A Prospective Multisite Observational Study Incorporating Bacterial Fluorescence Information Into the UPPER/LOWER Wound Infection Checklists

Introduction. The UPPER/LOWER infection checklists look for signs and symptoms of local/superficial infection (UPPER) and deep infection (LOWER) to assist clinicians in identifying and distinguishing between these infection levels, facilitating appropriate treatment. The presence of 3 or more UPPER or LOWER criteria is indicative of infection. Objective. This study evaluated the utility of incorporating real-time bacterial fluorescence imaging into the UPPER/LOWER checklists to enhance identification of infection in wounds. Materials and Methods. This prospective, multisite study assessed 43 chronic wounds. Infection was identified in 27 wounds (62.8%) according to the UPPER/LOWER checklist criteria; 3 wounds were positive for both UPPER and LOWER infection, 1 wound was positive for LOWER infection only, and 23 wounds were positive for UPPER infection only. Fluorescence images were taken to detect wounds with high bacterial loads (> 10⁴ CFU/g), indicated by the presence of red or cyan fluorescence. Results. Red or cyan fluorescence from bacteria was observed in 88% of wounds (n = 38); all wounds positive for UPPER/LOWER were also positive for bacterial fluorescence. In 18 (41.9%) of the 43 wounds, fluorescence information added a third check to the UPPER/LOWER threshold, turning a negative diagnosis into a positive diagnosis of infection. Bacterial load was detected in 22/27 wounds swabbed, 17 of which exhibited heavy growth; in all wounds with detectable bacterial load, fluorescence signal was observed (positive predictive value = 100%, negative predictive value = 83%). Using microbiology as ground truth, inclusion of fluorescence information as an additional item in the checklists increased the sensitivity of the UPPER/LOWER checklist from 82% to 95% (P < .01). Conclusions. These results suggest that the UPPER/LOWER checklist and fluorescence imaging work in a complementary manner to effectively identify wounds with high bacterial burden at the point-of-care.

Wound care currently accounts for 5% of total health care spending and much of this cost stems from management of bacterial infection.¹ Timely diagnosis of high bacterial burden and infection in wounds is critical to wound healing outcomes and preventing the wound from escalating to local, spreading, or systemic infections. Indiscriminate and routine wound cultures are not recommended for the diagnosis of wound infection (superficial or deep).² Recognizing that all chronic wounds are colonized, a wound swab will always yield a positive culture that does not necessarily confirm or refute wound infection. Tissue biopsy is the gold standard to detect wound infection,³ but it is not always feasible to obtain tissue samples (due to pain, bleeding, lack of expertise); hence, clinical evaluation is needed. Current best practices to diagnose wound infection involve inspection for clinical signs and symptoms, and, if necessary, collection of a wound sample for microbiological culture analysis.⁴ Clinical signs and symptoms are a proxy for the presence of infection-causing bacteria and reflect a host response to elevated bacteria levels in the wound. Evaluation of signs and symptoms of infection may be subjective and variable,^5-7 but assessment of these signs and symptoms of infection is the most common method used to guide selection and evaluate efficacy of treatment. To enable easier recall and documentation, these numerous signs and symptoms of infection are often grouped together into mnemonics and checklists (eg, NERDS [nonhealing, exudate, red friable tissue, debris (discoloration), and smell] and STONEES [size increasing, temperature elevation, os (probes to bone), new breakdown, erythema/edema, exudate and smell], International Wound Infection Institute [IWII] Wound Infection checklist).^4,8,9 Mnemonics facilitate easy recall of information and greatly enhance the communication of wound status among members of the wound care team, but do not convey information on the presence and location of bacteria, thus limiting timely deployment of appropriate treatment. 

