3.1 The evidence assessed by the external assessment centre (EAC) included 7 studies; 3 were full text peer reviewed publications (Gefan et al. 2018; O'Brian et al. 2018; Raizman et al. 2018) and 4 were abstracts (Hancock and Lawrance 2018; Okonkwo et al. 2017; Okonkwo et al. 2018; O'Keefe et al. 2019). The studies included 2,213 patients at risk of developing pressure ulcers in secondary care. Two of the studies were before-and-after comparative studies, the remaining 5 studies were single-arm observational studies. For full details of the clinical evidence, see section 3 of the assessment report.
The 2 before-and-after studies are relevant to the decision problem and report pressure ulcer incidence
3.2 Both studies compared pressure ulcer incidence before and after using SEM Scanner 200 as a risk assessment tool to be used alongside standard care. Both studies reported reduced pressure ulcer incidence after using SEM Scanner 200. One study reported that pressure ulcer incidence reduced from 2.17% to 0.95% (Hancock and Lawrance 2019) and the other reported a reduction from 13% to 1% (Raizman et al. 2018). Neither study included a detailed description of the protocol used for assessment and management in the standard care arm. Also, there was heterogeneity in the reporting of pressure ulcer incidence, with only 1 study including stage 1 pressure ulcers. These limitations made it difficult to be certain about how well SEM Scanner 200 works when used as the only test.
Diagnostic accuracy is reported in 3 of the observational studies but they use an inappropriate reference standard
3.3 All 3 studies reporting the diagnostic accuracy of SEM Scanner 200 used visual skin assessment (a standard clinical measure for detecting pressure ulcers based on visual signs of skin deterioration) as a reference standard. SEM Scanner 200 is intended to detect subepidermal moisture changes before visible signs of pressure ulcers are present and is not a diagnostic test for pressure ulcers. The EAC noted that using visual skin assessment for measuring the diagnostic accuracy of SEM Scanner 200 may underestimate its specificity. This is because non-visible damage correctly identified by SEM Scanner 200 would be recorded as a false positive.
In 3 of the observational studies SEM Scanner 200 detects subepidermal moisture changes earlier than visual skin assessment
3.4 All 3 studies reported that subepidermal moisture changes indicating pressure-induced damage were detected earlier than visible signs of skin deterioration reported by visual skin assessment. The studies provided no additional information about the effect of these findings on clinical management or on the clinical benefits of earlier detection.
The company's model compares the costs of using SEM Scanner 200 plus standard care with using standard care alone
3.5 The company submitted 10 studies relevant to the economic assessment of SEM Scanner 200. The EAC reviewed the literature and found 1 study (Burns et al. unpublished) that it considered to be relevant to the decision problem. The company used a decision tree, based on standard care as defined by NICE's guideline on pressure ulcers: prevention and management, to assess the effect of SEM Scanner 200 on the cost of preventing pressure ulcers, over a 1-year time horizon. In this model, the heels and sacrum of each patient were assessed and categorised as low risk, at risk or at high risk. Patients assessed to be at risk or at high risk had repositioning every 6 hours or 4 hours, respectively. The key clinical parameters were:
an assumed pressure ulcer incidence of 4.09% in the at-risk group
a pressure ulcer incidence of 1.637% in the standard care arm and 0.509% in the SEM Scanner 200 arm (a 68% reduction).
These parameters were from the unpublished Hancock and Lawrance (2018) before-and-after study.
3.6 The company used a cost of £18 per hour for band 5 nursing time as stated in NICE's costing statement for pressure ulcers published in 2014. The EAC considered this source to be outdated and updated the cost to £37 per hour (Curtis and Burns 2018). The EAC also added a 3.5% depreciation rate for the device, which had not been included in the company submission.
The updated company model results in cost savings of £59 per person from reduced pressure ulcer incidence
3.7 The updated company model resulted in cost savings of £59 per patient. Sensitivity analyses applied to the assumed percentage pressure ulcer reduction found SEM Scanner 200 to be cost-neutral at a 28% reduction in pressure ulcer incidence. The model included the costs of 1 scanner per 9 beds for 210 beds. The model showed that the increased costs for preventive measures were offset by cost savings related to the reduced need for pressure ulcer treatment. Results were reported to be robust to sensitivity analyses, however, the results were not presented. The EAC noted there was uncertainty around estimates from an unpublished study used to populate the company model.
3.8 The EAC used its preferred assumptions to calculate a pressure ulcer incidence of 8.05%. These assumptions were the predicted number of positive stage 1 pressure ulcers, the prevalence of pressure ulcers and the diagnostic accuracy of SEM Scanner 200 plus visual skin assessment. The model assumed that 50% of stage 1 pressure ulcers would progress to stage 2 without diagnosis and treatment and that 36.5% would do so with diagnosis and treatment. The EAC acknowledged that this model did not adequately capture any potential benefit of earlier identification of pressure-induced damage. The EAC's base case resulted in SEM Scanner 200 plus visual skin assessment being cost incurring by £45 per person when compared with visual skin assessment alone.
3.9 The EAC's base case assumed that 2 band 5 nurses were needed for repositioning. Experts advised the committee that repositioning can be done by other healthcare professionals. The EAC's sensitivity analyses reported that reducing the cost of repositioning had a considerable effect on the cost of SEM Scanner 200 and standard care. If repositioning was done by 1 nurse and 1 healthcare assistant or 2 healthcare assistants, SEM Scanner 200 would cost an additional £38 or £30 per person respectively, compared with standard care. The costs used in these analyses reflect a hospital setting.