Scotland 2012

What will it cost?

• Cost per screen £33.13• Cost per OCT screen £31.96• Total cost for ?oedema £65.09

• Cost of attending ophthalmology £90.00

• (Cost of Slit lamp within DRS £27.29)

TABLE 30 Screening and referral cost per true case of macular oedema detected for 3,170 patients; Adjusted for expected frequency of different patient categories and based on Scottish screening and referral costs

* Reference strategy; a figures in table based on assumption that fully automated grading can be implemented at zero net increase in grading costs;++ Represents a cost saving per case missed relative to the reference strategy; d strategy more costly and less effective than an alternative strategy (dominated)

What does it mean?

• At present we spend £13,750,000 a year – 250,000 people @ £55– Screening + 1st visit to

ophthalmology– £2,337,500 on ? M2

• If we do nothing, other than introduce OCT into the screening pathway

• we save money

Should we grade differently?

Current Scottish Criteria + OCT is the most cost effective of all strategies

What if we do nothing? 20 year “M2” Markov Model• Only 5.6% of M2 at risk of visual loss• Repetitive nature of screening

– 12% of non-referred MO modelled to progress at 12 months cf 5% of referred (laser Rx)

• More sensitive strategies– More OCTs, more referrals

• Bilateral incidence 12%– QALY determined by VA in better seeing eye

• Additional cost per QALY going to strategy 16– £882,307 at 5 years– £353,927 at 20 years– (£20-30,00 UK threshold for “cost-effectiveness)

What should we do?

Cost-effectiveness acceptability curves for the alternative strategies based on a 20 year time horizon and using quality adjusted life years as the measure of effect

How should we manage M2s?Is this the answer?

• Photos graded as M2

• Check VA

• Do an OCT if VA 6/12 or worse?

• Otherwise rescreen in 6 months?

Thank You

Modelled visual acuity changes for “CSMO”