1. Surveillance Methodology and Economic Burden of SSIs
Maureen Spencer, RN, M.Ed, CIC
Infection Preventionist Consultant
Boston, MA - USA

2. Purpose of the Infection Control and Prevention Program
Surveillance – detect cases
Control - outbreaks, clusters or increasing trends in data
Implement prevention measures

3. Surveillance System and CDC Definitions

4. Developed Algorithms For Surveillance (Each Category)

5. Case definition
Case definitions are designed to capture all potential cases of a disease/condition without contaminating the dataset with extraneous materials
NHSN is, by definition, our basic service
Special case definitions may be required for specific issues or for outbreaks

6. Case definitions Outbreak Case control studies
May want to date or unit define
May want to include symptoms or manifestations
Case control studies
Permit selection of control group (those without the condition under study)
Associated with the event or process

13. Data analysis Data are systematically compiled and interpreted
Data are analyzed using statistical methods
Date are compared over time to internal and external databases
Comparative databases are used when undesirable variation is identified

14. Numbers
Numerator – the “top” number which is also the number of cases identified
Denominator – the “bottom number” –(down below) is the total number of individuals studied
Rate – the result of dividing the numerator by the denominator and multiplying by a factor

15. The “Factor”
There is no established “factor” for most statistical math in epidemiology
Generally report surgical and other similar infection as x/100 events
Generally report device related infections by device day x/1000 device days

16. Measures of occurrence
Incidence
Measure of frequency with which an event occurs in a population over a specified period of time
New cases
Prevalence
Proportion of persons in a population with a particular disease at a specific point in time (point prevalence) or over a specified time period (period prevalence)
Existing cases

17. Studies
Case Control – two groups, identical, but one with the characteristic under study, and other without. General 1:3 (power)
Cohort – all people in a group (enter together, and then observe for occurrence of disease/condition)
Prospective – looking forward
Retrospective – looking backward
This slide for confidence intervals

18. Bias
Bias can be defined as “any systematic error in the design, conduct or analysis of a study that results in a mistaken estimate of an exposure’s effect on the risk of disease”
Selection Bias
Information Bias

19. The monthly record of cases
Record demographic data for each case
Use consistent methods
Column A: Last Name
Column B: First Name
Column C: Medical Record #Physician
Physician name
Physician identification # (check, as often there are two different numbers in the hospital)
Age – useful in stratification
Gender – equivocal data set
Admission date (critical!)
Onset date (used to calculate # hospital days admission to onset)

20. Line Listing
Line List: A line list is an organized, detailed list of each record of a surgical site infection
Example
Suppose you are interested in looking at all CLABSIs in 2010 that occurred in the ICU and the Orthopedic Unit
You would like to produce a line list that includes basic patient demographics (patient ID, DOB, gender, and age at event), information on the event (date admitted, date of surgey, date of onset, location of patient when SSI developed

21. Line list heading – Depends on the HAI
Infection site
Use standard nomenclature - NHSN
SSI
SST
CAUTI
Procedure codes
Procedure date
Surgeon code
Surgeon assistant and others in the room
Date of Admission
Date of Onset of Infection
Antibiotics
ASA score
Incision time
Closure time
Patient room number

22. Next columns Organism Culture site
Use standard nomenclature!
CNS vs. Coag neg staph vs. S. epidermidis
Spell the words correctly
Culture site
Final attribution – Hosp Onset, Comm Onset, Comm Acquired
Comment field– generally cannot sort by anything except the first word but useful for keeping notes

23. Frequency Table
Frequency Table: A frequency table is an organized display of counts and percentages
The data are organized by a row variable and a column variable, and the frequency table provides a count of the number of observations in the data set that meet the specifications of both the row and column variables
Example
Suppose you are interested in looking at the distribution of each SSI across the different services in your facility, for all events that were identified in 2012

