SCREENING FOR RETINOPATHY & NEPHROPATHY

1

Prof.V.Mohan.,M.D.,Ph.D.,D.Sc.

DIRECTOR M.V.DIABETES SPECIALITIES CENTRE,

PROFESSOR OF INTERNATIONAL HEALTH UNIVERSITY OF MINNESOTA, USA

VISITING PROFESSOR OF DIABETOLOGY SRI RAMCHANDRA MEDICAL COLLEGE, PORUR

PRESIDENT

MADRAS DIABETES RESEARCH FOUNDATION,

CHENNAI

CARDINAL PRINCIPLES FOR SCREENING

1. Important health problem with a presymptomatic state

2. Acceptable screening procedures (both by public and

health care professional)

3. Safe, effective and universally agreed treatment

4. Economic cost of screening and treatment should be

less than that for diagnosis and treatment

(WHO)

THE SCREENING PATHWAY

Healthy

Disease or precursor detectable

Symptoms develop

Advanced disease

Death

Screening possible

Intervention to avert disease development or its consequence

Life prolonged

CLASSIFICATION

NON - PROLIFERATIVE

DIABETIC RETINOPATHY

PROLIFERATIVE

DIABETIC RETINOPATHY

WITHOUT

MACULOPATHY

WITH

MACULOPATHY

DIABETIC RETINOPATHY

VISUAL IMPAIRMENT AND RETINOPATHY

By the year 2020 the number of blind people world-wide, over 60

years of age will reach 54 million (Practical Optometry ,1996)

90% of the blindness in the world occurs in developing countries

Diabetic retinopathy is seventh cause of blindness in India

Timely treatment can prevent up to 98% of vision loss from

diabetic retinopathy

Less than half of those with diabetes have their eyes

examined for retinopathy at the recommended frequency

BJO, 2001

IS SCREENING FOR RETINOPATHY JUSTIFIED?

is an important health problem

has a known natural history

has effective treatment

screening is

simple to perform

acceptable to patients

cost effective

comprehensive

Yes, because retinopathy….

DIABETIC RETINOPATHY - SCREENING

A simple diagnostic procedure, to identify

those patients in whom prompt treatment is

needed to prevent loss of vision

It is not a complete clinical examination in

itself

EYE EXAMINATION - ROUTINE

History

Visual acuity

Clinical examination of retina

Direct ophthalmoscopy

Indirect ophthalmoscopy

Retinal color photography

Fluorescein angiography

OCULAR FUNCTION EXAMINATION

Visual acuity (corrected), distance, reading

Colour vision

Visual field test - to test confrontation

eye movements

After dilation

Lens

Vitreous

Fundus including disc and macula

Ophthalmoscopy

Retinal photography

Polaroid photographs

35mm colour slides

Digital images

- Scanner

- Video

- Digital camera

RETINAL EXAMINATION

OPHTHALMOSCOPY

Direct ophthalmoscopy and

indirect ophthalmoscopy

through dilated pupil

inexpensive, rapid, efficient

Direct ophthalmoscopy enables adequate examination

of only the posterior pole

Indirect ophthalmoscopy provides insufficient

magnification

OPHTHALMOSCOPY

Slit lamp examination using either indirect

ophthalmoscopy with convex aspheric lens or

diagnostic contact lens yields more information on

retinal thickening and proliferative retinopathy

Seven 30 degree fields

Two 45 degree fields

Three photographs

spread across the posterior

pole

RETINAL PHOTOGRAPHY

OPHTHALMOSCOPY vs PHOTOGRAPHY

OPHTHALMOSCOPY PHOTOGRAPHY

No documentation Can be documented

is possible

Errors cannot be Photographs can be

detected regraded

Observer bias Mutiple grading is

possible

RETINAL PHOTOGRAPHS

RETINAL PHOTOGRAPHY

GOLD STANDARD FOR RETINAL SCREENING

Seven 30 - degree field of stereoscopic

photographs taken by a trained

technician

Photographs can be taken by a mobile

unit with a camera and later assessed by a

trained reader

Suited to serve even rural communities

Retinal photography is the gold standard for screening diabetic retinopathy

SPECIFICITY AND SENSITIVITY OF

OPHTHALMOSCOPY AND PHOTOGRAPHY

Ophthalmoscopy Photography

(%) (%) Sensitivity 65.7 87.3

Specificity 93.8 84.8

Owens et al, Diabetic Medicine, 1998

WHO CAN DO SCREENING ?

