Molekularpathologische Infektionsdiagnostik in der orthopädischen Pathologie

Synovial Tissue Biopsy Collection by Rheumatologists: Ready for Clinical Implementation?

Synovial tissue from arthritis patients is increasingly used for both basic pathophysiological and clinical translational research. This development has been spurred by the development of biotechnological techniques for analysis of complex tissues and the validation of ultrasound guided biopsies for easier tissue sampling. This increasing use of synovial tissue raises questions on standardization of methodologies for tissue processing and cellular & molecular analyses. Furthermore, it raises the question if synovial tissue biopsy analysis may be more widely implemented in clinical practice, what are the methodological hurdles for implementation and what are the lessons that can be learned from previous experience. This will be the focus of this review.

In MALDI-Mass Spectrometry Imaging on Formalin-Fixed Paraffin-Embedded Tissue Specimen Section Thickness Significantly Influences m/z Peak Intensity

BACKGROUND

In matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) standardized sample preparation is important to obtain reliable results. Herein, the impact of section thickness in formalin-fixed paraffin embedded (FFPE) tissue microarrays (TMA) on spectral intensities is investigated.

PATIENTS AND METHODS

TMAs consisting of ten different tissues represented by duplicates of ten patients (n = 200 cores) are cut at 1, 3, and 5 μm. MSI analysis is performed and mean intensities of all evaluable cores are extracted. Measurements are merged and mean m/z intensities are compared.

RESULTS

Visual inspection of spectral intensities between 1, 3, and 5 μm reveals generally higher intensities in thinner tissue sections. Specifically, higher intensities are observed in the vast majority of peaks (98.6%, p < 0.01) in 1 μm compared with 5 μm sections. Note that 28.4% and 2.1% of m/z values exhibit a at least two- and threefold intensity difference (p < 0.01) in 1 μm compared to 5 μm sections, respectively.

CONCLUSION

A section thickness of 1 μm results in higher spectral intensities compared with 5 μm. The results highlight the importance of standardized protocols in light of recent efforts to identify clinically relevant biomarkers using MSI. The use of TMAs for comparative analysis seems advantageous, as section thickness displays less variability.

Are There Benefits In Early Diagnosis Of Prosthetic Joint Infection With Multiplex Polymerase Chain Reaction?

Purpose Identification of bacteria and susceptibility are fundamental in periprosthetic joint infection (PJI). Especially in the case of systemic inflammatory response syndrome (SIRS) rapid detection of pathogens is essential for proper therapy. Bacterial cultures are time consuming. The polymerase chain reaction (PCR) is a non-culture molecular method and is able to rapidly identify pathogens and their resistance genes. Multiplex PCR (mPCR) can amplify several different DNA sequences simultaneously. The aim of this study was to show the value of mPCR for early diagnosis of PJI.

Methods 60 patients undergoing total hip or knee revisions were recruited in this prospective single-centre-study. Three groups were created: 26 patients with aseptic loosening (negative control), 26 patients with chronic PJI, and 8 patients with acute PJI/SIRS. We compared the results of joint aspirates obtained intraoperatively investigated by mPCR with the microbiology results of tissue specimens.

Results The overall sensitivity of mPCR was 78.8% (95% CI, 61.1 - 91.0%), the specificity was 100% (95% CI, 87.2 - 100%), the negative predictive value was 79.4% (95% CI, 62.1 - 91.3%), the positive predictive value was 100% (95% CI, 86.8 - 100%), and the overall accuracy was 88.3% (95% CI, 77.4 - 95.2%). The overall accuracy in acute infections/SIRS (87.5%) was greater than in late chronic PJI (76.9%). In PJI the mPCR was able to provide the results within 5 hours whereas the mean time for cultures was 6.4 days.

Conclusions Multiplex PCR is a reliable diagnostic tool in PJI management, especially in acute cases complicated with SIRS. Early diagnosis within several hours is possible, targeted antibiotic treatment can be started promptly.