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Key Terms

Key Terms
21% Rule

See Dialysis Event types.

80% Rule

See CDC Location.

Access-related
bloodstream
infection

See Dialysis access-associated infection types.

ASA Score

Assessment by the anesthesiologist of the patient’s preoperative physical
condition using the American Society of Anesthesiologist’ (ASA) Classification
of Physical Status. Patient is assigned one of the following which is used as
one element of the SSI Basic Risk index:
1. Normally healthy patient
2. Patient with mild systemic disease
3. Patient with severe systemic disease that is not incapacitating
4. Patient with an incapacitating systemic disease that is a constant threat to
life
5. Moribund patient who is not expected to survive for 24 hours with or
without the operation.

Aseptically
obtained

Obtained in a manner to prevent introduction of organisms from the
surrounding tissues into the specimen being collected.

Birthweight

Birthweight is the weight of the infant at the time of birth and should not be
changed as the infant gains weight. The birthweight categories are as follows:
A = ≤750 g; B = 751-1000 g; C = 1001-1500 g; D = 1501-2500 g; E = >2500 g.

Catheterassociated Urinary
Tract Infection
(CAUTI)

CAUTI is a healthcare-associated urinary tract infection (UTI) that occurs in a
patient who had an indwelling urinary catheter in place within the 48-hour
period before the onset of the UTI. NOTE: There is no minimum period of
time that the catheter must be in place in order for the UTI to be considered
catheter-associated. See also Indwelling urinary catheter, Device-associated
infection and Healthcare-associated infection.

CDC Location

A CDC-defined designation given to a patient care area housing patients who
have similar disease conditions or who are receiving care for similar medical or
surgical specialties. Each facility location that is monitored is “mapped” to one
CDC Location. The specific CDC Location code is determined by the type of
patients cared for in that area according to the 80% Rule. That is, if 80% of
patients are of a certain type (e.g., pediatric patients with orthopedic problems)
then that area is designated as that type of location (in this case, an Inpatient
Pediatric Orthopedic Ward).

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Central line

An intravascular catheter that terminates at or close to the heart or in one of the
great vessels which is used for infusion, withdrawal of blood, or hemodynamic
monitoring. The following are considered great vessels for the purpose of
reporting central line-associated BSIs and counting central line-days in the
NHSN system: Aorta, pulmonary artery, superior vena cava, inferior vena cava,
brachiocephalic veins, internal jugular veins, subclavian veins, external iliac
veins, common iliac veins, and femoral veins (not femoral arteries).
NOTE: In neonates, the umbilical artery/vein is considered a great vessel.
NOTE: Neither the insertion site nor the type of device may be used to
determine if a line qualifies as a central line. The device must terminate in one
of these vessels or in or near the heart to qualify as a central line.
NOTE: Pacemaker wires and other nonlumened devices inserted into central
blood vessels or the heart are not considered central lines, because fluids are not
infused, pushed, nor withdrawn through such devices.
NOTE: An introducer is considered an intravascular catheter, and depending on
the location of its tip, may be a central line.
NOTE: Intraaortic balloon pumps (IABP) are not considered central lines
because they are not generally used for infusion or withdrawal of blood, but are
used instead for therapeutic purposes. Neither are lines used for extracorporeal
membrane oxygenation (ECMO).
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Central Lineassociated
Bloodstream
Infection
(CLABSI)

A CLABSI is a healthcare-associated primary bloodstream infection (BSI) in a
patient that had a central line within the 48-hour period before the development
of the BSI and that is not related to an infection at another site. NOTE: There is
no minimum period of time that the central line must be in place in order for the
BSI to be considered central line-associated. See also Central line, Deviceassociated infection and Healthcare-associated infection.

Clean (Wound
Class)

See Wound Class.

Clean
Contaminated
(Wound Class)

See Wound Class.

Contaminated
(Wound Class)

See Wound Class.

