1. External Quality Assessment: Choosing an EQA program
University of Nairobi/University of Washington Peadiatrics Research Laboratory
John Gatimu
University of Nairobi/University of Washington Research Laboratory

2. External Quality Assessment (EQA)
Labs need to evaluate the various EQA programs to identify one that best suits
SOPs
Study protocols
EQA specimens should be analyzed the same way patient samples are analyzed
Applicable to a wide range of clinical laboratory assays

3. Analyzing Flow Cytometry Samples
Using FACS Calibur samples can be gated
automatically or manually
In general, good correlation between automatic and manual gating
Differences indicate a problem
In our lab only a small number of samples require manual gating

4. Objective
To identify an EQA program that best suits our laboratory’s SOPs and study protocols

5. Objectives cont and Methodology
Measured objectives by:
1. Evaluating percent change in absolute CD3, CD4 and CD8 cell count between gating methods
2. Analyzing statistical differences in SD intervals (SDI) from automated vs manual gating using a paired t-test
3. Obtaining failure rate from each company
Compared 10 EQA specimens from 2 companies
Used FACS Calibur SOPs

6. Patient samples: Similar Counts Between Gating Method
Automated gated
Manual gated
929
931
440
441
457
462

7. EQA Samples: Differences Between Gating Method
Automated gated
Manual gated
1121
1521
757
718
733
344

8. Results: Manual Gating results in increased absolute counts

9. Results: Using True Mean Derived from Company
Company A :
Lymphocyte Subset
Auto gated
Manual gated
P value
CD4
0.32 SDI
0.10 SDI
0.0095
CD3
3.10 SDI
SDI
0.0002
CD8
4.98 SDI
-0.66 SDI
0.0001
Company B
Lymphocyte
Subset
Auto gated
Manual gated
P value
CD4
-0.09 SDI
0.06 SDI
0.6529
CD3
-0.22 SDI
-0.31 SDI
0.0200
CD8
0.66 SDI
0.12 SDI
0.0005

10. Results: Percent Failure rate
Percent of tests > 2SD of true mean
Automated gating
Lymphocyte Subset
Company A
Company B
P value
CD4 0%
10%
0.3506
CD3
70%
0.0051
CD8
90%
0.0000

11. Summary and Conclusion
Differences were noted for:
Percent change in absolute CD3, CD4 and CD8 counts after manual gating
SDIs
Failure rate
Labs should evaluate specimens from various EQA programs in order to identify one that best suits the labs SOPs and study protocols
This process is applicable to other clinical laboratory tests

12. Barbara Lohman-Payne Judd Walson CFAR Tanja Hart UW Amy Liu KEMRI
Acknowledgements
Barbara Lohman-Payne
Judd Walson
Tanja Hart
Amy Liu
Michele Merkel
Nick Bright
Anna Wambugu
CFAR UW
KEMRI
UoN BD