General practitioner

Optometrists

Clinicians in a hospital - based diabetes centre

Ophthalmologists

Diabetologists

Retinal photography services

Combination of all these

ERROR RATES FOR DIAGNOSING DIABETIC

EYE DISEASE - OPHTHALMOSCOPY

Overall Serious

errors (%) errors (%) Internist 74 70

Senior medical resident 69 52

Diabetologist 66 50

Ophthalmologist 48 11

Retinal specialist 13 0

Stage of hyper- filtration

Microalbumi- nuria

Macroalbumi- nuria

Azotemia (Renal failure)

End stage Renal disease

Normoalbumi-nuria

NATURAL HISTORY OF NEPHROPATHY

IN TYPE 1 DIABETES

15 - 20 yrs 1 yrs 4 - 5 yrs

PREVALENCE OF DIABETIC NEPHROPATHY

Diabetic Nephropathy

Develops in 35 - 45% of Type 1 diabetic

patients

20 - 30% of Type 2 diabetic patients

Leading cause of ESRD in United States

PREVALENCE OF DIABETIC NEPHROPATHY IN DIFFERENT ETHNIC GROUPS

19 million Indians with diabetes

5 - 60% of type 2 diabetes depending on ethnic origin

Caucasians - 5 - 10%

African Americans - 10 - 20%

Pima Indians - 60%

Asian Indians - 10%

Even with 10%, 1.7 million Indian diabetics will

have Nephropathy

SCREENING FOR MICROALBUMINURIA

Routine urinalysis for protein

- For protein + For protein

Overt nephropathy

Quantitative protein

begin treatmentCondition that may

invalidate urine albumin excretion Wait until resolved

Test for microalbumin > 30 mg/24h

Repeat microalbumin test twice within 3 months period

2 of 3 tests > 30 mg/24h ?

Microalbuminuria, begin treatment

Repeat in 1 year

Yes

No

Yes

No

Yes

SPECIMEN COLLECTION

Collect freshly voided urine in a clean, dry

container

Preservatives should be avoided

Samples which cannot be tested within 3 days

of collection should be refrigerated

Samples should not be frozen

The test should be free from significant

interference from glucosuria, pH, ketonuria

or bacterial contamination

SCREENING FOR MICROALBUMINURIA

Albumin to creatinine ratio in random spot

collection

24 - h urine collection with creatinine

Timed collection (4-h or overnight)

Three methods

DEFINITION OF MICROALBUMINURIA

Stage 24h Timed Spot collection collection collection

Normoalbuminuria < 30 mg/24h <20g/min <30g/mg creat

Microalbuminuria 30-300 mg/24h 20-200g/min 30-300g/mg creat

Clinical albuminuria >300 mg/24h >200g/min >300g/mg creat

ADA, Diabetes Care, 1998

Random spot collection

First void or morning collection

Timed collection

Easy to perform

Generally provides accurate

information

Preferred due to diurnal variation

in albumin excretion

Gold standard

Notoriously labour and time

intensive Patients co-operation

difficult

ADVANTAGES AND DISADVANTAGES

METHODS OF MICROALBUMINURIA ANALYSIS

SPECIFICITY AND SENSITIVITY FOR MICROALBUMINURIA

Sensitivity Specificity

(%) (%) Random spot specimen 89 85

First morning void 70 93

Schwab et al, Diabetes Care, 1992

Timed urine collection - gold standard

3 -hourcollections

4 -hourcollections

Overnight collections

Brodows et al, Diabetes Care, 1981

Steno study group, Lancet, 1982

Viberti et al , Lancet, 1982

SHORTENED TIMED CLEARANCESSUGGESTIONS …..

1 -hourtimed

collections Sochett et al, J.Pediatr,1988

Qualitative

Dipstick method

Quantitative

Immunoturbidometric assay

Enzyme linked Immunosorbant assay

Radioimmuno assay

ASSAYS FOR MICROALBUMINURIA

MICRAL STRIPS

Micral strip screening tests offer a cost-

effective method of screening

Dip sticks show acceptable sensitivity

(95%) and specificity (93%)

All positive tests should be confirmed

by more specific methods

FALSE POSITIVES FOR ALBUMINURIA

Hyperfiltration (Newly diagnosed diabetes)

Exercise

Marked hypertension

Congestive Heart Failure

Urinary Tract Infection

Acute febrile illness

CONCLUSIONSScreening for retinopathy

Sensitive, specific and safe screening tests are available for retinopathy

Retinal photography is the gold standard, which can be modified from seven to four field

Training is necessary to grade retinal photographsNewer technologies including digital imaging may reduce the cost of screening

PRIORITIES

Screening

Diagnosis

Treatment

Counseling

Education

For preventing blindness due to diabetes

For all diabetic patients

CONCLUSIONSScreening for nephropathy

Screening tests for microalbuminuria are safe, simple at the same time specific and sensitive

Timed urine collection is the gold standard. However spot urine testing has also proved to be equally sensitive

Micral dip sticks are cost effective

Microalbuminuria provides information not only about nephropathy,but also generalized vascular disease (endothelial dysfunction)

PRIORITIES

Annual screening of Microalbuminuria

Glycemic control

Treatment modalities to slow down

the rate of progression of nephropathy

For preventing nephropathy due to diabetes

in all diabetic patients