THE DENOMINATOR DILEMMA
CALCULATING SURGICAL SITE INFECTION RATES
IN COLON SURGERY
NATIONAL HEALTH SAFETY NETWORK
VS
NATIONAL SURGICAL QUALITY IMPROVEMENT
PROGRAM
Albert W Dibbins MD, FACS
Robert A Cormier, BSN
B Stephen Prato AB, MS
Jennifer R Caiazzo RN
Maine Medical Center, Portland, Maine
Maine Medical Center
Maine Medical Center 2009-2010
Organ Space Infection Rates
Colon Operations
Operation
MMC OSI Rate
NSQIP OSI Rate
All Colon CPT Codes
9.5%
5.5%
Intra-abdominal
Colectomy/Anastomosis
8.2%
5.0%
Low Anterior
Resection/Anastomosis
13.8%
4.8%
National Healthcare Safety Network (NHSN)
Operative Procedure Category Mappings to ICD-9CM
Codes
Legacy Code – COLO
Operative Procedure – Colon Surgery
Description – Incision, resection, or anastomosis of the large
intestine: includes large-to-small and small-tolarge bowel anastomosis; does not include rectal
operations
ICD-9CM Codes – 17.31-17.36,17.39,45.03,45.26,45.41,45.49,45.52
45.71-45.76,45.79,45.81-45.83,45.92-45.95
46.03,46.04,46.10,46.11,46.13,46.14,46.43,46.52
46.75,46.76,46.94
Problems in NHSN Reporting
1. ICD9-CM Codes
2. Coding Rules
• use of multiple codes
• selection of cases for inclusion
• definition of a colon operation = segment resected
• low anterior resection code is 48.63 - not included in COLO
• colon biopsy (45.26) even if seromuscular only
• suture of colotomy (46.75) whether transmural or not
3. Coders
• use of proprietary software
• human error
Problems in NHSN Reporting
4. Definitions
“ The procedure represented by this ICD-9CM code may be performed
in a number of ways. However, if, at the end of the procedure, the
skin incision edges do not meet because of drains, wires, or other
objects extruding through the incision, the incision is not considered
primarily closed. Therefore the procedure is not considered an NHSN
operative procedure and any subsequent infection is not considered
a procedure associated infection (i.e. not an SSI..).”
5. Exclusions
“There must be no evidence that the infection was present or incubating
at the time of admission to the health care setting.”
“The following infections are not considered healthcare associated
- Infections associated with complications or extensions of infections
already present on admission, unless a change in pathogen or
symptoms strongly suggests the acquisition of a new infection.”
COLON CPT CODE COMPARISONS
Classic/Pediatric
44025
44110
44111
44140
44141
44143
44145
44146
44147
44150
44151
44155
44156
44157
44158
44160
44188
44204
44205
44206
44207
44208
44210
44211
44212
44227
44238*
44320
44322
44340
44345
44346
44620
44625
44626
44799
NHSN ? CMS
Targeted
44140
44141
44143
44145
44146
44147
44150
44151
44155
44140
44141
44143
44145
44146
44147
44150
44151
44160
44204
44205
44206
44207
44208
44210
44211
44212
44227
44160
44204
44205
44206
44207
44208
44210
Present At the Time Of Surgery
PATOS
1. Equivalent to the NHSN exclusion for infection present at admission
2. Workstation automatically deletes case from SSI list if PATOS collected
3. Need to keep PATOS file to know “true” SSI rate
Maine Medical Center
“True” SSI Rates for Colon Operations 2011
NSQIP Comparison = All Hospitals, All Beds
MMC 358 cases
Superficial SSI
4.2%
Deep SSI
0.0%
Organ Space SSI 6.4%
NSQIP 35,385 cases
6.4%
1.4%
3.5%
NSQIP Comparison = All NSQIP Pediatric Sites
MMC 35 cases
Superficial SSI
5.7%
Deep SSI
0.0%
Organ Space SSI 8.6%
NSQIP 1012 cases
4.9%
0.9%
1.6%
Maine Medical Center
NSQIP Colon Targeted Option SSI Rates 2011
NSQIP Comparison – Academic/Teaching Hospitals 500 or more beds
MMC 320 cases
NSQIP 15,898 cases
Superficial SSI
5.0% (4.2%)
6.7%
Deep SSI
0.0% (0.0%)
1.3%
Organ Space SSI 5.3% (6.4%)
4.0%
Maine Medical Center
NHSN Reported SSI Rates Colon Operations 2011
Number of Cases
“True”
NHSN
NQIP-T
358
194
320
Superficial SSI
4.2%
4.1%
5.0%
Deep SSI
0.0%
0.0%
0.0%
Organ Space SSI
6.4%
2.0%
5.3%
Calculating Hospital SSI rates
NHSN will calculate SSI rates based on their model using O/E ratios
The E comes from a multivariate logistic regression model
constructed by NHSN to represent a standard population
- it has been criticized as having poor predictive validity
“The Surgical Infection Rate will be calculated only if the number of
hospital associated infections is >1”
The basic SSI Risk Index uses
1. duration of operation
2. wound class 3 or 4
3. ASA classification 3,4,5
BUT we don’t know how !
A Proposal
1. CMS and NHSN will define procedure by name i.e. low anterior
resection
2. CMS, NHSN and AHA coding group will assign ICD-9CM code, CPT
code for each operation
3. AHA coding group will work with CMS, NHSN to define coding rules
and provide education to coders.
- interim solution for ICD-9CM, major effort for ICD-10CM
4. NSQIP and Colorectal societies should be heavily involved in the
process