Functions & Formulae

Each applied formula has its own function page, with a signature, implementations, and tests.

Average cost-effectiveness ratio function

a(C_i,E_i) = ACER_i

Maps the expected cost and expected health effect of one option, either in total or measured against a do-nothing baseline, to its cost per unit of health effect without reference to any competing option. Choices between mutually exclusive options rest instead on the pairwise ICER (HE-FM-ICER-001) and on net monetary benefit (HE-FM-NMB-001), which use the same cost and effect notation.

  • Total-form average cost-effectiveness ratio

    ACER_i = C_i / E_i

    Divides an option's expected total cost by its expected total health effect. The denominator counts all the health the patient group experiences while receiving the option, including health that would have occurred anyway, so the result is a cost per QALY lived rather than a cost per QALY gained.

  • Average cost-effectiveness ratio against doing nothing

    ACER_i0 = (C_i - C_0) / (E_i - E_0)

    Divides the cost of option i minus the cost of doing nothing by its health effect minus the health effect of doing nothing. It is the pairwise ICER (HE-FM-ICER-001) with doing nothing as the comparator, so it is informative when doing nothing is the real alternative and misleading when another option is available. When C_0 and E_0 are both zero it equals the total-form ratio HE-FM-ACER-001.