This document discusses quality control procedures for laboratory testing. It describes quantitative and qualitative quality control, including the use of control materials and charts. Quantitative quality control involves establishing value ranges for control materials using statistical analysis over many tests. Control charts are used to monitor tests for random and systematic errors over time. Qualitative quality control ensures proper evaluation of presence, absence or morphology. The document also discusses duplicate testing, delta checks, and references various quality control methods and their developers.

1. Quality Control
Gift Ajay Sam
Lecturer-Quality Management
Department of Transfusion Medicine and immunohaematology
CMC, Vellore

2. Overview
• Quality Control (QC)
• QC material
• Quantative methodologies
• Control chart analysis
• Duplicate checking
• Delta check
• Moving averages
• Qualitative QC

3. Introduction
• Process control: refers to the controlling of activities in handling and
examination of samples.
• Quality Control (QC): It is a part of process control, designed to
monitor the analytic activities.
• ISO 9000:2000 (3.2.10): QC is part of quality management focussed of
fulfilling quality requirements.

4. Laboratory
testing
Quantative Qualitative Semi-Quantative

5. Goal of QC: Serve as an error
detection methodology and identify
causes of failure (due to test system,
operator or environment) before the
results are delivered to the patient.

6. Quantative-QC
• A control is a substance that contains an established amount of
substance being tested.
• Should mimic the original testing procedure.
• Should cover the complete clinical decision making points i.e. low to
high.
• Should contain the same matrix as the patient sample.
• Controls can be frozen, freeze dried or preserved by adding
preservative.
• Can be purchased or made at the laboratory.

8. Establishing value ranges for QC materials
• Control material should be assayed over a period of time
• At least 20 data points should be collected over a 20-30 day period.
• Calculate the mean and Standard deviation (SD)
• In case of 1 or 2 outliers they can be omitted while determining the
range (>2 outliers the procedure should be repeated).
• When the QC values are plotted on the X-axis and the frequencies on
the Y-axis they form a bell shaped curve around the mean. This is
called a Gaussian Distribution.

9. 68.3% within 1S
95.5% within 2S
99.7% within 2S

10. Control chart
• Shewart chart/ Statistical process chart
• Graph used to study how a process changes over time
• The central line indicates the mean/ average
• Upper and lower lines indicate the upper control limit and lower
control limits (+SD).

11. When to use a control chart
• Controlling an ongoing process and correcting problems as they occur.
• Analysing patterns of variations
• Ensuring process stability

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12.2
12.1
12.0
11.9
11.8
11.7
11.6
11.5
11.4
Observation
IndividualValue
_
X=11.77
UCL=12.04
LCL=11.5
+4SL=12.13
-4SL=11.41
+3SL=12.04
-3SL=11.5
+2SL=11.95
-2SL=11.59
+1SL=11.86
-1SL=11.68
1
I Chart of DX3_L2_HGB

13. What to look for?
• Random error: Caused by unexplainable but inherent fluctuation in
the reading
• Systematic error: Predictable, constant and proportional to the true
value.

14. Analysing the control chart
• Extremes: 13S
• Bias: 22s,41s,10X
• Trend: 6 values in an increasing or decreasing order
• On the edge: 21s

15. Random Duplicate sample testing
• Verify machine performance between shifts.
• Alternate assessment for QC.
• Any 10 processed samples from the previous shift selected.
• Processed after the shift is completed.
• Results of 1st and next run are tabulated

16. Delta checks
• Identify wrong blood in tube
• Compare present result with previous result
• If variation is clinically acceptable or not.
• Prior result not more than 36 hours before.
• The rate of change in test result within a given period of time.

17. Bulls Algorithm
• Dr. Brain S Bull, Loma Linda University, 1974
• Was replaced by multi-rule Shewart chart post 1985.
• QC based on RBC indices- MCV, MCH, MCHC
• Based on population normal
• Batch of 20 donor samples tested and mean compared to the
established Bull’s mean (study from samples obtained from 1,767
hospitals).
• If variation <0.5% acceptable.
• Variation of 1 run >3%; 3 consecutive batch >2%: QC failed, calibrate

18. Qualitative-QC
• Qualitative tests: Evaluate presence or absence of substance or assess
morphology.
• Semi-quantative: Provides an estimated measure of quantity. E.g. 1+,
2+, 0-5/ hpf etc.
• Control materials
• Built-in: integrated into the test system
• Traditional controls: Mimic patient sample e.g. positive control, negative
control.
• QC for stains: Checked daily with known controls, precipitate and crystal
formation, bacterial contamination.

19. References
• Lab Quality Management-Handbook, WHO, CLSI, CDC
• https://asq.org/quality-resources/control-chart
• http://www.westgard.com/westgard-rules-and-multirules.htm
• John Robert Taylor (1999). An Introduction to Error Analysis: The
Study of Uncertainties in Physical Measurements. University Science
Books. p. 94, §4.1
• Et, J. (1981). James O Wesgard et al, A Multi rule Shewart Chart for
Quality Control in Clinical Chemistry. Clin. Chem. 1981; 27/3. 493-501
(pp. 493–501). pp. 493–501.

20. References
• Carstairs, K. C., Peters, E., & Kuzin, E. J. (1977). Development and
description of the “random duplicates” method of quality control for
a hematology laboratory. American Journal of Clinical Pathology,
67(4), 379–385. https://doi.org/10.1093/ajcp/67.4.379
• Rosenbaum, M. W., & Baron, J. M. (2018). Using machine learning-
based multianalyte delta checks to detect wrong blood in tube errors.
American Journal of Clinical Pathology, 150(6), 555–566.
https://doi.org/10.1093/AJCP/AQY085
• Nosanchuk, J.S and Gottmann, A. W. (1974). CUMS and Delta Checks.
Am J Clin Pathol., 62(5), 707–712.

21. References
• Shagufta, S., Shettigar, S. K. G., Gujral, S., & Kulkarni, R. K. (2011). Bull
’ s Multirule Algorithm , ( M ), An Excellent Means of Internal Quality
Control for Hematology Analyzers Merit Award. (October), 351–355.

22. James O Westgard
Who introduced the Shewart-Chart in Clinical Chemistry

23. Delta Check
One strategy to identify wrong blood in a tube

24. Random duplicate testing
Strategy to reduce QC runs

25. Control chart
A plot used to detect changes over a period of time

26. Traditional control
Control material that mimic a patient sample