Download - Levey jenning control charts
FICCI QUALITY FORUM 1 Training on assuring quality of test results
LEVEY - JENNINGS
CONTROL CHARTS
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THE LEVEY-JENNINGS CONTROL CHART
Dr. W.A. Shewhart invented the control chart in 1924
A Levey-Jennings chart is a graph on which quality control data is plotted to give a visual indication whether a laboratory test is working well.
The Levey-Jennings Chart displays information about the quality control samples performed on laboratory analytes
2 Training on assuring quality of test results
FICCI QUALITY FORUM
THE LEVEY-JENNINGS CONTROL CHART
METHODOLOGY
i) select appropriate control materialsii) analyze those materials to characterize
method performance by collecting at least 20 data pointsiii) calculate the mean and standard deviation of those dataiv) select the number of control measurements to be used per run
3 Training on assuring quality of test results
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Let the Control Material be a cholesterol sample of 200 mg/dL.This control is tested everyday for 25 days and the data generated are :198, 197, 201, 204, 200, 201, 199, 197, 197, 199, 200, 203, 199, 198, 197, 196, 196, 199, 196, 202, 201, 198, 203, 201, 199 mg/dL
= 199.24 mg/dL 199 mg/dL = 2.31 mg/dL 3 Control Limit = 3 = 192 to 206 mg/dL 2 Control Limit = 2 = 194 to 204 mg/dL
EXAMPLE - 1
4 Training on assuring quality of test results
FICCI QUALITY FORUM
LEVEY-JENNINGS CHART
+3 = 206 mg/dL
Average = 199 mg/dL
-3 = 192 mg/dL
DAYS
mg
/
dL
-2 = 194 mg/dL
+2 = 204 mg/dL
5 Training on assuring quality of test results
FICCI QUALITY FORUM
The laboratory shall run a minimum of one level QC (1 in every 20 samples tested) at least once a day
Where samples (parameter) exceed 20 a day, two level QC to be employed at least once a day for such parameters
Typically, QC should be around 5% of samples tested
6 Training on assuring quality of test results
FICCI QUALITY FORUM
Reject QC if:a) It is outside 3 SD (13s)
b) two consecutive values obtained are outside 2 SD on the same side but within 3 SD (22s)
c) ten consecutive values are above or below the mean, but within 2 SD (10x)
Rule for 1 level QC
7 Training on assuring quality of test results
FICCI QUALITY FORUM
The value of the Control tested for a period 11 days gave the following data :
CASE - 1
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
202 204 207 198 195 196 200 202 201 197 199
8 Training on assuring quality of test results
FICCI QUALITY FORUM
LEVEY-JENNINGS CHART - 1
+3 = 206 mg/dL
Average = 199 mg/dL
-3 = 192 mg/dL
DAYS
mg
/
dL
-2 = 194 mg/dL
+2 = 204 mg/dL
9 Training on assuring quality of test results
FICCI QUALITY FORUM
The value of the Control tested for a period 11 days gave the following data :
CASE - 2
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
202 205 205 198 195 196 200 202 201 197 199
10 Training on assuring quality of test results
FICCI QUALITY FORUM
LEVEY-JENNINGS CHART - 2
+3 = 206 mg/dL
Average = 199 mg/dL
-3 = 192 mg/dL
DAYS
mg
/
dL
-2 = 195 mg/dL
+2 = 204 mg/dL
11 Training on assuring quality of test resultsFICCI QUALITY FORUM
FICCI QUALITY FORUM
The value of the Control tested for a period 11 days gave the following data :
CASE - 3
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
201 204 203 200 200 203 200 202 201 203 199
Training on assuring quality of test results12
FICCI QUALITY FORUM
LEVEY-JENNINGS CHART - 3
+3 = 206 mg/dL
Average = 199 mg/dL
-3 = 192 mg/dL
DAYS
mg
/
dL
-2 = 195 mg/dL
+2 = 204 mg/dL
Training on assuring quality of test resultsFICCI QUALITY FORUM 13
FICCI QUALITY FORUM
The value of the Control tested for a period 11 days gave the following data :
CASE - 4
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
202 204 197 198 195 196 200 202 201 197 199
14 Training on assuring quality of test results
FICCI QUALITY FORUM
LEVEY-JENNINGS CHART - 4
+3 = 206 mg/dL
Average = 199 mg/dL
-3 = 192 mg/dL
DAYS
mg
/
dL
-2 = 195 mg/dL
+2 = 204 mg/dL
15 Training on assuring quality of test resultsFICCI QUALITY FORUM
FICCI QUALITY FORUM
EXERCISE - 6
Data generated from testing of the reference material are :
2.24, 2.11, 2.12, 2.36, 2.47, 2.21, 2.29, 2.13, 2.13, 2.34, 2.18, 2.20, 2.27, 2.44, 2.38, 2.41, 2.31, 2.25, 2.19, 2.33, 2.28, 2.22, 2.36, 2.42.
