Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General...
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![Page 1: Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General Hospital, Edinburgh National Stroke Audit Coordinators.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649f0c5503460f94c1f2ae/html5/thumbnails/1.jpg)
Control Charts
Robin Henderson Royal Infirmary of EdinburghMargrethe van Dijke Western General Hospital, Edinburgh
National Stroke Audit Coordinators
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Charts have been used in healthcare for a very long time! Carl Wunderlich 1861
Control Charts
![Page 3: Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General Hospital, Edinburgh National Stroke Audit Coordinators.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649f0c5503460f94c1f2ae/html5/thumbnails/3.jpg)
Florence Nightingale – the “passionate statistician” - is believed to have invented a type of chart
![Page 4: Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General Hospital, Edinburgh National Stroke Audit Coordinators.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649f0c5503460f94c1f2ae/html5/thumbnails/4.jpg)
A patient’s temperature chart from 1963 – a run chart.
![Page 5: Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General Hospital, Edinburgh National Stroke Audit Coordinators.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649f0c5503460f94c1f2ae/html5/thumbnails/5.jpg)
The horizontal line at 98.2 °F indicates “normal” temperature
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The red horizontal lines indicate the normal range 97.5 to 98.8 °F
![Page 7: Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General Hospital, Edinburgh National Stroke Audit Coordinators.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649f0c5503460f94c1f2ae/html5/thumbnails/7.jpg)
The run chart has now been converted to a control chart – Walter Shewhart 1924
![Page 8: Control Charts Robin Henderson Royal Infirmary of Edinburgh Margrethe van Dijke Western General Hospital, Edinburgh National Stroke Audit Coordinators.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649f0c5503460f94c1f2ae/html5/thumbnails/8.jpg)
Henderson, D. A. et al. JAMA 1999;281:2127-2137.
Typical Temperature Chart of Patient With Smallpox Infection
The control chart helps us to distinguish between “common cause” variation and “special cause” variation
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Month
Pro
port
ion w
ith r
eco
rded s
creen
Sep-06J ul-06May-06Mar-06J an-06Nov-05Sep-05J ul-05May-05Mar-05J an-05
100
90
80
70
60
50
40
30
Swallow Screening at RIE
A run chart of the monthly proportion of patients with recorded swallow screens at RIE
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To turn this run chart into a control chart we have to calculate a centre line and limits. The calculations are quite easy to do but most users get a computer to perform the calculations and plot the chart. An Excel tool may be downloaded from: -
http://www.indicators.scot.nhs.uk/SPC/SPC.html
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Month
Pro
port
ion w
ith r
eco
rded s
creen
100
90
80
70
60
50
40
30
_Average = 66
Upper Limit =100
Lower Limit = 30
Swallow screening at RIE
All points fall between the tram lines and there are no “unusual” patterns of variation so there is no evidence of any special cause variation
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Month
Pro
port
ion w
ith r
eco
rded s
creen
Apr-07Jan-07Oct-06Jul-06Apr-06Jan-06Oct-05Jul-05Apr-05Jan-05
100
90
80
70
60
50
40
30
_Average = 66
Upper limit = 100
Lower limit = 30
2
Swallow screening at RIE
We have evidence of improvement! If the average had remained at 66 then nine in a row above 66 would be most unlikely
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It appears that a campaign by SALT staff has been effective and increased the average monthly proportion of patients screened from 66% to 82%.
Month
Pro
port
ion w
ith r
eco
rded s
creen
Apr-07Jan-07Oct-06Jul-06Apr-06Jan-06Oct-05Jul-05Apr-05Jan-05
100
90
80
70
60
50
40
30
_Average = 82
UB=100
Lower limit = 51
1 2
Swallow screening at RIE
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Case Study – NV Clinic at WGH
Days from referral to examination for all patients
0
2
4
6
8
10
12
14
16
18
20
Months
Da
ys WGH Mean
WGH Median
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Days from receipt of referral to examination <= 14 days for DEFCVD patients and <= 7 days,
80% Meets NHS QIS Standard for both
0102030405060708090
100
Months
Pe
rce
nta
ge
<= 7 days
<= 14 days
Target
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18
16
14
12
10
8
6
4
2
0
Date
Days
_X=3.55
UCL=6.10
LCL=1.00
1 21 21 2
Mean days from referral to examination for DEFCVD patients
X=11.31_
The mean waiting time from referrals being received to patients being seen in the NV Clinic has decreased from 11.3 to 3.5.
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100
80
60
40
20
0
Date
Perc
enta
ge
_X=91.5UB=100
LCL=72.9
1 21 21 21 21 21 2
I Chart of Percentage of NV Clinic patients seen within 7 days
X=28.8_
The mean percentage of DEFCVD patients seen in the NV Clinic within seven days since referral has being received has increased from 28.8 to 91.5.
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How do you know that your stroke care is improving?
Control charts are a very useful tool for addressing this question.
“Display is an obligation!”
John Tukey 1986
Have a go!