Evaluation of a card collection-based faecal immunochemical test in screening for colorectal cancer using a two-tier reflex approach.
ABSTRACT The guaiac faecal occult blood test (gFOBT) has been proved as a screening investigation for colorectal cancer, but has disadvantages. Newer faecal immunochemical tests (FITs) have many advantages, but yield higher positivity rates and are expensive. A two-tier reflex follow-up of gFOBT-positive individuals with a FIT before colonoscopy has been advocated as an efficient and effective approach.
A new simple and stable card collection FIT was evaluated.
1124 individuals who were gFOBT positive were asked to provide samples. 558 individuals participated, 320 refused and 246 did not return samples. No evidence of sampling bias was found. 302 individuals tested FIT negative and 256 tested positive. In the 302 FIT-negative individuals, 2 (0.7%) had cancer and 12 (4.0%) had large or multiple (high-risk) adenomatous polyps. In contrast, of 254 positive individuals, 47 (18.5%) had cancer and 54 (21.3%) had high-risk polyps. 93 (30.8%) of the FIT-negative individuals had a normal colonoscopy, but only 34 (13.4%) of the FIT-positive individuals had no pathology. Sensitivity, specificity, and positive and negative likelihood ratios (and 95% CIs) for cancer were 95.9% (84.8 to 99.3), 59.2% (54.7 to 63.5), 2.35 (2.08 to 2.65) and 0.07 (0.02 to 0.27), and for cancer and high-risk polyps were 87.8% (80.1 to 92.9), 65.3% (60.6 to 69.7), 2.53 (2.19 to 2.93) and 0.19 (0.11 to 0.31), respectively.
A two-tier reflex screening algorithm, in which gFOBT-positive participants are tested with a FIT, is effective in identifying individuals at high risk of significant colorectal neoplasia. This strategy is transferable across different FIT formats. This approach has been adopted for the Scottish Bowel Screening Programme.
- SourceAvailable from: P. Davey[Show abstract] [Hide abstract]
ABSTRACT: Objective: Colorectal cancer (CRC) is the third most common type of cancer with resulting major mortality. In a bid to reduce the mortality, bowel cancer screening has been established in the United Kingdom. The screening programme was commenced in Northern Ireland in 2010 within the Northern Health and Social Care Trust, following its implementation in England and Scotland. This study aimed to look at early outcome data for bowel cancer screening in Northern Ireland and compare data with other regions in the UK. Design: A retrospective analysis was conducted of patients who tested faecal occult blood (FOB) positive and attended for pre-assessment between May 2010 and May 2011. Data was also collected from the computerised endoscopy database (Endoscribe®). Patient demographics, colonoscopic depth of insertion, findings and complications were documented. Subsequent surgical management, pathological staging and final outcome were also noted. Results: 182 patients attended for pre-assessment in the time frame and 178 patients proceeded to colonoscopy. The commonest pathology encountered was polyps, identified in 95 (52.7%) patients. Macroscopically 13 cancers were seen on endoscopy and a further two were found on post-operative histology of polyps that were not amenable to endoscopic resection. In addition, 5 malignant polyps were found on histological analysis of the excised polyps. The staging of cancers was favourable with 35% being Dukes' A stage. Conclusion: Outcomes from the first year of colorectal cancer screening in the Northern Trust are in keeping with early results from previous studies in terms of cancer detection rates per colonoscopy and proportion of early stage cancers. However, the adenoma detection rate was higher than anticipated.The Ulster medical journal 09/2013; 82(3):160-3.
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ABSTRACT: Cancer is a worldwide problem as it will affect one in three men and one in four women during their lifetime. Colorectal cancer (CRC) is the third most frequent cancer in men, after lung and prostate cancer, and is the second most frequent cancer in women after breast cancer. It is also the third cause of death in men and women separately, and is the second most frequent cause of death by cancer if both genders are considered together. CRC represents approximately 10% of deaths by cancer. Modifiable risk factors of CRC include smoking, physical inactivity, being overweight and obesity, eating processed meat, and drinking alcohol excessively. CRC screening programs are possible only in economically developed countries. However, attention should be paid in the future to geographical areas with ageing populations and a western lifestyle.19,20 Sigmoidoscopy screening done with people aged 55-64 years has been demonstrated to reduce the incidence of CRC by 33% and mortality by CRC by 43%.Clinical Medicine Insights: Gastroenterology 01/2014; 7:33-46.
