The sponsor submitted a new cost analysis based on a decision tree model with an embedded Markov model. This model evaluated the costs per patient and system impact of the PeritX peritoneal catheter drainage system for the drainage of treatment-resistant, recurrent malignant ascites in the community setting when compared with inpatient and outpatient large-volume paracentesis.
The time horizon of the model was 26 weeks (6 months) from the time of the initial PeritX peritoneal catheter insertion. The Markov model was run over 26‑weekly cycles to account for the short duration of survival in patients with malignant ascites. The cycles used transition probabilities based on 100% survival at week 0 to 4% survival at week 26. The cost of treatment was multiplied by the transition probability at each cycle; half-cycle corrections were used to incorporate changes in survival within a cycle.
The key assumptions used in the model were:
no change in the survival rate in both arms of the model
the need for 2 nurse visits to train patients to self-manage the drainage at home using the PeritX peritoneal catheter drainage system
similar levels of treatment monitoring needs in both arms of the model
a nurse visit length of 15 minutes for the PeritX peritoneal catheter drainage system to help with drainage at home
drainage volume of 9.2 litres per procedure in patients who have repeated large-volume paracentesis
average drainage volume of 3.5 litres per week using the PeritX peritoneal catheter drainage system
one nurse visit per litre of ascitic fluid drained using the PeritX peritoneal catheter drainage system
the cost of re-intervention being equivalent to a first-time catheter insertion procedure.
The model calculated the costs per patient of the PeritX peritoneal catheter drainage system and large-volume paracentesis as well as the incremental costs of the PeritX peritoneal catheter drainage system. The costs of the system included: inpatient stay (1 day), procedure consumables and other costs (including staff time), PeritX drainage kits, home nurse visits and treatment of complications (infection, catheter failure and re-intervention). The cost of large-volume paracentesis included: inpatient stay (2.8 days) or outpatient (1 day), procedure consumables and treatment of complications. In addition, the system impact was presented in terms of number of paracentesis sessions, number of litres of ascitic fluid drained, number of bed days, and number of nurse visits for both interventions.
The cost per patient for the management of malignant ascites using the PeritX peritoneal catheter drainage system was estimated to be £2,466, whereas for inpatient and outpatient large-volume paracentesis it was estimated to be £3,146 and £1,457 respectively.
The base-case analysis showed that managing treatment-resistant, recurrent malignant ascites with the PeritX peritoneal catheter drainage system may result in cost saving of £679 per patient when compared with inpatient large-volume paracentesis. In this scenario, 7.4 hospital bed days were saved per patient, but 23.5 more community nurse visits to the patients' home were needed. When the PeritX peritoneal catheter drainage system was compared with outpatient large-volume paracentesis, an additional cost of £1,010 per patient was incurred, including 23.5 extra nurse visits but 1.9 fewer hospital bed days used per patient.
The key drivers of the new cost analysis were: cost of a hospital bed day, number of bed days per large-volume paracentesis session, number of large-volume paracentesis procedures per month, number of bed days for PeritX peritoneal catheter placement, cost per drainage kit box (10 units), and number of drainage kits used per week per patient. The analysis showed that cost savings associated with the PeritX peritoneal catheter drainage system, when compared with inpatient large-volume paracentesis, were heavily dependent on a reduction in hospital stay. The cost of a bed day was estimated at £312.
The sponsor carried out one-way deterministic sensitivity analysis. All variables (except for population size) were tested, and were analysed using a variance of 20% regardless of the level of confidence in an input or the parameter-specific circumstances. Six key drivers were selected and subjected to further deterministic threshold analysis by the external assessment centre across a wide range of values, to identify the point at which the PeritX peritoneal catheter drainage system became more costly or cost saving compared with inpatient and outpatient large-volume paracentesis respectively.
The findings of the threshold sensitivity analysis showed that using the PeritX peritoneal catheter drainage system may incur additional costs when compared with inpatient large-volume paracentesis in the following scenarios: the cost of an excess bed day is reduced to less than £220 per day; the frequency of an inpatient large-volume paracentesis procedure is reduced to fewer than one per month; the average length of inpatient stay after the large-volume paracentesis procedure is decreased to 2.1 days; the number of inpatient bed days following the PeritX peritoneal catheter insertion procedure is increased to more than 3.1 days; the cost of the PeritX drainage kit is increased to more than £915 (per 10 units); more than 5.1 drainage kit units are needed per week. The PeritX peritoneal catheter drainage system may become cost saving when compared with outpatient large-volume paracentesis in the following scenarios: the cost of an excess bed day is increased to more than £825 per day; the frequency of an outpatient large-volume paracentesis procedure is increased to more than 2.5 per month; the average length of hospital stay after the outpatient large-volume paracentesis procedure is increased to more than 2.1 days; the cost of the PeritX drainage kit is decreased to less than £225 (per 10 units); fewer than 1.14 drainage kit units are needed per week.
The sensitivity analysis demonstrated that the PeritX peritoneal catheter drainage system is likely to remain cost saving when compared with inpatient large-volume paracentesis and is likely to incur extra costs when compared with outpatient large-volume paracentesis.
The new cost analysis showed that the PeritX peritoneal catheter drainage system was cost saving when compared with inpatient large-volume paracentesis, but incurred additional costs when compared with outpatient large-volume paracentesis. The additional costs, compared with outpatient treatment, were incurred mainly from an increased number of home nurse visits, with only a small offset saving in hospital bed days. However, the committee was advised that the additional cost burden imposed on community nursing staff as a result of the PeritX peritoneal catheter drainage system may have been overestimated, given that most patients will receive healthcare in the community regardless of whether or not they have a PeritX peritoneal catheter in place. The committee was advised that many patients may not prefer outpatient to inpatient large-volume paracentesis because it does not necessarily alleviate the intolerable symptoms associated with ascitic fluid build-up any better than inpatient large-volume paracentesis and yet still creates the need for repeated outpatient visits.
The committee recognised that large-volume paracentesis is currently offered as an inpatient, outpatient or day case procedure and that practice varies across the UK. Moreover, the resource costs for outpatient and day case large-volume paracentesis differ, with the day case procedure being more costly (although this was not reflected in the cost model). The committee was advised that the PeritX peritoneal catheter drainage system is likely to be cost saving when compared with day case large-volume paracentesis.
The clinical experts advised the committee that the mean hospital stay of 2.8 days following inpatient large-volume paracentesis that was used in the base-case analysis is a realistic estimate and reflects current practice in many NHS centres.
The committee recognised that the NHS tariff used for the calculation of excess bed days underestimated the cost of an inpatient stay and that correcting this may further increase the cost savings attributable to the PeritX peritoneal catheter drainage system.
For the 2022 guidance review, the external assessment centre revised the model to reflect 2020 costs. The largest changes compared with the costs from the 2018 guidance review were increases in the cost of hospital bed days (£355 to £367.78) and decreases in the cost of home visit per hour (£68 to £49). The new costs for the technology were also included. Base-case results for the 2022 revised model (values after first guidance review are given in brackets) show a cost saving of £1,095 (£1,051) per patient. The differential cost between PeritX and paracentesis as an outpatient procedure has increased to an additional cost of £896 (£871) per patient. [2022]