Based on a review of the literature^4,10, a set of wound infection checklists (UPPER and LOWER) were developed to describe 2 clusters of signs and symptoms associated with superficial/localized infection or deep tissue infection. There is no one individual sign or symptom that will accurately confirm the diagnosis of wound infection, but a combination of 2 or 3 of these possible signs is used to confirm diagnosis. Local infection involves unhealthy tissue, pain, poor healing, exudate, and reek (UPPER), while deeper infection includes a larger wound size, osseous tissue, warmth, edema, and redness (LOWER) (Figure 1). Using these mnemonics to distinguish between local and deeper infection at the time of evaluation provides valuable information to guide treatment decisions. For example, presence of 3 or more signs and symptoms from the UPPER checklist indicates the presence of a local infection, which may prompt the clinician to eliminate from consideration the need for antibiotics, whereas presence of 3 or more symptoms from the LOWER checklist including a larger wound size, presence of osseous tissue and edema indicates a deeper, systemic infection that may prompt the clinician to sample the wound to determine load and species of bacteria as well as commence application of antibiotics. 

Reliance on signs and symptoms of infection alone to infer whether critical levels of bacteria are present in the wound remains challenging due to the subjectivity of clinician evaluation and variability or absence of host response to bacterial infection.^11,12 For instance, patients who are immunocompromised may only present with a wound that is not healing or is worsening when an infection is present, as other signs and symptoms may be suppressed.¹³ Further, these criteria do not provide information on the location of bacteria, which is necessary to determine the location and extent of wound bed preparation. The inclusion of fluorescence imaging to detect bacteria during routine wound assessment may help to overcome these limitations when diagnosing for infection.

Fluorescence imaging (FL) entails the use of a handheld, non-contact imaging device (MolecuLight i:X; MolecuLight Inc) to detect fluorescence from bacteria and wound tissues at the bedside. This imaging device emits a safe violet light (405 nm) that excites tissue and bacteria. Most bacteria emit red fluorescence due to endogenous production of red fluorescent porphyrins,¹⁴ while Pseudomonas aeruginosa uniquely produces cyan fluorescence due to production of pyoverdine.¹⁵ Under violet light, red fluorescence is observed from most common wound pathogens (Gram positive and Gram negative, aerobes and anaerobes) including pathogens found in biofilm; however, it cannot distinguish between biofilm and planktonic bacteria.¹⁶ Multiple clinical studies have demonstrated that the presence of red or cyan fluorescence in wounds is indicative of moderate-to-heavy bacterial loads (> 10⁴ CFU/g), with positive predictive values (PPV) greater than 95%.^8,17,18 The images produced from this procedure provide objective diagnostic information on bacterial presence to improve assessment and treatment selection.⁸ In this multisite, prospective observational study, the authors evaluated the utility of integrating point-of-care bacterial FL into standard of care assessment using the UPPER/LOWER wound infection checklists and the effects of FL on the communication of wound status among the wound care team.

Patients
Forty-three chronic wound patients completed this prospective, multisite observational study. Patients had to be 18 years or older with at least 1 chronic wound to be eligible to participate. Eligible inpatients and outpatients were recruited from 2 sites: Lionsgate Hospital (Vancouver, BC, Canada) and West Park Health Center (Toronto, ON, Canada). Patients with a known wound infection status were excluded from participation in the study. Patients provided written informed consent for images of their wound to be published. 

Evaluation of clinical signs of infection
The UPPER/LOWER checklist was used to assess signs and symptoms of local/superficial infection (UPPER) and deep infection (LOWER) and assist clinicians in distinguishing between these infection levels to facilitate appropriate treatment with topical or systemic antimicrobials (Figure 1). Presence of 3 or more symptoms from either checklist was the threshold for infection-positive. 

Imaging procedure 
The wound was cleansed with sterile saline prior to imaging. A standard image under normal room lighting was acquired by the clinician using the handheld, non-contact imaging device. The examination room was then made dark (if not possible, a DarkDrape (MolecuLight Inc) was used to create sufficient darkness), and a fluorescence image was acquired to detect bacteria within the wound using the previously described imaging device.^8,17,19-24 This device emits safe violet light (405 nm) and uses specialized optical filters to capture informative fluorescence signals.²² When illuminated by violet light, tissues and bacteria emit fluorescence signals of various colors^17,22; most bacteria fluoresce red as a result of endogenously produced porphyrins,^16,25 while Pseudomonas uniquely fluoresces cyan.²⁶ The device captures all fluorescence in the field of view, including fluorescence from non-bacterial signals, such as tissue, which fluoresces shades of green due to fluorescence of extracellular matrix components (ie, collagen),²⁷ as well as fluorescent gels and pink chlorohexidine.²² Previous clinical studies have demonstrated the high predictive value of the imaging device to detect fluorescence from bacterial loads greater than 10⁴ CFU/g (moderate-to-heavy growth).^8,17 In these trials, a tissue biopsy was collected from regions of red or cyan fluorescence and quantified via 16S quantitative polymerase chain reaction. Results revealed minimum bacterial loads of 10⁴ CFU/g of bacteria wherever red or cyan fluorescence was observed. This real-time fluorescence information was used to guide wound assessment, sampling location, and treatment decisions. 

