Fig 2. Flowchart with the stages of elaboration, refinement, and validation of the USAPS.

Statistical tests (Table 1) used in refinement and final validation of the scale: 1) content validation (only in refinement); 2) multiple association; 3) intra-observer reliability; 4) inter-observer reliability; 5) criterion validity; 6) construct validity; 7) internal consistency; 8) sensitivity and specificity; 9) determination of the rescue analgesic point.