24. EXAMPLE OF HAI FREQUENCY TABLE IN EXCEL FILE
UHS HAI Dashboard

26. Descriptive Epidemiology
Cross tabulations:
infections/organisms
infections/nursing units
infections/services
infections/risk factors
Evaluate trends and clusters
Conduct studies and investigations
Retrospective case reviews, Case-Control Studies

27. Examples of Cross Tabulations
CLABSI by ICUs
CLABSI by device type
CLABSI by organisms
SSIs by services
SSIs by surgeons
SSIs by nursing unit
Risk factors by SSIs
SSI rates over a time period

28. SSI by Service - 2012 SERVICE CABG TOTAL HIP TOTAL KNEE ABD HYSTEC
COLON
Gen Surgery 4
Cardiac Surgery 2
Orthopedic Surgery 3
Gynecology Surgery

29. Example CLABSI Analysis 2011-2012
Nursing Unit
2011 (n=13)
2012 (n = 4)
SICU 34 24
NICU 3 1
PICU 2
MICU 42
4 WEST
5 SOUTH 16 23
What do these numerators mean?
Next calculate rates by line days

30. CLABSI BY ORGANISMS - 2012 5 8 2 1 4 10 12 6 23 14 7 SICU NICU PICU
NURS
UNIT
STAPH AUREUS
MRSA
CNS
ALPHA STREP
ECOLI
PSEUD
AERUG
CANDIDA
SICU 5 8 2 1 4
NICU
PICU
MICU 10 12
4 WEST
5 SOUTH 6
TOTALS 23 14 7

31. SSI RATES TYPE OF SURGERY # SSIs # PROCEDURES % RATE THA 2 100 2% TKA3 75 4%
CABG 25 8%
COLON 4 15
27%
ABD HYSTERCTOMY 16
19%

32. SSIs BY SURGEONS - RATES
CODE
CABG
TKA
THA
COLON
ABD HYSTER A
1.2 B
1.0 C
0.9 D
0.4
0.8 E
0.0 F
5.6 G
4.8 H
0.0 (0/6 cases) I
30.0 (3/10 cases)

33. Risk Factors for Infections
Surgery
Diabetes
Obese
(BMI > 30)
Hema-toma
Drains
Staples
Smoking
Steroids
THA
50%
75%
25%
90%
20%
10%
TKA
60%
80%
35%
85%
95% 5%
CABG
70% 0%
45%
COLON
ABD HYSTER
? What percentage of non-infected patients had risk factors
? What percentage of Surgeon I patients had these risk factors
Obesity diabetes risk factors at this institution
Staples are used often which may be increasing the risk
Drains being used in orthopedic surgery – increase risk

34. Pie Chart
Pie Chart: A pie chart is a graphical representation of data. The different slices of the pie represent different values of a variable, with the relative size of the slice representing the amount of data included in the slice

35. Pie Chart Example
The top value for each slice is the value of the “chart variable” (e.g., location).
The second value is a count of the number of events included in each slice of the pie
Example:
Distribution of HAIs

36. Bar Chart
Bar Chart: A bar chart is a graphical representation of data where the length or height of the bars represents counts of cases or rates

37. Number of Cases by Surgery Date

38. Days from Surgery to Infection - HPRO & KPRO

39. Orthopedic Surgical Site Infection Rates
OR Environmental controls:
Traffic, Attire,Scrub, Air Handling
Antibacterial sutures
MRSA and Staph aureus Elimination Program
CHG/Alcohol Prep
Laminectomy outbreak due to locally administered steroids (depomedrol)
7 x increase risk of infection if obese and diabetic
Increase in hematomas after use of Lovenox and Plavix

40. NEBH SSI Rates 2003 – 2010 (outpatient and inpatient infections)
Total hip investigation – increase in post-op hematomas in infected patients being evaluated by a case-control study
2008 – Total knee investigation – noticed increase rate in patients receiving toradol, marcaine and duromorph – needle on syringe was not being changed between each vial – changed practice
2007 – Laminectomy rate increased – case control study revealed locally adminiistered steroids increased infection rate in obese/diabetic pts 40