Microbiology
Semi-quantitative microbiological cultures of wound swabs were used to evaluate bacterial species and loads from wounds assessed. Of the 43 wounds assessed, 27 were swabbed using the Levine technique, which involves pressing the swab on a 1 cm² area of the wound,²⁸ for microbiological analysis. Twenty-two swabs were from fluorescence-positive wounds, suggesting the presence of moderate-to-heavy bacterial loads; 5 swabs were from fluorescence-negative wounds (no red or cyan present on images), suggesting light or no bacterial growth. 

UPPER/LOWER assessment 
A total of 43 wound care patients participated in this observational study (1 wound per patient). Of the participants, 62.8% (27/43) were male, and age of patients ranged from 22 years old to 98 years old (Table 1). Wounds of all etiologies were assessed, including diabetic foot ulcers (9), pressure injuries (12), venous leg ulcers (VLUs) (8), surgical site infections (5), and other skin injuries and ulcers (9). The UPPER/LOWER wound assessment criteria were employed by clinicians at initial evaluation of these wounds. Presence of 3 or more signs and symptoms from each checklist (UPPER or LOWER) denoted an infection. Of the wounds assessed, 60.5% (26/43) as 61% in this case were positive for UPPER signs and symptoms of infection, indicating local infection. In contrast, 9.3% (4/43) of wounds were positive for LOWER signs and symptoms of infection, denoting deeper bacterial infection. 

Microbiology swabs were collected from 27 of the wounds assessed; 81.5% of wounds sampled (22/27) were positive for bacteria, and of those positive for bacteria, 77.3% (17/22) had a heavy growth of bacteria. A diverse variety of Gram-positive and Gram-negative aerobic and anaerobic bacterial species were detected from these chronic wounds. The most prevalent species detected included: Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella, Staphylococcus lugdunensis, Escherichia coli, Enterococcus faecium, mixed anaerobes, and others. Microbiological results were compared with the UPPER/LOWER criteria to determine the sensitivity and specificity of these signs and symptoms in predicting wound infection. Of the wounds sampled, 18 were positive for infection according to UPPER/LOWER criteria and microbiological analysis confirmed presence of bacteria in these wounds. There were 5 true negatives (ie, negative for UPPER/LOWER and microbiology); no false positives were observed. The UPPER/LOWER criteria produced a diagnostic sensitivity of 81.8%, specificity of 100%, and PPV and negative predictive values (NPV) of 100% and 55.5%, respectively. Accuracy of the UPPER/LOWER checklists was 85.2% (Table 2). 

Bacterial fluorescence imaging 
Following evaluation of UPPER/LOWER criteria, standard and fluorescence images were captured for all wounds. Of the 43 wounds assessed, 38 (88.3%) exhibited bacterial (red or cyan) fluorescence, while 5 were negative for bacterial fluorescence. Examples of standard and fluorescence images captured, and their corresponding microbiology, are depicted in Figure 2. Addition of fluorescence information to the LOWER checklist criteria resulted in 10 wounds (23.3%) having 3 or more criteria of LOWER infection. The addition of fluorescence information resulted in 8 wounds (18.6%) fulfilling the criteria for UPPER infection. In total, fluorescence imaging helped to confirm superficial or deep infection in 62.8% (27/43) of wounds. 

