FAQs: Miscellaneous

HAI in patients awaiting organ harvest

If the date of specimen collection is on or after the date of documentation of evidence of consent AND the patient is being supported for organ donation purposes, an event identified using the specimen culture result or microbiologic non-culture based diagnostic test result should not be reported as an HAI. For criteria without a specimen collected, if the date of event (DOE) is on or after the date of documentation of evidence of consent AND the patient is being supported for organ donation purposes, the event identified should not be reported as an HAI. The patient should, however, still be included in device and patient day denominator data collection.


Yes. The repeat infection timeframe (RIT) is set by the date of event (DOE).  For surveillance purposes a POA infection may only have a DOE on the day of admission or the next day. If the first element within the infection window period (IWP) occurred in the 2 days before admission, the DOE is considered the day of admission. The RIT is the 14-day time period where no new infections of the same type are reported, beginning with the date of event.

Example: A UTI with E. coli identified with DOE on the day of admission is considered POA. If 10 days later a new urine culture shows K. pneumonia >100,000 CFU/ml, then the organism is added to the original UTI (no new event is cited but rather is considered a continuation of the original event). The UTI RIT remains Hospital Days 1-14.

NOTE:  If a patient is admitted with a POA BSI and subsequent blood specimens are collected, the POA BSI must be identified as either primary or secondary in nature.  A primary POA BSI will set a BSI RIT.  However, a POA BSI that is secondary to another site of infection will NOT set a BSI RIT.  It will only set an RIT for the type of infection to which the BSI is secondary. Please see the article on page 3 of the September 2015 NHSN Newsletter for more details. September 2015 NHSN Newsletter [PDF – 2 MB].

Rationale for definition of healthcare-associated infection (HAI)

Several studies have demonstrated there was subjective application of the NHSN HAI surveillance definitions by different IPs and facilities, prior to 2013.  During this time, the NHSN definitions allowed facilities to subjectively determine evidence that an infection was present or incubating on admission, which was not reportable to NHSN because it was not “healthcare-associated”.  Subjectivity, providing an opportunity for inconsistent data collection, must be removed from surveillance definitions whenever possible.  With this in mind, CDC and the HICPAC surveillance working group, a group made up of infectious disease professionals, healthcare epidemiologists, infection preventionists, and state public health representatives, developed a set of objective surveillance criteria to be implemented into NHSN and used by all facilities reporting data to NHSN.  Through the use of the same set of objective criteria it is expected that data reported to the system is useful for quality improvement activities.


For infections of all types except VAE, PedVAE, SSI, LabID Event, to make a proper determination regarding a possible healthcare-associated infection, proceed in this order:

1.      First, determine the date of the diagnostic test that is an element of the NHSN site-specific infection criterion that is met.

2.      Next determine the infection window period (3 days before the diagnostic test, the day of the test, and 3 days after for a total of 7 days).  NOTE: when the diagnostic test used to set the IWP is hospital day 3 or earlier, the days before the diagnostic test can only include those that occur in the POA timeframe, specifically the 2 days prior to admission.

3.      Then determine if all of the elements of the criterion are met during the infection window period.  If they are, there is an infection event.  If they are not, there is no event.

4.      If there is an event, next determine the date of event, specifically, the date that the first element used to meet the infection criterion occurs for the first time within the infection window period.

5.      Is the date of event in the POA time period (specifically, during the 2 days before admission, the day of admission, or the next day)?  If yes, the infection is POA; if not, it is an HAI. Please note, when assigning a repeat infection timeframe (RIT) for a POA event, if the date of event is determined to be either of the two days prior to inpatient admission then the date of event, and therefore day 1 of the RIT, is considered hospital day 1.

Chapter 2 of the NHSN PSC Manual – Identifying HAI for NHSN Surveillance provides guidance and examples.  Please see: Chapter 2 of the NHSN PSC Manual – Identifying HAI for NHSN Surveillance [PDF – 1 MB].