41. Run Chart
Run Chart: A run chart (or control chart) is a line graph showing change in a variable over a selected time period
This is a useful output if you would like to view, for example, the change in rates over time and
2 standard deviation above the mean

42. Instituted AMD Gauze and Standardized dressing technique
MRSA/MSSA Eradication Program
Instituted AMD Gauze and Standardized dressing technique

43. Standardized Infection Ratio (SIR)
Standardized Infection Ratio (SIR), a statistic used to measure relative difference in HAI occurrence during a reporting period compared to a common referent period (i.e., standard population).
SIR compares the actual number of HAIs with the predicted number based on the baseline U.S. experience (i.e., standard population), adjusting for several risk factors that have been found to be most associated with differences in infection rates

44. Next Step: Calculate SIR by HAI by facility and compare to national data from NHSN

45. The “p” value
The p value is the probability that an event will occur in a given set of trials
A p of 1 means it will occur every time the trial occurs (if there were 100 “z” in a pile of 100 scrabble tiles, the probability of getting a “z” is 1 “by chance”
Thus, a p of 0.05 means that 95% of the time or 95/100 you will not get a “z” if there were a random mix of tiles with only one z

46. Risk Factors for SSI MEDICAL
Patient-associated risk factors identified by studies in Malaysia and Vietnam
Country
Source
Risk variable
Surgical procedure
Risk estimate (95% CI)
P value
Malaysia
Praveen 20091
Intra-operative adhesions
Inguinal hernioplasty
Not reported
0.013
Post-operation haematoma
0.001
Yong 20012
Type 2 diabetes
Total hip replacement
OR 21.4 (1.53, 300.2)
0.023
Obesity
OR 20.2 (2.13, 191.5)
0.009
Vietnam
Nguyen 20013
Dirty wound
Any surgical procedure
OR 5.67 (1.92, 16.74)
0.002
Sohn 20024
OR 2.92 (1.35, 6.15) NR
Thu 20055
All orthopaedic surgery
OR 8.7 (4.55, 16.44)
<0.001
ASA > 2
OR 3.9 (1.77, 8.82)
1. Praveen S et al. Asian J Surg (1): Yong KS, et al. Med J Malays Suppl C:57-60.
3. Nguyen D et al. Infect Control Hosp Epidemiol (8): Sohn AH et al. Infect Control Hosp Epidemiol (7):
5. Thu LTA et al. J Hosp Infect (4):
MEDICAL

47. Surgical site infection
SSI classification by surgical procedure 1 2 3 4 5 6 7 8
1. Duerink DO et al. J Hosp Infect (2): Sohn AH et al. Infect Control Hosp Epidemiol (7):
3. Praveen S et al. Asian J Surg (1): Dhillon KS et al. Med J Malays (3):
5. Syahrizal AB et al. Med J Malays Suppl D: Yang K et al. J Arthroplasty (1):
7. Kehachindawat P et al. J Med Assoc Thai 2007;90(7): Thu LTA et al. Infect Control Hosp Epidemiol (8):
MEDICAL

48. Incidence of ssi MEDICAL Gastrointestinal surgery
Country
Source
Surgical procedure
Incidence (%)
Malaysia
Mahadeva 20091
Percutaneous endoscopic gastrostomy
33/103 (32%)
Thambidorai 20082
Appendectomy in children
Open: 34/61(55.7%)
Laparoscopic: 3/51 (5.9%)
Mahadeva S et al. Int J Clin Pract (5):
Thambidorai CR et al. Singapore Med J (12):
MEDICAL

49. Incidence of ssi MEDICAL Orthopaedic surgery Incidence of SSI: 4 – 15%
Country
Source
Surgical procedure
Incidence (%)
Malaysia
Dhillon 19951
All orthopaedic surgery
48/703 (6.8%)
Syahrizal 20012
Total knee arthroplasty
11/100 (11.0%)
Tay 20003
Total hip arthroplasty
10/109 (9.2%)
Dhillon KS et al. Med J Malays (3):
Syahrizal AB et al. Med J Malays Suppl D:5-8.
Tay BH et al. Med J Malays Suppl C:74-85.
MEDICAL

