MoorLDI2 Burns Imager a laser Doppler blood flow imager for the assessment of burn wounds: consultation document
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NICE medical technology guidance addresses specific technologies notified to NICE by manufacturers. The 'case for adoption' is based on the claimed advantages of introducing the specific technology compared with current management of the condition. This case is reviewed against the evidence submitted and expert advice. If the case for adopting the technology is supported, then the technology has been found to offer advantages to patients and the NHS. The specific recommendations on individual technologies are not intended to limit use of other relevant technologies which may offer similar advantages.
The National Institute for Health and Clinical Excellence (NICE) is producing guidance on using the MoorLDI2-BI laser doppler blood flow imager for burn wound assessment in the NHS in England. The Medical Technologies Advisory Committee has considered the evidence submitted and the views of expert advisers.
This document has been prepared for public consultation. It summarises the evidence and views that have been considered, and sets out the draft recommendations made by the Committee. NICE invites comments from the public. This document should be read along with the evidence base (the assessment report and assessment report summary), which is available from www.nice.org.uk/mt.
The Advisory Committee is interested in receiving comments on the following:
- Has all of the relevant evidence been taken into account?
- Are the summaries of clinical effectiveness and resource savings reasonable interpretations of the evidence?
- Are the provisional recommendations sound, and a suitable basis for guidance to the NHS?
- Are there any equality issues that need special consideration and are not covered in the medical technologies consultation document?
Note that this document is not NICE's final guidance on the moorLDI2-BI. The recommendations in section 1 may change after consultation. After consultation the Committee will meet again to consider the evidence, this document and comments from public consultation. After considering these comments, the Committee will prepare its final recommendations which will be the basis for NICE's guidance on the use of the technology in the NHS in England.
For further details, see the 'Evaluation Pathway Programme process guide' (available at www.nice.org.uk).
- Closing date for comments: 4 January 2011
- Second Medical Technologies Advisory Committee meeting: 21 January 2011
1. Provisional recommendations
1.1 The case for adopting the moorLDI2-BI in the NHS is supported when it is used to guide treatment decisions for patients in whom there is uncertainty about the depth and healing potential of burn wounds that have been assessed by experienced clinicians.
1.2 There is evidence of benefit for patients and for the NHS when the moorLDI2-BI is used in addition to clinical evaluation compared with clinical evaluation alone, in burn wounds of intermediate (also known as indeterminate) depth. By demonstrating which areas of any burn wound require surgical treatment and which do not, the moorLDI2-BI enables decisions about surgery to be made earlier and for surgery to be avoided in some patients.
1.3 The estimated average cost saving when the moorLDI2-BI is used in addition to clinical evaluation is £1248 per patient scanned (if the equipment is purchased) or £1232 per patient scanned (if the equipment is leased). This is based on an assumption of a 17% reduction in the number of skin graft operations at a cost of £2043 each.
2. The technology
Description of the technology
2.1 The moorLDI2-BI is a laser doppler blood flow imaging system for the non-invasive mapping of blood flow in an area of skin which has been burned. This can be used in addition to clinical evaluation to guide decisions about the need for surgical treatment of burn wounds.
2.2 The moorLDI2-BI includes a scan head, scan controller and a touch-screen panel computer, all mounted on a mobile stand that can be used in a ward, operating theatre, or consulting room as well as in rooms designed specifically for laser equipment.
2.3 The moorLDI2-BI uses a low-power laser beam, directed at the burn wound using a mirror. The laser beam scans across the burn wound by rotating the mirror and there is no direct contact with the burned skin. Laser light scattered from moving blood cells in the tissue undergoes a doppler frequency shift, proportional to the average speed of the blood cells. Some of the scattered laser light is focussed onto photodiode detectors and the resulting photocurrent is processed to calculate the blood flow in the tissue. Results are displayed as a colour-coded blood flow image and a colour video image of the burn wound. Depending on the size of the burn wound and required resolution of the image, the scan takes from 80 seconds to about 5 minutes. Healing potential results based on the blood flow image are calculated and reported in three categories: < 14 days, 14-21 days and > 21 days.
2.4 The moorLDI2-BI can be purchased at a cost of approximately £50,000 with an annual servicing cost of approximately £8,000, or it can be leased at an inclusive cost of approximately £22,000 per year.
