Statistical Report on Diagnoses
of C. difficile and Deaths among
Patients with C. difficile
Chris Robertson
Strathclyde University
Health Protection Scotland
May 09, 2012
1
Outline
• Aims and Methods
• Diagnoses of C. difficile
– Comparison of wards and periods
• Testing for C. difficile
– Where and when was testing taking place
• Rates of new diagnoses per 1000 occupied bed days
– Comparison of wards and periods
• Funnel plots to compare wards
• Death Rates among patients with C. difficile
– All cause deaths and deaths where C. difficile is a contributory cause
• Control Charts
– Were the number of cases per week typical
• Potential Outbreak Analysis*
– Number of cases in a ward at the same time *
• Trends in C. difficile reports over time *
May 09, 2012
* At request of Vale of Leven Inquiry Team
2
Aims and Methods
Aims
• Investigate pattern of Diagnoses of C. difficile
and the extent to which the pattern varies
over wards and time
• Investigate pattern of Testing for C. difficile
and the extent to which the pattern varies
over wards and time
• Investigate pattern of Deaths and report on
the extent to which the pattern varies over
the wards and period
May 09, 2012
3
Aims and Methods
Methods
• The rate of occurrence of events or the
proportion of patients with an event, which
require the use of an appropriate denominator.
• In some instance the denominator will be
– the number of patients with C. Difficile,
– the number tested for C. Difficile,
– the number of occupied bed days.
• The latter denominator is required for
comparison of wards as the wards are of different
sizes.
May 09, 2012
4
Aims and Methods
Methods
• Analysis of rates is based upon the Poisson
distribution
– Assessed using standard methods
– residual plots and index of dispersion test
• Comparison of proportions
– Fisher’s exact test and exact binomial confidence
intervals
• Time to event analysis
– Cox regression
May 09, 2012
5
Aims and Methods
Study Period
• 3 periods of particular interest:
– January to June 2007,
– July to November 2007 and
– December 2007 to June 2008
• The latter period is the period most under
scrutiny
• January to June 2007 is the period which is
most directly comparable (temporally) to the
main study period
May 09, 2012
6
New diagnoses of C. difficile
Distribution of new diagnoses of
C. difficile over time and ward
• Generally the ward of sample collection is the same
the same ward that the result is returned to but not
always
– Due to patient movement
– Admissions
– Transfers from and to another hospital
• 2 views
– By ward the sample was collected from
– By ward the positive result was returned to
• Descriptive analysis of where in the hospital C. difficile
was present
May 09, 2012
7
New diagnoses of C. difficile
New and Repeat Infections
Negative
Test was negative
Positive First
Test was positive for C. difficile and this was the
first positive test for the patient. The patient
may have had prior negative tests
Positive Continuation
Test was positive for C. difficile and in the
previous 28 days the patient has had a positive
test result. The patient may have had prior
negative tests
Positive Subsequent
(Assumed to be a new infection)
Test was positive for C. difficile and in the
previous 28 days the patient has not had any
positive test results. The patient will have had
at least one prior positive test result and may
have had prior negative tests
May 09, 2012
8
New diagnoses of C. difficile
All New Diagnoses of C. difficile by
ward of diagnosis
C Diff All New Diagnoses
HDU
F
Ward
6
5
4
3
15
14
Jan
Feb Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov Dec
Jan
Feb
Mar
Apr
May
Jun
Date: 01/01/2007 - 30/06/2008
May 09, 2012
Black spots are the first positive test; green dots are a presumed new infection in a
patient previously positive for C. difficile. Diagnoses from RAH, WIG, Home or community
are excluded
9
New diagnoses of C. difficile
All New Diagnoses of C. difficile by
ward of sample collection
C Diff All New Diagnoses
Ward Sample Colleced From
MAU
HDU
F
Ward
6
5
4
3
15
14
Jan
Feb Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov Dec
Jan
Feb
Mar
Apr
May
Jun
Date: 01/01/2007 - 30/06/2008
May 09, 2012
Black spots are the first positive test; green dots are a presumed new infection in a
patient previously positive for C. difficile. Diagnoses from RAH, WIG, Home or community
are excluded
10
New diagnoses of C. difficile
Summary – New Diagnoses
• C. difficile is present throughout the whole
period from January 2007 to June 2008,
– Especially in Wards 6, 14 and 15.
