Fig. 3

Item thresholds derived from Rasch analysis. Footnote: Items are situated on the vertical access and grouped into their respective domains. Note there are three items (30, 31, and 32) that are included in the ATAQ-LAM total score but do not contribute to any of the four domain scores. The small figures (circle, square, etc.) on the horizontal line extending from an item label represent threshold positions between response options for that item. Thresholds represent the logit position where a patient is equally likely to respond to either of two adjacent response options (1 or 2, 2 or 3, 3 or 4, 4 or 5, 5 or 6). For items with four thresholds, only five response options were used by the sample. The solid vertical line at “0” logits is the mean item difficulty. The dashed vertical line at −0.75 logits represents the mean patient severity. Each “X” along the top of the figure represents one respondent (LAM patient) and her HRQL severity location (in logits). HRQL impairment ranges from mild (left) to severe (right). Likewise, item difficulty ranges from easy (likely to be endorsed by someone with even mild HRQL impairment) on the left to difficult (likely to be endorsed only by someone with the greatest HRQL impairment) on the right