Speakers
Alex Read
Penny Cliff
Joanne Morris
Southern
Session Chair: Alex Read
11.00am Penny Cliff, Performance evaluation of the Viasure PCR assay for the diagnosis of mpox: A multicentre study
11.30am Joanne Morris, Measurement of free light chain - technical challenges and clinical utility
12.00am Isabelle Piec, Measuring FGF23 in patients treated with Burosumab
The Southern Region is home to a plethora of specialist labs that are often at the frontier of responding to disruptive changes. These include rapid responses to outbreaks of infectious disease like Mpox or vast overhauls in conventional practice in response to clinical guidelines. This session provides a illuminative glimpse into our response to these challenge across laboratory medicine.
Performance evaluation of the Viasure PCR assay for the diagnosis of mpox: A multicentre study - Penny Cliff
Following the first laboratory confirmed case of mpox in England in early May 2022, it soon became apparent that there was a rapidly evolving outbreak within the GBMSM community, with the majority of cases detected in London. Virology Laboratories from three major teaching hospitals in London worked together to verify a newly available commercial realtime PCR kit (Viasure MPXV PCR) for use within their departments. 217 paired samples were collected, one of each pair tested by the Rare and Imported Pathogens Laboratory and the other on the Viasure PCR. Viasure results were concordant with RIPL for 91.2% of samples, and the assay demonstrated good accuracy (88.6 – 94.7%), diagnostic sensitivity (89.7 – 100%), PPV (87.2 – 96.3%), and NPV (87.9 – 100%). The collaborative approach allowed rapid and robust verification of the assay, providing the laboratories with a timelier alternative to sending samples to the reference laboratory.
Measurement of free light chain - technical challenges and clinical utility - Joanne Morris
The analysis of free light chains in clinical laboratories to support the diagnosis and treatment monitoring of Myeloma has evolved over 6 decades. From urine analysis for Bence Jones Protein using gel electrophoresis in the 1950s to the launch of the first commercial assay for serum free light chain measurement in 2001. This talk will describe the biochemistry of free light chains, the benefits and challenges of the different methodologies available in laboratories today. I will also describe the complexity of clinical interpretation of results, highlighting relevant national guidance, recently developed diagnostic tools for clinicians and testing advice for laboratories.
Measuring FGF23 in patients treated with Burosumab - Isabelle Piec
X-linked hypophosphatemia (XLH) is a hereditary, progressive, and lifelong condition that affects both children and adults with an incidence of 1/20,000. The disease is characterised by elevated circulating fibroblast growth factor 23 (FGF23). High FGF23 induces hypophosphatemia, reduced 1,25 Dihydroxyvitamin D concentration and defective bone mineralisation (osteomalacia/rickets). Treatment with burosumab, a fully human IgG1 monoclonal antibody that binds intact FGF23 (iFGF23) decreases rickets severity, prevents enthesiopathy, improves growth, increases serum phosphate and 1,25(OH)2D as well as the ratio of tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR). However, symptoms in some patients are not fully resolved suggesting some free iFGF23 may remain circulating and acting in these patients while concomitantly paediatricians are keen to measure FGF23 to avoid overtreatment with associated potential calcification risk.
Measuring FGF23 in patients treated with burosumab is problematic as we and others have observed interference (false positive) of the therapeutic antibody in multiple assays (Immutopics c-terminal FGF23 [cFGF23], MedFrontiers and Immutopics iFGF23) while being seemingly low/normal in the DiaSorin iFGF23 (false negative).
We immunoprecipitated burosumab using magnetic A/G beads from samples obtained from treated patients. Cleanliness of the supernatant was checked by western blot and FGF23 was then measured in the supernatant using Immutopics cFGF23. This ELISA measures both intact and cFGF23. We also analysed for the presence of cFGF23 alone by western blot using anti-cFGF23 (186-206) antibody (Quidel). We were only able to detect intact FGF23 by these methods suggesting that either there is no free cFGF23 present or the technique is not sensitive enough to detect the circulating concentration of cFGF23 fragment in patients treated with burosumab.
The presence of sufficient circulating intact FGF23 and absence of cFGF23 in patients treated with burosumab could explain the persistence of some symptoms of XLH. In future we may be able to correlate outcome with circulating concentrations of free iFGF23. The changes in efficacy of burosumab in older children and adolescents may partly reflect a requirement for an increased dose of burosumab to fully capture iFGF23.
Alexander Read is a Senior Clinical Scientist in Biochemistry at North West London Pathology primarily based within the SAS Endocrine and Renin/Aldosterone labs in Charing Cross Hospital, and has worked in Clinical Biochemistry since 2014. In addition he is an Education lead for Biochemistry at Imperial College Healthcare Trust and the current meetings secretary for the ACB Southern Region.
Dr Penny Cliff is the Lead Scientist for the Synnovis Infection Sciences Laboratory based at Guy’s and St Thomas’ Hospital in London. Areas of interest are respiratory infections, sexually transmitted infections and the use of next generation sequencing technologies in the advancement of infectious disease diagnosis. She has been on the Microbiology Professional Committee of the ACB for 10 years, most recently in the role of Scientific Committee and Clinical Practice representative.
Joanne is a Consultant Clinical Scientist in Biochemistry with a specialist interest in protein analysis. She studied Biochemistry and Molecular Biology at Manchester University, before beginning her training as a Clinical Scientist in Biochemistry in south London in 1995 gaining an MSc in Clinical Biochemistry and later FRCPath. Her training included time with Dr Joanna Sheldon at the Protein Reference Unit at St George’s Hospital and with Dr Bruce Muller at Charing Cross Hospital, where her interest in protein analysis began. Joanne was the Lead Clinical Scientist in the Proteins Laboratory at the Royal Free Hospital, she has also worked at Epsom and St Helier Hospital in Special Chemistry. She has been a consultant scientist since 2013 and joined South West London Pathology in the Protein reference Unit in February 2020. She particular interest in the clinical utility of serum free light chains and specialist protein analysis.
Isabelle obtained her PhD from the University of Auvergne (France) investigating the proteomics of skeletal muscle healthy aging. She joined the University of East Anglia School of Biological Sciences in 2007 and moved to the Medical School, BioAnalytical Facility, in 2013. She has over 20 years’ experience in musculoskeletal research encompassing muscle ageing and regeneration and metabolic bone diseases. In her current role, she combines research and laboratory management. Her research focuses on the metabolic processes that underpin bone diseases with a specific interest in the Wnt/b-catenin signalling pathway (OPG/sRANKL/Sclerostin/FGF23). She specialises in molecular biology and biochemistry and has a keen interest in quality assurance and assay development, evaluation and harmonisation.