• This presentation does not take into account
ward size or occupancy.
• Little difference between results presented by
ward of sample collection and ward result
reported to and most subsequent analysis is
based upon ward of report
May 09, 2012
11
Testing for C. difficile
Testing for C. Difficile by ward and time
• The aim of this section is to see if testing is
spread throughout all the wards or is localised
to a few wards or a specific period
• Examples from 3 wards
May 09, 2012
12
Testing for C. difficile
Positive Continuation: Previous positive result may have been in another ward
Positive Subsequent: Previous first diagnosis may have been in another ward
May 09, 2012
13
Testing for C. difficile
May 09, 2012
14
Testing for C. difficile
Summary: testing for C. difficile throughout the whole period in virtually all
wards but especially in 14, 3, 5, 6, F and CCU/HDU
Even in wards with few cases
May 09, 2012
15
Testing for C. difficile
Summary
• Testing throughout the whole period in
virtually all wards but especially in
– 14, 3, 5, 6, F and CCU/HDU.
• This presentation does not take into account
ward size or occupancy
– 6, 14 and 15 with 19, 22 and 23 beds occupied on
average;
– 3, 5, F, Fruin are smaller at 17, 14, 15, 12 beds
– CCU/HDU at 9 beds.
May 09, 2012
16
Rates of C. Difficile per 1000 occupied bed days
Rates of C. difficile
• Rates per 100 occupied bed days so that
comparisons of wards and periods are
referred to a common baseline
• Aim
• Is there any evidence that the rate of new
diagnoses varies
– over period
– over ward
May 09, 2012
17
Rates of C. Difficile per 1000 occupied bed days
Rates of new C. difficile infections per month
Ja8 Ma8 Ma8
0 4 8
Ward 5
Rate per 1000
Ward 3
Se7 No7 Ja8 Ma8 Ma8
Ja7 Ma7 Ma7
Ju7
Se7 No7
Ja8 Ma8 Ma8
Month
Ward 6
Ward CCU/HDU
0 4 8
Month
Se7 No7 Ja8 Ma8 Ma8
Ja7 Ma7 Ma7
Ju7
Se7 No7
Ward F
Ward Fruin
Se7 No7 Ja8 Ma8 Ma8
Ja8 Ma8 Ma8
0 4 8
Month
Rate per 1000
Month
Month
May 09, 2012
Se7 No7
Month
0 4 8
Ja7 Ma7 Ma7 Ju7
Ju7
Month
0 4 8
Ja7 Ma7 Ma7 Ju7
0 4 8
Ja7 Ma7 Ma7
Rate per 1000
Ja7 Ma7 Ma7 Ju7
Rate per 1000
Se7 No7 Ja8 Ma8 Ma8
0 4 8
Rate per 1000
Ja7 Ma7 Ma7 Ju7
Rate per 1000
Ward 15
Rate per 1000
0 4 8
Rate per 1000
Ward 14
Ja7 Ma7 Ma7
Ju7
Se7 No7
Ja8 Ma8 Ma8
Ja7 is January 2007, Ja8 January
2008.
Occupied beds days data is not
available for every day and
imputed values are used when
necessary.
The horizontal dotted blue line is
the average rate of new infections
per week in the hospital over the
whole study period.
The vertical green dotted lines
separate the time axis into the
three periods.
Month
18
Rates of C. Difficile per 1000 occupied bed days
C Difficile Rates by Ward
No significant difference between
the two periods, Jan to May 2007
and Dec-Jun 2008, p = 0.59
Significant differences between
the wards, p < 0.0001
May 09, 2012
The dot is the rate and the horizontal line represents the 95% confidence
interval for the rate. The rates are derived from a Poisson regression model
adjusting for ward and period (Jan to Jun 2007 and Dec 2007 to June 2008)
19
Rates of C. Difficile per 1000 occupied bed days
Summary – Rates
• Ward F has two clear peaks in April/May 2007 and
January/February 2008.
