Spectra Optia for automatic red blood cell exchange in people with sickle cell disease

5.7 The external assessment centre revised some input parameters of the model concerning capital, procedural and chelation costs to reflect values which it considered were more plausible. However, it judged that the limited clinical evidence (and the associated uncertainty) should remain a key consideration when interpreting the results.

5.8 The company's model did not include capital costs (£52,052) or maintenance costs (£4,572 per year) for Spectra Optia, although it did report separate analyses on these costs. The external assessment centre considered it wrong to exclude these costs from the model, and so created scenarios to reflect the mixed use functionality of the technology and relatively low demand (due to low prevalence of sickle cell disease) in some areas of the country. The external assessment centre determined that treating 30 sickle cell patients per year would use 50% capacity of each Spectra Optia system, and 15 patients per year would use 30% of capacity. The external assessment centre also included sensitivity analyses in which 100% of the device's capacity was used exclusively for treating sickle cell disease (with patients incurring the full cost) or where 50% of capacity was used elsewhere. In these analyses, the external assessment centre also extended the lifespan of the device from 5 years to 7 years.

5.9 The external assessment centre also noted that the cost of chelation therapy in the company's model did not include diagnostic and monitoring costs. An estimate of the chelation costs used in the model for the monitoring of iron overload was provided in confidence to the committee. The proportion of patients having chelation therapy after top-up transfusion in years 2 to 5 of the model was 90%. These patients entered the model with no iron overload. The external assessment centre revised this value to 75% based on 250 of 332 patients in the Haemoglobinopathy Registry Report having regular chelation therapy (Foster 2014).

5.10 The company had also assumed that adults and children having manual exchange procedures would both need 4 units of packed red blood cells. The external assessment centre reduced this to 3 units in children. Similarly, the procedure time for manual exchange in children was reduced from 254 minutes to 208 minutes. The number of staff needed per patient for manual exchange was also reduced from 1.5 to 1.0, following expert advice.

5.11 Results from the economic modelling showed that:

5.12 The committee asked the external assessment centre to make some additional changes to the model. In the company's model, 90% of patients were assumed to have iron overload when beginning treatment with Spectra Optia (and were therefore having chelation therapy) whereas only 80% had iron overload when beginning manual exchange. The company provided no rationale for this difference so the external assessment centre set chelation treatment rates at 90% for both Spectra Optia and manual exchange.

5.13 The external assessment centre decided that it would be most helpful if the cost modelling included a range of scenarios reflecting device‑sharing schemes. The external assessment centre included scenarios for 30 patients using the device at 100% capacity (and so 100% of its capital cost), 50% capacity and 0% capacity (for centres that already have the device but do not use it for red blood cell exchange). From the external assessment centre's subsequent changes to the model, the committee concluded that Spectra Optia is cost saving in the following scenarios:

Abbreviations: SCD, sickle cell disease. Negative values indicate cost savings with Spectra Optia.

Abbreviations: SCD, sickle cell disease. Results in brackets are considered clinically unlikely. Negative values indicate cost savings with Spectra Optia.

5.14 The results show that Spectra Optia is cost saving compared with manual exchange and top-up transfusion in most patients with sickle cell disease. The highest cost savings are £96,512 (compared with manual exchange) and £81,493 (compared with top-up transfusion) per patient per year for adults with mild iron overload where an already functioning and purchased device can be used. The lowest cost savings are £1,484 (compared with manual exchange for primary prevention in children with moderate iron overload when the device has been procured at 50% of the capital cost) and £1,399 (compared with top-up transfusion in adults with moderate iron overload) per patient per year.

5.15 Spectra Optia is cost incurring compared with manual exchange for children with severe iron overload if the device is procured at 50% of the capital cost. If the device is purchased at 100% of the capital cost, it is cost incurring (at £2,715 to £13,605 per patient per year) compared with manual exchange for children with no or moderate iron overload and for all patients with severe iron overload. Using Spectra Optia is also cost incurring compared with top-up transfusion in some patients with moderate and severe iron overload. However, this comparator is considered to be a clinically poor treatment option for these patient groups and it is unlikely that it would be the preferred treatment option for people with iron overload.

5.16 The committee considered that local providers should take into account the availability of existing devices when planning services for people with sickle cell disease; the potential for device‑sharing schemes was discussed and these were represented in the revised cost modelling carried out by the external assessment centre.

5.17 The committee noted that the levels of iron overload in patients included in the model were not clearly defined. The company's cost model stated that these were based on serum ferritin levels but no ranges were provided for the mild, moderate and severe categories used. The expert advisers informed the committee that there were no routinely used and agreed values for this classification.

5.18 The committee noted that top-up transfusion was not included as a comparator in the scope because it is generally used to treat anaemia and emergency crises in patients with sickle cell disease. Top-up transfusion is not suitable as a long‑term regime because it is iron positive, and so is not an appropriate current standard comparator for automated exchange. However, several clinical experts stated that top-up transfusion is sometimes used as a long‑term therapy in hospitals where provision of treatments for sickle cell disease is limited, or in patients who have disease complications that preclude the use of exchange transfusions (such as poor venous access).

5.19 The committee noted that many values in the cost model for Spectra Optia are based on estimates. In particular, it was not possible to define the different categories of iron overload used in the model in terms of serum ferritin levels (or any other kind of measurement of iron).

5.20 Having noted these uncertainties, the committee concluded that Spectra Optia would be cost saving for most patients compared with manual exchange and top-up transfusion.