Date of Event

In the case of an infection event, the date when the first signs or symptoms of
infection (clinical evidence) appeared, or the date the specimen used to meet the
infection criterion was collected, whichever came first. In the case of a process
of care event, the date the process or intervention was done (e.g., day a central
line was inserted is the date of CLIP event). See also Transfer rule.

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Key Terms

Deep incisional
primary (DIP) SSI

A deep incisional SSI that is identified in the primary incision in a patient that
has had an operation with one or more incisions (e.g., C-section incision or
chest incision for CBGB).

Deep incisional
secondary (DIS)
SSI

A deep incisional SSI that is identified in the secondary incision in a patient that
has had an operation with more than one incision (e.g., donor site [leg] incision
for CBGB).

Device-associated
infection

A healthcare-associated infection in a patient with a device (e.g., ventilator,
central line or indwelling urinary catheter) that was used within the 48-hour
period before onset of infection. If the interval is longer than 48 hours, there
must be compelling evidence that the infection was associated with device use
NOTE: There is no minimum period of time that the device must be in place in
order for the infection to be considered device-associated. See also Healthcareassociated infection.

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Device days

A daily count of the number of patients with a specific device in the patient care
location during a time period. To calculate device days, for each day of the
month, at the same time each day, record the number of patients who have the
specific device (e.g., central line, ventilator, or indwelling urinary catheter).
When denominator data are available from electronic databases (e.g., ventilator
days from respiratory therapy), these sources may be used as long as the counts
are not substantially different (+/- 5%) from manually collected counts. At the
end of the month sum the daily counts and enter into NHSN the total for each
type of device.
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Device-associated denominator data should be collected at the same time each
day. When denominator data are available from electronic databases (e.g.,
ventilator days from respiratory therapy), these sources may be used as long as
the counts are not substantially different (+/- 5%) from manually collected
counts.
Dialysis accessassociated
infection types
(Outpatient
hemodialysis only)

Local access site infection: Pus, redness, or swelling of the vascular access site and
bloodstream infection was not present.
Access-related bloodstream infection: Blood culture positive with suspected
source identified as the vascular access site or uncertain.
Vascular access infection: Either local access site infection or access-related
bloodstream infection.

Dialysis event
types (Outpatient
hemodialysis only)
June, 2011

IV antimicrobial start: Include all outpatient IV antimicrobial starts, not just IV
vancomycin starts and not just starts for vascular access problems. There must be
21 or more days from the end of the first IV antimicrobial start to the beginning of

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Key Terms

a second IV antimicrobial start for two starts to be considered separate dialysis
events. If IV antimicrobials are stopped for less than 21 days and then restarted, the
second start is NOT considered a new dialysis event.
Positive blood culture: Include all positive blood cultures collected as an outpatient
or collected within 1 calendar day after a hospital admission. The date of a blood
culture result is based on the date the blood specimen was collected, not the date
the laboratory reported the result. There must be 21 or more days between positive
blood cultures for each positive blood culture to be considered a separate dialysis
event. If positive blood cultures occur less than 21 days apart, the second positive
blood culture(s) is NOT considered a new dialysis event.
Pus, redness, or increased swelling at the vascular access site: Include each new
episode where the patient has one or more symptoms of pus, redness or increased
swelling at a vascular access site. There must be 21 or more days between the onset
of a first and second episode of pus, redness, or increased swelling at a vascular
access site to be considered separate dialysis events. If an episode of pus, redness,
or increased swelling at a vascular access site resolves and then recurs within 21
days, the recurrence is NOT considered a new dialysis event.

Dialysis vascular
access types (for
Outpatient
hemodialysis only)

Nontunneled central line: a central venous catheter that is fixed in place at the
point of insertion and travels directly from the skin entry site to a vein and
terminates close to the heart or one of the great vessels, and provides vascular
access for hemodialysis.
Tunneled central line: a central venous catheter that travels a distance under the
skin from the point of insertion before terminating at or close to the heart or one
of the great vessels, and provides vascular access for hemodialysis.
Graft: a surgically created connection between an artery and a vein created with
implanted synthetic tubing for the purpose of creating a permanent vascular
access for hemodialysis.
Fistula: a surgically created connection between an artery and a vein for the
purpose of creating a permanent vascular access for hemodialysis.
Other access device: includes hybrid access devices (e.g., HeROTM), ports, and
any other vascular access devices not in the above definitions being used for
hemodialysis.