2.5 The assessment of burn wound depth and healing potential is fundamental in planning burn wound management. An experienced clinician can easily identify a burn that is epidermal and will heal without surgery, or a full thickness burn which requires surgical excision and grafting. However, it is often difficult to distinguish the superficial dermal burns which will heal well, from deep dermal burns, when a prolonged healing time will result in hypertrophic scarring (when the scar is swollen and red). It is difficult to assess burn wound depth and healing time in children because of the prevalence of mixed-depth scald burns and their thin skin. Diagnosis of burn wound depth and healing potential is also difficult in patients with dark skin (including those with suntan, birthmarks or tattoos). Identifying the level of burn injury can be complicated by other factors such as oedema, tissue hypoxia and burn wound conversion, when superficial burns progress into deeper wounds because of the death of severely injured cells.
2.6 Clinical evaluation is the most widely used method of assessing burn wound depth and healing potential. This method is based on visual and tactile assessment of the external characteristics of the burn. The accuracy of clinical examination depends on the experience of the clinician. Other less widely used methods such as thermography and fluoroscein injections are also available for burn wound assessment.
2.7 The surgical procedure for treatment of burn wounds usually involves removing (excision or debridement) the damaged skin followed by skin grafting. Skin grafting is the transplantation of skin from a healthy part of the body. This procedure is used because it reduces the wound healing time and wound complications, and it can improve the function and appearance of the wound area that receives the skin graft.
3. Clinical evidence
Summary of clinical evidence
3.1 The key outcome for this technology is the development of an appropriate treatment plan based on an accurate assessment of burn wound depth and healing potential. Other important performance measures are the sensitivity, specificity, negative predictive value and positive predictive value of the wound healing potential before 14 or 21 days. Important clinical utility outcomes associated with the technology are avoiding unnecessary operations, extent of surgery, number of dressing changes, complications and length of stay in hospital.
Accuracy of moorLDI2-BI
3.2 The accuracy of the moorLDI2-BI in the assessment of burn wounds was examined in eight studies with a variety of criteria including ability to predict healing within 14 or 21 days. Comparisons were made with clinical and histological evaluation of burn wound depth.
3.3 Pape et al. (2001) reported an audit of wound healing at 21 days for 76 intermediate depth wounds in 48 patients. Results showed the moorLDI2-BI to be 97% accurate (74/76) in predicting wound healing at 21 days compared with 70% (53/76) for clinical evaluation.
3.4 Hoeksema et al. (2009) investigated the changing accuracies of laser doppler imaging and clinical evaluation over days 0, 1, 3, 5 and 8 after injury. Forty patients with intermediate depth burn wounds were scanned using the moorLDI2-BI. The final assessment of wound depth showed a deep partial or full thickness burn in 14 patients, 12 of whom had a skin graft, and a superficial dermal burn in 26 patients. Accuracies on days 0, 1, 3, 5 and 8 were 41%, 62%, 53%, 71% and 100% by clinical evaluation, and 55%, 80%, 95%, 97% and 100% by laser doppler imaging. The burn wound depth accuracy using the moorLDI2-BI was significantly higher than clinical evaluation on day 3 (p < 0.001) and day 5 (p = 0.005).
3.5 Jeng et al. (2003) described a prospective blinded trial comparing the use of laser doppler imaging with the moorLDI2-BI with clinical evaluation by an experienced burn wound surgeon to decide whether or not to operate. Forty-one wounds of intermediate depth were analysed. There was agreement on wound depth between laser doppler imaging and clinical evaluation in 56% (23/41) of cases. The surgeon's determination of burn wound depth was accurate in 71% (15/21) of the 21 biopsied wounds. The moorLDI2-BI was 100% (7/7) accurate in wounds when the laser doppler scan determined a need for excision.
3.6 Monstrey et al. (in press) compared healing prediction based on interpretation of a moorLDI2-BI scan with actual wound healing as recorded photographically for 433 burn wounds in 139 patients. This assessment found an overall accuracy for the moorLDI2-BI of 96.3% with sensitivity 94.5%, specificity 97.2%, positive predictive value 94.5% and negative predictive value 97.2%.
3.7 La Hei et al. (2006) scanned 50 burns in 31 paediatric patients. Two experienced burn wound surgeons independently reviewed the burn wound scans, burn wound photographs and a basic patient history, without meeting the patient. One surgeon identified 82 areas of differing depth and the other identified 76 areas and both surgeons predicted healing times (superficial heal: < 14 days or deep heal: > 14 days or graft). Overall, 97% (154/158) of predicted healing times were correct with four deep burn areas incorrectly predicted to heal within 14 days. No superficial wounds were reported as deep.
