Assessing the efficacy of a tongue image analyzing system (TIAS) for the objective diagnosis of static blood: An observational, retrospective, single-center study of Japanese Kampo medicine

Aim: Static blood (SB) is an important pathological concept of Kampo medicine. Although tongue findings are very useful in the diagnosis of SB, the relation between the severity of SB and tongue color (TC) is unclear. The purpose of this study was to evaluate the relation between the severity of SB and TC obtained by the use of a Tongue image analyzing system (TIAS). Methods: We analyzed data from 227 new patients (age 20–85) who visited the Kyushu University Hospital Kampo Clinic between 2013 and 2018. The SB score was calculated based on the diagnostic criteria by Terasawa et al. and classified into three groups: non-static blood (NSB) ≤20 points, SB 20.5 to 39.5 points, severe static blood (SSB) ≥40 points. TC was measured by the device-independent international commission on Illumination 1976L*a*b* color space standards at four points: (i) edge; (ii) posterior; (iii) middle; and (iv) apex. Results: SB and SSB occurred significantly more frequently in women and patients were of younger age than in the NSB group (P < 0.05). Analysis of TC found 1L* and 4L* to be significantly lower (P < 0.05), and 1a*, 2a*, 3a*, and 4a* significantly higher in SSB than in NSB (P < 0.05). The cutoff value of 2a* and the combination of 1L* + 1a* for SSB prediction obtained from the ROC curve were 2a*, 25.78 (Se: 43%, Sp: 85%, AUC: 0.65), 1L* + 1a*: 1L*, 61.31 and 1a*, 26.16 (Se: 51%, Sp: 82%, AUC: 0.65). Conclusion: TC diagnosis with TIAS would be a useful screening tool for judging the severity of SB.