MALDI-TOF MS performance compared to direct examination, culture, and 16S rDNA PCR for the rapid diagnosis of bone and joint infections.

The rapid identification of bacterial species involved in bone and joint infections (BJI) is an important element to optimize the diagnosis and care of patients. The aim of this study was to evaluate the usefulness of matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS) for the rapid diagnosis of bone infections, directly on synovial fluid (SF) or on crushed osteoarticular samples (CS). From January to October 2013, we prospectively analyzed 111 osteoarticular samples (bone and joint samples, BJS) from 78 patients in care at the University Hospital of Rennes, France. The diagnosis procedure leading to the sample collection was linked to a suspicion of infection, inflammatory disease, arthritis, or for any bone or joint abnormalities. Standard bacteriological diagnosis and molecular biology analysis [16S rRNA polymerase chain reaction (PCR) and sequencing] were conducted. In addition, analysis by MALDI-TOF MS was performed directly on the osteoarticular samples, as soon as the amount allowed. Culture, which remains the gold standard for the diagnosis of BJI, has the highest sensitivity (85.9 %) and remains necessary to test antimicrobial susceptibility. The 16S rDNA PCR results were positive in the group with positive BJI (28.6 %) and negative in the group without infection. Direct examination remains insensitive (31.7 %) but more effective than MALDI-TOF MS directly on the sample (6.3 %). The specificity was 100 % in all cases, except for culture (74.5 %). Bacterial culture remains the gold standard, especially enrichment in blood bottles. Direct analysis of bone samples with MALDI-TOF MS is not useful, possibly due to the low inoculum of BJS.

Current role of CT and whole body MRI in multiple myeloma.

Radiology of bone lacunae can help differentiate between smouldering and symptomatic myeloma. CT seems to be more apt for this purpose than a standard X-ray but appropriate principles must be applied when performing and reading it. Lesions visible in an MRI above all allow myelomas to be monitored during treatment. Because of the radiation dose, whole body CT must be performed with a slice thickness of 2mm, increments of 1.5 and intensity of 40mAs. It should be read associating the reading of the axial slices with reading the mean coronal and sagittal projections of a thickness of 2cm. Whole body MRI must associate T1-weighted sagittal, STIR coronal and b-800 diffusion-weighted axial sequences. Changes in the disease correlate with changes in the diffusion, STIR and T1-weighted images interpreted together. While whole body CT has a place in clinical routine, the indication for whole body MRI still needs to be clarified and has yet to take its place in research protocols.