practical qc
DESCRIPTION
PRACTICAL QC. M.Jabari 2005. Quality assurance. « Do what you have written and write what you have done ». LEVEY-JENNINGS CONTROL CHART. It is generally useful first to try to classify the error as random or systematic. WESTGARD RULES. The set of rules recommended by westgard (1981 ). - PowerPoint PPT PresentationTRANSCRIPT
M.Jabari 2005M.Jabari 2005
«Do what you have written and write
what you have done»
It is generally useful first to try to classify the error as It is generally useful first to try to classify the error as
random or systematicrandom or systematic. .
The set of rules recommended The set of rules recommended by westgard (1981 )by westgard (1981 ). .
1:2S : one observation in the warning zone
(Outside 2S)
1:3S : one observation in the rejection zone
(Outside 3S)
2:2S : two consecutive control
observations in the warning zone, on the
same side of the mean (Outside 2S)
R:4S : two consecutive control observations in the
warning zone. ( The range of two results is greater than 4 SD)
4:1S : Four consecutive results outside
1SD on the same side of the mean.
10M : 10 consecutive observations on the
same side of the mean
CONTROLDATA
1:2s
1:3s 2:2s R:4s 4:1s 10 X
IN-CONTROL ACCEPT RUN
OUT-OF-CONTROL REJECT RUN
NO
YES
YES
NO NO NO NO
YES YES YES
NO
YES
When a systematic error is present , When a systematic error is present , the cusum values will steadily the cusum values will steadily
increaseincrease. .
The slope of the line will be related The slope of the line will be related to the size of the systematic errorto the size of the systematic error. .
Cusum techniques generally provide Cusum techniques generally provide
better detection of systematic errors better detection of systematic errors
than levey-jennings chartsthan levey-jennings charts . .
NOGLUCOSE mg%MEANX-M(X-M )2
110010000
298100-24
3102100+24
499100-11
5101100+11
610010000
798100-24
8101100+11
997100-39
1099100-11
1198100-24
12101100+11
1310010000
1499100-11
1599100-11
16101100+11
1797100-39
1810010000
19101100+11
2099100-11
)X-M( = -10
)X-M( = 442
SD =)X-M(2
n-1
SD = 44
19
SD = 1.7
94
96
98
100
102
104
106
GLUCOSE mg% 100 98 102 99 101 100 98 101 97 99 98 101 100 99 99 101 97 100 101 99
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
+3SD
+2SD
+1SD
-1SD
-2SD
-3SD
NO.GLUCOSE mg%MEANX-MCUSUM
110010000
298100-2-2
3102100+20
499100-1-1
5101100+10
610010000
798100-2-2
8101100+1-1
997100-3-4
1099100-1-5
1198100-2-7
12101100+1-6
131001000-6
1499100-1-7
1599100-1-8
16101100+1-7
1797100-3-10
181001000-10
19101100+1-9
2099100-1-10
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
GLUCOSE mg% 0 -2 0 -1 0 0 -2 -1 -4 -5 -7 -6 -6 -7 -8 -7 -10 -10 -9 -10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
-3SD
+2SD
+1SD
-2SD
-1SD
-10 SD
Accuracy control Recovery
Patients mean
Linearity
Glucose:
Specimen 1 : 150 mg%
Specimen 2 : 100 mg%Add together
Expected value : 250 mg%
Observed value : 230 mg%
% Recovery = 100 - 8 = 92%
Ideal recovery is greater than 95% Ideal recovery is greater than 95%
% Bias =250 - 230
250X 100 = 8
In this method mixed two specimen with In this method mixed two specimen with
different ( one high and other low) different ( one high and other low)
concentration ,and reassayconcentration ,and reassay. .
The chart of concentration and absorbaance The chart of concentration and absorbaance
must be strightforwardmust be strightforward. .
Good area < 1s
1s < warning area < 2s
rejection area > 2s
The dispersion is increased (CV 2, CV 3)
Accurate but not precise
Not systematic
The dispersion is the same
The target is moving
Precise but not accurate
Systematic
Not accurate and not
precise…
Systematic &non
Systematic bias…