50. Incidence of ssi MEDICAL Gynaecology & Obstetrics surgery
Country
Source
Surgical procedure
Incidence (%)
Malaysia
Huam 19971
Caesarean section
Antibiotic prophylaxis: 3/100
(3.0%)
No prophylaxis: 13/100 (13.0%)
Ramli 20092
Laparoscopic ovarian cystectomy
2/ (5.4%)
Huam SH et al. Med J Malays (1):3-7.
Ramli R et al. Int Med J (4):
MEDICAL

51. Incidence of SSI MEDICAL Other surgical procedures Country Source
Malaysia
Ahmad 19971
Free flap surgery
10/ (16.4%)
Hisham 20012
Total thyroidectomy
3/ (3.1%)
Ng 20043
CABG
34/ (2.1%)
Praveen 20094
Inguinal hernioplasty
15/ (7.4%)
Ahmad TS et al. Ann Acad Med Singapore (6):
Hisham AN et al. ANZ J Surg (4):
Ng CY et al. Asian Cardiovasc Thorac Ann (3):
Praveen S et al. Asian J Surg (1):59-63.
MEDICAL

52. Quality Process Tools for Infection Prevention

54. Peri-operative Team Factors Care Delivery problems (CDPs)
SSI Fishbone Diagram
Patient Factors
Surgeon Technique
Work Environmental Factors
Pre-operative Factors
Peri-operative Team Factors
Organizational and Management Factors
Care Delivery problems (CDPs)
Lack of traffic control – too many in room
Contaminated environment
Lack of hand hygiene
Financial constraints
Improper surgical hand antisepsis
Patient body colonization
Poor communication among team
Inadequate surgical prophylaxis
Poor leadership
Improper surgical attire
Lack of pre-op shower
Increase hospitalization days
Surgical irrigation
Unsterile instruments
Non-coated sutures
Use of Staples or steri-strips
MRSA or MSSA nasal colonization
Obese
Poor staff levels
Lack of discontinuation of antibiotics at 24 hrs
Use of Drains
Infection at another site
The fishbone is often used in root cause analysis and provides a systematic frame work to work through all the potential factors that may have contributed to the situation. If you have been to the Dept of Pediatrics M&M you have seen this used
Diabetic
Poor surgical technique
Workload and shift patterns
Smoker
Contamination of incision post-op
Lack of re-dosing of antibiotic
Contaminated environment
Immunosuppressive agents
Design, availability and maintenance of equipment
Environment and physical plant problems (air handling system)
Inadequate staffing for post-op care
Lack of hand hygiene
Lack of foley catheter removal within 48 hrs

55. How Much Do These Infections Cost???

56. Relative Economic Burden Associated with HAIs
Est. Annual # of Infections
Direct Cost per Patient (2007$)
Avg. Increased Length of Stay
Attributable Mortality
SSI Surgical Site Infections
CLA-BSI Central-Line Associated Blood Stream Infections
VAP Ventilator Associated Pneumonia
CA-UTI Catheter-Associated Urinary Tract Infections
Other / MDROs* Multi-Drug Resistant Organisms (e.g., MRSA, C. difficile, VRE, etc.)
290,485 (~17% of HAIs)
248,678 (~14% of HAIs)
250,205 (~15% of HAIs)
561,667 (~32% of HAIs)
386,090
(~22% of HAIs)
$34,670
$29,156
$28,508
$1, ~$30,000
~12 days
~10-24 days
~9-13 days
1 day ~9.1 days 4%
26%
24%
1% ~4%
* NOTE: MDRO often cause other infection types (e.g., SSI, BSI, VAP, UTI); MDRO statistics reflect CDC estimates for methicillin-resistant Staphylococcus aureus (MRSA) only. SOURCES: Klevens, et al., “Estimating Health Care-Associated Infections and Deaths in U.S. Hospitals, 2002,” Public Health Review, 2007; CDC: “The Direct Medical Cost of HAIs in U.S. Hospitals and the Benefits of Prevention”, March 2009; Kirkland, et al., “The Impact of Surgical Site Infections”, Infect Control Hosp Epidemiol, 1999; Arch Internal Med, 1988; Arch Internal Med, 1974; Infect Control Hosp Epidemiol, 2002; CareFusion MedMined Analysis, 2009. 56