• The double peak is also visible in ward 3 while the 2008
peak is visible in ward 6.
• The April 2007 peak can be identified in ward CCU(4)/HDU.
• Wards 5, 14 and 15 have fairly constant rates
• Rate of C. difficile infections varies among the three
periods, p = 0.010.
– The rates in the period Jul to Nov 2007 are 45% (95% CI 10%,
67%) lower than those in the first period (Jan to Jun 2007).
• No difference in rates between Jan to Jun 2007 and Dec
2007 to June 2008
May 09, 2012
20
Funnel Plots of Rates of C. Difficile
Funnel Plots
• Funnel plots show the anticipated variation in the
rates of new infections among the wards.
• Aim of this section is to see if there is evidence
that the rates of diagnoses of C. difficile in a ward
are higher or lower than the average in the
hospital taking into account
– the natural variation you would expect by chance,
and
– the size of the wards as measured by occupied bed
days.
May 09, 2012
21
Funnel Plots of Rates of C. Difficile
Monitoring
Funnel Plots – what variations should you expect if the rate is the same in all wards
Bed Occupancy increased? – one month extra observation time in latter period
No cases in Fruin Jan 2007-June 2007
May 09, 2012
22
Funnel Plots of Rates of C. Difficile
Summary Funnel Plots
• In the first two periods there is no evidence that any ward
has substantially higher rates of C. difficile with regard to
the others,
– though ward 15 and Fruin have lower rates in the first period.
• In the last period December 2007 to June 2008,
– Ward 6 has higher rates than the others,
– ward 5 and Fruin have lower,
– and all are outside the 95% funnel plot limits for the size of the
ward.
• Assuming that the Poisson model is valid this suggests that
there may be more variability among the wards than could
reasonably be attributed to chance (at the 95% confidence
limits).
May 09, 2012
23
Death Rates
Deaths
• Is there evidence that the rate of death among
patients who were diagnosed with C. difficile
vary
– over ward, and
– over period.
May 09, 2012
24
Death Rates
All Cause Deaths
• There are 130 C. difficile patients and for 80 there is a record of
death.
• Death Rate is 61.5% (95% CI 52.6%, 69.9%)
– percentage of patients who had C. Difficile who died
• Of the 80 patients who died,
– 25% died within 6 days of the confirmed diagnosis being reported to
the ward,
– 50% within 17 days,
– 75% within 2 months and
– 90% within 4 months.
• Three patients died on the day of report and 7 died before the
report came back to the ward (1 with a 3 day gap, and 3 with gaps
of 2 days, 3 with gaps of 1 day) – the sample was collected while
the patients was alive but the patient died before the laboratory
reported.
