Introduction
Screening colonoscopy has been shown to reduce incidence of and mortality from colorectal
cancer (CRC) [1]
[2]. In spite of recent methodological and technological advancements, colonoscopy remains
an imperfect test because up to 27 % of adenomas are missed, which could be responsible
for development of a significant percentage of the interval cancers [3]. The colon has several folds and curves that result in hidden areas where small
lesions may be not easily visible during colonoscopy. A longer withdrawal time (WT)
allows endoscopists to accurately visualize the hidden areas of the colon and to recognize
a higher number of lesions. A WT ≥ 6 minutes has been associated with increased detection
of both adenomas and advanced adenomas in several studies [4]
[5]
[6], and it is recommended as a quality indicator in recent European and American guidelines
[7]. However, efficacy associated with the implementation of a WT-based policies is
still uncertain: prospective interventions directed at optimizing WT yielded conflicting
results in terms of ability to increase adenoma detection rate (ADR) [8]. In addition, in randomized back-to-back studies using endoscopes able to enhance
the view behind the folds, use of standard scopes has been associated with a substantial
adenoma miss rate, even though an adequate WT protocol was in place [9]
[10].
A new scope with a wider angle of view, the full-spectrum endoscope (FUSE, EndoChoice,
Alpharetta, Georgia, United States), has been pioneered to increase visibility of
hidden areas of the colon [11]. The FUSE has three lenses, one on the forward tip and one on both sides of the
tip, that increase the maximum field of view from the ≤ 170° of standard forward-viewing
endoscope (SFVE) to 330°. In theory, use of the FUSE should optimize ADR, irrespective
of WT, as its wide angle of view could be a surrogate for the ideal inspection technique
that endoscopists try to apply to cover the colonic mucosa when retracting the SFVE.
To our knowledge, however, no studies have addressed it until now.
We designed the current study to evaluate whether an intervention directed at optimizing
WT alone or in combination with use of the FUSE was able to increase ADR in a cohort
of outpatient colonoscopies. In other words, we wanted to understand whether use of
the FUSE would further increase ADR, once WT had been optimized.
Patients and methods
Study design and population
This was a prospective, observational study performed in consecutive outpatients scheduled
for elective colonoscopy during a 6-months period (June 2016 – December 2016). The
study was conducted in two high-volume endoscopic centers belonging to the same Gastroenterology
Department. The study protocol was approved by the local ethics committee and was
registered at ClinicalTrials.gov (NCT02985944). Written informed consent was obtained
from all enrolled patients.
Inclusion criteria for enrollment were referral for diagnostic examination, age 18
to 85 years, and written informed consent provided. Patients were excluded if they
were hospital inpatients, had a history of colorectal resection or of recent major
abdominal surgery, had previously been diagnosed with a polyposis syndrome, or had
inflammatory bowel disease. Patients with incomplete colonoscopy were also excluded.
Study design
The study was designed within a quality audit program that began with introduction
of the new FUSE platform in the two Endoscopic Units. During the study period, the
endoscopists were not aware that a study was running. In the first 3-month period,
six expert endoscopists performed colonoscopy either with high-definition standard
forward-viewing endoscopy (SFVE) or with FUSE, according to local availability. In
the first phase (phase 1) of the study, colonoscopies were performed while a nurse
monitored WT with the endoscopists who were unaware of WT monitoring. During a subsequent
3-month period (phase 2) the same endoscopists performed additional colonoscopies
either with high-definition SFVE or with FUSE, but they were informed that their WT
would be monitored by a nurse to check the performance of each endoscopist with the
new FUSE scope in comparison with the old SFVE ([Fig. 1]).
Fig. 1 Flowchart of the study.
In both phases, assignment of the patients to undergo colonoscopy with SFVE or FUSE
was determined by scope availabilit in the endoscopic suite so that the patients underwent
colonoscopy with the one or the other scope at a 1:1 ratio. Because the endoscopists
could not be blinded to scope type, and no differences were expected in terms of age,
sex, and indication, a formal randomization process was not believed to improve the
validity of the study findings.
Examination procedure
Patients underwent bowel cleansing with 2 L of polyethylene glycol solution plus bisacodyl
in a split-dose or day-before regimen according to the scheduled time of colonoscopy.