57. Economic burden of SSI MEDICAL
Extended hospital stay associated with SSI
In Vietnam, SSI is associated with an increase in hospital stay of 7-19 days
Country
Source
Surgical procedure
Type of stay
Length of stay (days)
SSI
No SSI
Difference
P value
Vietnam
Nguyen 20011
Any surgical procedure
Total stay
14 (SD: 10.8)
9.1 (SD: 7.1)
4.9
<0.001
Sohn 20022
Post-operative 26 10 16
<0.0001
Thu 20053
All orthopaedic surgery
28.1 9
19.1
Thu 20064
Orthopaedic surgery 21 15
Neurosurgery 27 17
Thu 20075 7 NR
1. Nguyen D et al. Infect Control Hosp Epidemiol (8): Sohn AH et al. Infect Control Hosp Epidemiol (7):
3. Thu LTA et al. J Hosp Infect (4): Thu LTA et al. Infect Control Hosp Epidemiol (8):
5. Thu LTA et al. Infect Control Hosp Epidemiol (5):
MEDICAL

58. Economic cost of ssi MEDICAL
In Thailand, SSI is associated with an increase in hospital stay of 7-19 days
Source
Surgical procedure
Type of stay
Length of stay (days)
SSI
no SSI
Difference
P value
Danchaivijitr 20051
Any surgical procedure
Post-operative stay NS
12.6
Kasatpibal 20052
Craniotomy
48.0
16.8
31.2
<0.0001
Colectomy
27.4
8.7
18.7
0.0001
Cholecystectomy
16.7
8.1
8.6
0.0147
Appendectomy
17.2
4.2
13.0
Mastectomy
20.5
9.8
10.7
0.0038
Herniorrhaphy
2.0
11.0
Lohsiriwat 20093
Colorectal surgery
Hospital stay
15.9
8.3
7.6
<0.001
1. Danchaivijitr S et al. J Med Assoc of Thailand 2005;88 Suppl 10:S75-S Kasatpibal N et al. J Med Assoc of Thailand 2005;88(8):
3. Lohsiriwat V et al. J Med Assoc of Thailand 2009;92(1):12-6.
MEDICAL

59. Mean hospitalization cost (THB)
Economic cost of ssi
Hospitalization cost associated with SSI in Thailand
Surgical procedure
Mean hospitalization cost (THB)
SSI
no SSI
Difference
P value
Craniotomy
117,135
50,018
67,116
<0.0001
Colectomy
69,958
27,642
42,316
0.0170
Cholecystectomy
52,975
22,812
30,163
0.0341
Appendectomy
27,647
8,482
19,165
0.0004
Mastectomy
23,413
16,699
6,713
0.1449
Herniorrhaphy
17,801
6,882
10,919
0.0007
All 6 procedures
75,544
31,886
43,658
Source: Kasatpibal N et al. J Med Assoc of Thailand 2005;88(8):
MEDICAL

60. Edmiston, et al. APIC June 2012

61. Plus Antibacterial Sutures
One year prospective study of 3789 total joints
In July 2005, implemented a full-year evaluation of antibacterial sutures usage in an orthopedic setting
Changed product over July 4th holiday and did not tell all surgeons (only those involved with study)
At the end of the year-long trial period:
45% reduction in SSIs caused by Staph aureus and MRSA
Reduction in total joint infections rate during trial period
Infection rate dropped from 0.44% to 0.33% with three less infections
NAON Poster Presentation
Spencer M, et al: Reducing the Risk of Orthopedic Infections: The Role of Innovative Suture Technology