Surveillance vs. Clinical

Surveillance definitions are designed to study and identify trends in a population.  The application of these standardized criteria, and only these criteria, in a consistent manner allows confidence in aggregation and analysis of data. Alternatively, clinical diagnoses are patient specific. Unlike surveillance definitions, ALL available diagnostic data are considered in a clinical diagnosis, including additional clinical, epidemiological and laboratory data not used for NHSN surveillance. Therefore, a clinical diagnosis may be made even when a surveillance definition may not be met and vice versa is also true.  Failure to meet a surveillance definition should never impede or override clinical judgment during diagnosis, management, or treatment of patents. Nor should failure to meet clinical definitions result in non-reporting to NHSN infections meeting the NHSN surveillance criteria.

What are considered diagnostic tests

The following are considered diagnostic tests only when they are an element of the criteria that is met:

  • Laboratory specimen collection
  • Imaging test
  • Procedure or exam

Non-culture based microbiologic testing

This term refers to the identification of microorganisms using a method of testing other than a culture. Culture based testing requires inoculation of a specimen to culture media, incubation, and observation for actual growth of microorganisms. Depending on the organism identified, culturing can take several days to weeks for a final report. In contrast, non-culture-based testing (NCT) methods generally provide faster results, which can assist with early diagnosis and tailoring of antimicrobial therapy. Examples of non-culture-based testing include, but are not limited to, PCR (polymerase chain reaction) and ELISA (Enzyme-linked immunosorbent assay) as well as DNA sequencing.


Active Surveillance Culture/Testing (ASC/AST)

For purposes of NHSN surveillance, Active Surveillance Culture/Testing (ASC/AST) refers to testing that is intended to identify the presence/carriage of microorganisms for the purpose of instituting or discontinuing isolation precautions (for example, nasal swab for MRSA, rectal swab for VRE), or monitoring for eradication of a carrier state. ASC/AST does NOT include identification of microorganisms with cultures or tests performed for diagnosis and treatment purposes (for example, specimens collected from sterile body sites, including blood specimens).

In-plan vs. off-plan NHSN reporting

“In plan” surveillance is surveillance which a facility has indicated in their NHSN Monthly Reporting Plan (MRP) will be performed.  By including the data in the NHSN MRP, the facility is stating that the NHSN surveillance protocol(s) will be used, in its entirety, for that particular event.  Only in-plan data are submitted to CMS in accordance with CMS’s Quality Reporting Programs. Only data that are entered into NHSN “in-plan” are included in NHSN annual reports or other NHSN publications.

Facilities that share a CCN

If the facilities are physically separate buildings from each other, whether on the same property or over multiple campuses, then they should be enrolled separately in NHSN. Each facility should have its own, unique NHSN OrgID. When a CCN is shared across multiple facilities, the CDC will aggregate the data from all applicable NHSN OrgIDs and will send to CMS under the single CCN for CMS reporting purposes. Each distinct facility should monitor HAIs and prevention efforts separately, for the purposes of accurate tracking and targeted infection control.

Positive surveillance screening and HAI

A positive screening culture at admission does not mean that any subsequent infection with that organism is not a healthcare-associated infection (HAI). Many HAIs are caused by organisms from endogenous patient sources and prevention efforts may be employed to prevent these organisms from causing an HAI.  A positive screening culture without evidence of infection usually represents colonization NOT incubation. Unless such a patient meets all other required criteria to fulfill the present on admission (POA) definition, no POA infection is identified.

Temperature (Fever)

Because fever is a non-specific sign of infection, it is possible that an individual may run a fever due to more than one infection at a time. It would be impossible to determine which infection (if not both) was the cause of the fever. Therefore, in this example, if all other criteria besides fever are met, the patient would have both an NHSN PNEU and an NHSN UTI. This process negates the use of clinical, subjective decision making to determine NHSN HAI events.

Temperature measurement

The issue of the route of temperature measurement was considered here at NHSN and a decision was made to forego requiring a certain route of measurement, since our aim is not to direct care, but rather to measure the effect of care on outcomes.  A detailed literature search was performed and subject matter experts consulted regarding the many routes of measurement and what they may mean when compared to others.  The final determination was that there are no research-based guidelines concerning converting temperatures based on route of measurement.  When using fever as an element of an NHSN infection criterion, use the temperature documented in the patient’s medical record (no conversion of temperature based on route of collection).

Vital signs

If a specific value for a vital sign is not stated in a CDC/NHSN HAI definition criterion (for example bradycardia, hypotension), the facility should use the vital sign parameters as stated in its own policies and procedures for clinical practices.  Additionally, documentation of these conditions in the medical chart may also be used, for example, “…patient is hypotensive” would satisfy the element of “hypotension.”

