Evidence Based Medicine: Effective Diagnostic Testing

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Evidence-Based Medicine:
Effective Diagnostic Testing - Part 2

Certified for 1 Category 1 AMA Credit.

Presented by the University of Alabama School of Medicine
Division of Continuing Medical Education

Release Date: May 8, 2009

Expiration Date: May 8, 2012

Target Audience
Objectives
Source
CME Participation
Accreditation & Credit

Introduction
Case 1
Case Question #1
References

TARGET AUDIENCE:

Primary care physicians

OBJECTIVES:

Upon completion of this CME activity, participants should be able to:

Describe how to thoughtfully use diagnostic tests in caring for patients.
Understand the influence of pre-test probability on clinical decision making.
Describe how to calculate post-test probability.

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SOURCE:

FACULTY:

Terrence Shaneyfelt, MD
Associate Professor, Department of Medicine
Division of General Internal Medicine
University of Alabama at Birmingham
Birmingham, Alabama

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DISCLOSURE:

The faculty has no commercial affiliations to disclose.

Because of the nature of preliminary studies, some products mentioned are unlabeled and investigational. Dosages, indications, and methods of use of drugs mentioned in this publication may reflect the experience of the authors, clinical literature, or other resources. Therefore, please see the full prescribing information before using any licensed product mentioned.

CME PARTICIPATION:

To participate in this online course for CME credit, please review the objectives before beginning the program. Complete the course and the self-assessment test before May 8, 2012 to receive CME credit. Your certificate will then be available online. This process should take approximately 1 hour.

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ACCREDITATION:

The University of Alabama School of Medicine is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The University of Alabama School of Medicine designates this educational activity for a maximum of 1 AMA PRA Category 1 Credit™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

The boards of nursing in many states, including Alabama, recognize Category 1 continuing medical education courses as acceptable activities for the renewal of license to practice nursing.

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DISCLAIMER:

Dosages, indications, and methods of use of any drug referred to in this publication may reflect the clinical experience of the authors, clinical literature, or other clinical resources. Therefore, please see the full prescribing information before using any product mentioned. UAB is an equal opportunity/affirmative action institution.

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INTRODUCTION:

The previous online course covered the first two principles of the diagnostic paradigm - determining pretest probability and choosing a diagnostic test. Several methods of determining pretest probability (e.g., direct studies of disease probability, clinical prediction rules and clinical experience) were discussed. It is important to accurately determine pretest probability because posttest probability is dependent upon it, it determines if further testing is even necessary, and if so, it influences which diagnostic test is chosen.

Diagnostic testing is most useful for intermediate probabilities of disease. Patients with very high or very low probabilities usually do not need further diagnostic tests because false negative and false positive results, respectively, will not be helpful as we will see later in the newsletter. In choosing a test, we need to think about whether we want to rule in or rule out disease. When we want to rule in disease we need to choose a specific test. When we want to rule out disease we should choose a sensitive test. In the previous online course, we reviewed the utility of likelihood ratios (LR) in choosing a diagnostic test; the higher the positive LR the better the test when it is positive and the lower the negative LR the better the test when it is negative.

In the previous online course, there were three examples of patients with chest pain:

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Cases:

CASE 1: (pretest probability of significant CAD: 56%)
A 62-year-old male complains of substernal chest pain that he describes as a dull ache lasting 5-10 minutes. The pain occurs at rest, but is relieved with SL NTG. The pain radiates to his left shoulder, but he has no other associated symptoms. He has had “several” episodes over the past 1-2 months, but they seem to be getting more frequent over the last few weeks.
He is a nonsmoker.
Family history is negative
PMH: hypertension
Meds: HCTZ, NTG prn, lisinopril, aspirin
ECG: NSR without ischemic changes.

CASE 2: (pretest probability of significant CAD: 98%)
A 70-year-old male complains of precordial pressure-like chest pain with exertion. The pain does not radiate, but is associated with shortness of breath. The pain lasts 10-15 minutes, resolving with rest or SL NTG. Symptoms have been gradually worsening over the last 6 months. He smokes 1 ppd. Family history is negative.
PMH: DM with proteinuria, hyperlipidemia.
Meds: metformin, aspirin, glipizide, lisinopril, simvastatin
ECG: NSR with occas PVCs. Old inverted T waves in V1-2

CASE 3: (pretest probability of significant CAD: 6%)
A 52-year-old female complains of burning substernal chest pain occurring intermittently during the day. The pain has no relation to exertion or any emotional stressors, lasts 1-2 minutes, and resolves spontaneously. The pain does not radiate and has no associated symptoms. She smokes ½ to 1 ppd.
PHM: HTN
Meds: HCTZ
ECG: NSR with occas PACs. No ischemic changes.

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