Utility of routine laboratory testing for detecting intra-abdominal injury in the pediatric trauma patient.

OBJECTIVE: To assess the prevalence of laboratory abnormalities (complete blood cell count, electrolytes, blood urea nitrogen, creatinine, glucose, aspartate aminotransferase, alanine aminotransferase, amylase, lipase, urinalysis [U/A]) and the sensitivity and specificity of the physical examination (PE) and screening laboratory tests for identifying intra-abdominal injury (IAI) in moderately injured pediatric patients. DESIGN, PARTICIPANTS, AND
SETTING: Phase I: Retrospective chart review of 285 consecutive level II (moderately injured) trauma patients seen at a children's hospital emergency department/pediatric trauma center. All patients were received directly from the scene and had the following data recorded: mechanism of injury, Glasgow coma score, trauma score, pediatric trauma score, systematically recorded PE findings, laboratory results, and injuries detected during hospitalization. Phase II: To confirm the sensitivity of the PE and U/A found in phase I, the model was applied to 91 additional trauma patients identified by International Classification of Diseases, 9th revision (ICD-9) codes as having IAI. INTERVENTION: None.
RESULTS: Phase I: A total of 3939 tests were ordered for the 285 patients entered in phase I. Aspartate aminotransferase and alanine aminotransferase values were obtained in 59% of patients; glucose level was obtained in 78% of patients; complete blood cell count, U/A, and levels of electrolytes, blood urea nitrogen, creatinine, amylase, and lipase were obtained in more than 85% of patients. The overall prevalence of laboratory abnormalities was 5.7%. Fourteen patients (4.8%) were identified who had a total of 23 significant IAIs (9 pancreatic, 6 splenic, 5 renal, 3 hepatic). The PE combined with U/A showing more than five red blood cells per high-power field had a sensitivity of 100%, specificity of 64%, positive predictive value of 13%, and negative predictive value of 100% for the detection of IAI. The presence of laboratory abnormalities suggesting injury did not increase the sensitivity of the model and significantly decreased both specificity and positive predictive value. Phase II: The PE combined with U/A identified an abnormality in 89 (97.8%) of 91 cases (95% confidence interval = 94.8% to 100%).
CONCLUSIONS: In the moderately injured pediatric trauma patient, (1) there is a low prevalence of laboratory abnormalities; (2) the PE combined with U/A is a highly sensitive screen for IAI; and (3) in patients with a normal PE of the abdomen and a normal U/A, laboratory testing seldom identifies unsuspected IAI.