Quality control in clinical laboratory (Biochemistry)

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2. 2 of 58Quality Control in
Clinical Biochemistry
Ashok Katta
“Quality is never an accident; it is always the result of
high intention, sincere effort, intelligent direction and
skillful execution; it represents the wise choice of
many alternatives.”

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Clinical Biochemistry
Ashok Katta
Importance of laboratory test in
clinical medicine
Lab tests constitute only one part of the
diagnostic process in clinical medicine.
In fact, it has been stated that an experienced
physician may arrive at a relatively accurate
diagnosis in ~80% of cases, based solely on a
thorough history and physical examination.
However, there is no doudt that, nowadays,
biochemical and other lab tests are almost always
an important part of the overall diagnostic process.
The use of biochemical investigation and lab tests
is, helping physicians and healthcare workers make
diagnoses and other clinical judgment.

4. 4 of 58Quality Control in
Clinical Biochemistry
Ashok Katta
The results obtained from
laboratory analyses are used
to…
diagnose,
prescribe treatment, and/or
Monitor the health or progress
of the patient.
Since such importance is
placed upon test results, they
must be as reliable and
accurate as possible.

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Clinical Biochemistry
Ashok Katta
Who determines if a patient gets a statin?
We do !

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Clinical Biochemistry
Ashok Katta
Who determines if a patient gets a Dx of DM?
We do !

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Clinical Biochemistry
Ashok Katta
Who determines if a patient gets a prostrate biopsy?
We do !

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Clinical Biochemistry
Ashok Katta
Who determines if a patient gets dialysis?
We do !

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Clinical Biochemistry
Ashok Katta
How do we know we are right?
Do we?We do !

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Clinical Biochemistry
Ashok Katta
LAB-1
LAB-2
LAB-3

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Clinical Biochemistry
Ashok Katta
Fasting Plasma Glucose < 110mg/dl = Non-DM
On two or more occasions can make the diagnosis of Diabetes
Mellitus
Fasting Glucose >110 mg/dl = IFG
Fasting Glucose >126mg/dl = DM
LAB-1
LAB-2
LAB-3

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Clinical Biochemistry
Ashok Katta
To know the answer for this
question, first you should
understand
How Clinical Biochemistry
Lab works.
How do we know we are right?

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Clinical Biochemistry
Ashok Katta
Errors in the
clinical Laboratory

14. Equipment
Reliability
Reagents
Poor
trained
technicians
Work load
managemen
t
Poor result
verification
Non-
validated
tests
Time
pressures
Under-
staffed
Why do laboratory
errors occur?
Poor Quality
Management

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Clinical Biochemistry
Ashok Katta
Types of Error
Random error
An error which varies in an
unpredictable manner in…
Magnitude
Sign
Difficult to eliminate but
repetition reduces the influence
of random error
Example – error in pipetting
Can be minimized by training,
supervision and by SOPs
Systematic error
An error which, in the course of a
number of measurements of the same
value of a given quantity remains
constant under same condition.
Systematic errors create a
characteristic bias in the test results
and can be accounted for by applying a
correction.
Example - change in the reagent batch
or modifications in testing method.

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Clinical Biochemistry
Ashok Katta
Testing Response
Laboratory Workflow
Patient
Pre-analytical Analytical Post-analytical
Test Request
Patient preparation
Sample Collection
Sample Transport
Sample Receipt
Testing Review
Lab Interpretation
Reporting
Record Managment

17. Laboratory
Workflow
Patient Preparation
Sample Collection Sample Receipt
Sample
Transport
Reporting
•Data & Lab
Management
•Safety
•Customer
Service
Quality Control
Testing
Record
Keeping

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Clinical Biochemistry
Ashok Katta
3 phases of laboratory testing:
Pre-analytical,
analytical and
post-analytical
Pre-analytical—specimen
collection, transport and processing
Analytical—testing
Post-analytical—testing results
transmission, interpretation, follow-
up, retesting.

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Clinical Biochemistry
Ashok Katta
Effects of Pre-analytical Variables on the
Quality of Laboratory Testing
What are pre-analytical variables ?
These are variables that can occur from the time when
the test is ordered by the physician until the sample is
ready for analysis.
The pre-analytical stage is the most important.
Pre-analytical variables account for upto 75% of
laboratory errors.
The analytical stage & post analytical stages depend
primarily on the integrity of the specimen submitted to
the laboratory.
Laboratory staff involved in specimen collection have a
direct impact on the outcome of patients lab results.

