The SCRAP Rule: The derivation and internal validation of a clinical decision rule for computed tomography of the chest in blunt thoracic trauma.

OBJECTIVE: To derive and internally validate a clinical decision rule that will rule out major thoracic injury in adult blunt trauma patients, reducing the unnecessary use of chest computed tomographic (CT) scans. METHODS: Data were retrospectively obtained from a chart review of all trauma patients presenting to a Canadian tertiary trauma care centre from 2005 to 2008, with those from April 2006 to March 2007 being used for the validation phase. Patients were included if they had an Injury Severity Score > 12 and chest CT at admission or a documented major thoracic injury noted in the trauma database. Patients with penetrating injury, a Glasgow Coma Scale (GCS) score ≤ 8, paralysis, or age < 16 years were excluded. RESULTS: There were 434 patients in the derivation group and 180 in the validation group who met the inclusion criteria. Using recursive partitioning, five clinical variables were found to be particularly predictive of injury. When these variables were normal, no patients had a major thoracic injury (sensitivity 100% [95% CI 98.4-100], specificity 46.9% [95% CI 44.2-46.9], and negative likelihood ratio 0.00 [95% CI 0.00-0.04]). The five variables were oxygen saturation (< 95% on room air or < 98% on any supplemental oxygen), chest radiograph, respiratory rate ≥ 25, chest auscultation, and thoracic palpation (SCRAP). In the validation group, the same five variables had a sensitivity of 100% (95% CI 96.2-100%), a specificity of 44.7% (95% CI 39.5-44.7%), and negative likelihood ratio of 0.00 (95% CI 0.00-0.10). CONCLUSIONS: In major blunt trauma with a GCS score > 8, the SCRAP variables have a 100% sensitivity for major thoracic injury in this retrospective study. These findings need to be prospectively validated prior to use in a clinical setting.

Structural characterization of a novel Chlamydia pneumoniae type III secretion-associated protein, Cpn0803.

Type III secretion (T3S) is an essential virulence factor used by gram-negative pathogenic bacteria to deliver effector proteins into the host cell to establish and maintain an intracellular infection. Chlamydia is known to use T3S to facilitate invasion of host cells but many proteins in the system remain uncharacterized. The C. trachomatis protein CT584 has previously been implicated in T3S. Thus, we analyzed the CT584 ortholog in C. pneumoniae (Cpn0803) and found that it associates with known T3S proteins including the needle-filament protein (CdsF), the ATPase (CdsN), and the C-ring protein (CdsQ). Using membrane lipid strips, Cpn0803 interacted with phosphatidic acid and phosphatidylinositol, suggesting that Cpn0803 may associate with host cells. Crystallographic analysis revealed a unique structure of Cpn0803 with a hydrophobic pocket buried within the dimerization interface that may be important for binding small molecules. Also, the binding domains on Cpn0803 for CdsN, CdsQ, and CdsF were identified using Pepscan epitope mapping. Collectively, these data suggest that Cpn0803 plays a role in T3S.