3.8 Holland et al. (2002) investigated the ability of laser doppler imaging to evaluate burn wound depth in children by scanning 58 patients and comparing the predicted outcome (from either the scan or from clinical evaluation) with the subsequent wound outcome at 12 days. One patient was excluded because there was too much movement for the scan to be interpreted. Clinical evaluation correctly identified 66% (19/29) of deep partial or full thickness burns between 36 and 72 hours after injury compared with 90% (26/29) using moorLDI2-BI scans. MoorLDI2-BI scans were also more specific, correctly diagnosing 96% (27/28) of superficial partial thickness burns compared with 71% (20/28) from clinical evaluation alone.
3.9 Niazi et al. (1993) reported results from a pilot study that analysed 17 burn wounds in 13 patients. Punch biopsies were used to confirm burn wound depth at 72 hours after injury. Clinical evaluation was correct for 41% (7/17) burns, overestimated depth in 41% (7/17) and underestimated depth in 18% (3/17). Burn wound depth assessed from moorLDI2-BI scans was correct for 100% (17/17) of burn wounds.
3.10 Mill et al. (2009) compared moorLDI2-BI image colours with wound outcomes in 85 burns on 48 children. The predominant colour of the scan was found to be significantly related to re-epithelialisation (p < 0.003), grafting (p < 0.001) and active scar management (p = 0.003).
Clinical utility outcomes
3.11 Two studies provide evidence that using the moorLDI2-BI is associated with making appropriate skin grafting decisions sooner. Jeng et al. (2003) described a prospective blinded trial that compared the use of laser doppler imaging with clinical evaluation by an experienced burn wound surgeon in deciding whether to operate or not on 41 burn wounds of indeterminate depth. There was agreement between the imaging and clinical evaluation on wound depth in 56% (23/41) of cases. In these cases the use of the moorLDI2-BI saved a median of 2 days to determine wound depth (minimum = 0, maximum = 4) compared with clinical evaluation alone by the surgeon. Kim et al. (2010) described a non-randomised cohort study of 196 children with an acute burn injury that required surgical treatment. Laser doppler imaging was used in addition to clinical evaluation on 49% (96/196) and 51% (100/196) were assessed by clinical evaluation alone. The mean time from date of injury to the decision to graft was 8.9 days in the moorLDI2-BI group compared with 11.6 days in the group assessed by clinical evaluation alone (p = 0.01).
3.12 The Committee considered that there was good clinical evidence that information from moorLDI2-BI scans increases the accuracy of predicting burn wound healing and also that this information can be used to facilitate treatment plans. Use of the moorLDI2-BI in addition to clinical evaluation can enable earlier surgical treatment in some patients, avoid the need for surgery in others and might reduce the extent of surgery.
3.13 There are many factors that are known to have a detrimental effect on moorLDI2-BI images or their interpretation, including infected wounds, patient movement, old scars and tattoos. These are acknowledged in the published studies and also recognised by the manufacturer in their user guide. Therefore, moorLDI2-BI images should only be taken and interpreted by a clinician trained in use of the technique. La Hei et al. (2006) reported the increase in accuracy of interpretation of the laser doppler images by a new assessor from 83% (15/18) to 96% (73/76) over a 6 month period.
3.14 The Committee considered that there was no evidence to suggest that the use of moorLDI2-BI by trained healthcare professionals is harmful to patients.
4. NHS considerations
4.1 Cost savings associated with the use of the moorLDI2-BI for burn wound assessment are based on a reduction in length of hospital stay and an avoidance of unnecessary skin grafting operations.
4.2 Timing of moorLDI2-BI imaging is important because burn wounds change rapidly in the first 48 hours after injury. The evidence suggested that the best time for imaging is 48-72 hours after the injury, but the device can be used up to 5 days after injury.
4.3 The Committee was advised that the use of the moorLDI2-BI for burn wound assessment requires a trained healthcare professional to operate the device and an experienced, trained clinician to interpret the results.
4.4 Additional patient and system benefit can be obtained by using the moorLDI2-BI to define accurately the margins of surgical areas for the skin graft operations.
4.5 The cost model was based on the purchase and use of the moorLDI2-BI in 28 specialist burns centres in the NHS in England and Wales. The Committee was informed that the device had been available to the NHS for a number of years and was already used routinely in some burns centres. The Committee considered that burns units in other hospitals could also benefit from use of this device.
4.6 Burn wounds on dark skin (including racially, from suntan, birthmarks and tattoos) can be difficult to assess clinically. The Committee considered that use of the moorLDI2-BI offers particular advantages for assessing burn wounds on dark skin.
4.7 The Committee was advised that training staff to operate this device and interpret the images is very important. The cost model includes costs for 2 days training for one consultant, two registrars and three nurses every 2 years.
