Regular QC Analysis is
required for Hematology Analyzer to maintain precision. In addition to analysis of QC material, patient sample duplicate analysis is suggested as additional approach.
The below provided instructions illustrates on how to analyse patient duplicate
samples for precision testing, but it is not suggested by NABL for alternative use of
controls.
QC
Analysis by Performing Duplicate Tests on Patient Samples:
- Perform
duplicate testing of different patient samples (20 duplicate sample runs)
- Calculate
differences between results
- Calculate Standard Deviation (SD) of Differences between results
- Calculate
Mean of Difference between results
- Determine +/- 2SD Limits
- Monitor subsequent duplicate patient sample results (Differences) should be within these +/- 2SD defined limits
Example with sample data by using Microsoft excel:
|
S.No
|
Date & Time
|
WBC
|
|
|
|
|
||
|
Prev.
Value |
Rep.
Value |
Diff.
|
|
|
|
|
||
|
1
|
1.5.2020, 10:00 AM
|
10.7
|
10.6
|
0.1
|
|
|
|
|
|
2
|
1.5.2020, 10:05 AM
|
11
|
12
|
-1
|
|
|
|
|
|
3
|
1.5.2020, 10:10 AM
|
8
|
9.2
|
-1.2
|
|
|
|
|
|
4
|
1.5.2020, 10:15 AM
|
12
|
10
|
2
|
|
|
|
|
|
5
|
1.5.2020, 10:20AM
|
14
|
12.2
|
1.8
|
|
|
|
|
|
6
|
1.5.2020, 10:30AM
|
8.7
|
7.4
|
1.3
|
|
|
|
|
|
7
|
1.5.2020, 10:35AM
|
12.8
|
13
|
-0.2
|
|
|
|
|
|
8
|
1.5.2020, 10:40AM
|
14
|
11.2
|
2.8
|
|
|
|
|
|
9
|
1.5.2020, 10:45AM
|
10.7
|
10.6
|
0.1
|
|
|
|
|
|
10
|
1.5.2020, 10:50AM
|
11
|
12
|
-1
|
|
|
|
|
|
11
|
1.5.2020, 10:55 AM
|
8
|
9.2
|
-1.2
|
|
|
|
|
|
12
|
1.5.2020, 11:00 AM
|
12
|
10
|
2
|
|
|
|
|
|
13
|
1.5.2020, 11:05AM
|
14
|
12.2
|
1.8
|
|
|
|
|
|
14
|
1.5.2020, 11:10 AM
|
8.7
|
7.4
|
1.3
|
|
|
|
|
|
15
|
1.5.2020, 11:15 AM
|
12.8
|
13
|
-0.2
|
|
|
|
|
|
16
|
1.5.2020, 11:20 AM
|
14
|
11.2
|
2.8
|
|
|
|
|
|
17
|
1.5.2020, 11:25 AM
|
8
|
9.2
|
-1.2
|
|
|
|
|
|
18
|
1.5.2020, 11:30 AM
|
12
|
10
|
2
|
|
|
|
|
|
19
|
1.5.2020, 11:35 AM
|
10
|
10.4
|
-0.4
|
|
|
|
|
|
20
|
1.5.2020, 11:40 AM
|
9.2
|
10.7
|
-1.5
|
|
|
|
|
|
|
|
|
Mean
|
0.51
|
|
|
|
|
|
|
|
|
SD
|
1.47
|
|
|
|
|
|
|
|
|
CV%
|
2.92
|
|
|
|
|
|
|
|
|
(-) 2SD
|
-2.44
|
|
|
|
+/- 2SD Limits
|
|
|
|
|
(+) 2SD
|
3.45
|
|
|
|
|
In Microsoft excel use the below code
to link the specific data to calculate Mean & SD
Mean :
=AVERAGE()
SD : =STDEV()
Example: =STDEV(E7:E26)
Reference: NABL
112 Guideline - Specific Criteria for Accreditation of Medical Laboratories,
Issue 4, Issue date: 11.2.2019
POSTED BY:
Mr.V.SELVAM, M.Sc (Biochemistry)
Consultant - ISO 9001 & NABL (ISO 15189 & ISO 17025)
Chennai, Tamilnadu, India
✆ +91-9940014466
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