A novel mobile phone and tablet application for automatized calculation of pain extent

Background: Pain drawings (PDs) are used for assessing pain extent as a complementary outcome to other pain measurements, consisting of shading a body chart template to report the location and extent of pain. However, the accuracy and reliability of digital PDs remain controversial due to the heterogeneity of methods used. This study aimed to develop an easy-to-use application for assessing its diagnostic accuracy in comparison with the classic paper-and-pencil method. Methods: A test-retest reliability study was conducted, recruiting 95 patients with musculoskeletal pain symptoms. Participants shaded 2 sets of 3 different PDs (paper-and-pencil PD, digital PD using the finger and digital PD using the digital stylus). Intraclass correlation coefficients (ICC), standard error of measurement and minimal detectable changes (MDC) were calculated for each method. Finally, repeated measure analysis of variance assessed the mean differences between trials and methods and the convergent validity between methods was calculated using Pearson's correlation coefficients. Results: All methods were excellently reliable (all, ICC>0.94). However, digital PDs obtained higher ICCs (ICC >= 0.970) and greater accuracy to detect whether changes reflect a real change and are not due to a measurement errors (MDC = 0.72%- 0.80 % for digital PDs versus MDC = 1.13 % for paper-and-Pencil PDs). No significant score differences were found among the instruments for assessing pain extent (p > 0.05). Finally, the PAIN EXTENT app showed adequate convergent validity (r > 0.850). Conclusion: The PAIN EXTENT app is a fast and easy-to-use instrument compatible with operative systems and devices commonly used for assessing and monitoring pain extent in the clinical and research settings.