An evaluation of ten external quality assurance scheme (EQAS) materials for the faecal immunochemical test (FIT) for haemoglobin

Abstract

ObjectivesExternal quality assessment schemes (EQAS) are being established worldwide to support the faecal immunochemical test (FIT) for haemoglobin (Hb). FIT is widely used as a screening test for colorectal cancer and increasingly in assessment of patients presenting with symptoms. EQA for FIT is provided in several matrices, each unique to the individual scheme. These include Hb suspended in a faecal-like matrix, lyophilised samples and liquid samples. The aim of this study was to evaluate commercially available EQAS and assess their suitability for use.MethodsTen EQAS provided material for the study. EQA samples were analysed on four quantitative FIT systems. 15 faecal-like matrix samples were loaded per concentration per FIT system. Reconstituted lyophilised samples were examined five times on three separate occasions and liquid samples were examined 10 times per concentration per FIT system. The coefficient of variation (CV) was calculated per concentration of EQA for each FIT system.ResultsResults from faecal-like matrix schemes had a higher median CV (12.4–19.0%) when compared to those from schemes providing liquid matrices (0.8–2.3%). The spread of CV values was also higher for results from faecal-like matrix schemes with an interquartile range (IQR) 4.4–24.0% vs. liquid IQR range of 0.3–2.5%.ConclusionsHb results from faecal-like matrices, whilst more aligned to a patient or participant sample, are prone to pre-examination variation so do not assess the analytical accuracy of a FIT system. Liquid matrices are not prone to pre-examination variation and are better able to assess the accuracy of a FIT system.

Assessment of the analytical performance of point-of-care faecal immunochemical tests for haemoglobin

“…Using aqueous EQA limits the preanalytical variation which can arise from loading the sampling devices with faecal-like material used by some EQA schemes. 10 Samples were stored at 4 C upon receipt and brought to room temperature for at least 30 min before reconstitution following the manufacturer's instructions.…”

Assuring the quality of examinations using faecal immunochemical tests for haemoglobin (FIT)

“…The publications discussed here [8,10] provide further interesting insights to improve the state-of-the-art of testing for the presence of Hb in faeces: further studies are required to continue this work. Thankfully, the Working Group on FIT of the Scientific Division of the International Federation of Clinical Chemistry and Laboratory Medicine are actively pursuing strategies to improve the harmonisation of FIT systems.…”

“…The application of currently available EQAS across four FIT systems was also investigated [10]. Results of EQAS challenges usually give data on comparative bias between systems since the traditional view is that, while IQC monitors the imprecision of examinations (and also gives information on sudden or gradual shifts in performance), EQAS should be providing an assessment of bias with respect to the same and other methods.…”

“…In addition to assessing transferability of IQC materials across FIT systems discussed above [8] and comparing the examination performance characteristics of four FIT systems [9], the research group have studied this aspect of the quality assurance of quantitative FIT. The rationale for the study was that, since EQAS are being established worldwide to support FIT examinations, the suitability of the materials currently provided by commercially available EQAS should be assessed [10]. Further, the EQAS challenges available for FIT do come in a variety of formats, each unique to the individual EQAS, which might make it difficult for medical laboratories to decide in which one or more EQAS to participate.…”

Assuring the quality of examinations using faecal immunochemical tests for haemoglobin (FIT)

“…The application of currently available EQAS across four FIT systems was also investigated [10]. Results of EQAS challenges usually give data on comparative bias between systems since the traditional view is that, while IQC monitors the imprecision of examinations (and also gives information on sudden or gradual shifts in performance), EQAS should be providing an assessment of bias…”