Participants in both groups were instructed to have a light lunch on the day before
the colonoscopy; only clear liquid were allowed the day of the exam. All endoscopic
procedures were performed between 9 am and 2 pm.
Six experienced endoscopists (> 1000 standard colonoscopies) performed the endoscopic
procedures in accordance with colonoscopy quality practice. If not contraindicated,
endoscopies were performed using intravenous sedation with midazolam and/or fentanyl.
Colonoscopy was defined as complete when the appendix orifice and the ileocecal valve
were identified. Bowel preparation was evaluated by using the Boston Bowel Preparation
Scale (BBPS) score as previously reported [10]. Preparation was considered adequate when the BBPS score was ≥ 6 with a score of
at least two in any segments.
SFVE was performed by using high-definition, white-light, adult colonoscope (Pentax
90 I series HD Video colonoscopes). Full-spectrum colonoscopy was performed by using
the new high-definition FUSE system (FUSE, EndoChoice, Alpharetta, Georgia, United
States) consisting of a high-definition processor and an adult colonoscope with a
330-degree field of view. Images of colonic mucosa were displayed on three contiguous
screens.
All endoscopists had been trained to use the FUSE system before study initiation by
attending a lecture and performing at least 10 examinations with the FUSE.
Withdrawal time assessment
Colonoscopy WT was defined as time taken to withdraw the colonoscope from the cecum
to the anus. Time of endoscopic procedures such as polypectomy or taking a biopsy,
as well as washing and sucking, was not included in the calculation of WT.
In the first phase of the study, a trained nurse monitored colonoscopy WT using a
stopwatch, while the endoscopists were unaware that WT was being monitored. In the
second phase of the study, the endoscopists were informed of the WT monitoring.
Assessment
For each patient, demographic and clinical characteristics, indications for colonoscopy,
and colonoscopy characteristics (i. e. quality of colon preparation, cecal intubation
time, WT, and endoscopic findings) were collected. All polyps were removed and sent
to the pathologist. Polyps were described and classified according to their size,
location, and morphology.
For each arm, we calculated the mean number of adenomas per colonoscopy (APC) and
the ADR, i. e. the proportion of patients with at least one adenoma. Sessile serrated
adenomas/polyps were included in the calculation of ADR.
The primary endpoint of the study was the ADR, whereas APC and rate of adenomas located
proximally or distally to the splenic flexure represented a secondary endpoint of
the study.
Sample size and statistical analysis
The endoscopy database of our centers showed an observed prevalence of adenomas of
24 % in patients undergoing screening, surveillance or diagnostic colonoscopy. A previous
study reported an ADR of 36 % when WT was monitored [10]. Based on these data, the sample size needed to show a significant difference between
the SFVE and FUSE groups at the 0.05 alpha level with a power of 90 % would be 304
per group.
Categorical variables and continuous variables were expressed as percentages and means
± standard deviations, respectively. Pearson’s chi-squared test and Fisher’s exact
test were used for the categorical variables where appropriate. Student’s t-test and ANOVA test were used to evaluate differences in continuous variables among
the groups.
Binary backward stepwise logistic regression was performed with “withdrawal time ≥ 6
minutes” as binary dependent variable in phase 1 (the endoscopists were unaware of
the WT being monitored). Covariates included patient age (over 50 vs. under 50 years),
sex (male vs. female), adequate bowel cleansing (yes vs. no), bleeding (yes vs. no),
gastrointestinal symptoms (yes vs. no), colorectal cancer screening (yes vs. no),
adenoma surveillance (yes vs. no), detection of an adenoma during the examination
(yes vs. no), use of the FUSE (yes vs. no) and adenoma detection during the procedure
(yes vs. no). Effect size was expressed as odds ratios with 95 % confidence intervals
(CI).
Data analysis was performed by using IBM SPSS, version 20.0 and the statistical significance
was set at P < 0.05.
Results
Patient characteristics
A flow diagram of study design is shown in [Fig. 1]. In the two 3-month study periods, 1414 patients were considered for enrollment
and 94 patients were excluded because of violation of inclusion and exclusion criteria.
The remaining 1320 patients were included in the study, 660 patients in phase 1 and
660 in phase 2. In each phase of the study, 330 patients were allocated into the SFVE
group and 330 patients into the FUSE group.
[Table 1] shows characteristics of the participants in the four arms of the study. No significant
differences in demographic characteristics of patients and indications for colonoscopy
were observed among groups.
