title: Tangent function transformation of the Abbreviated Injury Scale improves accuracy and simplifies scoring.
abstract: BACKGROUND
  The Injury Severity Score (ISS) and the New Injury Severity Score (NISS) are widely used for anatomic severity assessments after trauma. We present here the Tangent Injury Severity Score (TISS), which transforms the Abbreviated Injury Scale (AIS) as a predictor of mortality.
  
  
  METHODS
  The TISS is defined as the sum of the tangent function of AIS/6 to the power 3.04 multiplied by 18.67 of a patient's three most severe AIS injuries regardless of body regions. TISS values were calculated for every patient in two large independent data sets: 3,908 and 4,171 patients treated during a 6-year period at level-3 first-class comprehensive hospitals: the Affiliated Hospital of Hangzhou Normal University and Fengtian Hospital Affiliated to Shenyang Medical College, China. The power of TISS to predict mortality was compared with previously calculated NISS values for the same patients in each data set.
  
  
  RESULTS
  The TISS is more predictive of survival than NISS (Hangzhou: receiver operating characteristic (ROC): NISS = 0.929, TISS = 0.949; p = 0.002; Shenyang: ROC: NISS = 0.924, TISS = 0.942; p = 0.008). Moreover, TISS provides a better fit throughout its entire range of prediction (Hosmer Lemeshow statistic for Hangzhou NISS = 29.71; p < 0.001, TISS = 19.59; p = 0.003; Hosmer Lemeshow statistic for Shenyang NISS = 33.49; p < 0.001, TISS = 21.19; p = 0.002).
  
  
  CONCLUSIONS
  The TISS shows more accurate prediction of prognosis and a linear relation to mortality. The TISS might be a better injury scoring tool with simple computation.
authors: Department of Emergency Medicine, Affiliated Hospital of Hangzhou Normal University, Hangzhou, China.
authors: Muding
authors: M
authors: Wang
authors: Department of Neurosurgery, Hangzhou Second Hospital, College of Medicine, Hangzhou Normal University, Hangzhou, China.
authors: Wusi
authors: W
authors: Qiu
authors: Department of Emergency Medicine, Affiliated Hospital of Hangzhou Normal University, Hangzhou, China.
authors: Fang
authors: F
authors: Qiu
authors: 3 Ward of Hand Surgery, Fengtian Hospital affiliated to Shenyang Medical College, Shenyang, China.
authors: Yinan
authors: Y
authors: Mo
authors: Department of Emergency Medicine, Affiliated Hospital of Hangzhou Normal University, Hangzhou, China.
authors: Wenhui
authors: W
authors: Fan
keywords: critical care; history; injury scale; trauma