Real-time bacterial fluorescence imaging accurately identifies wounds with moderate-to-heavy bacterial burden
Clinical evaluation of signs and symptoms (CSS) of infection is imperative to the diagnostic process. However, patients with heavily colonised and infected wounds are often asymptomatic, leading to poor diagnostic accuracy. Point-of-care fluorescence imaging rapidly provides information on the presence and location of bacteria. This clinical trial (#NCT03540004) aimed to evaluate diagnostic accuracy when bacterial fluorescence imaging was used in combination with CSS for identifying wounds with moderate-to-heavy bacterial loads.
Wounds were assessed by study clinicians using NERDS and STONEES CSS criteria to determine the presence or absence of moderate-to-heavy bacterial loads, after which the clinician prescribed and reported a detailed treatment plan. Only then were fluorescence images of the wound acquired, bacterial fluorescence determined to be present or absent and treatment plan adjusted if necessary.
We examined 17 VLUs/2 DFUs. Compared with CSS alone, use of bacterial fluorescence imaging in combination with CSS significantly improved sensitivity (22% versus 72%) and accuracy (26% versus 74%) for identifying wounds with moderate-to-heavy bacterial loads (≥104 CFU/g, p=0.002). Clinicians reported added value of fluorescence images in >90% of study wounds, including identification of wounds incorrectly diagnosed by CSS (47% of study wounds) and treatment plan modifications guided by fluorescence (73% of study wounds). Modifications included image-guided cleaning, treatment selection, debridement and antimicrobial stewardship.
Findings from this pilot study suggest that when used in combination with CSS, bacterial fluorescence may: (1) improve the diagnostic accuracy of identifying patients with wounds containing moderate-to-heavy bacterial loads and (2) guide more timely and appropriate treatment decisions at the point-of-care.
Chronic wounds frequently harbour moderate-to-heavy levels of bacteria, which can challenge the accuracy of clinical diagnosis and contribute to poor patient outcomes.1 Wounds with moderate-to-heavy bacterial loads take longer to heal2,3,4 and reduce patients' quality of life (QoL), while increasing health-care costs.5 Left untreated, these wounds can cause local or systemic infections and, in some cases, patient loss of limbs.3,6 While wound cultures remain a routine part of the standard of care (SoC), tools enabling real-time visualisation of bacteria in the wound remain an unmet need. Accurate bacterial cultures rely on accurate wound sampling, and culture results are often delayed by days and therefore have limited use in real-time assessment or informing treatment selection during a patient's visit.7 Accordingly, numerous detection schemes, mnemonics and checklists have been developed around the ‘classic signs and symptoms’ (CSS) of the bacterial-infection continuum such as pain, lack of healing, purulent exudate, erythema, heat and oedema.1,8,9,10,11,12,13,14 Examples are the NERDS and STONEES mnemonics,8 developed to evaluate the presence or absence of clinical signs of critical colonisation (NERDS) or infection (STONEES).8,9 Under this mnemonic NERDS is — non-healing, exudate, red and bleeding surface or granulation tissue, debris, smell or unpleasant odour; and STONEES — size is bigger, temperature is increased, osteomyelitis probe to or exposed bone, new or satellite areas of breakdown, exudate, erythema/oedema, smell.8,9 Note that the most recent International Wound Infection Institute (IWII) guidelines for assessing a wound for infection have replaced the term critical colonisation with local or covert infection.1 While these solutions have been found to be useful, their widespread adoption has been limited and inconsistent across the world.1
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