Study Setting and Population
This retrospective, nationwide, observational study analyzed data obtained from the JTDB, which registers data of patients with trauma and/or burn and records prehospitalization and hospital-related information. The JTDB records data of demographics, comorbidities, injury types, mechanism of injury, means of transportation, vital signs, Abbreviated Injury Scale (AIS) score, Injury Severity Score (ISS), prehospital/in-hospital procedures, trauma diagnosis as indicated using the AIS, and clinical outcomes. In most cases, physicians who are trained in AIS coding by using the 1990 revision of AIS (AIS90) [15] undertake the online registration of individual patient data. The Japan Association for the Surgery of Trauma permits open access and update of existing medical information, and the Japan Association for Acute Medicine evaluates the submitted data [6].
Figure 1 shows a flow diagram of the patient disposition. In this study, we used a JTDB dataset that included information for the period January 1, 2009, to December 31, 2018, which initially yielded the data of 313,643 patients. The inclusion criteria for this study were as follows: presence of trauma and age below 18 years. Patients aged more than 19 years, with burns or penetrating trauma, with cardiac arrest on hospital arrival, or with missing data of outcome and TRISS prediction were excluded from this study. Among 26,329 patients with blunt trauma and younger than 18 years, 2,480 (9.4%) patients had missing data of survival and 5,446 (20.7%) patients had missing date of TRISS predictor, and hence, the survival probability (Ps) was not calculated using the TRISS method. Furthermore, 683 (2.6%), 1,948 (7.4%), 1,608 (6.1%), and 3824 (14.5%) patients had missing data of ISS, Glasgow Coma scale (GCS) score, systolic blood pressure (sBP), and respiratory rate (RR), respectively. Table S1 shows the number of patients who had missing data by age category and each variable.
Data collection
We collected information of following variables from the JTDB: age (years), sex, AIS, AIS of the injured region, Revised Trauma Score [3], ISS [10], Ps, and in-hospital mortality. The TRISS ranges from 0 (certain death) to 1 (certain survival), and the survival probability (Ps) is calculated as follows:
where b=b0+b1(RTS)+b2(ISS)+b3(age).
RTS is calculated using the GCS score, the sBP, and the RR.
Data analysis
The estimated study outcomes were as follows: (1) patients’ characteristics and mortality by age groups (neonates/infants aged 0year, pre-school children aged 1−5 years, schoolchildren aged 6−11 years, and adolescents aged 12−18 years), (2) validity of Ps assessed using the TRISS methodology by the four age groups and six Ps-interval groups (0.00−0.25, 0.26−0.50, 0.51−0.75, 0.76−0.90, 0.91−0.95, and 0.96−1.00), and (3) the observed/expected survivor ratio by age- and Ps-interval groups . In the primary analysis, which was conducted to identify the characteristics of pediatric trauma patients during the study period, a Mann–Whitney U test and Kruskal–Wallis test were used for analyzing continuous variables, whereas a chi-square test was used for analyzing categorical variables. In the secondary analysis, the validity of TRISS was evaluated by the predictive ability of the TRISS method using the receiver operating characteristic (ROC) curves presents the sensitivity, specificity, positive predictive value, negative predictive value, accuracy, area under the receiver operator characteristic curve (AUC), and it’s 95% confidence interval (CI) of TRISS and shows the ability of TRISS to distinguish between positive and negative outcome. The AUC varies as < 0.7 (low performance), 0.7−0.9 (moderate performance), and > 0.9 (high performance). In the third analysis, the expected survival calculated using TRISS Ps was compared with the actual Ps. The expected number of survivors in each Ps-interval group was calculated by integrating mean Ps and the number of patients for six Ps-interval group. The results of these comparisons are expressed as the medians and interquartile ranges (IQRs; 25th–75th percentile) for continuous variables and as the mean and percentages for categorical variables. All statistical analyses were performed using STATA/SE software, version 16.0 (StataCorp; College Station, Texas, USA). A two-tailed P-value of less than 0.05 indicated statistical significance.