FOCUS ON INFECTION PREVENTION Calculation of Outcome Rates That Diagnose Bedside Performance: Central-Line-Associated Bloodstream Infection James Davis, MSN, RN, CCRN, CIC INTRODUCTION Sr. Infection Prevention Analyst Rates of central-line-associated bloodstream infection (CLABSI) have historically Edward Finley, BS Data Analyst been presented as the number of infections divided by the total number of central- Pennsylvania Patient Safety Authority line-days, multiplied by 1,000.1 The Pennsylvania Department of Health publishes an overall hospital CLABSI rate as part of its healthcare-associated infection (HAI) annual reports.2 While this traditional rate calculation is useful for evaluating overall ABSTRACT central-line infection prevention performance, it does not provide information about Historically, central-line-associated the different components of care for patients with central lines. The use of the stan- bloodstream infection (CLABSI) has dardized infection ratio (SIR) also holds no promise for use by the bedside clinician. been presented using one rate: infec- “In HAI data analysis, the SIR compares the actual number of HAIs reported with the tions per 1,000 central-line-days. While baseline U.S. experience,” writes the Centers for Disease Control and Prevention. The this calculation is useful for looking at SIR is designed to be “a summary measure used to track HAIs at a national, state, or overall central-line infection preven- local level over time.”3 tion, the calculation fails to provide A September 2011 Pennsylvania Patient Safety Advisory article, “Central-Line-Associated information specifically related to Bloodstream Infection: Comprehensive, Data-Driven Prevention,” delineated the inser- central-line insertion or maintenance tion and maintenance phases of the central venous catheter’s (CVC) life in terms of problems. Pennsylvania Patient Safety the frequency and timing of infection.4 In another study, Ryder et al. notes that the Authority analysts queried the National internal lumen can be the primary source of bacteremia in short-term catheters as early Healthcare Safety Network database to as day five postinsertion.5 In the Advisory article, analysts noted that 71.7% of hospitals determine the dates of CLABSI infection reported that CLABSI occurred more than five days after insertion.4 Observations by events for calendar years 2010 through Ryder et al. targeting the source of CLABSI at or after day five correlated with the find- 2012 in Pennsylvania hospitals, along ings published by the Pennsylvania Patient Safety Authority. with the accompanying dates of insertion The correlation between patient-level infection surveillance data4 and known patho- for central venous catheters (CVCs). The genesis related to intraluminal biofilm formation5,6 made it possible to differentiate analysis shows that both the combined between insertion-related bacteremia and maintenance-related bacteremia. If a patient CLABSI rate and the CVC insertion infec- experiences a CLABSI between days one and five, it is likely due to practices related to tion rate trend lines are trending upward CVC insertion. If a patient experiences a CLABSI on day five or later, it is likely due and that the CVC maintenance infection to CVC maintenance practices. To produce data that can be used by clinicians, facility rate trend line is essentially flat. This infection preventionists can split CLABSI infection rates in a manner that correlates to example of trending over three years the specific phase of CVC life, thereby enabling clinicians to track insertion and main- shows the limitation of using the tradi- tenance performance and directly target clinical practice improvement efforts. tional aggregate CLABSI rate to identify the CVC infection phase causing the increase. Authority analysts have shown METHODS that splitting CLABSI infection rates in Using fields readily available in the data analytics function of the Centers for Disease a manner that correlates to the specific Control and Prevention’s National Healthcare Safety Network (NHSN), Authority phase of CVC life enables clinicians to analysts queried the NHSN database to determine the dates of infection events occur- track insertion and maintenance perfor- ring from 2010 through 2012 in Pennsylvania hospitals. Analysts also extracted the mance. Insertion and maintenance of accompanying date of insertion for CVCs, when documented. Approximately 51% CVCs are separate processes; hence, of Pennsylvania hospital CLABSI events within the