The utility of FL information at time of assessment was evaluated in 2 ways: (1) FL information was either added as an additional “check” to the UPPER and LOWER criteria or (2) it was used as an independent predictor of high bacterial loads indicative of potential wound infection (Table 2). A Fisher's exact test was used to assess statistical difference in diagnostic accuracy between UPPER/LOWER alone and with addition of FL. Addition of FL as an additional check in the UPPER/LOWER checklists significantly improved diagnosis of infected wounds compared with UPPER/LOWER criteria alone (P < .01). Sensitivity was increased by 13.6% up to 95.4%, and NPV and accuracy also were improved (83.3% and 96.3%, respectively). When FL information was used independent of UPPER/LOWER criteria to identify wounds with bacterial loads greater than 10⁴ CUF/g, 11 additional wounds were identified as positive for bacterial loads greater than 10⁴ CFU/g compared with UPPER/LOWER criteria alone. This resulted in 22 true positives, 5 true negatives, and no false negatives or false positives corresponding to sensitivity, specificity, NPV, PPV, and accuracy of 100%, per wound microbiology data. In all cases where cyan fluorescence was sampled, microbiology confirmed the presence of Pseudomonas aeruginosa. Due to the low number of true negative wounds (n = 5), specificity and NPV should be interpreted with caution. 

Fluorescence-guided treatment outcomes
The information obtained from fluorescence images complemented the signs and symptoms reviewed as part of the UPPER/LOWER checklist assessment and was also used to guide treatment decisions. Fluorescence images greatly impacted treatment by facilitating more thorough cleansing and debridement in most study wounds. Fluorescence images also guided antimicrobial stewardship decisions, such as leading to avoidance of antibiotic administration (n=2), adding antibiotics where needed (intravenous [IV] = 2, oral = 1), and guiding the selection of appropriate antimicrobial dressings. In 3 instances, fluorescence information resulted in more frequent dressing changes. The impact that FL had on influencing treatment decision-making when combined with UPPER/LOWER checklist assessment is highlighted in the following case studies. Perhaps most importantly, fluorescence images improved communication to other members of the care team, resulting in clinically necessary, expedited interventions in 13.9% (6/43) of cases.  

Case 1 
In this patient with a DFU, local/superficial infection was diagnosed based on the presence of 3 UPPER symptoms: pain, exudate, and reek. Fluorescence imaging revealed red fluorescence indicative of bacteria at loads greater than 10⁴ CFU/g in the wound (Figure 3A), supporting the diagnosis of local/superficial infection. The substantial degree of red fluorescence observed in the wound promoted the infectious disease physician to prescribe oral antibiotics. 

Case 2
A patient developed an abdominal midline dehiscence wound (Figure 3B) after Hartman’s surgical procedure for a perforated bowel. The patient was previously on IV antibiotics and was about to be discharged. Based on the presence of 3 UPPER symptoms (unhealthy wound, exudate, and reek), the patient was diagnosed with a local/superficial infection. Bacterial (red) fluorescence was observed in the wound and confirmed the diagnosis of the local infection. The considerable amount of red fluorescence observed in and around the wound prompted the clinician to prescribe 2 oral antibiotics and request follow-up within 5 days. Swabs of the wound and microbiological analysis later confirmed heavy growth of K pneumoniae, S lugdunensis and mixed anaerobes.

Case 3
A patient with a venous leg ulcer exhibited edema and redness suggesting potential for deep infection according to the LOWER checklist. The wound had no observable signs and symptoms of Pseudomonas aeruginosa infection, but FL revealed significant cyan, glowing fluorescence signature (indicative of the presence of Pseudomonas) in and around the wound (Figure 3C). The presence of this fluorescence signature added an additional check to the LOWER checklist, confirming a deeper infection. The real-time information provided by the fluorescence images were used to target cleaning of the wound and a Pseudomonas-targeted dressing was selected. A notable decrease in cyan/white fluorescence signature was observed after cleansing with modified sodium hypochlorite solution. 

Case 4
A patient with a pressure injury presented with a healing dehisced flap procedure. Using the UPPER/LOWER checklist to guide assessment, exudate and reek were observed, but no LOWER symptoms were present. Fluorescence imaging at the bedside revealed bacterial (red) fluorescence in the wound and brought the total number of checks for the UPPER assessment to 3, indicating the presence of surface contamination. The fluorescence images provided information on where to clean the wound; after surface scrubbing with a modified sodium hypochlorite solution, no red fluorescence remained (Figure 4A). A swab of the wound post-cleansing further confirmed the presence of surface contamination as only light growth of mixed coliforms, and beta hemolytic Streptococcus was observed after eradication of the red fluorescent signal. 

