Optimizing the diagnostic performance of neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice

The detection of neural antibodies in patients with paraneoplastic and autoimmune encephalitis has majorly advanced the diagnosis and management of neural antibody-associated diseases. Although testing for these antibodies has historically been restricted to specialized centers, assay commercialization has made this testing available to clinical chemistry laboratories worldwide. This improved test accessibility has led to reduced turnaround time and expedited diagnosis, which are beneficial to patient care. However, as the utilization of these assays has increased, so too has the need to evaluate how they perform in the clinical setting. In this chapter, we discuss assays for neural antibody detection that are in routine use, draw attention to their limitations and provide strategies to help clinicians and laboratorians overcome them, all with the aim of optimizing neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice.

Statin-associated autoimmune myopathy: A distinct new IFL pattern can increase the rate of HMGCR antibody detection by clinical laboratories

BACKGROUND AND OBJECTIVE

Statin-associated autoimmune myopathy (SAAM) with anti-HMGCR antibodies has recently been described. Several specific immunoassays are in use to detect HMGCR antibodies. In the course of systematic autoantibody screening we recognized a new distinct IFL staining pattern on rat liver sections that regularly coincided with anti-HMGCR antibodies. In this study we investigated whether this new IFL pattern is specifically associated to statin-associated autoimmune myopathy and corresponds to anti-HMGCR antibodies.

PATIENTS AND METHODS

Twenty-three patients positive for anti-HMGCR antibodies (14 diagnosed with SAAM) were investigated for anti-HMGCR antibodies by two ELISA assays and confirmed by immmunoblot. HMGCR associated liver IFL pattern (HALIP) was detected by indirect IFL and the reactivity against HMGCR was confirmed by immunoabsorption using purified human HMGCR antigen. 90 patients with other autoimmune diseases and 45 non-autoimmune statin treated patients were studied as controls.

RESULTS

21 out of 23 (91%) anti-HMGCR positive patients were HALIP positive. The staining was completely and specifically removed by immunoabsorption with human purified HMGCR. None of the control sera from autoimmune patients or non-autoimmune statin treated subjects was positive for HALIP. Statistical concordance between HALIP and anti-HMGCR antibody specific tests was 98.7%, kappa 0.95.

CONCLUSIONS

A new and distinct IFL staining pattern (HALIP) is associated to HMGCR associated myopathy. Absorption and concordance studies indicate that the antigen recognized in the liver by HALIP is HMGCR or a closely related protein. Awareness of this new pattern can help to detect HMGCR autoantibodies in statin treated patients tested for autoimmune serology.

Evaluation of PCR-reverse blot hybridization assay, REBA Sepsis-ID test, for simultaneous identification of bacterial pathogens and mecA and van genes from blood culture bottles

Background

The aim of this study was to evaluate a newly developed PCR-based reverse blot hybridization assay (PCR-REBA), REBA Sepsis-ID (M&D, Wonju, Korea), to rapidly detect the presence of bacteremia and antimicrobial resistance gene in blood culture samples.

Methods

One thousand four hundred consecutive blood culture samples from patients with a delta neutrophil index greater than 2.7% were selected from March to July in 2013. Three hundred positive and 1,100 negative for bacterial growth in blood culture bottles samples were tested by conventional and real-time PCR-REBA, respectively.

Results

The overall agreement between the conventional identification test and the REBA Sepsis-ID test was 95.3% (286/300). Agreement for gram-positive bacteria, gram-negative bacteria, fungi, and polymicrobials was 94.5% (190/201), 97.3% (71/73), 100% (14/14), and 91.7% (11/12), respectively. The detection rate of the mecA gene from methicillin-resistant Staphylococcus isolates was 97.8% (90/92). The vanA gene was detected in one blood culture sample from which vancomycin-resistant Enterococcus was isolated. When the cycle threshold for real-time PCR was defined as 30.0, 2.4% (26/1,100) of negative blood culture samples tested positive by real-time PCR.

Conclusions

The REBA Sepsis-ID test is capable of simultaneously and quickly detecting both causative agents and antimicrobial resistance genes, such as mecA and van, in blood culture positive samples.