Introduction
The
monitoring of long term laboratory imprecision is very important for patient
management, especially in the follow up for the response to treatment based on
the laboratory data. Currently, the long term imprecision is based on the
combination of the intermediate CV as CV= √ (CV12+CV22+
CV32 +….). This formula provides bigger CV compared to the generated CV by the analyzer
for the same duration.
The
aim of this study is to determine alternative method in calculation for the
long term imprecision compared to the generated CV in the same duration.
Method
The Albumin quality control data,
Level 1 and Level 2 on the Architect c8000 analyzer for six months ( July,
August, September, October, November and December 2012) were used in this study. The analyzer
generated the mean, SD and CV for the last six months duration and on monthly
basis (July to December respectively). The monthly mean, SD and CV were entered
in the excel work sheet for calculation of the long term imprecision in two
methods:
i.
Based
on the combination of monthly CV and
ii.
Based
on the combination of the monthly variance.
The value of the total CV obtained
in the above method was compared to the generated CV for the last six month
(July to December).
Results
The results from the experiment are
as the following :
1.
Automated generated Total CV by the analyzer for the duration of
July to December
|
LEVEL 1
|
LEVEL 2
|
|||||||
|
N
|
MEAN (g/l)
|
SD
|
% CV
|
N
|
MEAN ( g/l)
|
SD
|
% CV
|
|
|
July to Dec
|
231
|
40.54
|
0.827
|
2.04
|
234
|
24.7
|
0.61
|
2.46
|
|
MONTH
|
N
|
LEVEL 1
|
LEVEL 2
|
||||
|
MEAN (g/l)
|
SD
|
CV
|
MEAN
|
SD
|
CV
|
||
|
JULY
|
2
|
41
|
0
|
0.00%
|
24.5
|
0.707
|
2.89%
|
|
AUGUST
|
57
|
40.54
|
0.569
|
1.40%
|
24.745
|
0.440
|
1.78%
|
|
SEPT
|
57
|
39.72
|
0.526
|
1.32%
|
24.18
|
0.563
|
2.33%
|
|
OCT
|
54
|
40.333
|
0.476
|
1.18%
|
24.91
|
0.446
|
1.79%
|
|
NOV
|
52
|
41.481
|
0.504
|
1.22%
|
25.245
|
0.434
|
1.72%
|
|
DEC
|
9
|
41.556
|
0.527
|
1.27%
|
25.111
|
0.333
|
1.33%
|
|
Imprecision
calculation (six month)
|
Level 1 QC
|
Level 2
QC
|
|
Based on the monthly CV
|
2.86%
|
4.99%
|
|
Based on the monthly Variance
|
2.04%
|
2.46%
|
|
Automated generated by analyzer (six month)
|
2.04%
|
2.46%
|
The results showed that CV
generated by automated analyser based on the QC data July to December were
2.04% for level 1 and 2.46% for level 2. The CV calculated based on the
combination of monthly CV from July to December on the same QC data were 2.86%
for level 1 and 4.99% for level 2. On the other hand, when the CV is calculated
based on the combination of monthly variance on the same QC data, it was found
that CV for level 1 was 2.04% and level 2 was 2.46%.
Conclusion
Based
on this study, it was found that the long term CV calculated based on the
combination monthly variance gave
comparable result to that of automatically generated CV by the analyser where as combination of the
monthly CV gave much bigger CV. Therefore, it can be concluded that the CV
calculated by monthly variance is more reliable compared to the combination of
the monthly CV.
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