Laboratory diagnosis

1. Module 2
The Diagnostic Testing
Process

2. Case Scenario 1
O 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:
O Draw daily CBC, CMP, PT, PTT,
Magnesium, Ionized Calcium and
Phosphorous x 30 days
O Comment on this approach to their care of
patients.
Photo by Elizabeth Wantuch,MD

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

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

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

6. Diagnostic Testing – 3 Phases
The diagnostic testing process can be separated
into three phases:
1. Preanalytic phase
2. Analytic phase
3. 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. 1. Clinician develops a clinical question
2. Specific laboratory test is selected
3. Test is ordered
4. Specimen is collected
5. Sample is prepared for analysis
6. Sample is analyzed
7. Result is verified
8. Result is reported
9. 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?
O 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. O In the upcoming modules, we will further
explore:
O The Preanalytic testing phase
O The Analytic testing phase
O The Postanalytic testing phase
O The process of establishing Reference
(normal) values

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