- YOU & US,S.A. 01/2009; Enrique Peña Forcada., ISBN: 978-84-692-6651-9
Evaluation of a card collection-based faecal immunochemical
test in screening for colorectal cancer using a two-tier reflex
Callum G Fraser, Catriona M Mathew, N Ashley G Mowat, John A Wilson, Francis A Carey, Robert
J C Steele
............................................................... ............................................................... .....
See end of article for
Professor C G Fraser,
Scottish Bowel Screening
Centre Laboratory, Kings
Cross, Dundee DD3 8EA,
Revised 13 February 2007
Accepted 15 February 2007
Published Online First
19 February 2007
Gut 2007;56:1415–1418. doi: 10.1136/gut.2007.119651
Background: The guaiac faecal occult blood test (gFOBT) has been proved as a screening investigation for
colorectal cancer, but has disadvantages. Newer faecal immunochemical tests (FITs) have many advantages,
but yield higher positivity rates and are expensive. A two-tier reflex follow-up of gFOBT-positive individuals
with a FIT before colonoscopy has been advocated as an efficient and effective approach.
Methods: A new simple and stable card collection FIT was evaluated.
Results: 1124 individuals who were gFOBT positive were asked to provide samples. 558 individuals
participated, 320 refused and 246 did not return samples. No evidence of sampling bias was found. 302
individuals tested FIT negative and 256 tested positive. In the 302 FIT-negative individuals, 2 (0.7%) had
cancer and 12 (4.0%) had large or multiple (high-risk) adenomatous polyps. In contrast, of 254 positive
individuals, 47 (18.5%) had cancer and 54 (21.3%) had high-risk polyps. 93 (30.8%) of the FIT-negative
individuals had a normal colonoscopy, but only 34 (13.4%) of the FIT-positive individuals had no pathology.
Sensitivity, specificity, and positive and negative likelihood ratios (and 95% CIs) for cancer were 95.9% (84.8
to 99.3), 59.2% (54.7 to 63.5), 2.35 (2.08 to 2.65) and 0.07 (0.02 to 0.27), and for cancer and high-risk
polyps were 87.8% (80.1 to 92.9), 65.3% (60.6 to 69.7), 2.53 (2.19 to 2.93) and 0.19 (0.11 to 0.31),
Conclusions: A two-tier reflex screening algorithm, in which gFOBT-positive participants are tested with a
FIT, is effective in identifying individuals at high risk of significant colorectal neoplasia. This strategy is
transferable across different FIT formats. This approach has been adopted for the Scottish Bowel Screening
by mail. However, they have many disadvantages including low
sensitivity and low specificity,5and require to be developed and
evaluated by well-trained personnel.6For these reasons, there is
considerable current interest in faecal immunochemical tests
(FITs),7and an ever-increasing body of work suggests that FITs
could be used in population screening programmes.8These tests
are specific for human haemoglobin and hence do not require
any drug or dietary restriction and are easy to use.5
However, FITs are expensive, and qualitative FITs have lower
analytical detection limits than gFOBTs, which leads to
positivity rates that would place an intolerable burden on the
scarce colonoscopy services available in many countries if used
as the preferred screening test. For this reason, we have
explored previously the use of a reflex two-tier strategy in
which individuals who are gFOBT positive are asked to perform
a FIT before colonoscopy, and we proposed that a population-
based screening programme for colorectal cancer could be
based on a combination of initial gFOBTs for all, followed by
FITs for individuals with positive gFOBT.9We have demon-
strated that use of this strategy would decrease the need for
colonoscopy by about 30%.
However, the FIT that was used required the collection of
faeces into tubes containing buffer solution. These tubes would
be difficult and expensive to post to and from participants in a
screening programme. Moreover, the material in the tubes must
be analysed within 7–8 days of faecal collection, which would
provide logistic difficulties.
uaiac-based faecal occult blood tests (gFOBTs) are
effective in population colorectal cancer screening.1–4
gFOBTs are inexpensive and easy to use and transport
Recently, a FIT has become available with an innovative
sampling method that uses a single simple card for collection of
two specimens of faeces, is stable for 30 days after the first
collection and requires only one specimen preparation tube and
one test cassette system for analysis. Being card based, this is
familiar to participants and is also easy and inexpensive to post
to and from them. We evaluated this system in phase 1 of the
Scottish Bowel Screening Programme to determine the clinical
characteristics of this particular FIT in our planned reflex two-
tier gFOBT/FIT approach to colorectal cancer screening9and to
assess, whether our previous results were transferable over
different FIT formats.
