One-piece closed bags for colostomies: late-stage assessment

There is a need for a standardised care pathway for people with a colostomy. After surgery, people with a colostomy will get their bags and other stoma supplies from local dispensing appliance contractors (DACs) or community pharmacies. Depending on local funding arrangements, ongoing support may be delivered by a clinical nurse specialist in stoma care (either in the community or hospital). Some people with a colostomy might also contact their DAC directly for support with managing their stoma. Appliance use reviews can be offered to support appropriate use and good prescribing practice. But these are not done consistently in all areas of England. They can also only be done by pharmacy contractors or a specialist nurse working directly with a DAC, which are often linked with stoma appliance suppliers or manufacturers (see the StoMap programme baseline report 2019). Clinical experts highlighted the importance of access to clinical nurse specialists in stoma care. They agreed that stoma care service provision, including the provision of clinical nurse specialists, is a 'postcode lottery' and that there is a lack of standardisation in stoma care pathways. The Association for Stoma Care Nurses UK stated it is developing a standardised mandatory stoma care pathway to ensure consistent quality of care. A patient and carer organisation submission stated that regular contact with a healthcare professional is vital to ensure people are using the right bag for them. The committee acknowledged that people with a colostomy should have regular access to healthcare professionals and have the same level of care across the country. It concluded that more standardisation of the care pathway is needed.

Over 80% of hospitals in England have a formal sponsorship agreement (awarded by an NHS tender process) with stoma appliance suppliers or manufacturers (see the StoMap programme baseline report 2019). These agreements may include funding for clinical nurse specialists in stoma care, training, IT equipment and admin support. There is limited published evidence discussing the impact of sponsorship in England with mixed opinions on its advantages and disadvantages. NHS England's commissioned report Delivering Excellence in Stoma Care (2020; PDF only) highlights that clinical nurse specialists in stoma care operate independently of the sponsoring company and may recommend competitor products. But, it also notes that they may receive training on sponsored products and be most familiar with bags from the sponsoring company. This can result in people who use colostomy bags being given sponsored products on discharge and continuing to use these products in the community, potentially impacting user choice. In the East of England it was reported that, for 12 out of 13 hospitals with formal sponsorship agreements, the sponsor was the market leader in product use (see the StoMap programme baseline report 2019). The committee concluded that more information is needed to understand the true impact of sponsorship on one-piece closed bag choice in England.

The evidence base for one-piece closed bags for adults with a colostomy is limited and of low quality. The EAG only identified 5 studies directly related to the decision problem in its evidence review. These included 4 crossover randomised controlled trials (RCTs) and 1 confidential internal company report. The 4 published crossover RCTs were based in Germany, Denmark, or Denmark and France. All of the published studies were company funded (with some authors having a financial conflict of interest). They evaluated the SenSura or SenSura Mio bags, comparing them with each other or with bags from Hollister and Dansac (Nova 1 or Moderma Flex). The EAG highlighted concerns related to:

• small sample sizes (there were fewer than 100 people in the published evidence)

• using unvalidated measures to collect outcomes

• a lack of consistency in how outcomes are measured across studies

• short follow-up length (maximum of 2 weeks)

• limited detail related to how people were assessed for inclusion in the studies.
  
  Clinical experts noted that, in clinical practice, people would typically be followed up for 6 months to 1 year to assess improvement in outcomes. They reiterated that short follow-up times may not be appropriate for key outcomes such as PSC. The committee acknowledged that the directly available evidence was limited and of poor quality. It stated that higher-quality evidence with validated outcomes and longer follow up would be needed to accurately assess certain key outcomes.

Because of the limited evidence base directly related to the decision problem, the EAG explored wider sources of evidence. This included evidence evaluating two-piece closed bags and evidence that used comparator arms including more than 1 range of bag. The EAG identified 8 additional studies that were relevant to the expanded evidence base. These included published before-and-after studies, RCTs, real-world evidence studies and unpublished studies. Studies on both two-piece bags and multiple bags in the comparator arm reported differences in outcomes relating to PSC and leakage or seepage. But clinical experts noted that, for two-piece bags, the baseplate remains on the skin for longer. So, outcomes related to the baseplate for two-piece closed bags (such as leakage and PSC) may not be generalisable. For evidence with more than 1 range of bag in the comparator arm, the EAG stated that it is not possible to determine the extent of the impact of a bag or feature, because it may vary between comparator bags. The committee concluded that there are uncertainties around the generalisability of the evidence for two-piece closed bags and studies with comparator arms including more than 1 range of bag to the decision problem.