Case 5
A patient with a pressure injury and obvious signs of superficial infection underwent assessment for deep infection and FL. Only 2 symptoms of LOWER were observed, but FL revealed presence of significant bacterial (red) fluorescence in and around the wound (Figure 4B), which indicated the presence of deep infection. Culture results confirmed heavy growth of methicillin-resistant S aureus. The wound was cleansed, resulting in a reduction in observable bacterial fluorescence. The substantial amount of red fluorescence observed prompted expedited intervention. A computed tomography (CT) scan was done, revealing the presence of an abscess. The clinician notified the plastic surgeon and plans ensued for scheduling an operating room procedure for incision and drainage, including a washout of the affected area.  

Case 6 
A 77-year-old patient with a dehisced abdominal incision postoperatively undergoing negative pressure wound therapy (V.A.C. Therapy; 3M + KCI) to help heal the wound. Two weeks after surgery, assessment of the wound revealed signs of UPPER infection (all criteria met) in addition to 3 LOWER symptoms (larger wound, warmth, and redness). Fluorescence imaging revealed bright red fluorescence in the wound bed (Figure 5). Swab analysis of the wound indicated heavy growth of mixed anaerobes and light growth of mixed coliforms. Information on bacterial load and location through FL prompted targeted cleansing and debridement of red (bacterial) fluorescing regions of the wound using saline and an antimicrobial wound cleanser. The bright red fluorescence that was observed in FL images triggered the wound care clinician to initiate IV antibiotics and request an expedited CT scan to rule out the possibility of a deeper abscess. One week after FL and wound assessment, the symptoms of LOWER infection had subsided and most UPPER symptoms dramatically improved, with pain being the only UPPER symptom that persisted. Fluorescence imaging at this time point indicated persistence of red/blush fluorescence but to a much lesser extent that previously observed. Fluorescence-guided debridement resulted in a reduction in the level of red fluorescence, indicative of bacteria, observed in the wound.

Effective wound management begins with an accurate assessment to determine the presence and extent of bacteria colonization and infection in the wound. These assessments play a crucial role in informing treatment decision-making and have traditionally been structured around mnemonics or checklists that group together signs and symptoms of infection to facilitate easy recall. In the present study, the authors evaluated whether use of a point-of-care fluorescence bacterial imaging device used in combination with mnemonic checklists designed to distinguish between local infection (UPPER) and systemic infection (LOWER) could improve detection and management of high bacterial loads and wound infection. Results from this study revealed that the addition of fluorescence imaging to wound assessment using UPPER and LOWER criteria enhanced detection of wounds with high bacteria loads (> 10⁴ CFU/g), improved communication of wound status across interdisciplinary wound care teams, and led to improved treatment planning and, when needed, expedited intervention of wounds. 

Use of the UPPER and LOWER checklists produced high sensitivity and specificity for the diagnosis of greater than 10⁴ CFU/g of bacteria in wounds. The signs and symptoms included in the checklists are based on criteria included in the NERDS and STONEES and IWII wound infection checklists that have been previously validated to identify critical signs of colonization indicative of infection.^4,10 The mnemonics UPPER and LOWER were crafted to help clinicians easily recall and communicate criteria when distinguished between local and superficial infection. Use of the checklists was effective in identifying superficial or deep infection in 63% (27/43) of wounds assessed. When used on its own, the UPPER and LOWER checklists produced sensitivity and specificity of 80% and 100%, respectively. These high values confirm the validity of these signs and symptoms as indicators of infection and are higher than those reported by Gardner et al, who used the Infectious Diseases Society of America (IDSA) criteria (comprised of purulent exudate, erythema, edema, heat, and increased pain) to diagnose wound infection (> 10⁶ CFU/g) in DFUs and reported sensitivity of 52% and specificity of 54%.²⁹ The higher sensitivity and specificity reported in this study was likely attributed to the greater number of criteria included in the UPPER and LOWER checklists, but it may also be a result of the patient population; many of the patients included in this study were recruited from an inpatient unit in which wound complications and severe infections are more common. 