Table 1
Demographics and clinical features of the different study groups.
|
Phase 1
|
Phase 2
|
P value
|
|
SFVE
(n = 330)
|
FUSE
(n = 330)
|
SFVE
(n = 330)
|
FUSE
(n = 330)
|
|
Age (yrs), mean±SD
|
60.5 ± 12.5
|
59.5 ± 13.8
|
59.6 ± 12.8
|
60.5 ± 13.6
|
0.674
|
|
Male sex, % (n)
|
178 (53.9)
|
182 (55.2)
|
181 (54.8)
|
185 (56.1)
|
0.959
|
|
Indications, % (n)
|
|
Screening
|
29.7 % (98)
|
27.9 %(92)
|
29.1 %(96)
|
34.8 %(115)
|
0.219
|
|
Bleeding
|
22.7 % (75)
|
25.2 %(83)
|
22.4 % (74)
|
23.9 % (79)
|
0.837
|
|
Post-polypectomy
|
22.1 % (73)
|
22.7 % (75)
|
22.7 % (75)
|
15.5 % (51)
|
0.056
|
|
Gastrointestinal symptoms
|
25.5 % (84)
|
24.2 % (80)
|
25.8 % (85)
|
25.8 %(85)
|
0.965
|
SFVE, standard forward-viewing endoscope; FUSE, full-spectrum endoscope
Colonoscopy characteristics
[Table 2] lists characteristics of the colonoscopy procedures. No difference in rate of adequate
cleansing was observed among the different arms. Cecal intubation time was significantly
longer in the FUSE arms compared to the SFVE arms in both phases (phase 1: 379 ± 182
vs. 340 ± 164 sec, P = 0.026; phase 2: 383 ± 160 vs. 334 ± 220 sec, P = 0.003; [Fig. 2a]). Overall, WT was shorter in phase 1 compared to phase 2 (SFVE: 269 ± 83 vs. 386 ± 60
sec, P < 0.001; FUSE: 289 ± 97 vs. 403 ± 65 sec, P < 0.001; [Fig. 2b]) and was longer for the FUSE in comparison to SFVE (phase 1: 289 ± 97 vs. 269 ± 83
sec, P = 0.006; phase 2: 403 ± 65 vs.386 ± 60 sec, P < 0.020). WT ≥ 6 minutes was observed in 151 colonoscopies in phase 1 and 587 colonoscopies
in phase 2 (22.9 % vs. 88.9 %, P < 0.001).
Table 2
Characteristics of colonoscopy procedures.
|
Phase 1
|
Phase 2
|
|
SFVE
(n = 330)
|
FUSE
(n = 330)
|
P value[1]
|
SFVE
(n = 330)
|
FUSE
(n = 330)
|
P value[2]
|
Overall P value[3]
|
|
Adequate cleansing, % (n)
|
86.4 % (285)
|
85.2 % (281)
|
0.738
|
89.1 % (294)
|
88.5 % (292)
|
0.805
|
0.391
|
|
Cecal intubation time (sec), mean ± SD
|
340 ± 164
|
379 ± 182
|
0.026
|
334 ± 220
|
383 ± 160
|
< 0.01
|
< 0.01
|
|
Withdrawal time (sec), mean ± SD
|
269 ± 83
|
289 ± 97
|
< 0.01
|
386 ± 60
|
403 ± 65
|
0.020
|
< 0.01
|
|
Withdrawal time ≥ 6 min, % (n)
|
17.0 % (56)
|
28.8 % (95)
|
< 0.01
|
92.4 % (305)
|
85.5 % (282)
|
< 0.01
|
< 0.01
|
|
ADR, % (n)
|
27.3 % (90)
|
33.0 % (109)
|
0.127
|
33.6 % (111)
|
41.8 % (138)
|
0.037
|
0.001
|
|
APC, mean ± SD
|
0.43 ± 0.85
|
0.56 ± 1.08
|
0.071
|
0. 65 ± 1.24
|
0.71 ± 1.08
|
0.502
|
0.004
|
|
Right colon ADR, % (n)
|
11.2 % (37)
|
12.7 % (42)
|
0.632
|
16.4 % (54)
|
18.9 % (62)
|
0.415
|
0.023
|
|
Left colon ADR, % (n)
|
20.0 % (66)
|
24.8 % (82)
|
0.081
|
21.9 % (72)
|
27.0 % (89)
|
0.147
|
0.153
|
|
≤ 5 mm ADR, % (n)
|
18.2 % (60)
|
21.5 % (71)
|
0.329
|
24.5 % (81)
|
37.0 % (122)
|
< 0.01
|
< 0.001
|
|
6 – 9 mm ADR, % (n)
|
7.9 % (26)
|
9.1 % (30)
|
0.675
|
11.8 % (39)
|
9.4 % (31)
|
0.376
|
0.373
|
|
> 10 mm ADR, % (n)
|
5.5 % (18)
|
8.5 % (28)
|
0.168
|
9.1 % (30)
|
7.0 % (23)
|
0.390
|
0.285
|
SFVE, standard forward-viewing endoscope; FUSE, full-spectrum endoscope; ADR, adenoma
detection rate; APC, adenoma per colonoscopy
1
P value SFVE vs FUSE (phase 1)
2
P value SFVE vs FUSE (phase 2)
3
P value all groups
Fig. 2 Cecal intubation time and withdrawal time in the two phases of the study.
