Leading Edge 2022 Issue 2

www.alphalabs.co.uk 13 for independent QC if the companies are able to make it available to customers. Effects of Hb-variants were also investigated on four FIT assays. 11 of the 13 variants gave expected results while β thalassemia major (reduced β chain) gave 50% of the expected result, though as patients have regular transfusions normal Hb would likely be detected. Additionally cord blood/Hb-F is gradually replaced by adult Hb in the majority of people. The BCSP group also carried out a clinical study examining the comparability of faecal haemoglobin analysed by the 4 FIT systems (6), and the outcomes of colonoscopy. 233 patients collected a faecal sample using the 4 different sample collection bottles from the same stool before their colonoscopy, and 189 patients collected 2 samples using the Extel Hemo/HM-JACKarc system, as a comparison. At 100 µg Hb/g faeces the sensitivity for CRC and SBD was the same for all methods, though differences were seen at 10 µg/g. ‘Further work is required to understand the clinical impact of these differences to minimise them. Comparison of f-Hb results for real clinical samples and clinical outcomes is needed’. Overall, Carolyn’s conclusion was that the four analysers included in the evaluations are fit for purpose though the lack of standardisation and harmonisation of FIT testing means that differences are observed in f-Hb quantification. Current status and future plans for the UK NEQAS for Faecal Haemoglobin Finlay Mackenzie, Director of Birmingham Quality, an NHS Department within University Hospitals Birmingham Finlay defined External Quality Assessment as a retrospective assessment of quality – ‘EQA is an independent assessment of quality and is an essential component of an accredited laboratory’s governance system and assesses the performance of in-vitro diagnostic examination procedures.’ Part of the role of EQA is to assess the stability of diagnostic tests over time, this includes the Alpha Laboratories’ HM-JACKarc system, in comparison to other faecal haemoglobin (f-Hb) detection systems that are available. EQA aims to send representative patient samples to a network of national laboratories. Finlay shared his observations on the variations associated with differing f-Hb cut-offs between the National Screening Hubs and how critical it is to ensure homogeneity of a specimen for true representation. He shared his concerns about the large differences in numerical data between FIT testing methodologies, although this is not limited to f-Hb testing, as it also affects most other clinical chemistry tests, so it is a wider problem. Furthermore, the stability of samples may affect the uniformity of assessments as he expanded on the fact that biological samples may not respond in the same way all the time due to: • Tolerance limits • Manufacturing systems • Antibodies present Lastly, adapting to the clamour for ‘sanitisation’ by both patients and laboratories is also a challenge. Having a pre-filled cartridge assumes that the sample was taken correctly, and you have to take on trust that it was an accurate representative sample of the whole, real, stool. Overall, EQA aims to evaluate the entirety of the process and not just the relatively simple, well controlled parts, like the analysis itself. That said, all EQA providers aim to send easyto-use materials to laboratories in order to provide a sample type that is representative of what the laboratory routinely receives. Quantitative Faecal Hb EQA Programme Update Samantha Jones and Gareth Davies – WEQAS Samantha Jones initially shared the considerations undertaken by Weqas when setting up a new EQA programmes. A robust EQA programme should have elements of pre-analytics, analytics and post analytics where possible. Weqas also provide an educational aspect with all programmes, including case studies, educational questionnaires and sharing of best practices. Weqas provides organic material which closely mimics human faeces, spiked with human whole blood (0-800 µg Hb/g). Material at a range of Hb concentrations is prepared to cover the pathological and analytical range for FIT including samples at or near the clinical cut-off of 10 ug Hb /g used for symptomatic testing pathways and the higher cut offs used in asymptomatic population screening programmes. Weqas surveyed participants to ask what they would like to see within a Faecal Hb EQA Programme, taking these views into consideration during development. Samantha discussed NICE guidelines and recommendations for FIT testing, and the scope and purpose of the Weqas EQA programme. The programme aims, in the first instance, to assess analytical performance across all current platforms and ultimately to assess pre-analytical aspect of patient testing. The HM-JACKarc system is often used to evaluate spiked Hb volumes, stability and percentage recovery of samples. Weqas provides samples for all FIT testing systems including Alpha Laboratories’ HM-JACKarc system. Samantha briefly discussed the work of the IFCC Fecal Immunochemical Testing Working Group (WG-FIT), sharing updates and recommendations. These include looking at the performance of different matrices. Poor reproducibility for faecal like material has been observed due to variability in test pickers/people/material, although faecal like matrices assess both pre-analytical & analytical imprecision. Weqas material has been shown to have CVs between 10-20% at concentrations of 50 to 450 ug Hb / g, with good recovery vs spiked concentration. Weqas future developments include potentially issuing patient samples periodically, auditing practices against current guidelines and also assess pre-analytics e.g. under / overloading of samples For more information, visit our website faecal-immunochemical-test.co.uk Please see the full article with references at www.faecal-immunochemical-test.co.uk/ug2022

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