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Clinical Biochemistry
Ashok Katta
The Pre-Analytical process
Identify the patient:
Get A Suitable Sample
Transport to Lab
Receive In Lab:
Prepare For Testing:

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Clinical Biochemistry
Ashok Katta
Examples of possible preanalytical variables:
Patient Identification:
- It is important to identify a patient accurately so
that blood is collected from the correct person.
- Drawing blood from the wrong person, or labeling
the correct patient’s sample with a different
patient’s label can certainly contribute to
laboratory error. (Mislabeling ???)

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Clinical Biochemistry
Ashok Katta
Analytical phase
Standardisation
Calibrators
Reagents
Test conditions
Quality Control
External Quality Assurance (EQA)
Internal Quality Control (IQC)
How do we know we are right?

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Clinical Biochemistry
Ashok Katta
Factors influencing quality:
Post-analytical
• Right recording and reporting
• Right interpretation
– Range of normal values
• Right turnaround time
• Report to right user

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Clinical Biochemistry
Ashok Katta
Quality control & Quality Assurance
Quality control
Refers to the measures that must be
included during each test run to verify that
the test is working properly
Aim:
• To ensure that the results generated by
the tests are correct
Quality Assurance
Defined as the overall program that
ensures that final results reported by the
laboratory are correct.
Aim:
• Ensure that
Right test is carried out on
Right specimen and
Right result and
Right interpretation is delivered to
Right person at
Right time.

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Clinical Biochemistry
Ashok Katta
Quality Assurance in Laboratory
Quality assurance in Laboratory involves……
Internal Quality Control (IQC)
External Quality Assurance (EQA)

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Clinical Biochemistry
Ashok Katta
Internal Quality Control (IQC)
Done daily in the laboratory
Applied to all work processes and to every
test done in the lab.
IQC procedures identify problems
immediately.

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Clinical Biochemistry
Ashok Katta
Internal Quality Control (IQC)
Examples
Daily recording of temp in refrigerator / incubator
Repeating tests
Following SOPs
Advantage
Mistakes can be avoided
Quality of test results are raised

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Clinical Biochemistry
Ashok Katta
IQC Program
Internal Quality Control program
depends on the use of....
Internal Quality Control (IQC) specimen
Levey Jennings Charts
The use of statistical methods for interpretation.

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Clinical Biochemistry
Ashok Katta
What is control?
Material that contains the substance
being analysed
Used to validate reliability of the
test system.
Run after calibrating the instrument
Run periodically during testing

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Clinical Biochemistry
Ashok Katta
Steps in Implementing Quality Control
Obtain control material
Run each control daily along
with patient sample. OR
Run each control 20 times over
30 days
Calculate mean and ± 1,2,3 SD
Mean
1SD
1SD
2SD
3SD
2SD
3SD

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Clinical Biochemistry
Levey- Jennings Chart
Graphically Representing Control Ranges

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Clinical Biochemistry
Ashok Katta
80
85
90
95
100
105
110
115
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Mean
Day
+1SD
+2SD
+3SD
-1SD
-2SD
-3SD
Levey-Jennings Chart
Mean = 100
±1SD = 95-105
±2SD = 90-110
±3SD = 85-115

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Clinical Biochemistry
Ashok Katta
Levey-Jennings Chart -
Record and Evaluate the Control Values
80
85
90
95
100
105
110
115
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Mean
Day
+1SD
+2SD
+3SD
-1SD
-2SD
-3SD

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Clinical Biochemistry
Ashok Katta

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Clinical Biochemistry
Ashok Katta

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Clinical Biochemistry
Ashok Katta
Westgard Rules
“Multirule Quality Control”
Uses a combination of decision
criteria or control rules
Allows determination of whether
an analytical run is “in-control” or
“out-of-control”

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Clinical Biochemistry
Ashok Katta
Westgard Rules
12S rule
13S rule
22S rule
R4S rule
41S rule
10X rule
(Generally used where 2 levels of control
material are analyzed per run)

38. WARNING RULES -
 Warning 12SD : One of two control results falls
outside ±2SD. Alerts tech to possible problems. Not
cause for rejecting a run.
Control Rules – Westguard Multirule Chart

39. WARNING RULES -
 Warning 22SD : It detects systematic errors & is violated
when two consecutive IQC values exceed the mean on the
same side of the mean by 2SD.
 SENSITIVE TO SYSTEMATIC ERROR
Control Rules – Westguard Multirule Chart

