Solving the Burn Depth Puzzle
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The LDF cut-off point for predictive validity was determined to optimize overall accuracy using receiver operating curve (ROC) analysis.
Results: The most significant predictor of healing was LDF flow at the 2 mm skin depth within 24 hours post-burn. Burns of LDF AU 100 were more likely to heal within 21 days. Lower vascular flux within 24 hours of admission and at days 3 and 6 post-burn were associated with deeper clinical burn depth assessment (P < 0.001). All 72 burns clinically assessed as superficial partial-thickness (mean flow 145 AU) healed in 3 weeks; the 58 burns clinically assessed as full-thickness (mean LDF 15 AU) were excised as early as feasible and were grafted. Of the 43 burns (mean LDF 60 AU) clinically assessed as deep partial-thickness burns, 30 (70%) required subsequent excision and grafting at a mean of 8 days post-burn. The remaining 30% healed within 21 days. All burns that healed in 21 days had a mean LDF of 100 AU—higher than the 30 AU for burns requiring excision and grafting (P < 0.005). Contralateral intact skin flow was also reduced (P < 0.007) but only in patients with full-thickness burns. Using a cut-off LDF blood flow value of 100, AU optimized overall accuracy (83.2%), diagnostic sensitivity (80.6%), specificity (88.2%), and screening positive (93.1%) and negative (69.8%) predictive value for predicting healing within 21 days.
Authors’ Conclusions: Using LDF can accurately diagnose burn depth within 24 hours post-burn, predict healing time and help avoid unnecessary operations.
LDF Imaging of Pediatric Burns Predicts 14-day Healing
Reference: Cho JK, Moon DJ, Kim SG, Lee HG, Chung SP, Yoon CJ. Relationship between healing time and mean perfusion units of laser Doppler imaging (LDI) in pediatric burns. Burns. 2009;35(6):818–823.
Rationale: LDF assesses burn depth. At the time of this study no research had used LDI to predict healing time.
Objective: Evaluate LDF imaging as a predictor of healing time and define ideal perfusion unit (PU) cut-off point to predict that a pediatric burn will heal within 14 days.
Methods: A prospective observational study used scanning LDF imaging on 103 consecutive patients < 15 years old with 181 partial-thickness burns in the Department of Emergency Medicine of Bestian Hospital, Seoul, Republic of Korea from May to November 2006. Mean perfusion units (PU) on each burn site were measured 2–3 days post-burn. Healing time was independently reported by two experienced physicians as the time to complete re-epithelization. Mean PU was compared between burns healed within 14 days (early) or after 14 days (late). A ROC curve analysis determined the ideal PU cut-off point to optimize LDF prediction of early healing.
Results: Early healers had a higher mean ± standard deviation PU of 380 ± 158 than late healers 186 ± 116 (P < 0.001). Using 250 PU as a cut-off value, early healing was predicted with 80.6% sensitivity and 76.9% specificity.
Authors’ Conclusions: LDF imaging is a good predictor of pediatric partial-thickness burn healing within 14 days and can be used to improve clinical therapy decision making.
Together, these two studies further validate LDF as a quick, reliable, noninvasive tool to assess burn depth and facilitate informed clinical decisions about the need for immediate burn excision and grafting. These studies also underscore the need for clear global operational definitions of effective LDF units and cut-offs for decision-making, as well as depth metrics and expected healing time for burns and wounds in general. Without these, important nuggets of truth may be obscured by babble.
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