4.8 The Committee considered that the moorLDI2-BI could offer advantages in burns units comparable with those in burns centres. However, the Committee was advised that specialist assessment of the burn wound image by an experienced clinician would continue to be required.
5. Cost considerations
5.1 The evidence comprised a cost analysis to assess the costs and savings to the NHS from use of the moorLDI2-BI for the assessment of burn wounds of intermediate depth, described in the manufacturer's submission. The costs and savings arising from the use of the moorLDI2-BI in addition to clinical evaluation were compared with those from using clinical evaluation alone. The cost analysis balanced the additional equipment and staff costs of burn wound assessment with the moorLDI2-BI against the cost benefits from earlier more appropriate treatment decisions based on information from moorLDI2-BI images.
5.2 The estimate of 10,000 patients admitted each year to the 28 specialist burns centres was based on Enoch et al. (2009). It was assumed that 70% of these patients would have intermediate burn wounds and be scanned. To calculate a per patient cost in the base case, each burns centre was assumed to have one imager with annual staff training costs of £3416. Nurse scanning time per patient was 1 hour and clinician time per patient for interpreting results was 15 minutes. The cost savings included were based on a reduction of 17% in the number of skin graft operations and a 2-day reduction in the length of hospital stay. These parameter values were based on evidence from clinical studies. In the model the cost per hour for an operation to treat burn wounds was £4593, based on the figures presented in Hemington-Gorse et al. (2009). Expert advice to the External Assessment Centre was that this hourly cost was high and the External Assessment Centre derived a lower figure of £2043 per hour.
5.3 A range of scenario analyses including a best- and worst-case scenario using the ranges for the proportion of patients scanned, number of bed days saved and operating time were done. Additional analyses were done by the External Assessment Centre to assess the impact of changing the hourly cost for an operation to £2043.
5.4 The cost saving per patient scanned from the use of the moorLDI2-BI in addition to clinical evaluation compared with clinical evaluation alone for the base case is £1248 for the purchase option (based on an hourly cost of £2043 per operation) and £1232 for the lease option. The worst-case scenario for the purchase option resulted in a cost saving of £734 per patient and the best-case scenario resulted in a saving of £2860 per patient scanned. All analyses presented in the Assessment Report showed that the total cost savings from reducing hospital length of stay and number of operations were greater than the costs associated with the purchase and operation of the moorLDI2-BI.
5.5 An area of uncertainty in the cost analyses was the impact on the cost per patient scanned of the assumption that all patients scanned would achieve on average a 2-day reduction in length of hospital stay. An additional analysis was undertaken that modelled the assumption that there was no length of stay reduction from using the moorLDI2-BI. This demonstrated that the moorLDI2-BI would still achieve a cost saving of £159 per patient scanned when a 17% reduction in operations is assumed (based on the purchase option and an hourly cost of £2043 per operation).
5.6 The base case in the manufacturer's submission included costs of 1 hour scanning time and 1 hour skin graft procedure associated with an average intermediate burn. The Committee was advised that 30 minutes scanning time is more appropriate for burn wounds that are treated with a 1 hour skin graft procedure. The cost saving per patient scanned in the base case was recalculated, using these times, as £1254 for the purchase option and £1270 for the lease option.
5.7 The cost analysis focused on cost savings associated with in-patient care. The Committee was advised that additional savings, including avoidance of hospital admission, might be obtained by using the device as an aid to clinical decision-making for out-patients with small burns of uncertain depth.
5.8 The time horizon for the cost analysis was the initial period of hospitalisation, and no longer-term cost consequences were included. The manufacturer described but did not quantify the longer-term cost benefits from improved treatment decisions. Avoiding unnecessary grafting or making earlier decisions to graft could avoid the need for long durations of prophylactic antiscar therapy or any therapy. Antiscar therapy includes fitting pressure garments and follow-up hospital.
6.1 The Committee concluded that the available evidence supported a clinical benefit and a cost saving when the moorLDI2-BI is used to guide treatment decisions for patients in whom there is uncertainty about the depth and healing potential of burn wounds that have been assessed by experienced clinicians.
6.2 The manufacturer's submission described the use of the moorLDI2-BI in NHS burns centres. The Committee considered that it could be assumed that similar patient and system benefits associated with the use of the moorLDI2-BI would arise in burns units and that further information to support this assumption would be useful.
7.1 NICE intends to develop tools in association with relevant stakeholders to help organisations put this guidance into practice.
Chairman, Medical Technologies Advisory Committee
This page was last updated: 08 December 2010