40. WARNING RULES -
 Warning 41SD: It is violated if 04 consecutive IQC values
exceed the same limit (mean  1SD) & this may indicate
the need to perform instrument maintenance or reagent.
 SENSITIVE TO SYSTEMATIC ERROR
Control Rules – Westguard Multirule Chart

41. MANDATORY RULES -
 Mandatory 13SD: It is violated when the IQC value
exceeds the mean by 3SD. The assay run is regarded as
out of control. SENSITIVE TO RANDOM ERROR
Control Rules – Westguard Multirule Chart

42. MANDATORY RULES -
 Mandatory R4SD : It is only applied when the IQC is
tested in duplicate. This rule is violated when the
difference in SD between the duplicates exceeds 4SD.
SENSITIVE TO RANDOM ERROR
Control Rules – Westguard Multirule Chart

43. MANDATORY RULES -
 Mandatory 10x : Reject the run when 10 consecutive
control measurements fall on one side of the mean.
SENSITIVE TO SYSTEMATIC ERROR
Control Rules – Westguard Multirule Chart

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Clinical Biochemistry
Ashok Katta
When a rule is violated
QC Data
12s
13s 22s R4s 41s 10x
Report Results
“Out of control” Take Corrective Action

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Clinical Biochemistry
Ashok Katta
If QC is out of control
Stop testing
Identify and correct problem
Repeat testing on patient
samples and controls
Do not report patient results
until problem is solved

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Clinical Biochemistry
Ashok Katta
Solving out-of-control problems
Identify problem
Refer to established policies
and procedures for remedial
action.

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Clinical Biochemistry
Ashok Katta
Possible Problems
Degradation of reagents or kits
Control material degradation
Calibration error
Operator error
An outdated procedure manual
Equipment failure

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Clinical Biochemistry
Ashok Katta
EXTERNAL QUALITY CONTROL /
ASSESSMENT
E Q A S

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Clinical Biochemistry
Ashok Katta
External Quality Assessment
A system for objectively checking the
laboratory’s performance using an external
agency or facility.

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Clinical Biochemistry
EQA
Important for improvement
A measure of laboratory
performance

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Clinical Biochemistry
Ashok Katta
EQA process
EQA organization / Provider Laboratory
Corrective Action
EQAS samples
Sent regularly
Analyze
Return results
Evaluation
EQAS performance
report

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Clinical Biochemistry
Ashok Katta
Calculation of VIS
Designated Value [DV] = 120 mg %
Participant's result = 95 mg%
% Variation [%V] = Participant's Result – [DV]
---------------------------------- X 100
Designated value
120-95 X 100 = 25 X 100
120 120
= 20.8
Variance
Index = %V X 100 = 20.8 X 100 = 277
CCV 7.5
VIS = 277

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Clinical Biochemistry
Ashok Katta
• Check the VIS & OMVIS values for each parameter
every month
• Check if your value is close to DV
• Closer it is lower will be your VIS & better is your lab’s
accuracy
• Remember If your VIS is < 50 it is regarded and given
as zero score
•Even if >400, it is still given as 400 only

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Clinical Biochemistry
Ashok Katta
Interpretation of VIS
VIS Performance
<100 Very good
100 -150 good
150 -200 satisfactory room for improvement
> 200 Not acceptable
• If VIS of >200 on two or more occasions for the same
analyte, them check your standardization procedures &
calibration
• Indicates an accuracy problem (systematic error / bias )

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Clinical Biochemistry
Ashok Katta
Interpretation of VIS
Check the monthly OMVIS.
OMVIS Performance
< 100 Very good - your result are very close to DV
150-200 Need to take care of those parameters
> 250 You are probably reporting many wrong
results & you should take urgent steps to locate the
problem and correct them

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Clinical Biochemistry
Ashok Katta
Performance of our Lab in EQAS

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Clinical Biochemistry
Ashok Katta

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Clinical Biochemistry
Ashok Katta

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Clinical Biochemistry
Ashok Katta

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Clinical Biochemistry
Ashok Katta

61. 61 of 58Ashok KattaQuality Control in
Clinical Biochemistry
Key Messages
A QC program allows the laboratory to
differentiate between normal variation and error.
The QC program monitors the accuracy and
precision of laboratory assays.
The results of patient testing should never be
released if the QC results for the test run do not
meet the laboratory target values.

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Contact no. – 07418831766
E mail – ashokkt@gmail.com
For more presentation visit - http://www.slideshare.net/ashokktt
Ashok Katta
Dept. of Biochemistry,
Dhanalakshmi Srinivasan Medical College,
Perambalur