trauma is considered one of the major causes of mortality and permanent disability and the 4 cause of death behind cardiovascular diseases , cancer , and stroke ( 1 , 2 ) . based on the statistics reported by the iranian legal medicine organization , trauma and its consequences are the most common cause of mortality in iran , as 75.9% and 74.1% of deaths were trauma related in 2003 and 2004 , respectively ( 3 ) . among injuries due to trauma , chest trauma is responsible for 25% of deaths due to trauma and 50% of trauma - related deaths ( 4 , 5 ) . diagnostic and treatment approaches may vary depending on the equipment of the center and the physician s decision . physical examination and chest radiography ( cxr ) are the first steps in diagnosis and treatment of multiple trauma patients . accuracy of the diagnoses are widely dependent on the type of injury , time of arrival , and the method of diagnosis used ( 6 ) . during the past decade , imaging diagnostic methods have improved and therefore , accuracy of pulmonary contusion , hemothorax , and pneumothorax diagnosis has increased . yet , these methods do not have high specificity in ruling out chest and abdominal injuries ( 6 ) . chest computed tomography ( ct ) scan as the gold standard , can diagnose pulmonary contusion , hemothorax , pneumothorax , and rib fracture with high sensitivity ( 7 ) . rapid diagnosis of pneumothorax in patients with traumatic injuries , has led to improvement in patient management . sensitivity of ct scan compared to cxr , is 100% compared to 42% in this regard ( 8 - 11 ) . yet , cxr is still considered a useful and non - expensive method providing valuable information in the initial evaluation of trauma patients ( 9 , 12 ) . considering global and national statistics on trauma , especially chest trauma and its high prevalence in the youth population , this study was designed to evaluate the diagnostic value of cxr in comparison to chest ct scan in diagnosis of traumatic intrathoracic injuries . baseline characteristics of the studied patients * based on injury severity score ( iss ) . screening performance characteristics of chest x - ray in detection of traumatic thoracic fractures . positive predictive value ;   . screening performance characteristics of chest x - ray in detection of traumatic intra - thoracic injuries . receiver operating characteristics ( roc ) curve of chest x - ray in comparison with computed tomography scan in the present prospective diagnostic accuracy study , the value of cxr for diagnosis of traumatic intrathoracic injuries was evaluated in comparison to ct scan . the participants of this study included multiple trauma patients admitted to emergency department ( ed ) of imam hossein hospital , tehran , iran , during march 2014 to february 2015 . multiple trauma patients over 15 years old with stable vital signs and those who had requests for both plain cxr and ct scan of chest were enrolled . exclusion criteria consisted of unstable vital signs , penetrating trauma , pregnancy , and not undergoing cxr or chest ct scan . demographic data of the patients , trauma mechanism and severity of injury based on injury severity score ( iss ) , and cxr and ct scan findings regarding presence of hemothorax , pneumothorax , pulmonary contusion , and fracture of rib , spine , and sternum were recorded in a checklist . finally , the correlation of cxr and ct scan findings in diagnosis of chest traumatic injuries was evaluated . physical examination , history , and data gathering for all patients was done by an emergency medicine resident in charge of trauma unit . since the accuracy of cxr interpretation has been proved to be high for emergency medicine specialists ( 13 ) , interpretation of cxr was done by a senior emergency medicine resident who was blind to the patients clinical conditions . chest ct scans were also reported by a radiologist blind to the clinical condition of the patients . none of the patients underwent cxr outside the treatment process and ct scan indications were determined based on the advanced trauma life support ( atls ) guidelines or the decision of in charge surgeon . all cxrs were performed as posterior - anterior while the patient was in upright position . statistical analysis :   sample size was calculated to be 87 cases considering 65% sensitivity of cxr in diagnosis of intrathoracic injuries , 10% desired precision , and 95% confidence interval ( ci ) . quantitative variables were reported as mean and standard deviation ( sd ) and qualitative ones as frequency and percentage . sensitivity , specificity , positive and negative predictive value ( ppv and npv ) and positive and negative likelihood ratio ( plr and nlr ) of cxr in comparison with ct scan were calculated with 95% ci . finally , area under the receiver operating characteristic ( roc ) curve of cxr was calculated . 353 patients with the mean age of 35.2  15.8 were evaluated ( 78.8% male ) . age 16 - 30 years with 121 ( 34.2% ) , motorcycle riders with 104 ( 29.5% ) cases and iss < 12 with 185 ( 52.4% ) had the highest frequency among patients . there was a significant correlation between the findings of two studied modalities (  = 0.68 ; p < 0.001 ) . screening characteristics of plain cxr in diagnosis of various traumatic intrathoracic injuries and fractures are presented in tables 2 and 3 , respectively . generally , screening performance characteristics of chest in diagnosis of chest traumatic injuries were as follows : sensitivity 50.3 ( 95% ci : 44.8  55.5 ) , specificity 98.9 ( 95% ci : 99.5  99.8 ) , ppv 97.8 ( 95% ci : 91.5  99.6 ) , npv 66.4 ( 95% ci : 60.2  72.03 ) , plr 44.5 ( 95% ci : 11.3 175.3 ) , and nlr 0.5 ( 95% ci : 0.4  0.6 ) . accuracy of cxr in diagnosis of traumatic intrathoracic injuries was 74.5 ( 95% ci : 69.6  78.9 ) and its area under the roc curve was 74.6 ( 95% ci : 69.3  79.8 ) ( figure 1 ) . based on the findings of the present study , cxr has low sensitivity in diagnosing traumatic intrathoracic injuries compared to ct scan . while its specificity and plr is high and close to that of ct scan .   