FAQs: Outpatient Procedure Component

OPC Training

The training materials for the Outpatient Procedure Component can be found here:  https://www.cdc.gov/nhsn/training/opc/index.html

NHSN OPC SSI Case Review

Please note it is very important to provide NHSN your thoughts regarding the case you are requesting for review.  Please provide specifics as to the criteria you have considered and which elements of the criteria you have determined the patient does or does not meet.  If you are unable to make a determination, please let us know specifically why you are unable to decide and clearly outline your question(s). Our hope is that the case review process will be educational for you for making future determinations. 

Please provide the following information when sending NHSN a question for SSI case review:

  • OR procedure(s) and date(s) of all OR procedures, including reoperations:
  • Whether the operative procedures are coded as NHSN operative procedures (if so, provide the NHSN operative procedure code(s) and category(s)).
  • If a return to OR via same incision/surgical space, was the start time of the return to OR procedure within 24 hours of finish time of the prior operative procedure?
  • Other procedures that access the surgical site during the SSI surveillance period and dates of these procedures (for example, CT-guided drainage, tap to knee). Please include findings from these procedures.
  • Patient signs and symptoms and dates of signs and symptoms.
  • Tissue level(s) that may be involved in the infection – superficial incisional, deep incisional and/or organ/space and dates of involvement.
  • Imaging tests performed and results of these tests – please include dates of these tests.
  • Other diagnostic testing performed – please include dates of these tests.
  • Culture or non-culture based microbiologic tests performed and the results – please include collection dates.
    • Include tissue level (If you are unsure NHSN recommends consulting with the surgeon/physician to make that determination).
    • Please provide any other evidence of infection – please includes dates.

NHSN Procedure/SSI Event/SDOM Reporting

NHSN does not mandate any reporting.  A facility selects reporting and indicates this via the NHSN Monthly Reporting Plan (MRP). A facility is required to report (procedure/SSI event/SDOM) data that represents what is included in their MRP.  What a facility includes in their MRP may depend on their own internal facility risk assessment and any state required reporting.

There is no federal mandate for ambulatory surgery centers (ASC) to use NHSN to report SSI data. We are aware of individual states with reporting mandates for ASCs. You will need to check with your state’s Healthcare Associated Infection (HAI) Coordinator for specifics regarding your state’s reporting requirement.

What we do know regarding Centers for Medicare & Medicaid Services (CMS) reporting requirements can be found at https://www.cdc.gov/nhsn/pdfs/cms/cms-reporting-requirements.pdf [PDF – 141 KB].


Additional, information regarding other reporting requirements for outpatient facilities can be found on the QualityNet website at https://www.qualitynet.org/asc;  HSAG: (866) 800-8756, weekdays from 7 a.m. to 6 p.m. Eastern Time.

Details regarding the voluntary use of the Outpatient Procedure Component can be found at https://www.cdc.gov/nhsn/opc/index.html.

SSI Surveillance Period and SSI attribution

Those procedures identified by CPT operative procedure codes as an NHSN operative procedure will begin an SSI surveillance period; only NHSN operative procedures are eligible for SSI attribution.  A return trip to the OR via the same surgical site ends the surveillance period for the prior NHSN operative procedure and begins a new SSI surveillance period if an NHSN operative procedure is performed.  Non-NHSN operative procedures do not set a surveillance period nor are they eligible for SSI attribution.

Pathogen Assignment

Yes. The only organisms excluded from SSI event reporting are found in the OPC SSI Protocol on page 18-Table 5.

Timeframe for SSI Elements

SSI surveillance is based on a 30- or 90-day SSI surveillance period, which is determined by the NHSN operative procedure category and the tissue level of SSI event.  SSI guidelines do not offer a strict timeframe for elements of criteria to occur but in NHSN’s experience, all elements required to meet an SSI criterion usually occur within a 7–10-day timeframe with typically no more than 2-3 days between elements. To ensure that all elements associate to the SSI, the elements must occur in a relatively tight timeframe. For example, an element that occurs on day 2 of the surveillance period with another element that occurs three weeks later should not be used to cite an SSI. Each case differs based on the individual elements occurring and the type of SSI but the DOE for an SSI must occur within the appropriate 30- or 90-day SSI surveillance period.

Event Detail – Level of SSI After BRST Procedures

  • Apply the superficial incisional SSI criteria if the infection involves the skin or subcutaneous tissue
  • Apply the deep incisional SSI criteria if the infection involves the muscle/fascial level
  • Apply the organ space BRST criteria 1 or 2 if the infection is deeper than the muscle/fascial level

Clarification of SSI Criterion – Purulence

There is no standard, clinically agreed upon definition.  The descriptors “pus” or “purulence” are sufficient evidence of infection.  When the terms ‘pus’ or ‘purulence’ are not written in the medical record, NHSN has allowed determinations for purulence based off descriptors. Documentation that uses a color descriptor and a consistency descriptor (from the list below) in combination is acceptable to indicate ‘purulence’.  For example, fluid only described as yellow, or only described as thick, is not sufficient. However, if the terms are combined, then they may be more representative of purulence (for example: fluid described as thick and yellow).

purulence definitions
Color Consistency
Green Milky
Yellow Thick


NHSN does not use ‘odor’ as a descriptor to define purulence/infection.