Died

The patient died during this facility admission. For outpatient hemodialysis
(Dialysis Event module): the patient died in relation to the event or problem,
with or without hospital admission.

Dirty or Infected
(Wound Class)

See Wound Class.

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Key Terms

Duplicate isolate
(in AUR protocol)

An isolate of the same species of bacteria, regardless of antimicrobial
susceptibility pattern, in the same patient, regardless of specimen site, during a
given reporting period (i.e., calendar month).

Duplicate isolate
(in MDRO/CDI
protocol - LabID
Event option)

Any MDRO isolate from the same patient after an initial isolation of the
specific MDRO during a calendar month, regardless of specimen source.

Emergency
Operative
Procedure

An operative procedure on a patient whose condition did not allow time for the
standard preoperative preparations normally done prior to a scheduled operation
(e.g., stable vital signs, adequate antiseptic skin preparation, colon
decontamination in advance of colon surgery, etc.). See also NHSN operative
procedure.

Event contributed
to death

The event either directly caused death or exacerbated an existing disease
condition which then led to death.

Event date

See Date of event.

Fistula

See Dialysis vascular access types.

Graft

See Dialysis vascular access types.

Healthcareassociated
infection (HAI)

A localized or systemic condition resulting from an adverse reaction to the
presence of an infectious agent(s) or its toxin(s). There must be no evidence
that the infection was present or incubating at the time of admission to the acute
care setting, unless a change in pathogen or symptoms strongly suggests the
acquisition of a new infection. See also Chapter 17.

Hospital type

Major teaching – Hospital that is an important part of the teaching program of a
medical school and the majority of medical students rotate through multiple
clinical services.
Graduate – Hospital is used by the medical school for graduate training
programs only (i.e., residency and/or fellowships).
Limited – Hospital is used in the medical school’s teaching program to only a
limited extent.
Nonteaching – Hospital is not affiliated with a medical school.

Implant

June, 2011

A nonhuman-derived object, material, or tissue that is permanently placed in a
patient during an operative procedure and is not routinely manipulated for
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Key Terms

diagnostic or therapeutic purposes. Examples include but are not limited to:
porcine or synthetic heart valves, mechanical heart, metal rods, mesh, sternal
wires, screws, cements, and other devices.
Indwelling
urinary catheter

A drainage tube that is inserted into the urinary bladder through the urethra, is
left in place, and is connected to a closed collection system; also called a Foley
catheter. Does not include straight in-and-out catheters.

Infant

A patient who is ≤ 1 year of age.

Infection date

See Date of event.

Infusion

The introduction of a solution through a blood vessel via a catheter lumen. This
may include continuous infusions such as nutritional fluids or medications, or it
may include intermittent infusions such as flushes or IV antimicrobial
administration, or blood, in the case of transfusion or hemodialysis.

Inpatient

See NHSN inpatient.

Inpatient
location

See Location.

Intensive care
unit (ICU)

A nursing care area that provides intensive observation, diagnosis, and
therapeutic procedures for adults and/or children who are critically ill. An ICU
excludes nursing areas that provide step-down, intermediate care or telemetry
only. Specialty care areas are also excluded (see definition).
The type of ICU is determined by the kind of patients cared for in that unit
according to the 80% Rule. That is, if 80% of patients are of a certain type (e.g.,
patients with trauma), then that ICU is designated as that type of unit (in this
case, trauma ICU). When an ICU houses roughly equal populations of medical
and surgical patients, it is called a medical/surgical ICU.

Local access
infection

See Dialysis access-associated infection types.

