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The nurse measurements can also reduce bias by making MAR more credible: withdrawal may depend on unobserved clinic QoL, but that QoL is partly represented by the post-dropout disability assessments. They also permit diagnostics comparing inferred QoL trajectories with an independently recorded proxy and can support sensitivity analysis for departures from MAR. They do not by themselves prove MAR, because the rough score may omit reasons for dropout related to QoL.