Result card
|
English
No adaptation help available for this domain
|
Authors: Mirjana Huic, Eleftheria Karampli, Silvia Florescu, Cristian Vladescu
Internal reviewers: Antonio Migliore, Pernilla Östlund, Frida Mowafi, Daniela d’Angela, Jesus Gonzalez
FIT (Faecal immunochemical test) is an alternative name for Immunochemical faecal occult blood test (iFOBT), a class of faecal occult blood tests. Faecal Occult Blood Tests (FOBTs) are tests for blood or blood products. They use blood as an indicator of the presence of tumour {1}.
A wide range of qualitative and quantitative iFOBT tests is presently available, with varying levels of sensitivity and specificity. They all use antibodies raised against human haemoglobin (Hb) to detect human blood present in faeces.
Similar to g FOBT, participants collect one or more stool samples. The sampling procedure varies: different sampling systems are available (wooden sticks, brushes) and samples may be applied either to a card (dry method) or to place into a vial (wet method). Samples can be analysed either using automated systems in the laboratory (for some manufacturers) or are read by the naked eye with a positive result indicated by a colour change on a strip {2}. The automated systems can be quantitative or qualitative. Qualitative tests produce a dichotomous result, with individuals categorized as either positive or negative if the amount of Hb in the faecal sample is above or below a specific analytical detection limit set by the manufacturers. In quantitative tests, specificity can be determined by the user {3}. The most frequently used values are 75 or 100 ng/mL. This is important due the fact that by increasing the positive cut-off limit, the test sensitivity and positivity rate decreases and specificity and positive predictive values for CRC detection increase. FIT kits with a visual result are designed as point-of-care devices and are qualitative. They can be adopted for use in clinical laboratories for population-based screening; however they retain a more manual approach than the automated systems.
In their report on the comparison of FITs vs. g FOBTs for population-based colorectal cancer screening in Ontario, CA {4} the FIT Guidelines Expert Panel has considered test processing in laboratories more suitable that point-of-care systems for a population-based screening program. Similarly, the NHS Centre for Evidence-based Purchasing in the UK adopted certain criteria that the iFOBTs had to meet in order to be evaluated for the CRC screening programme in the UK {5}. Only automated systems were included in the evaluation. Regarding staff requirements, more technical knowledge will be required than for gFOB tests. If the increased packing material is required to meet postal regulation, unpacking of iFOBT liquid sampling devices may take longer than for gFOBT.
Potential advantages and disadvantages of iFOBT are given in Table 1.
Table 1. Potential advantages and disadvantages of iFOBT (5)
Advantages of iFOBT |
Disadvantages of iFOBT |
Automated analysis |
Sample instability in liquid collection devices |
Specificity for human HB, reducing the number of false positive results |
Possible additional requirements for packaging of the liquid sample collection devices to meet different MSs postal regulation |
Increased sensitivity to human Hb |
Cost of the test |
Ability to adjust the cut-off Hb concentration in qualitative iFOBTs (except Hem-SP/MagStream HT method as qualitative method) |
|
Three iFOBT are presented here, as three analytical platforms using the three sample collection devices: OC-Sensor/OC-Sensor Diana & OC-Sensor Micro, Hem-SP/MagStream HT, FOB Gold/SENTiFOB analyser. In brief {6}:
The FOB Gold use an antigen-antibody agglutination reaction between human haemoglobin and polyclonal anti-human haemoglobin antibodies coated on polystyrene particles. The total reading time is 8 minutes, with speed of analyses of 75 tests/hr
Some of products characteristics are presented in Table 2.
Table 2. Product characteristics of OC-Sensor/OC-Sensor Diana & OC-Sensor Micro, Hem-SP/MagStream HT, FOB Gold/SENTiFOB analyser {5-9}.
Product characteristics |
OC-Sensor/OC-Sensor Diana & OC-Sensor Micro |
Hem-SP/MagStream HT |
FOB Gold/SENTiFOB analyser |
Analyser name |
OC-Sensor Diana OC-Sensor Micro |
MagStream HT |
SENTiFOB |
Manufacturer |
Eiken Chemical Co., Tokyo, Japan, www.eiken.co.jp/en/company/index.html |
Fujirebio Inc. Japan, http://www.fujirebio.co.jp/english/index.html |
Sentinel Diagnostics SpA, Milan, Italy, http://www.sentinel.it/uk/
|
Method |
Latex agglutination |
Magnetic particle agglutination |
Latex agglutination (open method) |
Sample collection system |
OC-Auto sampling bottle 3 |
New HEMTUBE |
FOB Gold tube |
Measuring range |
50-1050 ng/mL |
>20 ng/mL |
14-1000 ng/mL |
Analyser sample volume |
35 µL |
25 µL |
10 µL |
Throughput (claimed/measured) |
280 per hour/245 per hour |
960 per hour/800 per hour |
75 per hour/65 per hour |
Usual threshold |
175 ng Hb/ml in the buffer |
211 pixels (MSR=1.0) |
100 ng Hb/ml in the buffer |
CE mark |
Quantitative measurement |
Qualitative measurement |
Quantitative measurement |
Use in population screening |
The Netherlands, Northern Italy, US, Uruguay, France |
Japan, France and Slovenia
|
Italy, France |
Different authors {5-8} have compared the analytical performance of 3 iFOB tests: OC-Sensor/OC-Sensor Diana & OC-Sensor Micro, Hem-SP/MagStream HT, FOB Gold/SENTiFOB analyser. With regard to reproducibility and temperature stability, OC-Sensor performed better than Magstream and far better than FOB Gold. For all tests, variability was essentially related to sampling. Detected Hb levels were substantially lower for all tests at temperatures above 20 C. This loss is more important for FOB Gold than for other two tests. Some suggestion are made, like delay between sampling and test processing should be reduced to 3 days, or CRC screening programs should be stopped during the summer in countries with long period of very high temperatures >30 C. Patients should be advised to store faecal samples in the refrigerator at home before forwarding them by post.
