3. Introduction
Quality control is one of the most scientific and
significant tool to correct errors in analytical
phase in the clinical laboratories.
It is the procedures designed to monitor the
routine performance of testing processes in order
to detect possible errors, reduce and correct
deficiencies before the test results are reported.
From Customer ‘s perspective, quality of a good
service for the price of the product
The aim of quality control is simply to ensure
that the results generated by the test are correct.
4. Quality Assurance - the overall program that
ensures that the final results reported by the
laboratory are correct.
It is much more concerned with : that the right
test is carried out on the right specimen from the
right patient, and that the right result and right
interpretation is delivered to the right person at
the right time”
Internal quality control (IQC) and external quality
assessment (EQA) programs are used to assess
and improve analytical performance.
Introduction
5. IQC is self-assessing tool by using control
samples for the continuous and immediate
monitoring of the analytical part.
IQC : to observe precise and accurate results on
daily analytical phase
EQA is intended for periodic and retrospective
observing of laboratory results by an autonomous
external agency to specify to the laboratory about
the accuracy or bias in their systems methods and
results.
EQA : to monitor long term accuracy and bias of
their results and stability of methods over a
longer period of time.
Introduction
6. Aims of Quality assurance
Accuracy and precision
Satisfactory
Quality report
Economical
Aims at preventing defects rather than
detecting the defects
Minimize errors
Timely report
7. Quality Assurance vs. Quality Control
An overall
management plan
to guarantee the
integrity of data
(The “system”)
A series of analytical
measurements used to
assess the quality of
the analytical data
(The “tools”)
8. The Quality Assurance Cycle
•Data and Lab
Management
•Safety
•Customer
Service
Patient/Client Prep
Sample Collection
Sample Receipt
and Accessioning
Sample Transport
Quality Control
Record Keeping
Reporting
Personnel Competency
Test Evaluations
Testing
9. Few Terms:
Precision Accuracy
The degree of
fluctuation in the
measurements
The closeness of
measurements to
the true value
Quality Control is used to monitor both the
precision and the accuracy of the assay in order
to provide reliable results.
10. Precise and inaccurate Precise and accurate
Precision and Accuracy
12. Pre-analytical stage
• Test requisition slip
• Patient preparation
• Sample tube labeling
• Sample collection
• Sample
transportation
• Reagent storage
• Reagent preparation
• Quality control sera
storage
• Callibrator storage
• QC alliquet storage
• Quality monitoring
of refrigerator,
waterbath
• Maintenance and
cleaning of
instruments
Machine maintenance: Daily, Weekly, Monthly and
Annually
13. Analytical Stage
Daily machine startup
Daily Callibration: for Wet chemistry
Daily Internal QC :
Routine chemistry: BA 400 and Vitros 350
CLIA: Diasorin for common test like TFT, aTPO
Daily QC for i-Sens electrolyte analyzer
Daily TDS measurement of DI water
•Lot wise callibration and QC of HbA1c in Hb Vario
•Weekly/monthly control of all uncommon tests in CLIA
•Callibration of Vitros 350 on change of reagent LOT
14.
15. Selection of Control & Calibrators
Has a known concentration of the substance
(analyte) being measured
Used to adjust instrument, kit, test system in
order to standardize the assay
Sources of QC samples:
Appropriate diagnostic sample
Obtained from:
Another laboratory
EQA provider
Commercial product
16. Characteristics of a Good Control
The composition of the control material should be
as similar to the patient sample as possible,
reacting in the same manner
The analyte concentration should be at medically
significant levels
Stable under storage for longer period of time
prior to preparation & even after prep
Low vial-to-vial variability
Requiring a minimum preparation or ready to use
Reasonable in price
17. At DH-KUH
For IQC: Callibrators:
Dialab autocal
Biosystem cal
Reagent Pack Cal for
HbVario
Reagent pack Cal for
Diasorin-CLIA
Reagent Cartridge
cal for iSens
Vitros Cal kit
For IQC: Controls:
Biorad
Dialab controls
Biosystem controls
Reagent Pack Con
for HbVario
Control Diasorin-
CLIA
Mission control for
iSens
PV for Vitros
18. For EQAS: samples from
1. CMC Vellore, India
2. Chung-Ang University College of Medicine,
South Korea
3. NPHL, Nepal
At DH-KUH
19. Storage of QC Samples
Controls are aliquoted into smaller ‘user friendly’
volumes for storage
Establish a storage protocol:
store at -20oC
in use vials stored at 4oC
use 0.5 ml vial maximum of one week
20. Monitoring QC Data
Use Levey-Jennings chart
Plot control values each run
Acceptance of run
Monitor precision and accuracy of repeated
measurements
Review charts at defined intervals, take
necessary action, and document
21. Findings Over Time
Ideally should have control values clustered about
the mean (+/-2 SD) with little variation in the
upward or downward direction
Imprecision = large amount of scatter about the
mean. Usually caused by errors in technique
Inaccuracy = may see as a trend or a shift,
usually caused by change in the testing process
Random error = no pattern. Usually poor
technique, malfunctioning equipment
22.
23.
24.
25.
26. 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”
Atleast run 2 control samples
12S rule R4S rule
13S rule 41S rule
22S rule 10X rule
27. Westgard – 12S Rule
“warning rule”
One of two control results falls outside ±2SD
Alerts tech to possible problems
Not cause for rejecting a run
Must then evaluate the 13S rule
12S rule
violation
28. Westgard – 13S Rule
If either of the two control results falls outside of
±3SD, rule is violated
Run must be rejected
If 13S not violated, check 22S
13S rule
violation
29. Westgard – 22S Rule
2 consecutive control values for the same level
fall outside of ±2SD in the same direction, or
Both controls in the same run exceed ±2SD
Patient results cannot be reported
Requires corrective action
22S rule
violation
30. Westgard – R4S Rule
One control exceeds the mean by –2SD, and the
other control exceeds the mean by +2SD
The range between the two results will therefore
exceed 4 SD
Random error has occurred, test run must be
rejected
R4S rule
violation
31. Westgard – 41S Rule
Requires control data from previous runs
Four consecutive QC results for one level of
control are outside ±1SD, or
Both levels of control have consecutive results
that are outside ±1SD
41S rule
violation
32. Westgard – 10X Rule
Requires control data from previous runs
Ten consecutive QC results for one level of control
are on one side of the mean, or
Both levels of control have five consecutive
results that are on the same side of the mean
10x rule
violation
34. When a rule is violated!!!!!
Warning rule = use other rules to inspect the
control points
Rejection rule = “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 and controls indicate proper
performance
45. Future plans:
Sample bar coding
Test requisition coding
Reduce use of requisition form
LIS to all department
Full access of patient history and other
department finding via LIS