The evaluation of smartphone versions of the visual analogue scale and numeric rating scale as postoperative pain assessment tools: a prospective randomized trial

PurposeThe Pain assessment using a novel digital application (Panda) is a smartphone application that contains the digital versions of the visual analogue scale (VAS-100) and numeric rating scale (NRS-11). This study aimed to investigate if the Panda versions of these two pain scales are equivalent to the paper versions in adult patients.MethodsThis was a prospective, randomized, cross-over-controlled trial of subjects aged 19-75 yr undergoing procedures with anticipated post-surgical pain. Each subject used both the Panda and paper versions of VAS-100 or NRS-11 pain scores after emergence from anesthesia and after meeting postanesthesia care unit (PACU) discharge criteria. Correlations between the two tools were analyzed, and Bland-Altman agreement was calculated. The smartphone and paper versions were considered equivalent at each time point if the differences (and their 95% confidence interval [CI]) between them were less than 20 points for the VAS-100 and 2.1 for NRS-11.ResultsThe two versions of the VAS-100 correlated strongly after emergence (Pearson's r=0.93; P<0.001) and upon meeting discharge criteria (r=0.94; P<0.001); the mean (standard deviation [SD]) Panda score after emergence was 35 (27) compared with the paper score of 37 (26) (mean difference, -2; 95% CI, -22 to 19). The mean (SD) VAS-100 Panda score upon meeting discharge criteria was 21 (20) compared with the paper score of 23 (21) (mean difference, -2; 95% CI, -17 to 13). For the NRS-11, Panda again correlated strongly with the original tool scores after emergence (r=0.93; P<0.001) and upon meeting discharge criteria (r=0.96; P<0.001); the mean (SD) Panda and paper scores after emergence were both 4 (3) (mean difference, 0.05; 95% CI, -1.87 to 1.96). The mean (SD) NRS-11 Panda and paper scores upon meeting PACU discharge criteria were both 3 (2) (mean difference, -0.08; 95% CI, -1.41 to 1.26).ConclusionFollowing emergence from anesthesia in adult patients, the digital Panda version of the NRS-11, but not the VAS-100, is equivalent to the validated paper version. In those who are ready for discharge from the PACU, the digital Panda versions of both the VAS-100 and NRS-11 agreed adequately and can be used in place of the original paper versions.