Interval faecal occult blood testing in a colonoscopy based
screening programme detects additional pathology
P A Bampton, J J Sandford, S R Cole, A Smith, J Morcom, B Cadd, G P Young
See end of article for
Dr P Bampton, Department
of Gastroenterology and
Medical Centre, Bedford
Pk 5042, South Australia;
Revised version received
24 January 2005
Accepted for publication
1 February 2005
Gut 2005;54:803–806. doi: 10.1136/gut.2004.043786
Background: Colonoscopic based surveillance is recommended for patients at increased risk of colorectal
cancer. The appropriate interval between surveillance colonoscopies remains in debate, as is the ‘‘miss
rate’’ for colorectal cancer within such screening programmes.
Aims: The main aim of this study was to determine whether a one-off interval faecal occult blood test
(FOBT) facilitates the detection of significant neoplasia within a colonoscopic based surveillance
programme. Secondary aims were to determine if invitees were interested in participating in interval
screening, and to determine whether interval lesions were missed or whether they developed rapidly since
the previous colonoscopy
Patients: Patients enrolled in a colonoscopic based screening programme due to a personal history of
colorectal neoplasia or a significant family history.
Methods: Patients within the screening programme were invited to perform an immunochemical FOBT
(Inform). A positive result was followed by colonoscopy; significant neoplasia was defined as colorectal
cancer, adenomas either >10 mm or with a villous component, high grade dysplasia, or multiplicity (>3
adenomas). Participation rates were determined for age, sex, and socioeconomic subgroups.
Colonoscopy recall databases were examined to determine the interval between previous colonoscopy
and FOBT offer, and correlations between lesion characteristics and interval time were determined.
Results: A total of 785 of 1641 patients invited (47.8%) completed an Inform kit. A positive result was
recorded for 57 (7.3%). Fifty two of the 57 test positive patients completed colonoscopy; 14 (1.8% of those
completing the FOBT) had a significant neoplastic lesion. These consisted of six colorectal cancers and
eight significant adenomas.
Conclusions: A one off immunochemical faecal occult blood test within a colonoscopy based surveillance
programme had a participation rate of nearly 50% and appeared to detect additional pathology,
especially in patients with a past history of colonic neoplasia.
personal history of colorectal neoplasia are recommended to
have colonoscopic surveillance.1There is significant debate
over the recommended interval between colonoscopies
within surveillance programmes. The American Polyp Study
has demonstrated that post polypectomy colonoscopy at one
and three years has a similar yield, leading to recommenda-
tions that post polypectomy colonoscopy can be delayed for
3–5 years, depending on histology.2However, in clinical
practice, actual intervals vary widely and colonoscopy is
often performed more frequently than this, presumably
because of concerns of missed lesions and lesions with a
more rapidly evolving biology.3While a miss rate of lesions
>10 mm in size has been quoted as up to 8%,4it is doubtful
that this justifies a repeat colonoscopy at one or even two
years as the majority of sporadic adenomas do not appear to
progress to cancer within that time frame.5
One way to manage the possibilities of missed or rapidly
progressive lesions and give added reassurance to both
clinician and the person under surveillance is to perform a
faecal occult blood test (FOBT) in the interval (‘‘interval
FOBT’’) between colonoscopies, so as to aid detection of such
The aims of this study were therefore to determine whether
individuals at increased risk for colorectal cancer and
registered in a colonoscopic surveillance programme would
participate in interval FOBT, and whether this would result in
detection of significant lesions.
atients with a significant family history of colorectal
cancer (two or more relatives affected, or one first degree
relative under the age of 55 years) and those with a
Individuals within a colonoscopy based surveillance pro-
gramme were invited by mail to perform an interval FOBT.
