1. The Diagnostic Testing Process
Module 2
The Diagnostic Testing Process

2. Photo by Elizabeth Wantuch,MD
Case Scenario 1
In order to make their daily work-flow smoother, a resident and intern on a busy inpatient service include the following order when they admit any patient:
Draw daily CBC, CMP, PT, PTT, Magnesium, Ionized Calcium and Phosphorous x 30 days
Comment on this approach to their care of patients.

3. Case Scenario 1 Discussion
4 major roles for laboratory tests in patient care:
Diagnosis of disease
Monitoring of disease, therapies, interventions
Screening for disease
Research

4. Case Scenario 1 Discussion
The resident and intern (though perhaps well-intentioned) are not properly utilizing laboratory testing and the clinical laboratory
They are not ordering specific laboratory tests based on clinical questions
AND in doing so they are
Increasing the cost of healthcare
Contributing to the development of iatrogenic anemia
Leading to potentially unnecessary work-up if any errors in the diagnostic testing process occur

5. Laboratory testing begins and ends with patient care
Clinician develops a clinical question
Specific laboratory test is selected
Test is ordered
Specimen is collected
Sample is prepared for analysis
Sample is analyzed
Result is verified
Result is reported
Test result is interpreted in context of clinical scenario
Action is taken
Patient care is affected
Image by Theresa Kristopaitis, MD

6. Diagnostic Testing – 3 Phases
The diagnostic testing process can be separated
into three phases:
Preanalytic phase
Analytic phase
Post analytic phase
Variables that may affect proper interpretation of test results are present in each phase.
Test result changes due to clinical factors must be interpreted in consideration of these variables.

7. Clinician develops a clinical question
Specific laboratory test is selected
Test is ordered
Specimen is collected
Sample is prepared for analysis
Sample is analyzed
Result is verified
Result is reported
Test result is interpreted in context of
clinical scenario
10. Action is taken
11. Patient care is affected
PREANALYTIC
Phase
ANALYTIC
Phase
POSTANALYTIC
Phase

8. Why is this important?
When a physician orders a lab test and receives a test result, there are a multitude of factors (variables) that could (and usually should) be considered in interpreting the test result

9. In the upcoming modules, we will further explore:
The Preanalytic testing phase
The Analytic testing phase
The Postanalytic testing phase
The process of establishing Reference (normal) values

10. Proceed to “Module 3 - Preanalytic Phase of Laboratory Testing”