Effect of WT and endoscope type on ADR
Overall, 1110 polyps were detected, 779 of which were adenomas.
In phase 1, ADR was higher when endoscopists used the FUSE, but this difference was
not statistically significant (33.0 % vs. 27.3 %; P = 0.127). In phase 2, ADR was significantly higher for the FUSE than for SFVE (41.8 %
vs. 33.6 %, P = 0.037). When endoscopists were aware of being monitored, ADR increased both for
SFVE (33.6 % vs. 27.3 %; P = 0.090) and FUSE (41.8 % vs. 33.0 %; P = 0.024). Overall, when endoscopists were aware of being monitored and used the FUSE,
ADR resulted to be significantly higher in comparison to other arms of the study ([Fig. 3a] and [Table 2]).
Fig. 3 Adenoma detection rate in the different study arms.
Similar results were observed for mean APC, which was lower in the SFVE arm of phase
1 compared to the SFVE and FUSE arms of phase 2 (0.43 ± 0.85 vs 0.65 ± 1.24, P = 0.040; 0.43 ± 0.85 vs. 0.71 ± 1.08, P = 0.003)([Table 2]).
The ADR for adenomas located proximally to the splenic flexure was higher when endoscopists
were aware of being monitored (SFVE arms: 11.2 % vs. 16.4 %, P = 0.056; FUSE arms: 12.7 %vs. 18.9 %, P = 0.033). Use of the FUSE added only a little to the diagnostic gain obtained by
SFVE after optimization of WT (SFVE 16.4 % vs FUSE 18.9 %) ([Fig. 3b] and [Table 2]). Conversely, the ADR for adenomas located distally to the splenic flexure tended
to be higher in the FUSE arms compared to SFVE arms, although these differences were
not statistically significant (phase 1: 20.0 % vs. 24.8 %, P = 0.081; phase 2: 21.8 % vs. 27.0 %, P = 0.147)([Fig. 3c] and [Table 2]).
Improvement in the diagnostic gain obtained by optimizing WT and using the FUSE was
seen only for adenomas ≤ 5 mm while no differences were found in ADR for adenomas
≥ 6 mm among the different arms of the study ([Table 2]).
Overall on univariate analysis, both WT monitoring [OR 1.403 (95 % C. I. 1.116 – 1.765);
P = 0.004] and use of a FUSE [OR 1.366 (95 % C. I. 1.086 – 1.717); P = 0.009] positively influenced ADR. In particular, detection of proximal adenoma
was associated with WT monitoring [OR 1.577 (95 % C. I. 1.158 – 2.148); P = 0.004], whereas detection of distal adenoma was associated with use of the FUSE
[OR 1.320 (95 % C. I. 1.022 – 1.705); P = 0.037] ([Fig. 4]).
Fig. 4 Effect of SFVE and FUSE on rate of detection of adenomas according to their position
(proximal or distal to the splenic flexure).
On multivariate analysis, patients aged older than 50 years, colorectal cancer (CRC)
screening as indication to colonoscopy, and adequate bowel cleansing were positively
associated witho detection of at least one adenoma. Also WT monitoring and use of
the FUSE resulted in a significantly higher ADR. Conversely, female sex and other
indications for colonoscopy (bleeding, adenoma surveillance, gastrointestinal symptoms)
were negatively associated with adenoma detection ([Table 3]).