Patient identification

The patient ID is the key identifier in NHSN for each facility. Therefore, the patient ID should be an identifier that remains constant for the patient on any subsequent visits; oftentimes, this is the medical record number. The use of an identifier that changes with each visit to the facility, for example, would result in the inability to link an SSI to a procedure, as well as inappropriate assignment and calculation of LabID events and subsequent measures.

Observation patients & denominator counts

For determining accurate device and/or patient day counts in inpatient locations, any patient present in an inpatient location at the time of the count(s) should be included, regardless of whether they spend the night. The facility’s designation of a patient as “inpatient” is not necessary to meet the NHSN inpatient definition.

Observation patients, swing bed patients, or hospice patients in inpatient units

Yes. All patients residing in an inpatient unit should be included in the surveillance efforts for that unit regardless of the facility’s categorization as “observation” or “hospice” patient (including patients being provided only palliative or supportive care), or that they are in a swing bed within an inpatient location.

Mixed-acuity units

The designation of Mixed Acuity Unit should be used only when both of the following are true:

  • Less than 80% of the patients are of the same acuity level, for example, critical care, step down, or ward level;


  • “Virtual” locations cannot be set up within NHSN to identify groups of patients of the same acuity levels.

Use of virtual locations requires the ability to identify separate patient days and device days for these groups of patients.  Correct mapping of facility locations is vital for appropriate comparison and calculation of device-associated SIRs. Detailed guidance can be found at http://www.cdc.gov/nhsn/PDFs/pscManual/15LocationsDescriptions_current.pdf [PDF – 677 KB]. For CMS IPPS reporting, CLABSI reporting is mandatory for adult & pediatric ICUs, medical wards, surgical wards, and combined medical/surgical wards as well as neonatal ICUs for acute care facilities.   Long-Term Acute Care facilities are required to report CLABSIs for all inpatient locations.   The data that NHSN shares with CMS will not include data for locations mapped as Mixed Acuity Units. For more details regarding the reporting requirements for CMS Quality Reporting Programs, as they pertain to NHSN surveillance, please visit: CMS Requirements.

Location codes

Please refer to the guidance that is provided in the CDC Locations and Descriptions Chapter (Chapter 15). The beginning of this chapter offers a guide which will help you set up your locations properly.  CDC Locations and Descriptions Chapter (Chapter 15) [PDF – 1 MB]

Physician diagnosis

Only if physician diagnosis is a part of an NHSN site-specific infection criteria may it be used in the determination that an infection was present on admission (POA). For example, since the BSI criteria do not include physician diagnosis as part of the criteria, a physician documentation of BSI cannot be used to meet CDC/NHSN criteria for a BSI.  As a reminder, the date of event of a CDC/NHSN site-specific infection criterion must occur within the POA time period (specifically the 2 days before admission, the day of admission, or the day after admission) for the infection to be considered present on admission. This is regardless of admitting diagnosis or treatments the patient may be receiving upon admission (for example, antibiotics).

Counting device days

If a device is present for any part of a calendar day, then that day contributes to the minimum day requirement for the device-associated infection. Examples include when a device is removed and then reinserted on that calendar day or the next.  If instead, a full calendar day passes without device presence, then the day count begins anew for device days if the device is reinserted. An example is the removal of a device on Monday, without reinsertion until Wednesday or later.

Device counts

Denominator data are collected at the same time, every day, per location.  Alternatively, a denominator sampling method can be used where the number of patients in the location (patient days) and the number of patients with an indwelling device (urinary catheter/central line/ventilator) is collected on a designated day each week at the same time.  For accuracy, do not use Saturday or Sunday for sampling purposes and only non-oncology ICUs and wards with an average of 75 or more device days per month in the previous year are eligible to use this method.  When using this method, the patient days must also be counted each day of the week.


Broth only cultures

Positive cultures from broth only are considered a positive culture result and treated as such for surveillance purposes.  Such media can be enriched to identify organisms that might otherwise be missed.

NHSN requirements and recommendation for application use

Please see NHSN’s Requirements and Recommendations on usage NHSN’s Requirements and Recommendations.

