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To determine the incidence of missed femoral head avascular necrosis (AVN) on pelvic computed tomography (CT) performed for clinical indications other than assessment for AVN.The study was a Health Insurance Portability and Accountability Act (HIPAA)-compliant retrospective study. The picture archiving and communication system (PACS) database was queried for patients with diagnosis of femoral head AVN on magnetic resonance imaging (MRI), who also underwent pelvic multidetector CT after or30 days before the MRI examination. The MRI and CT images of 144 hips of 72 patients (39 patients with reported AVN on MRI and 33 age-matched controls; mean age = 60 years, 28 male, 44 female), were reviewed in consensus by two readers in a randomized, blinded manner. Using MRI-proven CT-visible AVN as a reference standard, the incidence of missed AVN on initial CT interpretation was determined.Readers confirmed AVN in 33 patients on the MRI images. Nine hips with AVN underwent joint replacement of the affected joint(s) prior to subsequent CT and were excluded. Forty-three MRI-proven AVN cases in 28 patients (15 bilateral, 13 unilateral) were available for analysis. The study readers diagnosed 35/43 (81%) MRI-proven AVN cases in 22/28 (79%) patients. Four of the 35 (11%) cases of MRI-proven, CT-visible AVN were prospectively reported in 3/22 (14%) patients at initial clinical interpretation, with a miss rate of 89% per hip and 86% per patient.Multidetector CT has high accuracy for detection of AVN; however, this is frequently missed as an incidental finding (89% missed in the present study). Assessment for signs of femoral AVN should be part of routine search pattern in interpretation of pelvic CT.

Summary A microattachment assay for quantitating adherence of radiolabelled Mycoplasma pneumoniae to human WiDr cell culture monolayers is described. Preincubating the WiDr cell monolayers with a protein-rich extract of M. pneumoniae inhibited the subsequent attachment of radiolabelled organisms. Competitive attachment inhibition provided a quantitative procedure to determine M. pneumoniae -binding components in the extract. The microattachment assays also measured attachment inhibition by the sialoglycoconjugates ceruloplasmin, orosomucoid and gangliosides, indicating that these reagents may be structural analogues of the mammalian cell receptor. Attachment of virulent M. pneumoniae strains to glutaraldehyde-treated monolayers was reduced approximately 60% and showed a different temperature dependence compared with untreated cells. These results suggest that maximal attachment of virulent M. pneumoniae may require two or more different receptors and binding components.

DNA chromosomic sequences from Ureaplasma urealyticum were shown, by DNA hybridization, to possess homology with Providencia stuartii urease genes. The homologous ureaplasmal DNA fragment was cloned in Escherichia coli and a DNA probe, designated IC61, was obtained. Interspecies hybridization urease-producing U. urealyticum among the Mollicutes. Genetic homology shown between the IC61 probe and urease genes from Campylobacter pylori, E. coli and P. stuartii suggests that (1) the cloned DNA fragment from U. urealyticum contains urease encoding sequences, and that (2) the urease genes possess conserved sequences among phylogenetically distant prokaryotes.