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FAQs: Multidrug-Resistant Organism & Clostridium difficile Infection (MDRO & CDI)

Multidrug-Resistant Organism & Clostridium difficile Infection

Numerator Reporting for LabID Events: Definition of CDI Assay

Q1: When reporting a CDI LabID, what lab result should be reported as an event?

For NHSN reporting purposes, a CDI LabID event is a positive laboratory test result for C. difficile toxin A and/or toxin B OR any detection of toxin-producing C. difficile organisms by culture or other laboratory means on an unformed stool specimen that conforms to the container. Testing methods include, but are not limited to, molecular assays such as PCR and/or toxin assays such as EIA.

If a multi-step testing algorithm is used to test for C.difficile toxins, refer to question #2 below.

The CDI lab result (Antigen ONLY detected for C. difficile,*No Toxin detected) does not meet NHSN definition of a CDI-positive laboratory assay since the toxin result is negative.

Numerator Reporting for LabID Events: Testing for CDI

Q2: Our facility uses a multi-step process to test for C. difficile toxins, should we report an event if the screening test is positive and the confirmatory test is negative or the opposite (screening test is negative and confirmatory test is positive)?

Regardless of the method or sequence of testing, the result of the last test finding which is placed onto the patient medical record will determine if the CDI Laboratory Assay definition is met and a LabID event is submitted to NHSN.

Numerator Reporting for LabID Events: Acceptable specimens for CDI reporting

Q3: Are specimens collected from colostomy bags considered acceptable for C. difficile LabID event reporting?

An unformed stool specimen testing positive for C. difficile toxin A and/or toxin B that meets the definition of CDI laboratory assay should be reported as a CDI LabID Event and/or a healthcare-associated infection for GI-CDI if the specific criteria are met (positive testing performed on unformed stool specimen).

Reporting should be done irrespective of method of collection (for example, stools collected from ostomies), and/or there being a change from the normal consistency or amount of the stool.  These reporting instructions align with the intent of LabID Event Reporting to decrease the burden for gathering information beyond the specimen collection date and admission date, and will remove subjectivity and simplify interpretation of the GI-CDI infection criteria.  Specimens labeled something other than ‘stool’ are not eligible for use.

Numerator Reporting for LabID Event: Transfer rule

Q4: How does the transfer rule apply to the patient at the time of discharge for FacWideIN?

The transfer rule does not apply to LabID Event reporting. LabID Events are categorized based on the location of the patient at the time of specimen collection. The location of attribution for LabID Events is based on the location of the patient when the specimen is collected, regardless of time spent or procedures performed in the location.

Numerator Reporting for LabID Event: Discharged in past 4 weeks

Q5: Why is the question, “Has the patient been discharged from your facility in the last 4 weeks?” required for answer?

The question is used to define a LabID Event as community-onset healthcare facility-associated (CO-HCFA) (collected from a patient who was discharged from the same facility ≤4 weeks prior to the current date of stool specimen collection). The question refers to prior discharge from the same facility after an inpatient stay and offers meaningful information for appropriate event categorization.


Q6: Does this question “Has the patient been discharged from your facility in the past 4 weeks?” include ED visits?

No, this question refers to discharge from an inpatient unit in your facility. Discharge from an outpatient location (also known as an encounter) such as emergency department and 24-hour observation unit are not eligible for use.

Numerator Reporting for LabID Event: ED & 24-hour observation locations

Q7: How should a positive specimen collected in the ED or 24-hour observation unit be submitted

When entering LabID Events collected from these outpatient locations, select ‘YES’ for “Outpatient” so that the drop down selections for ‘location’ will display mapped outpatient locations such as ‘ED’ and ’24-hour Observation’.

Numerator Reporting for LabID Event: Date admitted to facility

Q8: For specimens collected in the ED or 24-hour observation (outpatient) locations, what date should be entered for “Date Admitted to Facility”?

Since visits to outpatient locations are considered encounters and not admissions, the “Date Admitted to the Facility” question can be left blank when entering a LabID Event for ED or 24-hour observation locations.  This question is optional for outpatient LabID events.

