Table 1

Description of various summary scores for expressing changes in HRQOL scores over time

NameFormulaDescription
AD Embedded Image Simple difference in the HRQOL between two time points.
The mean of the AD values from all subjects corresponds to the Osoba’s MID (Osoba et al 4).
pAD Embedded Image Applying AD per subgroup c=1 to 4, where c is based on baseline QOL values grouped as; 0–25, 26–50, 51–75 and 76–100.
RD1 – ordered Embedded Image Per cent change from previous value.
RD2 – sum Embedded Image Per cent change compared with sum.
Convention: if Q2=Q1=0 then RD2=0.
RD3 – baseline Embedded Image Per cent change compared to baseline value (Q B).
Fixed value Embedded Image MID is dependent on the observed value. This will result in a fixed threshold, not dependent on change in HRQOL score from previous value.
Slope Embedded Image The absolute difference between two time points is weighted by the corresponding time period.

  • Qx , HRQOL outcome at time point Tx.

  • AD, absolute difference; HRQOL, health-related quality of life; MID, minimally important difference; pAD, piecewise absolute difference; RD, relative difference; RS, raw scores; QOL, quality of life.