May 09, 2012
25
Death Rates
Percentages of Patients with C. difficile
who died by Ward
Ward of Diagnosis
Ward Sample Collected From
Ward Total Dead Percent Lower Upper Total Dead Percent Lower Upper
3
20
14
70.00 45.72 88.11
19
13
68.42
43.45
87.42
4
5
3
60.00 14.66 94.73
6
4
66.67
22.28
95.67
5
9
2
22.22
2.81 60.01
7
1
14.29
0.36
57.87
6
33
20
60.61 42.14 77.09
31
20
64.52
45.37
80.77
14
17
10
58.82 32.92 81.56
17
11
64.71
38.33
85.79
15
11
10
90.91 58.72 99.77
11
9
81.82
48.22
97.72
F
16
9
56.25 29.88 80.25
17
8
47.06
22.98
72.19
Fruin
2
2
100.00 15.81 100.00
2
2
100.00
HDU
4
3
75.00 19.41 99.37
3
2
66.67
9.43
99.16
5
3
60.00
14.66
94.73
118
73
61.86
52.47
70.65
MAU
Total
117
73
62.39 52.96 71.18
15.81 100.00
There is a great deal of variation – some wards had few C Difficile patients, but
no statistically significant differences, p=0.14
May 09, 2012
26
Death Rates
Percentages of Patients with C. difficile
who died by Period
Period
Total
Dead
Percent
Lower
Upper
Jan-Jun 2007
53
31
58.49
44.13
71.86
19
11
57.89
33.50
79.75
58
38
65.52
51.88
77.51
Jul-Nov 2007
Dec-Jun 2008
No statistically significant differences, p=0.73
May 09, 2012
27
Death Rates
Percentages of Patients with C. difficile
dying within 30 days by Ward
Ward Total
3
20
4
5
5
9
6
33
14
17
15
11
F
16
Fruin
2
HDU
4
MAU
Total 117
Ward of Diagnosis
Dead Percent Lower
9
45.00 23.06
2
40.00 5.27
1
11.11 0.28
13
39.39 22.91
6
35.29 14.21
6
54.55 23.38
6
35.29 14.21
1
50.00 1.26
1
25.00 0.63
45
Ward Sample Collected From
Upper Total Dead Percent Lower Upper
68.47
19
8
42.11 20.25 66.50
85.34
6
2
33.33 4.33 77.72
48.25
7
1
14.29 0.36 57.87
57.86
31
12
38.71 21.85 57.81
61.67
17
7
41.18 18.44 67.08
83.25
11
6
54.55 23.38 83.25
61.67
17
5
29.41 10.31 55.96
98.74
2
1
50.00 1.26 98.74
80.59
3
1
33.33 0.84 90.57
5
2
40.00 5.27 85.34
38.46 30.15 47.51 118
45
38.14 29.88 47.14
There is a great deal of variation – some wards had few C Difficile patients, but
no statistically significant differences, p=0.75
May 09, 2012
28
Death Rates
Percentages of Patients with C. difficile
dying within 30 days by Period
Total
Jan-Jun 2007
Jul-Nov 2007
Dec-Jun 2008
Dead
53
19
58
Percent Lower
Upper
18
33.96
21.52
48.27
5
26.32
9.15
51.20
24
41.38
28.60
55.07
No statistically significant differences, p=0.45
May 09, 2012
29
Death Rates
Cause of Death of the 60 patients who had a
diagnosis of a new infection of C. difficile between
December 1st, 2007 and 30th June 2008
Ward Diagnosis reported to
Dead
Ward Sample Collected From
Dead
C Difficile
Percent C
C Difficile
Percent C
not a
C Difficile a Difficile
not a
C Difficile a Difficile
contributory contributory contributory
contributory contributory contributory
Ward Total Alive cause
cause
cause
Lower Upper Total Alive cause
cause
cause
Lower Upper
3
8
2
1
5
62.5 24.5 91.5
7
2
1
4
57.1 18.4 90.1
4
2
0
1
1
50.0
1.3 98.7
2
0
0
2
100.0 15.8 100.0
5
2
1
0
1
50.0
1.3 98.7
1
0
0
1
100.0
2.5 100.0
6
16
5
3
8
50.0 24.7 75.3
14
4
4
6
42.9 17.7 71.1
14
8
2
2
4
50.0 15.7 84.3
7
1
2
4
57.1 18.4 90.1
15
5
0
0
5
100.0 47.8 100.0
6
1
0
5
83.3 35.9 99.6
F
9
5
1
3
33.3
7.5 70.1
8
5
1
2
25.0
3.2 65.1
Fruin
2
0
0
2
100.0 15.8 100.0
2
0
0
2
100.0 15.8 100.0
HDU
1
1
0
0
0.0
0.0 97.5
1
1
0
0
0.0
0.0 97.5
MAU
4
1
1
2
50.0
6.8 93.2
7 patients with unknown ward of diagnosis excluded
8 patients with unknown ward of collection excluded
No evidence that having C. difficile as a contributory cause of death is related to the ward of
collection of the sample, p=0.31, or ward of diagnosis, p = 0.29.
