Abstract
Currently, NICE recommends the use of faecal immunochemical test (FIT) at faecal haemoglobin concentrations (f-Hb) of 10μg Hb/g faeces to stratify for colorectal cancer (CRC) risk in symptomatic populations. This f-Hb cut-off is advised across all analysers, despite the fact that a direct comparison of analyser performance, in a clinical setting, has not been performed. Two specimen collection devices (OC-Sensor, OC-S; HM-JACKarc, HM-J) were sent to 914 consecutive individuals referred for follow up due to their increased risk of CRC. Agreement of f-Hb around cut-offs of 4, 10 and 150µg Hb/g faeces and CRC detection rates were assessed. Two OC-S devices were sent to a further 114 individuals, for within test comparisons. A total of 732 (80.1%) individuals correctly completed and returned two different FIT devices, with 38 (5.2%) CRCs detected. Median f-Hb for individuals diagnosed with and without CRC were 258.5 and 1.8µg Hb/g faeces for OC-S and 318.1 and 1.0µg Hb/g faeces for HM-J respectively. Correlation of f-Hb results between OC-S/HM-J over the full range was rho=0.74, p<0.001. Using a f-Hb of 4µg Hb/g faeces for both tests found an agreement of 88.1%, at 10µg Hb/g faeces 91.7% and at 150µg Hb/g faeces 96.3%. A total of 114 individuals completed and returned two OC-S devices; correlation across the full range was rho=0.98, p<0.001. We found large variations in f-Hb when different FIT devices were used, but a smaller variation when the same FIT device was used. Our data suggest that analyser-specific f-Hb cut-offs are applied with regard to clinical decision making, especially at lower f-Hb.
Highlights
Developing and refining the performance of diagnostics tests is crucial in improving both the efficiency of clinical care pathways and the patient experience.The use of faecal immunochemical testing (FIT) for detecting occult blood in faeces is currently recommended for both symptomatic testing and asymptomatic colorectal cancer (CRC) screening, as its superior sensitivity and specificity compared to previous methodologies of detecting occult blood is increasingly evidenced[1,2,3,4,5].There are a number of manufacturers who produce FIT assay kits to measure faecal haemoglobin concentration (f-Hb), and these all have unique patented systems
Two FIT kits were sent to a 1030 individuals (914, OCS/HM-J, 116 OC-S/OC-S) investigated within a two week wait setting as described previously[4]
Results were reported guided by the FITTER guidelines for reporting faecal haemoglobin concentrations (f-Hb) levels[17,18,19] and STARD guidelines, quality control materials were utilised, and quality management procedures were in line with UKAS 15189 standards
Summary
Developing and refining the performance of diagnostics tests is crucial in improving both the efficiency of clinical care pathways and the patient experience.The use of faecal immunochemical testing (FIT) for detecting occult blood in faeces is currently recommended for both symptomatic testing and asymptomatic colorectal cancer (CRC) screening, as its superior sensitivity and specificity compared to previous methodologies of detecting occult blood is increasingly evidenced[1,2,3,4,5].There are a number of manufacturers who produce FIT assay kits to measure faecal haemoglobin concentration (f-Hb), and these all have unique patented systems. A few studies have been carried out that directly compare analyser performance in healthcare settings These have been performed within population screening programmes in Europe, and the importance of comparing quantitative FIT tests before selecting one for population screening has been highlighted[7]. Given the capacity issues faced by colonoscopy services and the potential unnecessary requirement for invasive investigation for many patients the use of FIT to risk stratify is highly beneficial. Pathways of this type are being recommended and implemented across the country with little understanding of the optimal cut-offs for referral or the potential differences in referral patterns the use of different assays may create. Utilising the “Getting FIT” study[4] we aimed to determine a) the diagnostic yield for CRC of pre-specified cut-offs for two commonly used FIT assays; and b) the inter-assay f-Hb variability
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