Forty-two may be the answer to the meaning of life, the universe and everything, but in mental health the answer seems to be £334.

That is the average unit cost of a mental health admitted patient bed day, according to the first ever set of national reference costs calculated on the basis of the 21 new mental health tariff “clusters” (22 if you count the largest, “cluster 99” - inevitably this is “patients not assessed or clustered”).

‘Is there a risk finance teams will take these reference costs too seriously?’

NHS mental health tariff clusters should not be confused with NHS organisational clusters. Whereas the latter are designed, ultimately, to facilitate administrative redundancies, the former are part of the payment by results revolution, allegedly coming to a mental health service near you soon.

The clusters categorise groups of patients according to their care needs as a means to form a currency akin to the healthcare resource groups in acute care.

So, where in acute care we have “CZ10U - major ear procedures, 18 years and under” (£2,955 average non-elective unit cost), in mental health we have “cluster 01: common mental health problems, low severity” (£326 average admitted patient cost per day) or “cluster 15: severe psychotic depression” (£334 average cost).

The recently published first batch of cluster reference costs matter because, for the time being at least, reference costs are the means by which the Department of Health determines a sensible tariff price.

What then should we make of the fact that after a year of careful “bottom up” costing and coding by over 50 different providers, there is a mere £49 a day difference between the lowest cost admitted patient cluster (“cluster 18: cognitive impairment, low need”, £319) and the highest cost (“cluster 16: dual diagnosis”, £366)?

The lack of apparent granularity is perhaps not surprising for a sector dominated by block contracts and only a smattering of active patient level costing systems. But in acute care, the theory behind the tariff was to use changes to prices to drive desirable service change. The shift towards day care for certain procedures, for example.

Will there be room for such sophisticated pricing mechanisms in a sector where all patients are pretty much deemed to cost the same? And perhaps more importantly, is there a risk finance teams will take these reference costs too seriously as the basis for allocating ward resources?

Sally Gainsbury is a news reporter for the Financial Times, sally.gainsbury@ft.com