Measurement of Complement Activation via Plasma-Soluble C5b-9 Comparison with Terminal Complement Complex Staining in a Series of Kidney Biopsies.

INTRODUCTION: With the emergence of therapeutic complement inhibitors, there is a need to identify patients with complement-driven inflammation. C5b-9 is the terminal product of the three complement pathways and therefore a marker of total complement activation. We present a pilot study which aims to assess whether plasma soluble C5b-9 (sC5b-9) correlates with terminal complement complex (TCC) staining in kidney tissue. The secondary aim was to assess the utility of plasma sC5b-9 as part of routine workup in kidney patients undergoing kidney biopsy. METHODS: Thirty-seven patients undergoing kidney biopsy had plasma sC5b-9 and TCC staining on kidney tissue performed. Additional blood markers including creatinine, haemoglobin, CRP, factor H, factor I, and midkine levels were also taken. These parameters were correlated with the histological diagnoses. Patients were divided into a diseased group (n = 31) and a control group (n = 6) consisting of transplanted kidneys with minor or no changes. Of the biopsies in the control group, 50% were performed as per protocol, and the other 50% were performed due to clinical need. RESULTS: There was no correlation found between plasma sC5b-9 and TCC kidney staining. Elevated sC5b-9 levels were found in a heterogeneous group of patients but were associated with higher CRP and lower haemoglobin levels. Overall, there was more TCC kidney staining in the diseased group compared with the control group, and a trend was observed of diabetic, primary membranous nephropathy, and amyloidosis patients having more intense glomerular and peritubular/interstitial staining. CONCLUSION: Plasma sC5b-9 as a marker of total complement activation does not correlate with TCC kidney staining. This discordance suggests that plasma sC5b-9 and TCC staining are distinct markers of disease. TCC staining reflects chronicity and tissue deposition of complement over time. Conversely, plasma sC5b-9 concentrations change rapidly and reflect systemic complement activation. Complement activation was present in a heterogeneous group of kidney disease, indicating the underlying role of complement in many disorders.

Anti-tissue transglutaminase (tTG) screening using relative light units to identify IgA deficiency.

IgA deficiency is more common in patients with coeliac disease (CD). Total IgA levels are often recommended as part of first line coeliac testing along with anti-tissue transglutaminase (tTG) IgA, to identify these patients and reduce falsely negative results. This study aimed to identify patients with complete IgA deficiency by determining a cut-off threshold on chemiluminescent tTG IgA testing. A chemiluminescent assay QUANTA Flash h-tTG was reviewed using the BIO-FLASH automated platform. tTG relative light units (RLU) were analysed in relation to total IgA levels. Correlation analysis was performed and distributions of tTG RLU were compared between the IgA deficient and IgA detectable groups, and ROC analysis was performed to identify a suitable threshold. A total of 203 samples were reviewed in our initial cohort. There was a strong correlation between IgA and tTG RLU levels (Pearson correlation coefficient 0.495, p<0.001). There was a statistically significant difference of 170.57 RLU between the means of the IgA deficient and IgA detectable group (p<0.001, 156.50-184.64). A receiver operating characteristic (ROC) curve was generated with area under the curve of 0.997. A cut-off of less than 300 tTG RLU for identification of IgA deficiency was chosen, which had a sensitivity and specificity of 100% and 98.9%, respectively. A prospective validation cohort was conducted which confirmed the initial results. Our study has validated an algorithm to identify complete IgA deficiency by implementing a threshold of 300 RLU during tTG IgA testing by chemiluminescent immunoassay. This approach resulted in a sensitivity of 100% to detect patients with complete IgA deficiency. Widespread uptake would result in improved workflow, workload and turnaround time, and reduce the need for unnecessary blanket testing of total IgA in the screening for coeliac disease.

Laryngoceles with airway compromise complicating mucous membrane pemphigoid.

Mucous membrane pemphigoid (MMP) encompasses a group of autoantibody-mediated, subepithelial blistering diseases, which primarily affect mucosal surfaces including oral, ocular, skin, genital, nasopharyngeal and oesophageal sites. We present a first description of laryngoceles as a manifestation of mucous membrane pemphigoid resulting in dynamic airway closure. Mucosal injury at other sites had previously resulted in pathergy and localised cicatrisation. We discuss successful combined medical and transcutaneous surgical intervention designed to avoid tracheostomy and minimise iatrogenic laryngeal cicatrisation.