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Center for Health Sciences
Medical Physiology - Evidence-Based Medicine
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Introduction

What is EBM?

Patient Care Model
Life-long Learning
Why is EBM Important?
Available Evidence?
EBM Issues

The Well-built Question

The EBM Process
Anatomy of a Question

Finding Evidence

Selecting a Resource
Searching the Resource
Reviewing Search Results
Returning to the Patient

Evaluating Evidence

Evaluating the Validity
Validity Questions

 

Knowledge Test

Multiple Sclerosis
Case #2
Case #3
Case #4

 

Reference/
Glossary
Feedback

 

In the following exercise, click an answer and a pop-up box will appear that contains feedback.

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Case 3: Age-Related Macular Degeneration

The Patient

1. Start with the patient - a clinical problem or question arises out of the care of the patient.

A 71-year-old man has no significant past medical history with a previous diagnosis of dry macular degeneration . He has a significant social history for smoking 50 pack/year. He has blurred vision and is seeing a "wavy" line when he looks at Amsler grid with his left eye.

On examination his visual acuity is 20/20 OD and 20/40 OS. The anterior segment examination and intraocular pressure are all within normal limits. Dilated fundus examination reveals normal optic nerve with cup to disc ratio of 0.3 ou and normal appearing periphery and retinal vessels. In the macula of the right eye there are multiple drusen. In the left eye there is an area of subretinal elevation approximately 1 disc area in size that appears to involve the fovea.

A fluorescein angiogram is obtained which shows a well-demarcated area of hyperfluorescence that leaks on late frames of the angiogram and involves the fovea. A diagnosis of a classic subfoveal CNV membrane is made and the patient is given the choice of photodynamic therapy or thermal laser treatment. The patient chooses photodynamic therapy.

Photosensitizing dye is injected intravenously and 692-nm laser is applied to the whole lesion. The patient is advised to stay out of the sunlight and bright light for 5 days and to be followed in 3 months to determine if another treatment is necessary.

The patient's granddaughter is a fourth-year medical student and decides to find the best evidence for her grandfather's choice of photodynamic therapy for wet ARMD.

The Question

2. Construct a well-built clinical question derived from the case.

Based on this scenario, choose the best, well-built clinical question:

A. For an elderly male diagnosed with wet age-related macular degeneration is photodynamic therapy a more efficacious treatment than thermal laser for decreasing the rate of vision loss?

B. For a patient diagnosed with age-related macular degeneration is thermal laser the best therapy?

C. For an elderly male with macular degeneration is thermal laser better than photodynamic therapy?

The Resource

3. Launch UpToDate (on-CHS campus only) and conduct a search using the well-built question from Answer A above. (Hint: In point-of-care databases it is best to start by searching for the pre-dominant medical condition, in this case "age-related macular degeneration.")

Based on your UpToDate search results please answer the following question.

Which of the following are given by UpToDate as effective therapies for wet type ARMD?

A. Intravitreous injection of a VEGF inhibitor

B. Thermal laser photocoagulation

C. Photodynamic therapy

D. Probably macular translocation surgery

E. All of the above

The Evaluation

4. Appraise the evidence for its validity (closeness to the truth) and its applicability (usefulness in clinical practice).

As stated previously, evaluating medical research reports is a complex and time-consuming undertaking. The best resources in the clinical setting are the point-of-care databases which provide pre-evaluated answers to specific clinical questions in the practical time frame needed by a practicing physician.

UpToDate is a good example of a database providing patient-oriented, evidence-based clinical answers that are pre-evaluated for validity. Evidence in UpToDate is labeled in one of three levels so clinicians can quickly grasp the reliability of conclusions and recommendations.

Based on your UpToDate search results please answer the following question.

In UpToDate what level of evidence is assigned to photodynamic therapy as treatment for a patient with active wet ARMD with non-acute lesions, preserved vision in a second eye, and unlikely to achieve reading vision in the affected eye?

A. Grade 1A [strong recommendation and high-quality evidence]

B. Grade 2B [weak recommendation and moderate-quality evidence]

C. Grade 2C [weak recommendation and low-quality evidence]

We now go to the Knowledge Test: Case No. 4.