PARTICIPANTS AND METHODS
All participants in the first 13.5 months of phase 1 of the
Scottish Bowel Screening Programme who had a positive
gFOBT were offered colonoscopy: the population here was not
the same as in our previous work.9Exactly as per the pilot study
in the UK,4the population invited for screening comprised
individuals aged 50–69 years. A conventional gFOBT kit (hema-
screen, Immunostics, Ocean, New Jersey, USA) was used. The
screening algorithm was similar to that mandated for the UK
pilot study4: participants collected two samples of faeces
without any dietary restriction from each of three consecutive
bowel movements directly on to filter paper containing guaiac
Abbreviations: FIT, faecal immunochemical test; gFOBT, guaiac faecal
occult blood test; Hb, haemoglobin
gum through oval shapes in the gFOBT kit card. Participants
who had five or six positive ovals on the gFOBT were classified
as strongly positive, and were offered colonoscopy without
further testing. Participants with one to four positive ovals were
classified as weakly positive and asked to perform a second
gFOBT (again without dietary restriction) and, if any oval was
positive, colonoscopy was offered.
Participants with a positive gFOBT were offered an appoint-
ment to discuss colonoscopy with a specialist nurse at one of
four centres. At the end of the discussion, nurses asked
attendees to take part in this study. Attendees were told that
the results of the FIT would not be used to influence the
decision to proceed with colonoscopy and that the result would
be unavailable to them so that their decision to proceed with
further investigation would not be influenced. The study was
approved by the National Health Service Tayside Medical Ethics
Committee, and all participants gave written informed consent.
gFOBT and FIT analyses
All gFOBTs (hema-screen, Immunostics, supplied by Alpha
Laboratories, Eastleigh, Hampshire, UK) were analysed in the
Scottish Bowel Screening Centre Laboratory, which is accre-
dited by Clinical Pathology Accreditation (CPA, UK) to ISO
15189-based standards and only performs analyses of faecal
samples. In general, four bowel screener staff performed the
analyses, and they had all received detailed training as required
by CPA and by the Bowel Screening Programme standards of
National Health Service Quality Improvement Scotland.10The
FIT analyses were also performed in the Centre Laboratory,
generally by a single senior bowel screener. The faeces collected
on the card (hema-screen DEVEL-A-TAB) were delivered via
the tab into a specimen preparation tube containing phosphate-
buffered saline (hema-screen SPECIFIC). After mixing on a
horizontal rotary mixer for 30 min, a portion of the faeces in
buffer was dropped into the specimen well of a test cassette. At
5 min, positive results are detected for haemoglobin (Hb) at a
concentration of 50 ng Hb/ml buffer. This is equivalent to
50 mg Hb/g faeces. Faeces in buffer flows up through the test
cassette and labelled–antibody-dye conjugate binds to the
globin of any haemoglobin present in the specimen, forming
an antibody–antigen complex. This complex binds to anti-
globin antibody in the positive test reaction zone and produces
a coloured line. In the absence of Hb, there is no line in the test
reaction zone. A coloured line in the control reaction zone
demonstrates that the reagents and devices are functioning
Comparison of FIT analytical detection limit
To compare the analytical detection limit of the FIT under study
with that of the method used in our previous study,9200
consecutive faecal specimens were analysed using Instant-View
FIT (Alfa Scientific Designs, Poway, California, USA) test
cassettes using the samples in the SPECIFIC specimen
Colonoscopy and pathology
Colonoscopy was performed in each of the four centres. Data on
colonoscopy were recorded on a specific form with information
on the quality of the investigation (quality of preparation and
completeness of colonoscopy) and on the results including
number, size and localisation of colorectal cancers and
adenomas, and whether biopsy was performed. Full patholo-
gical data were available on all excised biopsy specimens,
including polyp type, presence or absence of malignancy and, in
all adenomas, the severity of dysplasia.
Analysis of results
Exactly as described previously,9sampling bias was analysed
between those who participated, refused or did not participate
by gender and by degree of gFOBT positivity. Colonoscopy
results in FIT-positive and FIT-negative groups were compared
using Fisher’s exact test. Sensitivity, specificity, and positive
and negative likelihood ratios (all with 95% CIs) of FIT were
calculated for identification of cancer, with or without high-
risk11adenomatous polyps primarily to facilitate comparison of
the results with data on the previously studied FIT.9
Table 1 shows the number of participants by centre, gender and
gFOBT positivity. Of the 1124 invited, 558 (49.6%) individuals
participated, 320 (28.5%) refused or were judged inappropriate
for colonoscopy by the specialist nurses, and 246 (21.9%) did
not return samples. No evidence of sampling bias according to
gender was found, since the percentages of men and women
who returned the FIT, refused to take part or were judged
inappropriate by the specialist nurses, and took the FIT but did
not return it were similar. This lack of sampling bias also held
for degree of gFOBT positivity.