Numerator Reporting for LabID Event: Prior evidence of infection

Q9: Why will the system not let me answer “Yes” to the question “Documented prior evidence of infection or colonization with the specific organism type from a previously reported LabID event?”

This is a non-editable data field and will auto-fill by the system based whether a MDRO LabID Event was submitted for the same MDRO and same patient in a prior month (not the current month) at this reporting facility. If there is a previous LabID event for this organism type entered into NHSN in a prior month, the system will auto-populate with a “YES.”

The auto-fill response is used in the calculation of the MDRO Infection/Colonization Incidence Rate for “All Specimens” reporting (not Blood Specimen only) which may represent colonization events.

All “YES” previous positive events are excluded which prevents facilities from being penalized for the overall (All Specimens) infection/colonization incidence rate.

Note:  This data field is NOT used in the calculation of SIRs.

Instructions for completion of the LabID Event form (57.128).

Numerator Reporting for LabID Event: Skilled Nursing Facility (SNF)/ Long Term Care Facility (LTCF)/Long Term Acute Care Hospitals (LTACs)

Q10: Should LabID events collected from affiliated SNF/LTCF/LTAC be included in the acute care hospital’s “FacWideIN” LabID Event reporting?

No. SNFs, LTCFs, and LTACs with a different CCN from the acute care hospital are considered a different facility type than the acute care hospital. If a facility is interested in reporting LabID Events or other infections from SNFs or LTCFs, these facilities must be enrolled in NHSN as a different facility type. Data from SNFs/LTCFs/LTACs with a unique CCN should never be included in counts for the acute care hospital.

More information in relation to SNF/LTCF surveillance and reporting using NHSN can be found on the Long Term Care Facility Component webpage.

Numerator Reporting for LabID Event: Admission date for inpatient rehabilitation facilities (IRF)

Q11: What admission and discharge date should be entered when the patient is admitted into an IRF that is located inside of an acute care hospital (ACH)?

For NHSN purposes, if the IRF is located inside of the ACH:

  • Movement between the ACH and the IRF location is considered a location transfer and is treated as a single facility continuous stay (one admission and discharge).
  • The facility admission date for a LabID event should reflect the date the patient was physically admitted into either the inpatient location for the acute care hospital or the IRF location, whichever comes first during that patient’s stay.

Numerator Reporting for LabID Event: MRSA bacteremia, all specimen source

Q12: When following All Specimen sources for MRSA LabID Event reporting, if a MRSA blood isolate is entered as the first specimen of the month, can a second MRSA non-blood specimen (for example, urine) be entered that month for the same patient and same location?

No. If monitoring all MRSA specimens, any MRSA isolate from the same patient and location after an initial isolation of MRSA during a calendar month is considered a duplicate MRSA isolate and should not be entered, except if it is a unique blood source.

This means that if the first MRSA isolate for the month is from a blood source, no other non-blood MRSA isolates should be reported for the calendar month for that patient and location.  If there is another positive MRSA blood isolate from same patient and location, there should be a full 14 days with no positive blood MRSA isolates for the patient and location before another MRSA Blood LabID Event is entered into NHSN for the patient.

See Figure 1 in MDRO and CDI Module (Chapter 12) for algorithm for ALL SPECIMENS.

Denominator Reporting for LabID Events: Outpatient encounter

Q13: Define encounter

NHSN defines an encounter as a patient visit to an outpatient location (ED, 24-hour observation) and is independent of admission to the inpatient facility.  Each encounter must be included in the total encounter count regardless of admission to the facility. Instructions for completion of denominator data for Infection Surveillance and/or LabID Events is found at: Outcome Measures Monthly Monitoring form (CDC 57.127).

Denominator Reporting for LabID Event: Facility count

Q14: What is the difference between Total Facility Counts (admissions and patient days) and MDRO and CDI Counts (patient days and admissions)?

Total Facility Patient Days/Admissions include all inpatient locations in the facility including units with separate CCNs such as inpatient rehabilitation facility (IRF) and inpatient psychiatric facility (IPF) locations.

MDRO Counts are total facility counts minus counts from CMS-certified inpatient rehabilitation units (IRFs) and inpatient psychiatric units (IPFs) with a unique CCN. This is not a count of patients with an MDRO.

