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

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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

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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