selected time period had a docu- there is a need for separate measure- mented insertion date. Date of CVC insertion and date of infection event were the ments to better target resources and two fields chosen to isolate data related to the determination of early versus late-onset improvement efforts. (Pa Patient Saf CLABSI, yielding numerator data. Denominator data was determined as the overall Advis 2013 Sep;10[3]:107-9.) number of central-line-days reported. Denominator data for CLABSI is entered into Scan this code NHSN as one complete data set. with your mobile Currently, there is no mechanism within NHSN that would enable splitting the device’s QR Reader denominator data into specific patient-level data sets matching insertion phase or to access the maintenance phase numerators. Therefore, the same denominator data set was used Authority's CLABSI for each of the two numerator data sets. It is important to note that this calculation is prevention toolkit. a best possible fit designed to produce actionable data for performance tracking within Vol. 10, No. 3—September 2013 Pennsylvania Patient Safety Advisory Page 107 ©2013 Pennsylvania Patient Safety Authority FOCUS ON INFECTION PREVENTION each CVC phase given the current limita- Figure. CLABSI Rates: Maintenance Phase versus Insertion Phase, by Month, tions of the NHSN database. The Figure 2010 through 2012 shows the insertion and maintenance rates as compared with the traditional INFECTION RATES CLABSI rate per month for those facili- (PER 1,000 CENTRAL-LINE DAYS) ties that reported insertion dates. 0.7 RESULTS 0.6 The Figure shows that the combined R2 = 0.0251 CLABSI rate for the Pennsylvania facili- 0.5 ties that enter insertion dates in NHSN is trending upward. The maintenance 0.4 R2 = 0.0002 CLABSI rate trend line is essentially flat, and the CLABSI insertion rate trend 0.3 line is elevating faster than the combined trend over time. This example of trending over three years shows the limitation of 0.2 the traditional combined CLABSI rate R2 = 0.1298 for identifying the CVC infection phase 0.1 (insertion) causing the increase. The com- bined rate alone provides no data as to 0.0 which CVC phase is actually influencing Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Sep the rate increase, but as illustrated in the Figure, it appears that the maintenance 2010 2011 2012 phase infections have less influence over MONTH the increase in the combined rate. Insertion phase rate Maintenance phase rate Combined rate MS13388 This method of data presentation shows (insertion date provided) the importance of knowing which phases Insertion phase trend Maintenance phase trend Combined trend influence the increase in the overall Note: Data is from the Centers for Disease Control and Prevention’s National CLABSI rate. This observation will have Healthcare Safety Network database. increased value on a monthly basis at the facility level, as clinicians need to react the facility is able to link the number of of utilizing the EHR incorporates the as quickly as possible to determine why CLABSIs that occur at less than five days workflow of the inserting clinicians and infections occurred and to implement to a matching denominator representative the staff performing maintenance. The strategies to prevent future infections. of central-line-days for those patients with insertion date could be tagged within the CVCs for less than five days. Likewise, EHR for all patients with a CVC through DISCUSSION rate calculation for the maintenance phase a procedural note or upon first entry in a Data Collection at the would be similar, substituting the numera- progress note. The EHR could then begin Facility Level tor data for the number of CLABSIs the algorithm for calculation of central- The Authority has demonstrated herein occurring at five or more days and the line-days on a patient-specific basis. The an approach utilizing the same denomi- denominator data representative of central- endpoint for insertion rate calculation nator data set used for each of the two line-days for those patients with CVCs for within the system would be development numerator data sets due to limitations five or more days. of infection at less than five days. Patient- related to the NHSN data. However, specific central-line-days data for those It is possible to utilize the electronic when a facility is able to produce denomi- patients with and those patients without health record (EHR) in order to collect nator data that matches numerator data infection at less