Effect of multiple loading FIT sample collection devices on faecal haemoglobin concentration

BACKGROUND

Faecal immunochemical tests (FIT) are routinely used in colorectal cancer (CRC) screening programmes around the world. More recently, quantitative FIT has been recommended to help triage patients presenting to primary care with symptoms suggestive of CRC. Participants collect faecal samples using sampling probes which are inserted into sample collection devices (SCDs) containing preservative buffer. The SCDs have an internal collar designed to remove excess sample. The aim of this study was to investigate the impact of multiple loading on faecal haemoglobin concentration (f-Hb) using SCDs of four FIT systems.

METHODS

Pools of f-Hb negative samples were spiked with blood, homogenised and loaded into SCDs 1, 3 and 5 times, with insertion of the sampling probes into the SCDs with and without mixing between loads. The f-Hb was measured using the relevant FIT system. The percentage change in f-Hb for multiple loads was compared with a single load for each system for the mixed and unmixed groups.

RESULTS

The p values show a significant difference (p < 0.05) in the mass and f-Hb for the mixed and unmixed group, for 1-3 and 1-5 loads for all systems. The median percentage change in f-Hb for the mixed is higher than the unmixed group.

CONCLUSION

This study showed that multiple loading does significantly increase the f-Hb in the SCDs.

Faecal immunochemical tests for haemoglobin: Analytical challenges and potential solutions

Quantitative faecal immunochemical tests for haemoglobin (FIT) are being used increasingly around the world in colorectal cancer screening programmes, and in patients presenting with lower bowel symptoms to determine who should proceed to further bowel visualisation investigations, usually colonoscopy. The clinical utility of FIT is well reported. There are a number of analytical challenges including pre-analytical variation, difficulty setting up external quality assessment schemes, access to third party internal quality control material and a lack of standardisation or harmonisation of FIT methods. Here we report the work of the International Federation of Clinical Chemistry FIT Working Group. We provide an overview of the main pre-analytical variables; discuss different approaches to external quality assurance of FIT; propose a solution to third party internal quality assurance materials and summarise the challenges of standardisation and harmonisation of FIT.

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

BACKGROUND

The faecal immunochemical test (FIT) detects the presence of haemoglobin (Hb) in faeces. It is used as a screening tool for colorectal cancer (CRC) and increasingly to triage patients presenting with symptoms of CRC. A number of quantitative point-of-care (POC) FIT systems marketed for professional use and intended for use in a clinical setting are available. Here we reviewed the POC FIT systems available; three (Eurolyser Cube, OC-Sensor iO and QuikRead go) were evaluated to assess their performance against manufacturers' claims and suitability for use in a clinical setting.

METHODS

The analytical evaluation of the POC FIT systems was undertaken using Hb lysates, patient samples and an external quality assessment sample. The evaluation focused on linearity, recovery, imprecision, prozone effect, Hb variant detection and suitability for use in a clinical setting.

RESULTS

All three POC FIT systems performed to their manufacturer's claims and demonstrated good analytical performance with acceptable linearity, recovery, within- and between-run imprecision. The QuikRead go and OC-Sensor iO were able to accurately detect samples with results above their measuring range. However, because of a prozone effect the Eurolyser Cube gave falsely low results when using high concentrations of Hb. The QuikRead go performed best in the usability assessment due to portability and timeliness of result.

CONCLUSION

Each system performed according to their manufacturers' claims. The QuikRead go and OC-Sensor iO are suitable for use. The Eurolyser Cube is not recommended because of the risk of falsely low results.

Analytical evaluation of four faecal immunochemistry tests for haemoglobin

Objectives

Faecal immunochemical tests (FIT) for haemoglobin (Hb) are being used in the investigation of colorectal cancer. These tests use antibodies raised to the globin moiety of human Hb. Here, four automated quantitative FIT systems (HM-JACKarc, NS-Prime, OC-Sensor PLEDIA and SENTiFIT 270) are evaluated analytically to confirm whether the performance of the systems meet the manufacturers' claims.

Methods

Assessment of the analytical performance of the FIT systems was undertaken using Hb lysates, real patient samples and external quality assessment (EQA) samples. This analytical assessment focused on detection characteristics, imprecision, linearity, prozone effect, recovery and carryover.

Results

All four methods demonstrated good analytical performance, with acceptable within- and between-run imprecision, good recovery of f-Hb and limited carryover of samples. They also all show good linearity across the range of concentrations tested. The results of EQA samples showed different variations from the target values (-52 to 45%), due to the absence of standardisation across the different methods.

Conclusions

All four systems are fit for purpose and have an analytical performance as documented by their manufacturers.

Setting up a service for a faecal immunochemical test for haemoglobin (FIT): a review of considerations, challenges and constraints

Quantitative faecal immunochemical tests for haemoglobin (FIT) have now been advocated by the National Institute for Care and Health Excellence (NICE: DG30) to assist in the triage of patients presenting with symptoms that suggest a low risk of colorectal (bowel) cancer. The evidence is that FIT provides a good rule out test for significant bowel disease. However, a small number of cases will be missed, and robust safety-netting procedures are required to follow up some FIT-negative patients. A range of diagnostic pathways are possible, and there is no best approach at present. Introduction of FIT requires careful consideration of the logistics of supply of devices and information to requesting sites and of transport to the laboratory. A number of FIT analytical systems are available. Three are documented as appropriate for use in assessment of patients with symptoms. However, preanalytical, analytical and postanalytical challenges remain. The methods have different specimen collection devices. The methods use polyclonal antibodies and there is no primary reference material or method to which FIT methods are standardised. Third-party internal quality control is lacking, and external quality assessment schemes have many difficulties in providing appropriate materials. Reporting of results should be done using µg Hb/g faeces units and with knowledge of the limit of detection and limit of quantitation of the analytical system used. FIT can be used successfully in an agreed diagnostic pathway, along with other clinical and laboratory information: this requires a multidisciplinary approach, providing opportunities for professionals in laboratory medicine involvement.