Location

The patient care area to which a patient is assigned while receiving care in the
healthcare facility.
NOTE: Only locations where patients are housed overnight (i.e., inpatient
locations) and where denominator data are collected can be used for reporting
infection events when the Device-associated Module is included on a Monthly
Reporting Plan (except for Dialysis Event surveillance). Operating rooms
(including cardiac cath labs, c-section rooms, and interventional radiology) and
outpatient locations are not valid locations for these types of surveillance. See
also CDC Location.

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Key Terms

Location of
attribution

The location to which the event is being attributed. See also Date of event and
Transfer rule.

Neonatal
intensive care
unit (NICU)

There are two types of NICU in NHSN: combined Level II/III NICU and Level
III NICU.

NICU (Level
II/III)

Combined nursery housing both Level II and III newborns and infants.
NOTE: In NHSN, a Level II nursery is considered a Step Down Neonatal
Nursery ward, which provides care for preterm infants with birthweights of ≥
1500 g. Care provided includes resuscitation and stabilization of preterm and/or
ill infants before transfer to a facility at which newborn intensive care is
provided.

NICU (Level III) A hospital unit organized with personnel and equipment to provide continuous
life support and comprehensive care for extremely high-risk newborn infants and
those with complex and critical illness. Level III is subdivided into 4 levels
differentiated by the capability to provide advanced medical and surgical care.
NOTE: The categories of Level III, listed below, are classifications from the
American Academy of Pediatrics, Definitions of hospital-based newborn
services1. These classifications are all considered Level III NICUs in NHSN.
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Level IIIA – Hospital or state-mandated restriction on type and/or duration of
mechanical ventilation.
Level IIIB – No restrictions on type or duration of mechanical ventilation. No
major surgery.
Level IIIC – Major surgery performed on site (eg, omphalocele repair,
tracheoesophageal fistula or esophageal atresia repair, bowel resection,
myelomeningocele repair, ventriculoperitoneal shunt). No surgical repair of
serious congenital heart anomalies that require cardiopulmonary bypass and /or
ECMO for medical conditions.
Level IIID - Major surgery, surgical repair of serious congenital heart anomalies
that require cardiopulmonary bypass, and/or ECMO for medical conditions.
Neonate

A patient who is ≤ 30 days of age.

NHSN inpatient

A patient whose date of admission to the healthcare facility and the date of
discharge are different calendar days. NOTE: A patient who is admitted to an
inpatient location as an “observation” patient is identified as an inpatient on the
first and subsequent days for the purposes of counting a location’s total patient
days and device days.
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Key Terms

NHSN operative
procedure

A procedure:
1) that is performed on a patient who is an NHSN inpatient or an NHSN
outpatient; and
2) takes place during an operation, which is defined as a single trip to an
operating room (OR) where a surgeon makes at least one incision through the
skin or mucous membrane, including laparoscopic approach, and closes the
incision before the patient leaves the OR; and
3) that is included in Table 1, Chapter 9.
NOTE: If the skin incision edges do not meet because of wires or devices or other
objects extruding through the incision, the incision is not considered primarily
closed and therefore the procedure is not considered an operation. Further, any
subsequent infection is not considered a procedure-associated infection (i.e., not
an SSI or PPP).
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NHSN
outpatient

A patient whose date of admission to the healthcare facility and the date of
discharge are the same day.

Non-autologous
transplant

See Transplant.

Nontunneled
central line

See Dialysis vascular access types.

Operating room
(OR)

A patient care area that meets the American Institute of Architects (AIA) criteria
for an operating room2. This may include an operating room, C-Section room,
interventional radiology room or a cardiac catheterization lab, among other areas.

Operation
(Procedure)

A single trip to the operating room (OR) where a surgeon makes at least one
incision through the skin or mucous membrane, including laparoscopic approach,
and closes the incision before the patient leaves the OR. NOTE: If the skin
incision edges do not meet because of wires or devices or other objects extruding
through the incision, the incision is not considered primarily closed and therefore
the procedure is not considered an operation. Further, any subsequent infection is
not considered a procedure-associated infection (i.e., not an SSI or PPP). See also
NHSN operative procedure.