CDI Counts are total facility counts minus counts from CMS-certified inpatient rehabilitation units (IRFs) and inpatient psychiatric units (IPFs) with a unique CCN, and minus counts from all baby locations.  This is not a count of patients with CDI.

NOTE: MDRO Patient Days/Admissions (Row 2 on the FACWIDEIN form) and CDI Patient Days/Admissions (Row 3 on the FACWIDEIN form) refer to the total number of patients housed in eligible inpatient locations (FACWIDEIN) in your facility, regardless of the patient’s MDRO or C.difficile infection status.

Step-by-step instructions for completing this information can be found in the Instructions for Completion of MDRO and CDI Prevention Process and Outcome Measures Monthly Monitoring form (CDC 57.127).

Categorizations: Previous admissions

Q15: If a patient is discharged and is readmitted two weeks later from another healthcare facility (such as rehabilitation center, different hospital, etc.) with CDI, how is the infection categorized in NHSN?

Although a patient may have spent time at another facility in the time between previous discharge and readmission, the categorization of the current event is based on date admitted to facility and date of this event. NHSN reporting is by single facility and information regarding a patient’s status between admissions is not included in the LabID event reporting because of burden for retrieving such information outside of one’s own facility. Facilities interested in tracking such information may use custom fields.

LabID Events are categorized as healthcare facility-onset (HO), community-onset (CO), or community-onset healthcare facility-associated (CO-HCFA, for C.difficile only) based almost exclusively on laboratory data and limited admission date data. This is irrespective of the patient having a prior history of C. difficile.

Categorizations: History of CDI

Q16: If a patient with a history of CDI is admitted without symptoms but on HD 5 has diarrhea and test positive for C. difficile – should a CDI LabID Event be reported? Will the admitting facility be penalized for the event? 

The positive C. difficile specimen should be reported and the NHSN application will categorize it as a healthcare facility-onset (HO) CDI for the admitting facility if the specimen collection date was ≥ 4 days after inpatient admission to the facility. The categorization is irrespective of testing performed prior to admission to a facility. LabID Event reporting and categorizations are based on a single reporting facility and for FacWideIN include inpatient, emergency department, and 24-hour observation locations in the reporting facility. The challenges of decreased specificity as it relates to true infection vs. colonization are balanced by the intent of the categorizations used for LabID Events Reporting, which are:

  • Enabling the use of laboratory testing data without clinical evaluation of the patient
  • Allowing for more effective standardization of reporting across all facilities
  • Minimizing the burden data collection by the facilities and IPs Providing less subjectivity and being well-suited for public reporting

Categorizations: Recurrent and incident

Q17: Please define recurrent and incident C. difficile.

These categorizations are based on the length of time between C.difficile LabID Events for the same patient while in the same facility.  Specifically:

  • Incident CDI Assay = A CDI LabID Event from a specimen obtained >56 days after the most recent CDI LabID Event (or with no previous CDI LabID Event documented) for that patient.
  • Recurrent CDI Assay = A CDI LabID Event from a specimen obtained >14 days and ≤ 56 days after the most recent CDI LabID Event for that patient.

Locations: Swing beds & observation patients

Q18: Should patients in a swing bed and/or observation status be included in FacWideIN inpatient reporting?

All patients admitted to and housed in an eligible inpatient unit should be included in counts (numerator and denominator) for FacWideIN LabID Event reporting, including patients designated as “swing bed” and “observation” status.

Analysis: Determination healthcare-associated infection (HAI) and LabID events

Q19: How does determining a HAI GI-CDI case differ from a CDI LabID event?

These are two very different CDI event reporting methods that are each governed by different sets of rules and date timeframes.

CDI LabID Event Reporting is based strictly on the number of hospital days between the specimen collection date and the date the patient is admitted to the facility.  Facility admission date is considered Day 1. There is no consideration for clinical presentation.