Prepare a Levy-Jennings chart from the above data
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EXERCISE - 7
Subsequent data generated from the reference material for the next 11 days are :
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
2.14 2.61 2.43 2.09 2.51 2.23 2.39 2.16 2.13 2.62 2.34
Check whether the daily controls are within acceptable limits
FICCI QUALITY FORUM
2-Level Quality Control Material (QC) is used for analysis of Blood Glucose covering the low range and the normal range. The value of the QCS are :
Low level - 50 to 60 mg/dL
Normal level - 90 to 110 mg/dL
These two controls are tested everyday for 25 days and the data generated together with the data analysis are stated on the following slides.
EXAMPLE - 2
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Low level - 50 to 60 mg/dL
58, 56, 58, 55, 55, 59, 63, 60, 57, 54, 56, 63, 64, 62, 63, 59, 58, 62, 59, 57, 58, 57, 62, 63, 61 mg/dL
= 59.2 mg/dL 59 mg/dL
= 3 mg/dL
3 Control Limit = 3 = 50 to 68 mg/dL
2 Control Limit = 2 = 53 to 65 mg/dL
EXAMPLE - 2 (Contd)
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Normal level - 90 to 110 mg/dL
94, 96, 93, 98, 105, 106, 109, 104, 105, 107, 106, 99, 98, 99, 102, 103, 106, 92, 97, 103, 109, 110, 99, 105, 94 mg/dL
= 102 mg/dL
= 5 mg/dL
3 Control Limit = 3 = 86 to 118 mg/dL
2 Control Limit = 2 = 91 to 113 mg/dL
EXAMPLE - 2 (Contd)
FICCI QUALITY FORUM
Reject QC if:a) either QC values is outside 3 SD (13s)
b) both QC values are outside 2 SD on the same side, but within 3 SD (22s)
c) difference between both QC values is > 4 SD i.e. one level QC is > 2 SD and other level QC is < 2 SD (R4s)
d) 10 consecutive values of the same level QC are above or below the mean, but within 2 SD (10x)
e) 5 consecutive values of one same level QC and 5 consecutive values of the other level QC are above or below the mean, but within 2 SD (10x)
Rule for 2 level QC
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The value of the Controls tested for a period 11 days gave the following data :
EXAMPLE OF ACCEPTABLE QC
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
52 57 61 63 60 59 53 64 59 66 65
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
99 104 111 95 107 97 96 93 105 98 90
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Average = 59 mg/dL
-2 = 53 mg/dL -3 = 50 mg/dL
+2 = 65 mg/dL
+3 = 68 mg/dL
-3 = 86 mg/dL
-2 = 91 mg/dL
Average=102 mg/dL
+2 =113 mg/dL
+3 =118 mg/dL
FICCI QUALITY FORUM
The value of the Controls tested for a period 11 days gave the following data :
CASE - A
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
52 62 61 60 63 64 58 64 59 66 70
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
99 107 110 98 109 97 99 97 102 98 100
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+3 =118 mg/dL +2 =113 mg/dL
Average=102 mg/dL
-2 = 91 mg/dL
-3 = 86 mg/dL
+3 = 68 mg/dL
Average = 59 mg/dL
+2 = 65 mg/dL
-2 = 53 mg/dL
-3 = 50 mg/dL
Reject since on Day 11, Low Level QC value exceeds 3 (13s)
Normal QC
Low Level QC
FICCI QUALITY FORUM
The value of the Controls tested for a period 11 days gave the following data :
CASE - B
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
55 63 60 57 64 62 58 64 52 64 67