The clinical evidence base included bags with potentially innovative features that could impact outcomes for people with a colostomy. But the EAG stated that these findings were from low-quality studies and not conclusive because of the limitations highlighted in section 3.9. The results from the directly relevant published evidence showed improvements in some outcomes related to filter function, such as ballooning. But other outcomes related to filter function, such as pancaking and odour control, did not show differences between the bags being evaluated. Other differences such as bag security, adhesion, ease of removal and comfort were not measured using validated scales, so the EAG considered them to be difficult to interpret and unreliable. No difference was reported in PSC or leakage in the published evidence base. Clinical and patient experts noted that the studies covered a small number of bags currently available for prescription on the NHS, and these were often not the most recent ranges from companies. The committee concluded that there is insufficient evidence to show whether any bags with potentially innovative features offer greater benefit for people with a colostomy compared with other bags or bags without potentially innovative features.

There is limited evidence reporting the impact of bags or bag features on the outcomes that are important to users. Only 3 published studies directly related to the assessment evaluated the impact of bags or bag features on leakage. Only 1 study reported the impact on PSC and no studies reported the impact on psychological outcomes. Patient experts highlighted that people with broken or damaged skin (such as people with PSC) were excluded from the 4 published RCTs in the direct evidence base. They reiterated the huge physical and psychological impact that PSCs have on people with a colostomy and highlighted the importance of collecting evidence for this group of people. The committee also noted that studies excluded people having chemotherapy or radiotherapy as part of cancer treatment, or those who irrigate their stoma. The committee concluded that more evidence is needed that focuses on the outcomes highlighted as important to users in populations that are generalisable to the colostomy population.

The EAG excluded studies evaluating one-piece closed bags in people without a stoma and evaluations of bags or their features that were done in a laboratory. This was because they do not provide clinical outcomes relevant to this assessment. Evidence reporting outcomes for people with an ileostomy was also excluded because it was found not to be generalisable to people with a colostomy. Clinical experts stated that people with an ileostomy often have a more liquid output compared with people with a colostomy. They agreed that the baseline characteristics for key outcomes (such as leakage and PSC) and the impact of bag features on these outcomes would not be comparable because of this difference. The committee agreed that excluding this evidence was appropriate for the assessment.

Factors other than the presence of potentially innovative features may influence the current prices of one-piece closed bags. The EAG found that potentially innovative features accounted for 40.3% of the price variation for flat bags and 22.5% for non-flat bags (including convex, concave and mouldable bags). The feature that impacted price most was flushable disposal in flat bags. No other feature had a significant impact in the initial regression analysis. After removing a bag identified as a potential outlier from the analysis (Opus Naturfit), baseplate additives and an inspection window were also significant predictors of bag price. The EAG stated that the results suggest that current pricing may not be driven by the presence of potentially innovative features. The committee acknowledged that the current pricing of one-piece bags may be driven by factors other than potentially innovative features, which may include competitive pricing models.

Because of the limited clinical evidence, the EAG could not evaluate the cost effectiveness of features of one-piece closed bags. Instead, the EAG used multiple discrete state-transition models to calculate the economically justifiable price (eJP; maximum cost-effective price) for a bag that can completely prevent complications identified by experts. The complications were:

• PSC

• leakage

• pancaking

• ballooning

• odour

• issues with discreetness, appearance and comfort.
  
  An incremental eJP was added to a baseline bag price for flat and non-flat bags to create a total eJP. Clinical experts agreed that no bag was considered standard care. So, the prices of the least expensive bags and the least expensive bags with a minimum of 5% market share on the Drug Tariff (at the time of the evaluation) were used as the baseline bag price The least expensive bag on the Drug Tariff was the Opus NaturFit range (flat bag £1.85, non-flat bag £2.30). The least expensive bags available with a minimum of 5% market share were the Nova colostomy bag (flat bag, £2.80) and Confidence natural soft convex bag (non-flat bag, £3.26). The EAG used a 1‑year time horizon, representing an average year for a person experiencing a complication after they have adjusted to their colostomy.