  • ≤ 3 days = community-onset (CO)
  • ≤ 3 days but patient had prior discharge from the reporting facility in the previous 4 weeks = community-onset healthcare facility-associated (CO-HCFA)
  • ≥ 4 days = healthcare facility-onset (HO)
  • GI-CDI HAI surveillance is based on specific infection criteria that are met within the HAI timeframe:

Day of admission or the day after = present on admission (POA) Hospital day 3 or greater = HAI

GI-CDI HAI surveillance based on specific infection criteria being met within timeframe

Each method requires a positive test for toxin-producing C. difficile on an unformed stool specimen.

Note:  Although diarrhea is not a specific element for a GI-CDI event, it must be checked when entering the event to validate that testing was performed on the appropriate specimen type.

Analysis: SIR

Q20: Which MRSA and C. difficile LabID Events are included in the standardized infection ratio (SIR) for my acute care hospital?

MRSA Bacteremia: Only events categorized as healthcare facility-onset (HO) and ‘Unique’ blood isolates from blood specimens are included in the numerator of the SIR.

C. difficile: Only HO incident events are included in the numerator of the SIR. If a patient has a second LabID event from the same organism within 14 days of the first, the second event is not counted in the SIR.   Users can run a line list to determine which events are counted in the SIRs.

Data from IRFs and IPFs with separate CCNs are excluded from acute care hospitals’ LabID event SIRs.

The complete list of algorithms used to determine which events are counted in the SIR (for all facility types) can be found here: Troubleshooting the MRSA Bacteremia and CDI LabID Event SIR.

Analysis: Line listing, indicator variable

Q21: How do I know which MRSA bacteremia and CDI LabID Events are counted in the SIR when looking at the line listing?

The MRSA bacteremia and CDI LabID Event Line Lists contain indicator variables that identify which events are counted in the SIR. The indicator variables for acute care hospitals are listed below:

Facility-wide incidence (SIR) for MRSA bacteremia: FWMRSA_bldIncCount

Facility-wide incidence (SIR) for C. difficile: FWCDIF_facIncHOCount

Variable will display as 1 or 0 for each event

1: event is counted in the SIR

0: event is NOT counted in the SIR

NOTE: separate indicator variables are available for CMS-certified IRF units. Refer to the Troubleshooting Guide.

Analysis: Line listing, categorizations of MRSA bacteremia LabID Events

Q22: If the first MRSA bacteremia LabID event appears on the line listing as a community-onset (CO) event, why does a second MRSA bacteremia LabID Event collected within 14 days from a different inpatient location in the facility, get categorized as healthcare-facility onset (HO)?

To show risk at the location/unit level where the patient has been housed, all location/unit level LabID events reported into the NHSN application will appear on the line list.  However, the categorizations assigned (HO vs. CO) on the line list are based on facility-wide inpatient (FacWideIN) data (date admitted to the facility and date specimen collected).

This means that although the first reported LabID Event is categorized as CO if the specimen is collected fewer than four days after inpatient admission, a subsequent LabID Event entered into the application for the same patient, but a different location will be categorized as HO if the specimen is collected on Day 4 or later after inpatient admission to the facility. Each LabID event is viewed independently of other events at this level.
Note: For FacWideIN reporting, however, duplicate LabID Events will be removed during analysis. Your SIR report will provide a more accurate description of your FacWideIN numbers.

CMS Inpatient Quality Reporting (IQR) Program for Acute Care Hospitals (ACH): CMS reporting requirements & data submitted

Q23: Where are CMS reporting requirements found and what facility data are being submitted to CMS for FacWideIN MRSA bacteremia and C. difficile LabID Events?

CMS guidance documents and reporting requirements can be found on the NHSN home page under “CMS Supporting Materials” (must copy and paste the link):

FacWideIN standardized infection ratios (SIRs) are sent to CMS for those hospitals participating in the Hospital Inpatient Quality Reporting program.  The numerator of the SIR is a count of the following events:

  • Healthcare facility-onset (HO) MRSA bacteremia LabID Events (Unique blood events)
  • HO CDI LabID Events (incident cases).

NOTE: SIRs are calculated for FacWideIN surveillance only and duplicate LabID Events reported at the location level are excluded from SIR calculations. For more information about the algorithms used to determine which events are counted in the SIR, refer to our LabID Troubleshooting Guide.