Of the 200 samples analysed using the FIT, 112 were negative
and 88 were positive. Identical results were obtained with the
Number of participants by centre, gender and faecal occult blood test positivity
Potential participantsReturned FIT (%)
Refused or regarded as
Did not respond
Overall1124558 (49.6) 320 (28.5)246 (21.9)
By gFOBT positivity
FIT, faecal immunochemical test; gFOBT, guaiac faecal occult blood test.
The percentages are across rows.
1416 Fraser, Mathew, Mowat, et al
previously studied FIT. In consequence, k, the preferred statistic
because it accounts for chance, was 1.00.
Table 2 shows data for the 556 participants who had
information on colonoscopy. The numbers of cancers, adeno-
mas and high-risk adenomas were statistically significantly
higher in the FIT-positive participants than in the FIT-negative
participants, and the number of normal colonoscopies was
significantly lower. Other pathology, comprising inflammatory
bowel disease, diverticular disease and angiodysplasia, was not
different in the groups, nor were the number of incomplete
colonoscopies and the number of participants who did not
Table 3 shows the sensitivity, specificity and positive and
negative likelihood ratios for cancer alone and cancer and high-
risk adenomatous polyps in the gFOBT-positive participants.
Overall, 558 (49.6%) invitees returned satisfactory samples for
analysis. It was surprising that the response was not higher
than in our previous study (53.9%) since the card collection
technique is simple and since all had already completed at least
one gFOBT and the collection format was familiar. Moreover, it
has been shown that, by simplifying sampling (and removing
the need for restrictions of diet and drugs), FIT increases
participation in screening.12As in our previous study,9it was
disappointing that 320 (28.5%) potential participants who
attended an interview with a specialist nurse either refused to
take part or were regarded as ineligible for the study. This low
uptake might have arisen because they were reluctant to do yet
another collection of faeces since most had performed two
gFOBTs already. In addition, the results could not influence the
decision regarding colonoscopy. Moreover, the request to
participate came at the end of an interview. Further, 246
(21.9%) took information and materials home, but did not
participate. However, it is highly likely that our two-tier
approach would be successful with regard to participation in
our national programme since we have found that most who
are weakly positive on initial gFOBT, and are then asked to
undertake a second, do comply.13
We again found that the four sites of interview location
differed slightly in the number of participants. In contrast to
our previous study,9the percentage of men and women who
participated was the same. Although it could be argued that a
higher uptake in this study could have affected the results, no
evidence for sampling bias was found between those who
participated and those who did not with regard to both gender
and gFOBT positivity.
We showed that the analytical detection limit of the FIT
cassettes used in this study and in our previous study9were
identical and, in consequence, differences in findings would be
due to either the characteristics of the participants or the
sample collection technique, particularly the amount of faeces,
since the participants were from the same geographical area.
Colonoscopy revealed that this FIT was highly sensitive for
colorectal cancer in this group of gFOBT-positive individuals
since, of the 49 cancers found, 47 were FIT-positive and only 2
negative. This was similar to our earlier results,9where 38 were
FIT-positive and 2 negative. The two cancers were from the
weakly positive gFOBT group and both were polyp cancers, one
of 2 mm diameter and the other 18 mm. Of the 12 FIT-negative
individuals with high-risk adenoma, again all were gFOBT
weakly positive and 7 had a single adenoma ranging from 11 to
17 mm, 3 had 2 adenomas, all ,15 mm, and 2 had 3
adenomas, all ,12 mm. In contrast, in the FIT-positive group,
7 were polyp cancers and 13, 10 and 17 were Dukes’ stages A, B
and C, respectively.
For cancer and high-risk adenoma, the findings were again
similar to our results with the previously studied FIT.9However,
for detection of all polyps, 139 (54.6%) were in FIT-positive
participants and 116 (45.4%) in the FIT-negative participants,
in contrast to the 78.8% and 21.2%. This is highly likely to be
due to a smaller amount of faeces being collected on the card
compared with into the tubes when used as collection devices.