62. Three Less Staph Aureus Infections
Incremental cost: $
3 x $40,000 Sensitive Staph aureus = $120,000
3 x $100,000 MRSA = $300,000
UHS – to convert a 25 hospital system will increase the budget by 1% or $35,000

63. NEBH SSI Rates 2003 – 2010 (outpatient and inpatient infections)
Total hip investigation – increase in post-op hematomas in infected patients being evaluated by a case-control study
2008 – Total knee investigation – noticed increase rate in patients receiving toradol, marcaine and duromorph – needle on syringe was not being changed between each vial – changed practice
2007 – Laminectomy rate increased – case control study revealed locally adminiistered steroids increased infection rate in obese/diabetic pts 63

64. Potential Savings Orthopedic Surgical Site Infections
Cost: ~ $25,000/each
FY03 – 63/8837 cases (0.7%) million
FY04 – 60/9669 cases (0.6%) 1.5 million
FY05 – 49/9216 cases (0.5%)  1.2 million
FY06 – 46/8986 cases (0.5%) 1.1 million
FY /9027 cases (0.4%) $975,000
FY /8884 cases (0.4%) $925,000 64 64

65. First Year Potential Cost Savings
UHS Healthcare-Acquired Infections
2010
2011 (through October)
% Rate Reduction
UHS 2011 Benchmark Rate
# HAIs
Reduced
Potential Cost Savings
Catheter Associated UTI (rate per Foley days)
1.39
0.64
54%
0.2 97
$90,630
CLABSI rate by catheter days)
1.44
0.66
0.0 59
$1,486,956
VAP (rate by ventilator days)
1.41
0.91
35% 47
$912,256
CABG SSI (overall rate by surgical procedures)
0.71
0.20
73% 4
$138,680
Total Hip (overall rate by surgical procedures)
0.73
0.53
27% 6
$208,020
Total Knee (overall rate by surgical procedures)
0.57 0% 12
$416,040
C.Difficile (rate per 10,000 patient days)
3.23
2.41
25%
7.0
150
$948,900
MRSA (rate per 1,000 patient days)
0.36
0.14
61%
0.4
252
$7,560,000
Total
627
$11,761,482

66. Healthcare Acquired Infections
% Reduction
UHS 2012 Benchmark Rate
Infection Prevention Measures in Process
Catheter Associated UTI
(rate per Foley days)
57%
0.0
Infection Control Foley Catheter Tray and Silver Foley Catheter, CHG washcloths
CLABSI
(rate by catheter days)
54%
Central Line Insertion Kits, Alcohol Caps for Injection Hub Protection, CHG washcloths, Central Line Checklist
VAP (rate by ventilator days)
11%
CHG rinse with oral care kits, VAP bundle checklist, CHG washcloths, nebulizer cleaning procedures, VAP rounds
CABG SSI (overall rate by surgical procedures)
71%
MRSA screening before surgery, CHG preop showers/cloths , Incisional sealants, CHG/alcohol skin prep
Total Hip (overall rate by surgical procedures)
15%
Total Knee (overall rate by surgical procedures)
50%
C.Difficile (rate per 10,000 patient days)
12%
4.0/10,000 patient days
Bleach wipes and bleach disinfectant solution, Rapid PCR Diagnostics for Early Diagnosis and Precautions, Enhanced environmental cleaning, cubicle curtain changes, room decontamination units for high rates
MRSA (rate per 1,000 patient days)
62%
0.4
CHG Washcloths, Pre-admission and Pre-op Screening, Rapid PCR Diagnostics for Early Diagnosis and Precautions

67. Conclusions
The overall incidence of SSI in South East Asia varies between 1-20%. SSI account for approximately 20% of all HAI.
Variability in SSI incidence related to surgical procedure and risk factors (eg, diabetes, wound classification).
SSI have a substantial economic impact through increased hospital stay, additional treatment and consequently loss of productivity
Clinical studies in patients undergoing abdominal, spinal and cardiac surgery show that VICRYL Plus sutures significantly reduce the incidence of SSI
MEDICAL