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Other access
device

See Dialysis vascular access types.

Outpatient

See NHSN outpatient.

Patient days

A daily count of the number of patients in the patient care location during a time
period. To calculate patient days, for each day of the month, at the same time
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each day, record the number of patients. When patient days are available from
electronic databases these sources may be used as long as the counts are not
substantially different (+/- 5%) from manually collected counts. At the end of the
month, sum the daily counts and enter the total into NHSN.
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Permanent
central line

A central line that is tunneled, including certain dialysis catheters and implantable
catheters (including ports).

Post-procedure
pneumonia
(PPP)

A pneumonia that meets one of the criteria for pneumonia (PNEU) and occurs
after an inpatient operation takes place, but prior to discharge.

Procedure

See Operation.

Secondary
bloodstream
infection (BSI)

A culture-confirmed BSI associated with a documented HAI at another site (i.e.,
meets CDC criteria of infection at another site such as UTI). If the primary
infection is cultured, the Secondary BSI must yield culture of a same organism as
the primary HAI site, regardless of antibiogram. For example, if blood culture is
positive in a patient with a healthcare-associated SUTI and at least one organism
of both blood and urine specimens is the same, infection is reported as SUTI with
secondary BSI, regardless of the antibiograms of the organism. Secondary BSI is
not reported separately. Report the shared organism(s) to the genus/species level
only once, and if antibiogram data are available, report the results from the most
resistant panel. Also, report any additional organisms found in either of the
cultures. If, on the other hand, for example, an organ/space SSI is identified by
CT scan and no surgical site culture is used to meet the criteria for SSI-IAB, and
a blood culture grows Bacteroides fragilis, then the SSI-IAB is recorded as an
SSI with a secondary BSI. The pathogen for the SSI is recorded as Bacteroides
fragilis. See IAB criteria in Chapter 17 of the NHSN Manual, CDC/NHSN Surveillance
Definition of Healthcare-Associated Infection and Criteria for Specific Types of
Infections in the Acute Care Setting. See also the Secondary BSI Guide containing

the Positive Blood Culture flowchart which is posted under NHSN Guides within
the NHSN Resource Library for this most up-to-date information.
Specialty care
area (SCA)

June, 2011

Hospital location in which specialized care of the following types is provided:
Bone marrow transplant
Solid organ transplant
Inpatient acute dialysis
Hematology/Oncology
Long term acute care
See also Chapter 15 for descriptions.

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NHSN Patient Safety Component
Key Terms

SSI risk index

A score used to predict a surgical patient’s risk of acquiring a surgical site
infection. The risk index score, ranging from 0 to 3, is the number of risk factors
present among the following:
a patient with an American Society of Anesthesiologists’ physical status
classification score of 3, 4, or 51,
an operation classified as contaminated or dirty/infected4, and
an operation lasting longer than the duration cut point in minutes, where the
duration cut point varies by the type of operative procedure performed.
NOTE: As of 2010, NHSN began using standardized infection ratios (SIR)
based on operative procedure category-specific multivariate risk models
rather than risk index-stratified SSI rates. For duration cut point values and
risk index-stratified SSI rates, see NHSN Report: Data summary for 2006
through 2008, issued December 2009 found at
http://www.cdc.gov/nhsn/dataStat.html.
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Superficial
incisional
primary (SIP)
SSI

A superficial incisional SSI that is identified in the primary incision in a patient
that has had an operation with one or more incisions (e.g., C-section incision or
chest incision for CBGB). See also Chapter 9 for criteria.

Superficial
incisional
secondary (SIS)
SSI

A superficial incisional SSI that is identified in the secondary incision in a patient
that has had an operation with more than one incision (e.g., donor site [leg]
incision for CBGB). See also Chapter 9 for criteria.