Thus, about half of those individuals with low-risk adenomas
would be missed by this approach, but since 96% of cancers and
88% of cancers and high-risk adenomas were detected, this
represents an efficient and effective disease detection strategy
while simultaneously reducing the need for screening colono-
scopy. Over 80% of those with high-risk polyps are detected
with the FIT, and there now seems to be a growing view that
there is little harm in not detecting, removing and following up
those with single small polyps. Even large polyps (.1 cm)
become cancers at the low rate of ca 1% per year14and the
development of invasive cancer from a small (,10 mm)
adenoma is extremely unlikely in ,5 years.15
Our strategy would reduce the colonoscopy demands. The
actual reduction would depend on the screening round. In the
second Scottish screening round, the reduction in colonoscopy
demand was shown to be ca 30%.9In this study, which involved
the third screening round of essentially the same population,
the gFOBT positivity rate had fallen from 1.9% to 1.0% and the
proposed strategy of gFOBT followed by FIT would save ca 50%
of colonoscopies. Although FITs are more expensive than
gFOBTs, often by a factor of 10, and cost about £5 (US$9.85,
J7.34), colonoscopy in Scotland is documented to cost £350
FIT-positive (%) FIT-negative (%) p Value
Hyper-/metaplastic polyps 32 (12.6)
Did not attend
FIT, faecal immunochemical test.
The percentages are down columns: other pathology encompasses
inflammatory bowel disease, diverticular disease, angiodysplasia and non-
and cancer and high-risk adenomatous polyps
Sensitivity, specificity, and positive and negative likelihood ratios for cancer alone
ratio (95% CI)
ratio (95% CI)
Cancer and high-risk
95.9 (84.8 to 99.3)
87.8 (80.1 to 92.9)
59.2 (54.7 to 63.5)
65.3 (60.6 to 69.7)
2.35 (2.08 to 2.65)
2.53 (2.19 to 2.93)
0.07 (0.02 to 0.27)
0.19 (0.11 to 0.31)
High-risk adenomatous polyps are either .10 mm diameter or .3 polyps or both in an individual participant.
Evaluation of a card collection FIT in colorectal cancer1417
(US$689.62, J514.17)16: thus, significant overall cost savings
for a bowel screening programme would be achieved through
adoption of the approach advocated here.
Although using FIT as the preferred test in bowel screening
programmes has many advantages,8the positivity rate and the
expense mean that, at this stage at least, our two-tier reflex
strategy, combining gFOBT and FIT, would seem to have
advantages when colonoscopy is limited. Moreover, although
there is information on the clinical performance characteristics
in large average-risk populations for certain FITs,17comparisons
in large populations are not yet available. However, since the
basic immunochemistry seems to be similar for all, the real
advantages for one over another may be in sampling methods
and development: a simple stable card collection system would
seem to have advantages.
Our current findings again show that a population with a high
probability of cancer and high-risk adenomatous polyps can be
identified by the useof FIT and that results from different FITs for
this purpose are transferable. Our findings have informed the
Scottish Bowel Screening Programme that will be rolled out to all
50–74-year olds,an extended age range compared with this study,
beginning in 2007.16At this point in time at least, our two-tier
reflex strategy, combining gFOBT and FIT, will be used. All
participants will initially be sent a gFOBT. Participants who have
strong positive gFOBT results will be offered colonoscopy
immediately. Participants who are weakly positive will be asked
to perform a FIT rather than a repeat gFOBT, since this strategy
directs colonoscopy to those with significant disease, Individuals
screening again after 2 years.
We thank all the staff of the Scottish Bowel Screening Centre, in
particular Joy C Gordon, for some laboratory analyses and for their
assistance in sending out the FIT kits to potential participants, and all
the specialist colorectal nurses for their efforts in recruiting partici-
Callum G Fraser, Catriona M Mathew, Scottish Bowel Screening Centre
Laboratory, Kings Cross, Dundee, UK
N Ashley G Mowat, Department of Gastroenterology, Aberdeen Royal
Infirmary, Foresterhill, Aberdeen, UK
John A Wilson, Department of Gastroenterology, Victoria Hospital,
Kirkcaldy, Fife, UK
Francis A Carey, Department of Pathology, Ninewells Hospital and
Medical School, Dundee, UK
Robert J C Steele, University Department of Surgery and Molecular
Oncology, Ninewells Hospital and Medical School, Dundee, UK
Funding: This study was funded by the Chief Scientist Office of the Scottish
Executive Department of Health.
Competing interests: Declared (the declaration can be
viewed on the Gut website at http://www.gutjnl.com/
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