May 09, 2012
30
Death Rates
Summary - Deaths
• There is no evidence that the percentage of C. difficile
patients who died varied over period or ward.
• There is no evidence that percentage of C. difficile
patients who died with C. Difficile is a contributory
cause varied over ward in the period December 2007
to June 2008.
• Analysis takes into account, age and gender and time
to death from first diagnosis but does not adjust for co
morbidity of patient
• The relatively small sample size and large number of
wards make it difficult to detect differences unless they
were very large.
May 09, 2012
31
Control Charts
Control Charts for new infections
• In this section the use of elementary control charts on
the weekly new notifications of C. difficile infections
per ward is investigated.
• The aim is to see if or when there would have been
statistical evidence suggesting that there were an
exceptionally large number of C. difficile cases in the
hospital i.e. exploratory.
• The study period is divided into two separate periods
– Jan-Nov 2007 and Dec 2007 to Jun 2008.
• The main focus is the period Dec 2007 to Jun 2008 and
data from the earlier period is used to set the baseline
control limits.
May 09, 2012
32
Control Charts
Control Charts Dec 2007-Jun 2008
The mean number of new diagnoses of C. difficile in patients residing in the hospital
from the period Jan to Nov 2007 is used to construct the control chart – 1.69 per week.
In the period Dec 2007 to Jun 2008 there are two instances where the statistical process
control methods signal
- the week beginning 21 January 2008 and the week beginning 28 April 2008
May 09, 2012
33
Control Charts
Control Charts - Summary
• Using the period January 2007 to November 2007
to set the baseline, there is evidence of 2 periods
of a large number of new diagnoses of C. difficile
in the hospital than would be expected by chance
• Conclusions unchanged when using the period
January to June 2007 as baseline
• Analysis is retrospective and does not reflect the
situation which would have been observed as the
data evolved prospectively
May 09, 2012
34
Potential Outbreaks
Potential Outbreaks of C. difficile
• During the period Jan 2007 to June 2008
guidelines for defining the occurrence of an
outbreak existed.
• Aim of this investigation is to see if there were
any dates when an outbreak may have
occurred.
• Investigation carried out at the request of the
Vale of Leven Hospital Inquiry team
May 09, 2012
35
Potential Outbreaks
Potential outbreaks
Generic
Two or more linked cases (or isolates) of unexplained
illnesses which indicates the possibility that they may be
due to a known or unknown infectious agent identified in
health care premises
Gastrointestinal
Three or more cases, with two or more episodes of
unexplained vomiting and/or diarrhoea, within a 24 hour
period in healthcare premises
NHS Greater Glasgow and Clyde Control of Infection Committee Policy.
Outbreak Policy for outbreaks in healthcare premises. Effective from July,
2006; Review Date July 2010; Replaces previously issued outbreak policies
May 09, 2012
36
Potential Outbreaks
Re - creation of C. difficile burden in
hospital - Assumptions
• A patient with C. difficile has it for 7 days (range 3-10)
following any positive test, not just the first positive
test.
• Movement of patients between wards and transfers
out and death taken into account
• Analysis is fraught with difficulties because of the lack
of absolute certainty in the data.
– Although the ward to which the diagnosis was reported is
known there is no guarantee that the patient remained in
the same ward for the subsequent 7 days if there is no
mention of death, discharge, transfer out to another
hospital or movement to another ward.
– analysis is the weakest and the one which is most sensitive
to the data quality.