Gram stain results such as WBCs or PMNs cannot be used define purulence within the OPC Manual.

Yes.  Patient-reported signs and symptoms are an important aspect of SSI surveillance and are useable within the SSI definitions if documented within the patient medical record.  Patient reported purulence documented in the medical record by a healthcare professional is acceptable for use with SSI criterion.  A specific date/timeframe must be documented in the patient medical record to indicate the purulence occurred within the SSI surveillance period.

Procedure – Contaminated Procedure

Contamination does not exclude a procedure from being reported in your denominator if the procedure is one selected for surveillance on the facility MRP nor would it exclude an SSI event from being reported if SSI criteria are met within the surveillance period following the procedure.

Denominator – Wound Class

The wound class should be assigned by someone participating in the surgical case. NHSN does not make recommendations on wound class aside from the fact that the application does not offer Clean (C) as a choice for the following procedure categories: APPY, BILI, CHOL, COLO, REC, SB and VHYS. Procedures in these categories that are assigned a Clean (C) wound class do not meet the definition of an NHSN operative procedure and should not be included in denominator reporting for NHSN SSI surveillance. Excluding a procedure from the denominator for procedure data should be made on a case-by-case basis with knowledge of the procedure and after review of the operative report. We recommend that you document the rationale for excluding a procedure in your facility’s surveillance records in the event an explanation is needed in the future.

The IP should not modify the wound class based on their interpretation of the operative note. If it is determined that an error was made in wound class assignment, the IP should work with the OR to validate this error with the OR making any such change in the medical record.

Event Detail – Aseptic Technique

NHSN defines aseptically obtained as “obtained in a manner to prevent introduction of organisms from the surrounding tissues into the specimen being collected”.  Swabs collected at the bedside or in the OR can be aseptically obtained.  There is a misconception by some that only cultures obtained in the OR are aseptic.  While there are general guidelines for the collection of optimum wound specimens, specific procedures for specimen collection and transport are institution dependent.  Infection prevention professionals should review these practices with their clinical staff and laboratory colleagues to ensure that aseptic technique is being used to obtain wound specimens.

For purposes of NHSN surveillance, it is the expectation that proper technique for specimen collection is being performed.  If a wound specimen was collected and sent to the lab for culture, the findings are eligible for use in SSI criteria (no exclusions).  Culture results such as “Mixed flora” or “Mixed cutaneous flora” alone cannot be reported to NHSN as there is no such pathogen option in this list of pathogens.  Wound culture results with this finding may require review for proper technique based on the facility/lab protocol for proper wound specimen collection.

Surgical Site – Invasive Manipulation

This will depend on the individual details of the case, keeping in mind the invasive manipulation reporting instruction must be met in its entirety before the exclusion can be applied.  Note that tissue levels that are not entered are still eligible for SSI.

For example, if within an SSI surveillance period a superficial debridement of the surgical site is performed, and the deep incisional level and organ/space level are not entered, a subsequent deep incisional or organ/space SSI following the superficial debridement may be an SSI attributable to the index BRST procedure.

This reporting instruction does NOT apply to closed manipulation (for example, closed reduction of a dislocated hip after an orthopedic procedure).  Invasive manipulation does not include wound packing or changing of wound packing materials as part of postoperative care. (See SSI Event Reporting Instruction #8, OPC SSI protocol, p. 19)

Denominator – Height & Weight

First, confirm that all available data sources have been reviewed, including the surgical records, to locate a height and weight.  Within the application, the height and weight field must have a value > 0.

If a height and/or weight is not available, NHSN recommends a height of 1ft, 0 in and weight of 1 lb. This will signal to NHSN that these data are outliers due to unavailable data.

Surgical Site – Post op Complications

No.  Post-op occurrences and complications are not an exclusion for monitoring for an SSI and reporting an SSI if SSI criteria are met.  If SSI criteria are met within the appropriate SSI surveillance period, an SSI is reported. This is addressed in the OPC SSI protocol under SSI Event Reporting Instruction #9 on page 20.

Surgical Site – Hematomas and Seromas

The fact that wounds can be labeled in various ways by different physicians is the reason that criteria rather than labels or diagnoses are used for SSI determinations.  If a wound described as a hematoma or seroma meets an SSI criterion (for example, an organism is identified from a hematoma) it must be reported as an SSI.

Event Detail – Level of SSI

When monitoring an NHSN operative procedure category in your MRP, the entire SSI protocol must be followed, and you must report all SSIs for that procedure category. This includes superficial incisional, deep incisional and organs/space SSI events.

If a superficial incisional SSI progresses to meet criteria at a deeper tissue level within the designated surveillance period following an NHSN operative procedure, the event type and date of event must be edited to reflect the deepest tissue level where SSI criteria are met during the surveillance period.  See SSI Event Reporting Instruction #3 on p. 17 in the OPC SSI Protocol for full details.