Table 3. Analytical methods comparisons for 3 iFOB tests: OC-Sensor/OC-Sensor Diana & OC-Sensor Micro, Hem-SP/MagStream HT, FOB Gold/SENTiFOB analyser {5}
OC-Sensor/OC-Sensor Diana method (quantitative) |
Hem-SP/MagStream HT method (qualitative) |
FOB Gold/SENTiFOB analyser method (quantitative) |
Good imprecision, results consistent with the manufacturers claims |
Poor imprecision, results not consistent with the manufacturers claims at low Hb concentration |
Poor imprecision, results not consistent with the manufacturers claims at low Hb concentration |
Linear in the range 50-500 ng Hb/ml buffer |
Not linear since the method is not designed to be linear accross a broad measuring range |
Linear in the range 50-500 ng Hb/ml buffer |
Identified a problem with samples with very high Hb concentration and did not produced a result |
|
Identified a problem with samples with very high Hb concentration and did not produced a result |
According the authors of this report {5}, all 3 analytical platforms are easy to operate and maintain once appropriate training has been received. For all three tests, the liquid samples stored at room temperature for more than three days are not suitable for analysis, due to deterioration of any Hb present. This should be taken in account when sending samples via different MSs postal systems (should be returned within this time). The OC-Sensor/DIANA analyser was the most suitable system for the UK bowl cancer screening programme, despite limited reagent, wash and waste capacity (regular attention will be required in a busy screening laboratory). The FOB Gold/SENTiFOB analyser has a very low sample throughput. The HemSp/MagStream HT has a non-adjustable cut-off, the method is not CE marked for quantitative measurement of human Hb. The system gave negative results for samples that were positive by other methods.
For all three tests sample collection devices should be stored between 2 and 10 C in case of any delay in analysis, so refrigerated storage space is required. The number of analysers required will depend on the laboratory workload; number required for a 5,000 sample per day workload will be 1 for HemSp/MagStream HT; 5 for OC-Sensor/DIANA, and 15 SentiFOB and 1 chemistry analyser for FOB Gold/SENTiFOB. Specialist training is provided by the manufacturers (instructions on routine use and maintance of the analyser). Staff will be required to authorise each batch of results generated from the iFOBT analysers and transfer the data to the bowel cancer screening programme database, if such exists {5}.
1. Young GP, St John DJ, Winawer SJ, Rozen P. Choice of fecal occult blood tests for colorectal cancer screening: recommendations based on performance characteristics in population studies: a WHO (World Health Organization) and OMED (World Organization for Digestive Endoscopy) report. The American journal of gastroenterology. 2002;97(10):2499-507. eng.
13. Exact Sciences Corp. Top-Line Data Show Exact Sciences' Cologuard Test Demonstrates 92 Percent Sensitivity in the Detection of Colorectal Cancer. [Internet]. 2013, April 18 [cited 2013 Aug 9]. Available from: http://investor.exactsciences.com/releasedetail.cfm?ReleaseID=757341.
14. ClinicalTrials.gov. Multi-Target Colorectal Cancer Screening Test for the Detection of Colorectal Advanced Adenomatous Polyps and Cancer (DeeP-C) [Internet]. U.S. National Institutes of Health; 2013, Jun 18 [cited 2013 Aug 9]. Available from: http://prsinfo.clinicaltrial.gov/ct2/show/record/NCT01397747?id=NCT01397747&rank=1).
17. Epigenomics AG. Epigenomics AG submits the fourth module and completes its PMA submission to the FDA for Epi proColon®. [Internet]. Epigenomics AG,; 2013, Jan 7 [cited 2013 Oct 26]. Available from: http://clinicaltrials.gov/ct2/show/record/NCT01580540.
18. ClinicalTrials.gov. Head to Head Study Epi proColon and FIT. [Internet]. U.S. National Institutes of Health; 2013 [updated 2013, Feb 6; cited 2013 Oct 26]. Available from: http://clinicaltrials.gov/ct2/show/record/NCT01580540.
19. Epigenomics AG. Results of Comparative Study between Epigenomics Epi proColon® and FIT to be Presented at Digestive Disease Week. [Internet]. Epigenomics AG,; 2013, Mar 15 [updated 2011; cited 2013 Oct 26]. Available from: http://clinicaltrials.gov/ct2/show/record/NCT01580540.