than five days would be the numerator and denominator data for insertion and maintenance phase combined to construct the total insertion- needed to calculate separate insertion and infections, the data has the ability to related denominator for the month. The maintenance rates. A hypothetical example become more meaningful. For example, algorithm for maintenance central-line-day Page 108 Pennsylvania Patient Safety Advisory Vol. 10, No. 3—September 2013 ©2013 Pennsylvania Patient Safety Authority calculation would then be the patient- in order to create stable, well-performing and money. For example, in reference to specific central-line-day data for those systems of CVC care. According to insertion, is the bundle of best practices patients with and those patients without Wiemken, “Adequate data collection and being followed? Depending on the answer, infection at or after day five. Numerator critical analysis of control charts, [will clinicians performing insertion could be data would then be the number of CLAB- allow] the infection preventionist [to] surveyed for potential causes of a rate SIs. Once a facility is able to generate data detect aberrant data early, which allows that falls outside the limit. Likewise, if as described above, it is possible to plot the for prompt intervention and mitigation of the maintenance rate signals an increase, data over time and add confidence limits any poor outcomes.”7 clinicians who perform maintenance enabling the facility to establish limits of When the traditional CLABSI rate is plot- could be surveyed for possible causes. For stability for the data. ted over time, it offers little data about example, is daily review for CVC neces- performance regarding the two separate sity being performed, are the appropriate CONCLUSION CVC phases of care that together form dressings being used, and are the dressings a combined rate. When the CLABSI intact? Understanding CVC care variation In order to prevent CLABSI, the processes rate is divided into insertion and main- through trending CLABSI insertion and that protect the patient need to be stable. tenance performance calculations, maintenance rates could help healthcare For low infection rates to be sustained, targeted improvement strategies can be facilities target their improvement efforts facilities must actively design specific data implemented, potentially saving time and prevent further CLABSI events. collection related to process performance NOTES 1. Dudeck MA, Horan TC, Peterson KD, Newsletters/NHSN_NL_OCT_2010SE_ 6. Ryder MA. Catheter-related infections: it’s et al. National Healthcare Safety Network final.pdf all about biofilm [online]. Top Adv Pract (NHSN) report, data summary for 2010, 4. Davis J. Central-line-associated blood- Nurs 2005 Aug 18 [cited 2013 Jul 12]. device-associated module. Am J Infect stream infection: comprehensive, http://www.medscape.com/viewarticle/ Control 2011 Dec;39(10):798-816. data-driven prevention. Pa Patient Saf 508109 2. Pennsylvania Department of Health. Advis [online] 2011 Sep [cited 2013 Jul 7. Wiemken T. Statistical process control. Healthcare-associated infection (HAI) 12]. http://patientsafetyauthority.org/ Chapter 6. In: APIC text of infection control annual reports [online]. [cited 2013 Jul ADVISORIES/AdvisoryLibrary/2011/ and epidemiology. 3rd ed. Washington (DC): 12]. http://www.portal.state.pa.us/portal/ sep8(3)/Pages/100.aspx Association for Professionals in Infection server.pt/community/healthcare_ 5. Ryder M, Gunther RA, Breznock EM, Control and Epidemiology, Inc.; 2009. associated_infections/14234/hai_annual_ et al. The effect of chlorhexidine antimicro- reports/1403644 bial coating on the reduction of intraluminal 3. Centers for Disease Control and Preven- biofilm formation in a clinically simulated tion. NHSN e-news: SIRs special edition ovine model (pilot study). Abstract at: [online]. 2010 Dec 10 [cited 2013 Jul 12]. SHEA 2011 Annual Scientific Meeting; http://www.cdc.gov/nhsn/PDFs/ 2011 April; Hilton Anatole, Dallas. Vol. 10, No. 3—September 2013 Pennsylvania Patient Safety Advisory Page 109 ©2013 Pennsylvania Patient Safety Authority PENNSYLVANIA PATIENT SAFETY ADVISORY This article is reprinted from the Pennsylvania Patient Safety Advisory, Vol. 10, No. 3—September 2013. The Advisory is a publication of the Pennsylvania Patient Safety Authority, produced by ECRI Institute and ISMP under contract to the Authority. Copyright 2013 by the Pennsylvania Patient Safety Authority. 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