The addition of bacterial fluorescence imaging to UPPER and LOWER checklists improved diagnostic accuracy. Previous studies have suggested that reliance on assessment of signs and symptoms of infection alone is inadequate as many signs of infection are poor predictors of wound infection and many infected patients with wounds who have comorbidities fail to mount an immune response that exhibits these “classic” signs. Indeed, Reddy et al reported that many signs of infection are no better than chance at predicting high bacterial burden indicative of infection in wounds.¹² Similarly, Serena et al found a lack of signs of infection in 26% of 352 VLUs.³ In contrast, bacterial fluorescence imaging has been shown to produce high diagnostic accuracy to detect wounds with high bacterial loads.^17,18 

Here, the authors reported that when fluorescence imaging was added to the evaluation of UPPER/LOWER criteria, diagnostic accuracy of the checklists significantly improved by 20% to 25%. These findings are similar to those reported by Serena et al, who also observed significant improvements in sensitivity when FL was added to evaluation using the NERDS and STONEES checklist to detect moderate-to-heavy bacterial loads (>10⁴ CFU/g) in 19 wounds (primarily VLUs).⁸ Furthermore, the increased sensitivity of FL over CSS reported in this study is comparable to improvements reported in a recent clinical trial of 350 patients with various wound types in which the addition of FL to standard assessment (based on IWII checklist) significantly increased detection of wounds with bacterial loads greater than 10⁴ CFU/g by 4-fold.³⁰ The improvements resulting from FL reported in these prior publications were much greater than observed in the present study for 2 likely reasons. First, the checklists used to guide assessment of clinical signs and symptoms of infection may have produced relatively lower sensitivity (15%–22%) than reported in the present study. Second, these studies were performed primarily in the outpatient setting where the severity of infection and resulting symptoms may not be as pronounced, lowering checklist sensitivity. 

Fluorescence imaging and UPPER/LOWER checklists worked in a complementary manner to enhance detection and efficient triage of infected wounds and identify wounds in need of antimicrobial treatment. Fluorescence imaging at point-of-care enabled immediate detection of bacteria at moderate-to-heavy loads (> 10⁴ CFU/g), which may or may not be indicative of infection.^8,17 It is well established that bacteria at loads at or above this threshold delays healing,³¹ thus the capacity to locate the regions in and around the wound where these high levels of bacteria may be present can significantly enhance targeted cleansing and debridement of these wounds, as has been previously demonstrated.^19,24,32 These and other studies have made it clear that clinical signs and symptoms fail to mount in some infected patients. Having information on the presence and location of bacteria can therefore improve detection of infection at the point-of-care. The benefit of having information on the location of bacteria at point-of-care is highlighted in case 3. Presence of cyan fluorescence indicative of Pseudomonas facilitated targeted cleaning of the wound and guided the selection of a Pseudomonas-specific wound dressing. The ability of bacterial fluorescence imaging to uniquely identify and locate Pseudomonas in the wound is particularly beneficial, considering it is one of the most common wound pathogens associated with the presence of a biofilm.³³ Use of the UPPER and LOWER checklists can address this limitation by providing additional information to determine whether the infection remains in the wound or has potentially spread to deeper levels of tissue. This additional information is valuable to ensure efficient triage of the wound, which was observed in case 5 in which 2 LOWER criteria combined with a large amount of red fluorescence alerted the clinician to the deeper infection present in the wound. The combination of LOWER criteria and bacterial fluorescence in the wound prompted the clinician to expedite a computed tomography (CT) scan, revealing an abscess that then was drained. Incorporation of objective information on bacterial presence and location into infection checklists had high utility, helping to identify additional patients in need of topical or systemic antimicrobial treatment. For example, in a case where UPPER signs triggered wound cleansing, additional information from FL (ie, presence of cyan fluorescence indicating Pseudomonas) directed the selection of a silver-based dressing. A decrease in antibiotic and topical antimicrobial use, due to evidence provided by FL, was observed in other instances; this is in line with improved antimicrobial stewardship practices. In these cases, FL informed the location and extent of cleaning and debridement, prompted an additional round of cleaning or debridement, and eliminated the need for antibiotic or antimicrobial administration. These findings are in line with a previous publication reporting that fluorescence imaging can reduce the use of unnecessary antibiotics by providing evidence of eradication of bacterial burden at the point-of-care,¹⁹ thus the use of this imaging procedure can facilitate more judicious application of antimicrobials. Information provided by FL did not contradict outcomes of UPPER/LOWER assessment; no false positives were reported using either method. 