May 09, 2012
37
Potential Outbreaks
Example Patient Trajectories
Day
1
2
3
4
5
6
7
8
9
10
11
Ward A
Same ward for all 7 days – No subsequent positive test
Ward A
Same ward - subsequent positive test on day 3
Ward A
Same ward - Died or transferred out on day 4
Denotes patient with C. difficile diagnosis on ward
May 09, 2012
38
Potential Outbreaks
Example Patient Trajectories
Day
1
2
3
4
5
6
7
8
9
10
11
Ward A
Ward B
Moved ward day 3 - No subsequent positive test
Ward A
Ward B
Moved ward day 3 - subsequent positive test day 7, died day 10,
moved back to original ward day 10
May 09, 2012
39
Potential Outbreaks
Example Ward Trajectories
Day
1
2
3
4
5
6
7
8
9
10
11
Patient A
Moved ward day 3, returned day 6
Patient B
Patient died on 5th day post diagnosis
Number
of Positive
patients
in ward
May 09, 2012
1
1
2
1
1
2
2
0
0
0
0
40
Potential Outbreaks
Estimated numbers of C. difficile
Patients in the hospital per day
Seldom is there a period with no C. difficile cases in the hospital,
29% of the whole period
May 09, 2012
41
Potential Outbreaks
Potential Outbreaks in the wards
A black spot corresponds
to an occasion when
there are 2 patients with
C. Difficile in the ward on
the same date;
A red spot corresponds
to 3 or more patients.
No episodes were
observed in the wards
not listed in the graphs.
May 09, 2012
42
Potential Outbreaks
Potential outbreaks in the wards
3 day period after positive test
A black spot corresponds
to an occasion when
there are 2 patients with
C. Difficile in the ward on
the same date;
A red spot corresponds
to 3 or more patients.
No episodes were
observed in the wards
not listed in the graphs.
May 09, 2012
43
Potential Outbreaks
Outbreak - Summary
• Analysis sensitive to assumptions and data
quality
• Evidence of instances where potential
outbreaks are possible even with most
favourable conditions (1 day post diagnosis)
– Both in the January to June 2007 and in the
December 2007 – June 2008 period
May 09, 2012
44
Time Trends
Comparison with C. difficile cases prior
to 2007
• Investigation carried out at the request of the
Vale of Leven Hospital Inquiry team
• This investigation is likely to be subject to
ascertainment bias due to
– Introduction of mandatory reporting of C. difficile
cases from September 2006 onwards
– More detailed investigation of hospital and
laboratory data in the period January 2007 – June
2008
May 09, 2012
45
Time Trends
New Reports of C. difficile from 2003
to June 2008
• Data were collected as part of a police investigation and were typed
into a spreadsheet from the Vale of Leven infection control team
records.
• Potentially useful for describing the historical trends in the numbers
of cases of C. difficile in the Vale of Leven Hospital prior to the
period under investigation in this report.
• Comparisons of the early with cases from 2007 onwards must
always bear in mind that mandatory reporting of all cases of C.
difficile in patients over 65 was established as from 1st September
2006.
• With mandatory reporting came
– a national case definition,
– rules for case finding and definitions;
– reporting practices prior to September 2006 may not be comparable
with reporting practices after this period.
May 09, 2012
46
Time Trends
New Reports of C. difficile from 2003
to June 2008
• In the period 2003-2006 there were on average 2.3 new
patients with C. difficile per year
– some evidence of an increasing trend, p = 0.042
– rates increasing by 19.7% (95% CI 0.7%, 42.3%) per year.
• In the three periods which were wholly after the
introduction of mandatory reporting for C. difficile among
those aged 65 or over there was a big increase in the rates
of new patients per month, p < 0.0001, adjusting for trend
May 09, 2012
47
Time Trends
Summary – 2003-June 2008
• It is not easy to interpret the increase in rates
as mandatory reporting was introduced in
September 2006
– part of the increase may be due to changes in
reporting and ascertainment practices.
– Part of the increase may also be associated with a
continuation of the increasing trend from 2003 to
2006.
May 09, 2012
48
Summary
Summary - Data
• There are data issues.
• There were rather a large number of data corrections and this
leads to a reduction in confidence in the data.
• Some of the problems will stem from data recording issues in
case notes and missing information in cases notes.
• The database in the legal office was not set up for a rigorous
analysis as much information was contained within the same
text entry field.
