Beyond the Fever

In Aged Care Facilities (ACF), identifying infections in older adults can be very challenging. Residents often have multiple and complex health issues and may not show the classic signs of an illness that we are used to seeing in younger populations. Fever might be subtle, or symptoms might manifest as something less obvious, like a behaviour change. This is where the McGeer Definitions come in, providing a standardised framework specifically designed for infection surveillance in this specific setting. As there are limitations in acute care definitions, McGeer has been developed to help healthcare professionals consistently recognise potential infections, ensuring more accurate data collection and better infection control strategies. Join us as we explore in this blog how looking "beyond the fever", using these specialised criteria, is essential for the safety of our residents in Aged Care.

The journey to standardised infection surveillance in ACFs began because a clear need was recognised: there wasn't a consistent way to define infections in these settings. The McGeer criteria originated in the late 1980s and were published in the American Journal of Infection Control in 1991. This was the result of collaborative work led by Dr. Allison McGeer and a team of experts, including infectious diseases physicians, geriatricians, and infection control nurses with hands-on experience in long-term care facilities. They adapted existing surveillance models, like the CDC's National Nosocomial Infection Surveillance (NNIS) system, but made careful modifications to fit the specific needs of ACFs.

The primary purpose was clear: to establish a consistent, reliable framework for both infection surveillance and research studies in ACFs. This included the specific aim to create a standardised approach to identifying infections and supporting robust research, allowing facilities to compare infection rates meaningfully. They were then better able to evaluate how well infection control programs were working, and with a more reliable way to measure outcomes. Developing these criteria early on showed foresight about the growing importance of the ACF sector and its unique infection control challenges. This collaborative, expert-driven process gave the McGeer criteria strong credibility right from the beginning.

One of the brilliant aspects of the McGeer criteria is their recognition that infections in older adults often don't present with dramatic, localised symptoms as in younger adults. Instead, systemic changes can be the first or only clue. This is why the criteria include Constitutional Criteria – general signs and symptoms indicating a body-wide response to an infection. These are crucial because they capture those subtle yet significant shifts in a resident's health.

The main constitutional criteria include:

• Fever: Defined specifically as a single high oral temperature (>37.8°C / >100°F), or repeated lower oral or rectal temperatures (>37.2°C / 99°F or >37.5°C / 99.5°F), or even just a notable rise (>1.1°C / 2°F) from the individual resident's baseline temperature, regardless of where it's measured.

• Leukocytosis: Defined as either a total leukocyte count over 14,000 cells/mm³ or a "left shift" in the differential count, meaning more than 6% band neutrophils or at least 1,500 bands/mm³.

• Acute change in mental status from the baseline: Requires all four of these components: an acute onset, a fluctuating course, inattention, AND either disorganised thinking or an altered level of consciousness. The detailed definition for mental status changes is vital because delirium is a common, and often the sole, sign of infection in ACF residents.

• Acute functional decline: Defined as a new increase of 3 points or more from their baseline score on a specific 7-item Activities of Daily Living (ADL) scale. The scale covers bed mobility, transferring, dressing, eating, etc., indicating the level of dependence.
  
  

By including these non-specific indicators and providing clear definitions for terms like "Acute Onset" and "Fluctuating", McGeer ensures a more consistent and reliable way to identify potential infections, especially when classic signs are absent.

While constitutional symptoms raise a flag, the McGeer criteria take a step further by providing detailed definitions for common types of infections seen in ACFs. These syndrome-specific definitions combine clinical observations with laboratory or radiographic evidence to pinpoint the source of the infection.

Examples include:

So, how do these detailed definitions make a difference in the real world of an aged care facility? Their impact is significant and far-reaching. Because McGeer provides a common language and consistent criteria, facilities can collect comparable data on infections from other facilities. With consistent data, facilities can produce a benchmark for their infection rates against others, identify concerning trends and patterns, and accurately evaluate the effectiveness of their infection prevention and control programs. This will allow for data-driven decisions, making interventions more targeted and effective.

Perhaps one of the most vital impacts is on Antibiotic Stewardship Programs. In ACFs, accurately identifying whether a resident truly has an infection requiring antibiotics or is showing non-infectious symptoms is crucial. By providing clear, standardised criteria for identification, McGeer's definitions directly support more appropriate antibiotic prescribing. When staff can confidently determine if surveillance criteria for an infection are met, it guides them and clinicians in deciding if antibiotics are necessary. This is a prime strategy in the fight against antimicrobial resistance, a major health threat globally. Accurate identification means antibiotics are used only when truly needed, minimising risks to the resident and reducing the development of resistant bacteria.

No framework stays relevant forever without updates, and the McGeer criteria are no exception to this. To keep pace with new medical knowledge and better diagnostic tools, they underwent a significant revision process in 2012, led by an expert consensus panel. The 2012 revisions incorporated new evidence and aimed to address some limitations of the criteria. For UTIs, there was a stronger emphasis on needing localised urinary symptoms in non-catheterised residents and reinforced recommendations for microbiological confirmation. New surveillance definitions were added for Norovirus gastroenteritis and Clostridioides difficile infection (CDI), reflecting their growing recognition as significant issues in aged care.

However, even with revisions, it's important to acknowledge that the McGeer criteria aren't perfect and have faced criticisms and limitations since their creation. A major challenge is their potential sensitivity and specificity in the elderly population, especially those with cognitive impairment like dementia. Residents with dementia may not be able to articulate symptoms that are central to some McGeer definitions, making their application difficult. Some argue the criteria might be overly sensitive, potentially leading to the overdiagnosis of infection.

Another key limitation is that the McGeer criteria were primarily designed for retrospective surveillance, for counting and tracking infections after they've occurred. This can limit their use in guiding real-time clinical decisions about whether to start antibiotics at the resident’s bedside. This is a key difference when compared to criteria like the Loeb criteria, which were developed specifically to guide the use of an antibiotic based on minimum clinical signs. Studies have shown that McGeer and Loeb criteria don't always agree with each other.

Despite their limitations, the McGeer definitions have undeniably left a deep mark on infection surveillance in ACFs. They provided a critical, standardised framework where none truly existed before. This standardisation has significantly improved our understanding of the true burden of infections, fuelled valuable research, and directly supported the implementation of essential infection control practices.

As the field continues to evolve, so too will the need for ongoing research and refinement. Future efforts could focus on confirming the revised criteria, developing more tailored criteria specifically for residents with significant cognitive impairment, exploring how objective measures like biomarkers could be incorporated, and working towards greater harmonisation with other national surveillance systems like the CDC's NHSN definitions. While different criteria like NHSN are being increasingly adopted by facilities, the historical and ongoing value of McGeer as a comprehensive framework for understanding infection patterns remains.

Ultimately, maintaining a strong commitment to robust and accurate infection surveillance in ACFs, guided by standardised criteria like McGeer, is crucial. It's about continually striving to understand, prevent, and manage infections more effectively, therefore improving resident safety and achieving better healthcare outcomes for those who call these facilities home.

This blog is for those who have enquired about the McGeer criteria and wanted to know more about it. There is more information on the HUB for your reference, including the McGeer surveillance tool. 

Look out for our last blog in this series, looking at the financial side of outbreaks in Aged Care Facilities in Australia and New Zealand. Follow us on Facebook and LinkedIn, comment and share!