Surveillance
cultures

Those cultures reported as part of infection control surveillance such as stool
cultures for vancomycin-resistant enterococci (VRE), not for use in patient
diagnosis. Also called active surveillance cultures or testing (AST).

Temporary
central line

A central line that is not tunneled or implanted.

Transfer rule

If an HAI develops within 48 hours of transfer from one inpatient location to
another in the same facility, the infection is attributed to the transferring location.
Likewise, if an HAI develops within 48 hours transfer from one inpatient facility
to another, the infection is attributed to the transferring facility. Facilities should
share information about such HAIs with the transferring facility to enable
reporting.

Transplant

Human cells, tissues, organs, or cellular- or tissue-based products that are placed
into a human recipient via grafting, infusion, or transfer. Examples include the
following: heart valves, organs, ligaments, bone, skin, corneas, and bone marrow
cells.

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Autologous or “autograft” transplants are products that originate from the
patient’s own body.
Non-autologous or “allograft” transplants are tissues or other products derived
from another human body, either a donor cadaver or a live donor.
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Blunt or penetrating injury.

Trauma

Tunneled central See Dialysis vascular access types.
line
Umbilical
catheter

A central line inserted through the umbilical artery or vein in a neonate.

Vascular access
infection

See Dialysis access-associated infection types.

Ventilator

A device to assist or control respiration continuously, inclusive of the weaning
period, through a tracheostomy or by endotracheal intubation.
NOTE: Lung expansion devices such as intermittent positive pressure breathing
(IPPB); nasal positive end-expiratory pressure (PEEP); continuous nasal positive
airway pressure (CPAP, hypoCPAP) are not considered ventilators unless
delivered via tracheostomy or endotracheal intubation (e.g., ET-CPAP).

Ventilatorassociated
Pneumonia
(VAP)

A VAP is a healthcare-associated pneumonia (PNEU) that occurs in a patient
who was intubated and ventilated at the time, of or within 48 hours before, the
onset of the PNEU. NOTE: There is no minimum period of time that the
ventilator must be in place in order for the PNEU to be considered ventilatorassociated. See also Ventilator, Device-associated infection and Healthcareassociated infection.

Wound Class

An assessment of the degree of contamination of a surgical wound at the time of
the operation. The wound class system used in NHSN is an adaptation of the
American College of Surgeons wound classification schema4. Wounds are
divided into four classes:

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Clean: An uninfected operative wound in which no inflammation is encountered
and the respiratory, alimentary, genital, or uninfected urinary tracts are not
entered. In addition, clean wounds are primarily closed and, if necessary, drained
with closed drainage. Operative incisional wounds that follow nonpenetrating
(blunt) trauma should be included in this category if they meet the criteria.
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Clean-Contaminated: Operative wounds in which the respiratory, alimentary,
genital, or urinary tracts are entered under controlled conditions and without
unusual contamination. Specifically, operations involving the biliary tract,
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appendix, vagina, and oropharynx are included in this category, provided no
evidence of infection or major break in technique is encountered.
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Contaminated: Open, fresh, accidental wounds. In addition, operations with
major breaks in sterile technique (e.g., open cardiac massage) or gross spillage
from the gastrointestinal tract, and incisions in which acute, nonpurulent
inflammation is encountered are included in this category.
Dirty or Infected: Includes old traumatic wounds with retained devitalized tissue
and those that involve existing clinical infection or perforated viscera. This
definition suggests that the organisms causing postoperative infection were
present in the operative field before the operation.
1

Anonymous. New classification of physical status. Anesthesiology 1963;24:111.

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2

American Academy of Pediatrics, Policy Statement: Levels of neonatal care. Pediatrics,
2004;114 (5): 1341-1347.
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3

Facilities Guidelines Institute. Guidelines for design and construction of health care facilities.
American Society for Healthcare Engineering; Chicago IL; 2010.
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4

Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR, and the Hospital Infection Control
Practices Advisory Committee. Guideline for prevention of surgical site infection, 1999. Infect
Control Hosp Epidemiol 1999;20:247-80.
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