Faculty Bibliography

OBJECTIVES/OBJECTIVE:To identify predictors of positive computed tomographic (CT) yield and to measure the impact of CT yield on the disposition of patients referred for computed tomography after presenting to an emergency department with nontraumatic abdominal pain. MATERIALS AND METHODS/METHODS:Computed tomographic reports, laboratory data, and emergency department and hospital records were retrospectively analyzed in 604 consecutive patients undergoing CT examinations. Computed tomographic yield was correlated to age, gender, leukocyte count, specified precomputed-tomography clinical diagnosis, and patient disposition. RESULTS:Forty-eight percent of CT scans (298 of 621) had positive results. Computed tomographic results were positive in 76% of children (13 of 17) and 47% of adults (285 of 604) (P < .03) and in 45% of female patients (155 of 343) and 51% of male patients (143 of 278) (P < .2). Fifty-two percent of CT scans (223 of 426) with and 38% (75 of 195) without specified precomputed-tomography clinical diagnoses had positive results (P < .01). Fifty-eight percent of CT scans (161 of 278) with elevated and 40% of CT scans (135 of 336) with normal patient leukocyte counts had positive results (P < .001). Sixty-seven percent of patients (171 of 256) admitted and 35% of patients (127 of 365) discharged had positive CT results (P < .001). Computed tomography revealed unsuspected diagnoses in 27% of patients (165 of 621). Thirteen percent of patients (12 of 93) without any clinical predictors for positive CT yield were admitted after positive CT results. Thirty-eight percent of patients (104 of 273) with clinically suspected diagnoses requiring admission were discharged after negative CT results. CONCLUSION/CONCLUSIONS:Clinical indicators of positive CT yield include pediatric age, leukocytosis, and a specified precomputed-tomography diagnosis. Positive CT results are a predictor for hospital admission. In one quarter of cases, computed tomography identifies clinically unsuspected diagnoses and thereby adds information important for patient management, even after clinical evaluation.

Hepatitis delta virus (HDV) contains a viroid-like circular RNA that is presumed to replicate via a rolling circle replication mechanism mediated by cellular RNA polymerases. However, the exact mechanism of rolling circle replication for HDV RNA and viroids is not clear. Using our recently described cDNA-free transfection system (L. E. Modahl and M. M. Lai, J. Virol. 72:5449-5456, 1998), we have succeeded in detecting HDV RNA replication by metabolic labeling with [32P]orthophosphate in vivo and obtained direct evidence that HDV RNA replication generates high-molecular-weight multimeric species of HDV RNA, which are processed into monomeric and dimeric forms. Thus, these multimeric RNAs are the true intermediates of HDV RNA replication. We also found that HDV RNA synthesis is highly temperature sensitive, occurring most efficiently at 37 to 40 degrees C and becoming virtually undetectable at temperatures below 30 degrees C. Moreover, genomic HDV RNA synthesis was found to occur at a rate roughly 30-fold higher than that of antigenomic RNA synthesis. Finally, in lysolecithin-permeabilized cells, the synthesis of full-length antigenomic HDV RNA was completely resistant to high concentrations (100 microg/ml) of alpha-amanitin. In contrast, synthesis of genomic HDV RNA was totally inhibited by alpha-amanitin at concentrations as low as 2.5 microg/ml. Thus, these results suggest that genomic and antigenomic HDV RNA syntheses are performed by two different host cell enzymes. This observation, combined with our previous finding that hepatitis delta antigen mRNA synthesis is likely performed by RNA polymerase II, suggests that the different HDV RNA species are synthesized by different cellular transcriptional machineries.