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
97 105 111 99 107 96 100 101 93 98 115
FICCI QUALITY FORUM
Reject since on Day 11, both QC values are between 2 & 3 on the same side (22s)
Normal QC
Low Level QC
+3 =118 mg/dL +2 =113 mg/dL
Average=102 mg/dL
-2 = 91 mg/dL
-3 = 86 mg/dL
+3 = 68 mg/dL
Average = 59 mg/dL
-2 = 53 mg/dL -3 = 50 mg/dL
+2 = 65 mg/dL
FICCI QUALITY FORUM
The value of the Controls tested for a period 11 days gave the following data :
CASE - C
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
55 64 61 58 67 60 57 61 59 66 63
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
99 107 110 98 89 99 108 104 96 92 105
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CASE – C (contd)
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
55 64 61 58 67 60 57 61 59 66 63
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
99 107 110 98 89 99 108 104 96 92 105
Day – 5, 67 = 2.67 89 = - 2.6
2.67 - (- 2.6 ) = 5.27 and thus > 4
FICCI QUALITY FORUM
Reject since difference between 1 & 2 level QC values on Day 5 is > 4 (R4s)
Normal QC
Low Level QC
+3 =118 mg/dL +2 =113 mg/dL
Average=102 mg/dL
-2 = 91 mg/dL
-3 = 86 mg/dL
+3 = 68 mg/dL
+2 = 65 mg/dL
Average = 59 mg/dL
-2 = 53 mg/dL -3 = 50 mg/dL
FICCI QUALITY FORUM
The value of the Controls tested for a period 11 days gave the following data :
CASE - D
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
55 64 61 58 67 60 57 61 59 63 66
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
99 98 95 101 97 99 100 97 101 98 104
FICCI QUALITY FORUM
Reject since 10 consecutive values of level 2 QC, are on the same side of mean (10x)
Normal QC
Low Level QC
+3 =118 mg/dL
+2 =113 mg/dL
= 102 mg/dL
-2 = 91 mg/dL -3 = 86 mg/dL
+3 = 68 mg/dL
= 59 mg/dL +2 = 65 mg/dL
-2 = 53 mg/dL -3 = 50 mg/dL
FICCI QUALITY FORUM
The value of the Controls tested for a period 11 days gave the following data :
CASE - E
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
63 64 61 62 64 58 57 61 59 63 56
LOW LEVEL
NORMAL LEVEL
Day1
Day 2
Day3
Day4
Day 5
Day 6
Day 7
Day 8
Day9
Day10
Day 11
107 98 111 105 104 112 100 97 101 98 100
FICCI QUALITY FORUM
Reject since 5 consecutive values each of both QC levels are on the same side of mean (10x)
Normal QC
Low Level QC
+3 =118 mg/dL
+2 =113 mg/dL
= 102 mg/dL
-2 = 91 mg/dL
-3 = 86 mg/dL
+3 = 68 mg/dL
+2 = 65 mg/dL
= 59 mg/dL -2 = 53 mg/dL
-3 = 50 mg/dL
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Three types of change is commonly observed in LJ Plots, which results from different sources:
1. Drift or Trend
2. Dispersion
3. Shift
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DRIFT
Seen when the control value moves progressively in one direction from the mean for a minimum of three (3) days
Suggests that a problem is gradually developing, such as deterioration of a reagent or control
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DISPERSION
Increase in Random Errors and Lack of Precision
Suggests inconsistency of technique or fluctuations in instrumentation function
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SHIFT
Abrupt changes observed when a problem develops suddenly
May be due to instrument malfunction or an error in technique