• Patient movement data may not be complete
• Not absolutely certain that the database for the trend analysis
had all cases of C. difficile,
– testing regime may have been different 2007 onwards
May 09, 2012
49
Summary
Summary C. Difficile Cases
• C. Difficile is present throughout the whole period from
January 2007 to June 2008 notably in in Wards 6, 14 and
15.
• Using data from Jan – Jun 2007 and Dec 2007-Jun 2008
– there are higher rates of new C. Difficile infections in wards 6
and F,
– no differences in the rates between the two periods.
• The funnel plot analysis suggested that in the last period
December 2007 to June 2008 the level of variation among
the wards was greater that anticipated:
– Ward 6 had higher rates of new C. Difficile infections than the
other wards and ward 5 had lower rates.
May 09, 2012
50
Summary
Summary Deaths
• No statistical evidence that the proportion of C. Difficile
patients who died varies significantly over the wards.
• No statistical evidence that the proportion of C. Difficile
patients who death was associated with C. Difficile varied
significantly over the wards in the Dec 2007 to June 2008
period.
• There was no evidence that the proportion of C. Difficile
patients who died varied over the three periods.
• From a statistical perspective there are few C. Difficile
patients and this contributes to the lack of precision in
the estimates and a reduced power for the tests.
May 09, 2012
51
Summary
Summary - Outbreaks
• It seems likely, even allowing for caveats in the
data, that there have been a number of
occasions, in the periods January-June 2007
and Dec 2007- June 2008 especially, when
there were 3 or more patients with C. Difficile
in a ward at the one time.
May 09, 2012
52
Summary
Summary Trends
• Increasing rate of cases in the period 20032006.
• In Jan-June 2007 and Dec 2007 – June 2008
there were more cases per month than that
predicted by the continuation of the
increasing trend
• Unknown impact of introduction of
mandatory reporting of C Difficile among
patients 65+ and possible ascertainment bias
May 09, 2012
53
May 09, 2012
54
Extra slides showing simulation results
• Even when the length of time a patients is
assumed to have C. difficile is varied there is
never an occassion when there is not at least
one instances with at least 3 patients in a
ward on the same day with C. Difficile.
May 09, 2012
55
W.5
W.other
0
2
4
6
8
0
0
0 100
600
600
W.6
10
0
600
0
80
2
4
6
8 10
13
16
600
0
300
7
0
1
2
3
4
Assumed a case for 3 - 10 days
0
600
W.Fruin
6
1
W.4
0
0
5
0
W.15
200
W.14
4
2
W.3
0
0
0
3
1
W.F
600
W.HDU
0
0
3+ cases in a day
0
W.5
W.other
17
22
27
32
37
60
0
0
0
600
40 80
W.6
42
0
W.F
1
15 19
23 27 31 35 39
7
9 11
17
600
0
3
4
5
6
7
8
9 10
Assumed a case for 3 - 10 days
0
600
W.Fruin
14
22
26
12 15 18 21
W.4
0
80
0
5
5 7 9
W.15
150
W.14
3
18
0 60
0
0
0
14
W.3
60
600
W.HDU
7 10
0
2+ cases in a day
0
W.5
W.other
0 100
0
0
600
100
W.6
1 3 5 7 9
12
15
19
0
W.F
W.3
0
0
0
0
600
100
150
W.HDU
2 3 4 5 6 7 8 9
4
6
8 10
16
1 2 3 4 5 6 7 8 9
W.4
1
2
3
4
5
7
1
2
3
4
5
Assumed a case for 1 - 5 days
0
600
W.Fruin
6
0
0
0
200
600
W.15
200
W.14
13
0
2+ cases in a day
0
11
W.other
0
1
0
0
0 400
600
W.5
600
W.6
2
W.3
0
0
600
W.F
200
0
0
0
600
W.HDU
0
0
2
3
4
2
3
5
600
0
Assumed a case for 1 - 5 days
0
600
W.Fruin
4
W.4
0
0
0 200
1
0
W.15
600
W.14
1
0
3+ cases in a day
0