The surveillance programme at Flinders Medical Centre
(FMC) and the Repatriation General Hospital Daw Park
(RGHDP) follows the guidelines recommended by the
Australian National Health and Medical Research Council.1
These guidelines were the result of an evidence based
medicine review, withcolonoscopic
recommended for those individuals with a significant
increase in risk of colorectal cancer, specifically those with
a family history of two or more first or second degree relatives
affected with colorectal cancer, or one relative affected under
the age of 55 years. In those with previous colonic polyps,
recommended post polypectomy colonoscopy intervals are:
(a) three years for tubulovillous or villous adenomas or
tubular adenomas >10 mm, or for more than two adenomas
of any size), and (b) five years for single or two tubular
adenomas ,10 mm. Patients with a previous colorectal
cancer would have a repeat colonoscopy at 3–5 yearly
Patients registered on a colonoscopy recall database, who
were not scheduled for colonoscopy in the study year, were
invited by mail to participate in FOBT based surveillance
screening. In the first and second years of the study (2000
and 2001), only patients enrolled in the FMC programme
were invited. In the next year (2002) the study was extended
Abbreviations: FOBT, faecal occult blood test; FMC, Flinders Medical
Centre; RGHDP, Repatriation General Hospital Daw Park
to include those enrolled at RGHDP as well as FMC. Patients
on the recall database were divided into two groups—either
those who had entered the database purely due to a family
history or those who had a personal history of colorectal
neoplasia, irrespective of whether they also had a family
Individuals who were invited to participate received an
immunochemical FOBT (Inform OBT; Enterix Pty Ltd,
Sydney, Australia). Participation in FOBT was defined as
return of correctly completed sample cards within 12 weeks
of mailing out the invitations. The Inform samples were
developed at the Enterix laboratory (North Ryde, NSW,
Australia).6Only FOBT sample cards that were correctly
completed by participants were included for the purposes of
Individuals who returned any positive result had their
planned colonoscopy brought forward. If colonoscopy was
judged to be incomplete by the proceduralist, then a
radiological examination of the colon was also undertaken.
Colonoscopic diagnoses were determined on the basis of
the examination and from any pathology specimens.
Significant colorectal neoplasia was defined as a carcinoma
or adenomas with any of the following characteristics:
>10 mm villous change, high grade dysplasia, or multiple
Demographic characteristics of the invited population (sex,
age structure, and socioeconomic status) using the Socio-
economic Index for Areas (SEIFA, postcode based, Australian
Bureau of Statistics) were extracted from the colonoscopy
recall databases (SCOOP database (Department of Gastro-
enterology, Flinders University, Australia) and Kintrak data-
base (Pecol Software, Adelaide, Australia)). Demographic
characteristics of participants and non-participants were
similarly determined and compared using the x2test and
by Wilcoxon sum of ranks analyses. The time between
previous colonoscopy and FOBT was calculated from the
recall databases and participants were allocated to one of
two groups ((2 years, .2 years). Significant pathology
was compared for the two groups using x2analysis.
The study was approved by the Flinders Medical Centre
Clinical Research Ethics Committee.
FOBT participation and positivity rates (tables 1, 2)
A total of 1641 patients were invited for the first time to
participate in interval screening, comprising 672 from FMC in
2000, 421 from FMC in 2001, 367 from FMC in 2002, and 181
from RGHDP in 2002 (table 1).
A total of 792 patients responded to the invitation and
participated in FOBT screening; in seven cases the FOB kits
had been incorrectly completed, leaving 785 valid kits. In
1558 patients where the initial reason for entering the
colonoscopic surveillance programme was well documented,
1033 were entered due to a personal history of colonic
neoplasia, of which 538 (52%) participated—a significantly
greater participation than those who has entered the
programme due to family history alone (219/525 (42%);
p=0.0001). In total, 57 of the 785 participants returned a
positive result (7.3%). A FOBT positive result was more likely
in the group who had a personal history of colorectal
neoplasia (51/538 (9.5%)) than those who entered the
programme due to family history alone (6/219 (2.7%);
p=0.0001). Participants did not differ significantly from
non-participants for age, sex, or socioeconomic status
Pathology findings (tables 3, 4)
Fifty seven patients had a positive FOBT result; 16% had
significant colorectal neoplasia detected (six colorectal
cancers and eight significant adenomatous polyps) (table 3).