carrying out physical examination and plain cxr el wakeel et al . in the study of 100 blunt chest trauma patients showed the higher sensitivity of ct scan compared to cxr in detection of intrathoracic injuries ( 7 ) . as shown in table 2 and 3 , the screening characteristics of cxr are higher than 90% in all pathologies except pneumothorax . it seems that this matter has a great impact on the general screening characteristics of the test . the pneumothorax cases , which were missed with cxr and diagnosed by ct scan are frequent and named occult pneumothorax , which usually are benign in nature . in a study , eckstein et al . estimated the sensitivity of cxr to be 42% in diagnosis of pneumothorax ( 10 ) . diagnosis of hemothorax in cxr is difficult due to different reasons such as : the patient not being able to sit up , poor quality of the radiography , and improper preparation before radiography ( being in sitting or upright position for at least 15 minutes before radiography performance ) . in the present study , sensitivity and specificity of cxr in diagnosis of pulmonary contusion these measures were 40 and 100% , respectively in the eckstein study ( 10 ) . chest ct scan as the gold standard can diagnose pulmonary contusion , hemothorax , pneumothorax , and rib fracture with high sensitivity ( 8 - 12 ) . despite the efficiency and high diagnostic value of ct scan in trauma patients , few evidence therefore , using it as a routine screening method is still a matter of debate ( 10 ) . believed that use of chest ct scan as an initial screening tool in trauma patients with stable hemodynamics can change the patient management and outcome ( 14 ) . although ct scan can be very useful for evaluation of chest trauma patients , especially those with lung parenchyma injuries , hemothorax , and pneumothorax , the nephrotoxicity due to contrast material , cumulative dose of radiation , and the high cost of ct scan are problems that can not be overlooked ( 6 ) . on the other hand , performing plain cxr and then ct scan to confirm the results doubles the problem . therefore , a decision on whether all chest trauma patients with stable hemodynamics should undergo ct scan from the start can not be made yet . it seems that making a decision based on a combination of physical examination , history , trauma mechanism , as well as imaging can be very helpful in this regard . the new methods suggested for chest trauma evaluation , tend to use scoring systems and clinical decision rules to some extent ( 15 , 16 ) . it seems that routine use of cxr based on atls protocol for all multiple trauma patients is questionable . in this regard , new clinical decision rules similar to nexus ( 16 ) and tirc ( 15 ) that have been designed for clinical triage of patients in need for chest imaging , can be implemented after validation studies . based on the findings of the present study , the screening performance characteristics of cxr in diagnosis of traumatic intrathoracic injuries were higher than 90% in all pathologies except pneumothorax . it seems that this matter has a great impact on the general screening characteristics of the test ( 74.3% accuracy and 50.3%sensitivity ) . it seems that , plain cxr should be used as an initial screening tool for all the chest trauma patients more carefully . cite this article as : abedi khorasgani m , shahrami a , shojaee m , alimohammadi h , amini a , hatamabadi h. the accuracy of plain radiography in detection of traumatic intrathoracic injuries . emergency . all authors passed four criteria for authorship contribution based on recommendations of the international committee of medical journal editors .
introduction : rapid diagnosis of traumatic intrathoracic injuries leads to improvement in patient management . 
 this study was designed to evaluate the diagnostic value of chest radiography ( cxr ) in comparison to chest computed tomography ( ct ) scan in diagnosis of traumatic intrathoracic injuries . 
 methods : participants of this prospective diagnostic accuracy study included multiple trauma patients over 15 years old with stable vital admitted to emergency department ( ed ) during one year . 
 the correlation of cxr and ct scan findings in diagnosis of traumatic intrathoracic injuries was evaluated using spss 20 . screening characteristics of cxr were calculated with 95% ci . 
 results:353 patients with the mean age of 35.2  15.8 were evaluated ( 78.8% male ) . 
 age 16 - 30 years with 121 ( 34.2% ) , motorcycle riders with 104 ( 29.5% ) cases and iss < 12 with 185 ( 52.4% ) had the highest frequency among patients . 
 generally , screening performance characteristics of chest in diagnosis of chest traumatic injuries were as follows : sensitivity 50.3 ( 95% ci : 44.8  55.5 ) , specificity 98.9 ( 95% ci : 99.5  99.8 ) , ppv 97.8 ( 95% ci : 91.5  99.6 ) , npv 66.4 ( 95% ci : 60.2  72.03 ) , plr 44.5 ( 95% ci : 11.3 175.3 ) , and nlr 0.5 ( 95% ci : 0.4  0.6 ) . accuracy of cxr in diagnosis of traumatic intrathoracic injuries was 74.5 ( 95% ci : 69.6  78.9 ) and its area under the roc curve was 74.6 ( 95% ci : 69.3  79.8 ) . 
 conclusion : the screening performance characteristics of cxr in diagnosis of traumatic intrathoracic injuries were higher than 90% in all pathologies except pneumothorax ( 50.3% ) . 
 it seems that this matter has a great impact on the general screening characteristics of the test ( 74.3% accuracy and 50.3%sensitivity ) . 
 it seems that , plain cxr should be used as an initial screening tool more carefully .