Figure 2. Comparison of ALS/SURV to CAFS and its alternatives.

For all comparisons, an observation falling on line with a slope = 1 indicates that the two composite statistics ranked participants equally; an observation falling above a line with slope = 1 indicates that the comparison ranked participants higher compared to ALS/SURV; finally, an observation below the line with slope = 1 indicates that the ALS/SURV ranked participants higher. (A) CAFS versus ALS/SURV. Participants withdrawing at 6 months (blue circles) are ranked higher in CAFS compared to ALS/SURV as these participants had less observation time compared to other participants, but were ranked based on data at the end of the trial. This is also the case for participants withdrawaling at 12 and 18 months, but not as extreme. Participants completing the trial were on a monotonic line until about ALS/SURV rank = 200 and then deviate below this line as the withdrawals were assigned extreme scores compared to completers under CAFS. (B) CAFS-alt1 versus ALS/SURV. Using CAFS-alt1, a withdrawing participant is compared to all others at their time of withdrawal. Thus completers are more monotonic, but the spread about line with slope = 1 for completes is scattered as withdrawals are interspersed with completers. (C) CAFS-alt2 vs ALS/SURV. Under CAFS-alt2, ranks of completers are not modified by withdrawals, therefore, the completers line is monotonic with most falling on a line with slope = 1. (D) ALS-R/SURV versus ALS/SURV. In this case, the variability of those participants withdrawing is related to using the ALSFRS-R score instead of the ALSFRS-R decline.

mo, month; WD, withdrawal.