McCrone and colleagues found that CBT and Graded exercise (GET) were cost effective for CFS on Healthcare costs alone. But they also emphasised that, from a societal perspective, the cost-effectiveness for CBT and GET relative to Specialised Medical care (SMC) was far greater. This was due to additional savings from the reduced need for informal care. They also state that from the societal perspective both CBT and GET are dominant to SMC, i.e give more benefit with lower costs, which is an ideal situation.

Missing Sensitivity Analysis Results
However, it appears that some of these conclusions would not hold if informal care was valued at the minimum wage of £5.93 rather than mean average earnings of £14.60 per hour. While this scenario was investigated in the sensitivity analysis, the actual results are not given. Instead there is a comment that changing the value of informal care did not have a 'large impact' on informal care costs, and that ‘the results were robust for alternative assumptions’.

The paper goes on to argue that investment in CBT & GET ‘would be justified in terms of improved quality of life of patients and “would actually be cost saving if all costs including societal costs are considered.” ’

Data from the paper suggests results would be substantially different if informal care was valued at the lower rate
The major contributor to CBT & GET Societal savings were from informal care, since lost employment was not significantly different between any of the groups.

Compared with SMC (and adjusted for baseline costs), CBT and GET showed informal care saving of £1,165 and £1,173 respectively when valued at mean average earnings of £14.60 per hour. Therefore, at the lower rate of £5.93, the minimum wage, these savings would reduce to £473 and £476 respectively.

The reduction in informal care costs would reduce societal gains, relative to SMC, by a corresponding amount:

Impact on societal costs (vs SMC) of using minimum wage to value informal care

CBT [informal care “@ mean earnings”]: -£698 (of which- £1,165 due to informal care]
CBT [informal care “@ minimum wage”]: -£6 (of which -£473 due to informal care)

GET [“mean earnings”]: -472 (-£1,173)
GET [“minimum wage”]: +225 (-£476)

This changes this situation substantially. GET now has a cost of £225 (as opposed to a saving of £472) while CBT is effectively neutral, with a per-patient gain of £6 gain at minimum wages instead of saving nearly £700. So the claim that: "there would actually be cost saving if all costs including societal costs are considered" appears not to hold in the minimum wage scenario (for GET and CBT combined), suggesting that the sensitivity analysis would show this finding was not robust. Similarly, GET would no longer be dominant to SMC as its societal costs would be higher; CBT would be technically dominant, but only thanks to a £6 margin per patients. Finally, the QALY-based cost-effectiveness acceptability curves (societal perspective, Figure 2) might look different in such a scenario.

My apologies if these calculations are flawed, and I trust the authors will point out any errors, but I only went down this route as the results of the sensitivity analysis were not available, when they could perhaps been provided as an appendix. Could the authors now publish the results of their sensitivity analysis for informal care?