Wound care requires an interdisciplinary team. Best practice guidelines highlight the importance of constant, accurate, and multidirectional flow of meaningful information within the wound care team and across care settings.³⁴ Team members depend on the patient needs and care setting, extending through patient discharge where homecare nurses can join this team. In this primarily inpatient study, regular consultation between advanced practice wound nurses (WOCNs in Canada), infectious disease physicians, plastic surgeons, and vascular surgeons was essential. Clinicians performing primary wound assessment are considered the “wound navigator” and are responsible for acting as the patient’s advocate to the larger wound care team.³⁵ The wound care navigator must concisely and objectively communicate wound status to advocate for needed interventions. Without an image to document the extent of bacteria or infection in a wound, it is challenging to convey the extent of the problem. In 6 of 43 cases (13.9%) in this study, bacterial images were instrumental in communicating the severity of infection and the need for expedited consultation and intervention. This included expediting referral to an infectious disease physician to prescribe antibiotics (microbiology later confirmed that need), as well as rapid CT scan and immediate referral for a plastic surgeon consult to manage an infected dehisced abdominal incision, as described in case 6. When these needs go unrecognized, this puts the patient at high risk for worsening complications. The benefit of bacterial fluorescence imaging to expedite intervention and enhance communication among care providers has, to the authors’ knowledge, not previously been reported. For inpatient care teams, this adds tremendous value. The authors anticipate this value also would extend to outpatient communication between the wound navigator and the homecare team. It should be emphasized that the patient is the most important member of their wound care team, and bacterial images aid in patient education on their wound’s infection status and patient compliance with their care plan.^8,23

There are several limitations to this study. Both clinicians performing the assessments were experts and familiar with the mnemonics and fluorescence imaging. Validation of the content of the mnemonics is warranted to determine reliability of results among non-experts. Microbiology culture analysis was not available for all study wounds, thus the diagnostic accuracy measures reported here described 27 of 43 study wounds. The fluorescence imaging device can detect bacteria in wounds up to a maximum depth of 1.5 mm and does not provide real-time information on the bacterial species present or nonbacterial components (ie, fungi) that may be present; wound sampling is needed to obtain this information. However, the high PPV of fluorescence reported here, and in other studies, indicates that sampling may not always be needed. The single visit nature of this observational study prevented follow-up visits in most cases to determine whether the treatment selections based on checklist classification and fluorescence information were appropriate. As outcomes data were not available for all patients to validate treatment plan changes, additional studies assessing the impact of fluorescence-guided treatment selection are warranted. However, in patients that were followed over multiple visits (eg, case 6), reduction of UPPER/LOWER symptoms and bacterial fluorescence was observed at follow up. Due to the nature of the patient population, there was a low proportion of true negative study wounds (ie, wounds with bacterial loads less than 10⁴ CFU/g), thus specificity and NPV results should be interpreted with caution. 

The UPPER/LOWER mnemonic checklist and fluorescence imaging procedure work in a complementary manner to provide information on the presence, location, and type of infection that led to expedited treatment intervention and guided treatment selection. Incorporation of a bacteria-specific component into these infection checklists had high utility, identifying patients in need of additional cleaning/debridement or patients requiring topical or systemic antimicrobial treatment. Fluorescence images provided the documentation and visual confirmation required to rapidly activate the care team, expediting referrals, surgical procedures, and advanced therapies in this study. Based on the results of this and other studies^8,18,30, the field should consider incorporating fluorescence imaging as part of routine assessment. 

Authors: 

Affiliations: ¹Lion’s Gate Hospital, Vancouver Coastal Health, North Vancouver, British Columbia, Canada; and ²Queen’s University, Kingston, Ontario, Canada

Correspondence: Rosemary Hill, BSN, CWOCN, Lion’s Gate Hospital, Vancouver Coastal Health, British Columbia, Canada; Rosemary.hill@vch.ca

Disclosure: Rosemary Hill is on the Clinical Advisory Board for MolecuLight Inc. and has received funding from MolecuLight for conference attendance. No funding was received to perform this study.