This represents a prevalence of FOBT detectable significant
pathology of 1.8% (14/785) in those who participated in the
Those patients who were enrolled into the screening
programme because of a personal history of neoplasia were
more likely to have a cancer or advanced adenoma (11/538
(2%)) than those enrolled because of a family history (1/219
The date of colonoscopy prior to FOBT was known for 764/
785 patients (97.3%). A total of 549 had previously had a
colonoscopy within two years of the FOBT; in this group, 11
(2%) had significant colorectal neoplastic lesions. A total of
215 patients had a colonoscopy more than two years prior to
Programme participation and positivity rates
Invitation round (institution, year)
Total FMC 2000FMC 2001RGHDP 2002 FMC 2002
Returned valid test
Tested positive (n)
FMC, Flinders Medical Centre; RGHDP, Repatriation General Hospital Daw Park.
Demographic characteristics of the invited, participating, and non-participating
Characteristic Invited ParticipatingNon-participating
Sex (% female)
Age (y) (at invitation) (median [range]
Median SES indicator (SEIFA rank)
Reason for colorectal surveillance*
SEIFA, Socioeconomic indicator for areas, Australian Bureau of Statistics (NB only first time offers included).
*Reason for initial inclusion not clear in 83 patients.
804Bampton, Sandford, Cole, et al
their FOBT. Two significant colorectal neoplastic lesions were
found in this group (0.9%; NS) (table 4).
This study demonstrates that additional pathology is found
when interval FOBT is incorporated into colonoscopic based
screening for individuals with past colonic neoplasia or
significant family history. In our study, a first time
immunochemical interval FOBT detected significant neopla-
sia (colorectal cancer, adenomas >10 mm, with villous
change, with high grade dysplasia, or multiple (>3)
adenomas) in 1.8% of subjects who participated in screening.
Six cancers were identified (0.8% of those completing the
FOBT), two of which were advanced (Dukes’ C).
The participation rate of 47.8% was perhaps a little
disappointing as these were high risk patients who were on
an established screening programme. While significant
interval neoplasia is detected in 1.8% of participants, this is
reduced to 0.9% of all those within the surveillance
programme given the non-participation rate. Participation
in interval faecal occult blood testing needs to be improved to
maximise the effect of this intervention. It could be improved
by telephoning patients to encourage their participation and
notifying patients’ general practitioners that the patient is
due for a faecal occult blood test (this is done for the
surveillance colonoscopies in the programme).
It is possible that patients, having performed an interval
FOBT, might be reassured by a normal result and not
participate in their colonoscopy screening. We examined our
participation rate for screening colonoscopies due in 2003.
We found that of 283 patients due, 30 (11%) did not
participate for legitimate reasons (unwell, deceased, or age
related), with 221 of the remaining 257 (87%) participating.
We felt this represented a fairly high participation rate,
suggesting that participation in interval faecal occult blood
testing does not adversely affect participation in screening
FOBT screening has been shown to be able to detect
colorectal cancer in this setting. Skaife et al performed
immunochemical FOB testing (using the same test as in this
study) on samples obtained on digital rectal examination,
prior to planned colonoscopy, in patients in a surveillance
programme because of a past history of colorectal cancer. In
611 patients there was a 9.7% positivity rate, with nine
cancers being detected in the FOBT positive group and none
in those who were FOBT negative. In four cases the cancer
was a local recurrence and in five it was a metachronous
The lesions that we detected may have been missed or may
have been rapidly developing lesions. A miss rate for
significant adenomas (polyps >10 mm) has been demon-
strated to be as high as 8%, and up to 15% for adenomas
greater than 5 mm.4If the lesions we detected were new
rapidly developing lesions, we might have expected a greater
proportion in the group that had their prior colonoscopy 3–5
years earlier rather than 1–2 years earlier. The converse
appeared to be true, with 34% of test positives in the group
with recent colonoscopy having significant neoplasia versus
10% in the group with a colonoscopy greater than two years
previously. This may imply that the lesions were missed,
rather than rapidly developing, but the numbers are small
and the difference did not reach statistical significance. This
could reflect poor colonoscopy technique, although when we
audited all colonoscopies performed for screening in 2000
Results of follow up and pathology found
Personal history of adenomatous
polyps or cancer
Significant family history of
Cancer or polyps detected*
Other pathology detected?
Pathology reports available
Adenoma not advanced?
FOBT, faecal occult blood test.
*Includes all patients with either cancer or polyps (including hyperplastic), with or without other non-neoplastic
?Includes patients where the only pathology was non-neoplastic (that is, diverticulosis, colitis, haemorrhoids, etc).