Bags with features that can improve PSC and leakage have the biggest impact on cost and quality of life. The incremental eJP per bag to completely prevent a single complication ranged from £0.37 for odour to £2.39 for PSC. When this is added to the cost of the least expensive bag, the total eJP for flat bags ranged from £2.66 for odour to £4.24 for PSC. For non-flat bags it was £2.66 for odour to £4.69 for PSC. When this was added to the least expensive bag with at least 5% market share, the total eJP for flat bags ranged from £3.17 for odour to £5.19 for PSC. For non-flat bags it was £3.63 for odour and £5.65 for PSC. The average mean bag price for all bags available on the Drug Tariff in 2023 to 2024 was £3.02, which sits within the range of these total eJPs. The EAG highlighted that a 100% reduction in these complications is unlikely and explored scenarios with lower reductions in complications. Although decreasing the proportion of complications resolved decreases in the incremental eJP, the change in the incremental eJP is not linear because some costs are unavoidable. The economic evaluation reported that improving PSC had the largest impact on costs and quality of life, followed by leakage, pancaking, ballooning, discreetness, appearance and comfort, and odour.

The EAG looked at several scenarios. It found that scenarios that substantially reduce the total eJP included lower costs for resource use, more bags used per day for people with no complications, and less time to resolution for complications. Increasing the impact of complications on utilities, increasing the time to resolution for complications and assuming support is not sought with more frequent leakage events increased the eJP. An alternative source of utility data for leakage and PSC (Brady et al. 2025) found that the results were relatively insensitive to the new data. Key model drivers were the unit cost, frequency of healthcare professional interactions, cost of supporting products and expected improvements in quality of life. The committee concluded that further evidence is needed to evaluate the cost effectiveness of bags with potentially innovative features. Bags with features that can improve PSC and leakage may have the biggest impact on costs and quality of life for people with a colostomy.

The model has a number of limitations and the results from the economic evaluation should be interpreted with caution. The EAG highlighted that the lack of evidence directly related to the assessment and uncertainty around the accuracy of model parameters is a key limitation. This is because some inputs were from structured expert elicitation or taken from published studies in mixed populations with a high proportion of people with an ileostomy. Some studies also used vignettes, which may be less accurate at capturing quality of life than patient-reported outcomes. The EAG noted that the model used optimistic estimates for the resource-use impact of PSC and leaks. Some of the model assumptions were also based on clinical expert opinion where no relevant evidence was available. The EAG used the following as bag price comparators:

• the least expensive bag on the Drug Tariff, which has less than 1% of the market share, and

• the least expensive bag with at least a 5% market share.
  
  It assumed that these bags are priced appropriately and do not resolve complications. The EAG also stated that the model looks at complications discretely. Although it created a scenario for all complications being additive, it also highlighted that the total eJP for preventing multiple complications is unknown. Patient and clinical experts confirmed that, in reality, the impact of a bag or features on complications will likely overlap. For example, leakage may lead to PSC, which may then impact the fit of the baseplate around the stoma, leading to more leaks. The EAG stated that the actual incremental eJP is likely between the incremental eJP for the single most impactful complication and the sum of the incremental eJP of all of the complications. The committee concluded that because of uncertainty in model parameters, the model results should be interpreted with caution.

The committee considered a hypothetical scenario that calculated how many clinical nurse specialists could be funded with a 10% reduction in mean bag price (reported as £3.02 from a mean of all bags available on the Drug Tariff in 2023). The scenario did not consider potential clinical differences. It concluded that this overall cost reduction could fund about 1 band‑6 clinical nurse specialist in stoma care per trust in England (141 acute NHS trusts). This included residual savings to account for travel and non-pay costs. The scenario did not take into account a mixture of band‑6 and band‑7 nurses. The committee acknowledged that this is a simplistic scenario and that any cost savings may be used in other parts of the NHS.