Construct validity for the RDFS was supported by this demonstration of strong associations between the RDFS and the FSS and MFIS.
This comparison analysis of ICCs demonstrates that the RDFS is more reliable and that the differences in reliability between the RDFS and the FSS and MFIS are significant.
Therefore, it also likely provides a more responsive, accurate, and up-to-the-moment assessment of self-reported fatigue than the FSS and MFIS questionnaires in which subjects are asked to make difficult retrospective reports of their fatigue level from the preceding 1 week and 1 month for the FSS and MFIS, respectively.
Because of the multiple observations, the RDFS data set provides statistical advantages for analysis over the traditional FSS and MFIS scores.
Even if many scheduled fatigue scores are not entered, the collective volume of RDFS data still contrasts significantly with the isolated scores of FSS and MFIS assessed for each individual during the study.
Furthermore, both FSS and MFIS have been validated for use in men and women with MS, and RDFS correlates well with both.
A significant interest will be to observe how the analysis of an RDFS data set by a mixed-model repeated-measures approach responds to change compared with the analysis of FSS or MFIS in a clinical trial.