`Includes two intramucosal carcinomas; T is lesions according to the WHO classification.
1Includes adenomas with any of the following characteristics: >10 mm, with villous change, high grade dysplasia,
or multiple (>3).
?Includes all adenomas excluding advanced or hyperplastic.
(FOBT) and pathology found
Relationship between date of colonoscopy prior to faecal occult blood test
Time between FOBT and prior colonoscopy (y)
Completed FOBT and previous
colonoscopy date known
Completed follow up
11 (2.0% of participants,
34.4% of test positives)
4 (0.7% of participants,
11.1% of test positives)
2 (0.9% of participants,
10% of test positives)
1 (0.5% of participants,
5.0% of test positives)
Interval FOBT and colonoscopy 805
and 2001 we demonstrated an acceptable standard, with a Download full-text
97% caecal intubation rate.8We have now also introduced
colonic extubation time to our audit as another measure of
The rate of interval neoplasia was higher than we expected.
It may be that patients with minimal symptoms that might
reflect neoplastic change were more likely to participate in
the study than those with no symptoms, although only three
cancers (Dukes’ B and above) would be expected to cause
Addition of interval FOB testing to a colonoscopic based
screening regimen does add cost to the surveillance pro-
gramme. The positivity rate was relatively high, at 7.3%,
although this is within the range seen when an immuno-
chemical FOBT was performed in a population based
screening setting (which varied from 2.5% to 7.5%9–12). The
rate of cancers found (of 0.8%) was similar to that seen in
some population based studies of screening guaiac-FOBT.9–11
FOBT in this latter setting is felt to be appropriate and cost
effective.1 13It is possible that a delay in detection of the
interval neoplastic lesions until the next surveillance colono-
scopy was due would not have affected the outcome, but this
is not the case in all, especially the cancers, and possibly the
advanced adenomas which constituted the majority of the
interval neoplastic lesions detected. Given that the positivity
rate and yield are similar when comparing our group having
colonoscopic surveillance to the population studies, it seems
reasonable to add in at least one interval FOBT between
colonoscopies, especially in those patients enrolled in a
screening colonoscopy programme because of a personal
history of colorectal neoplasia.
The next issue to resolve is whether interval FOBT repeated
at annual or other intervals would give a further increase in
yield compared with a one-off interval FOBT. If the majority
of lesions being detected are those that have been missed at
the preceding colonoscopy, and given the sensitivities of a
one-off immunological FOBT of 68.8–84.6% depending on
test type,14 15it could be argued that a one-off FOBT
performed just once between surveillance colonoscopies is
sufficient. While repeated FOBT improves sensitivity in
population screening,16whether or not this is efficient or
worthwhile in colonoscopic surveillance programmes where
most lesions will have been removed by colonoscopy is
uncertain and would need a very large ongoing study to
demonstrate its value.
In conclusion, individuals in a high risk colonoscopic
surveillance programme are willing to perform interval FOBT,
confirming its feasibility. The participation was lower than
hoped but a first time FOBT detected significant neoplasia in
1.8% of patients who participated. It must be remembered
that faecal occult blood testing has a false negative rate, and
so the rate of interval neoplasia would be expected to be
higher than this. While it is possible that repeated interval
FOBT within such colonoscopic surveillance programmes
may decrease this false negative rate, our data certainly
suggest that at least one FOBT should be considered in the
interval between surveillance colonoscopies, particularly in
those patients who have a past history of colorectal neoplasia
(that is, either adenoma or cancer), in which interval faecal
occult blood testing has a higher yield for additional
pathology than those who have a family history alone.
P A Bampton, J J Sandford, Department of Gastroenterology and
Hepatology, Flinders Medical Centre, Australia
S R Cole, Department of Medicine, Flinders University of South Australia,
Australia, and Division of Medicine, Repatriation General Hospital Daw
A Smith, J Morcom, B Cadd, Division of Medicine, Repatriation General
Hospital Daw Park, Australia
G P Young, Department of Gastroenterology and Hepatology, Flinders
Medical Centre, Australia, and Department of Medicine, Flinders
University of South Australia, Australia
Conflict of interest: None declared.
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