Try logging completely out of the application. Close your browser, clear your cookies. (Go to Tools, Internet options, then delete, check off cookies, etc.) Instead of using Internet Explorer please try using Microsoft Edge or Google Chrome. Attempt to enter data again.  If you continue to have issue, contact NHSN@cdc.gov.

Gross anatomical

Gross anatomic evidence of infection is evidence of infection elicited or visualized on physical examination or observed during an invasive procedure.  This includes findings elicited on physical examination of a patient during admission or subsequent assessments of the patient and may include findings noted during a medical/invasive procedure, dependent upon the location of the infection as well as the NHSN infection criterion.


  • An intraabdominal abscess will require an invasive procedure to actually visualize the abscess.
  • Visualization of pus or purulent drainage (includes from a drain).
  • SSI only: Abdominal pain or tenderness post Cesarean section (CSEC) or hysterectomy (HYST or VHYS) is sufficient gross anatomic evidence of infection without an invasive procedure to meet general Organ/Space SSI criterion ‘c’ when a Chapter 17 [PDF – 621 KB] Reproductive Tract infection criteria is met. Allowing the documentation of abdominal pain or tenderness as gross anatomic evidence of infection to meet general Organ/Space SSI criterion ‘c’ enables the user to report an SSI-OREP, SSI-EMET, or SSI-VCUF event.  Note that abdominal pain or tenderness cannot be applied as ‘other evidence of infection on gross anatomic exam’ to meet Deep Incisional SSI criterion ‘c’ or to meet any Chapter 17 [PDF – 621 KB] site-specific criterion (for example, OREP ‘2’).

Note: Imaging test evidence of infection cannot be applied to meet gross anatomic evidence of infection.  Imaging test evidence has distinct findings in the HAI definitions (for example, IAB ‘3b’).

Imaging test findings

For NHSN surveillance purposes, an imaging finding of ‘free fluid’ is not definitive or equivocal for an NHSN infection criterion. ‘Free fluid’ is not indicative of an infectious process and is considered a negative imaging finding.  However, a ‘fluid collection’ imaging finding could be indicative of infection (such as an abscess or early formation of an abscess) and therefore is considered an equivocal imaging finding and eligible to cite an NHSN site-specific infection if clinical correlation is also present.  Clinical correlation is physician documentation of antimicrobial treatment for site-specific infection related to equivocal findings (not clearly identified) of infection on imaging test.

Pathogen reporting in NHSN

Up to three pathogens may be reported. If multiple pathogens are identified, enter the pathogen judged to be the most important cause of infection as #1, the next most as #2, and the least as #3 (usually this order is indicated on the laboratory report). If the species is not given on the lab report or is not found on the NHSN drop down list, then select the genus only.  (Report all site-specific pathogens before secondary BSI pathogens).

Additional pathogens recovered during the Repeat Infection Timeframe (RIT) from the same type of infection are added to the event.  Example:  Patient admitted 1/1/23 meeting criteria of Symptomatic Urinary Tract Infection (SUTI), urine culture = E. coli >100,000 CFU/ml.  On 1/12 another urine culture shows K. pneumoniae >100,000 CFU/ml.  The assignment is SUTI – E. coli and K. pneumonia.  The exception to this is that excluded organisms for a specific type of infection cannot be added to that type of infection.  For example, Candida albicans cannot be added to a previously reported UTI, as Candida is an excluded pathogen for UTI.

Protocols for Patient Safety Component Modules

  • The COVID-19 question is required for all HAI events occurring on or after January 1, 2022 and is intended to gather data on HAIs related to the COVID-19 condition. To reduce subjectivity, the lab finding of the most recent COVID-19 viral test prior to or on the date of event (HAI) should be used for the response.
    • Answer COVID-19 as ‘YES’ if the patient is lab test confirmed COVID-19 prior to or on the date of event (HAI).  Keep in mind that patients may undergo repeat testing post-treatment and may move from a ‘confirmed’ to ‘negative’ COVID-19 status.
    • Answer COVID-19 as ‘NO’ if the most recent lab test prior to or on the date of event (HAI) is negative.

    We did not include in our definition a length of time for the patient to be considered ‘confirmed’; however, we focus strictly on the current hospitalization and the response should be based on the lab test available within the current patient record.

    It is our hope that the data received over time will enable us to identify the risk of the COVID-19 condition on HAIs.