Table 3
Univariate and multivariate logistic regression model for adenoma detection.
|
Binary outcome “detection of at least one adenoma” (yes vs. no)
|
|
Univariate model
Odds ratio (95 %CL)
|
P value
|
Multivariate model
Odds ratio (95 %CL)
|
P value
|
|
Female sex
|
0.400 (0.314 – 0.509)
|
< 0.001
|
0.397 (0.308 – 0.511)
|
< 0.001
|
|
Age over 50 years
|
4.192 (2.925 – 6.007)
|
< 0.001
|
4.204 (2.890 – 6.116)
|
< 0.001
|
|
Adequate bowel cleansing
|
1.471 (1.024 – 2.113)
|
0.037
|
1.597 (1.091 – 2.338)
|
0.016
|
|
Bleeding
|
0.726 (0.550 – 0.958)
|
0.024
|
0.579 (0.414 – 0.808)
|
0.001
|
|
CRC screening
|
1.861 (1.460 – 2.372)
|
< 0.001
|
1.728 (1.238 – 2.414)
|
0.001
|
|
Adenoma surveillance
|
1.107 (0.838 – 1.463)
|
0.474
|
0.635 (0.455 – 0.885)
|
0.007
|
|
Gastrointestinal symptoms
|
0.586 (0.444 – 0.774)
|
< 0.001
|
0.594 (0.424 – 0.832)
|
0.002
|
|
Use of full-spectrum scopes
|
1.366 (1.086 – 1.717)
|
0.009
|
1.425 (1.131 – 1.843)
|
0.004
|
|
Withdrawal time monitoring
|
1.403 (1.116 – 1.765)
|
0.004
|
1.444 (1.117 – 1.819)
|
0.003
|
CRC, colorectal cancer.
Factors affecting WT
In phase 1 of the study, WT was affected by several factors ([Table 4]). On multivariate analysis, detection of a first adenoma during the examination,
adequate bowel cleansing, colonoscopy performed for CRC screening, and use of the
FUSE were positively associated with WT ≥ 6 minutes, whereas female sex was negatively
associated with WT ≥ 6 minutes. In phase 2, the only factor that was positively associated
with WT ≥ 6 minutes was detection of a first adenoma during the procedure (data not
shown).
Table 4
Factors affecting the withdrawal time in the phase 1 of the study: univariate model
and multivariate logistic regression model for withdrawal time ≥ 6 minutes.
|
Binary outcome “withdrawal time ≥ 6 min” (yes vs. no)
|
|
Univariate model
Odds ratio (95 %CI)
|
P value
|
Multivariate model
Odds ratio (95 %CI)
|
P value
|
|
Female sex
|
0.331 (0.221 – 0.495)
|
< 0.001
|
0.416 (0.270 – 0.643)
|
< 0.001
|
|
Age over 50 years
|
1.562 (0.964 – 2.532)
|
0. 071
|
0.970 (0.564 – 1.669)
|
0.913
|
|
Adequate bowel cleansing
|
2.009 (1.085 – 3.720)
|
0.024
|
2.162 (1.126 – 4.152)
|
0.021
|
|
Adenoma detection
|
3.693 (2.526 – 5.399)
|
< 0.001
|
2.466 (1.626 – 3.740)
|
< 0.001
|
|
Bleeding
|
0.561 (0.350 – 0.900)
|
0.017
|
0.612 (0.370 – 1.012)
|
0.056
|
|
CRC Screening
|
2.909 (1.989 – 4.252)
|
< 0.001
|
2.698 1.545 4.714
|
< 0.001
|
|
Adenoma surveillance
|
1.110 (0.723 – 1.704)
|
0.657
|
1.512 (0.823 – 2.779)
|
0.183
|
|
Gastrointestinal symptoms
|
0.361 (0.215 – 0.607)
|
< 0.001
|
0.815 (0.418 – 1.589)
|
0.548
|
|
Use of full-spectrum scopes
|
1.978 (1.362 – 2.873)
|
< 0.001
|
2.039 (1.361 – 3.053)
|
0.001
|
CRC, colorectal cancer.
Discussion
Our study demonstrates that combining WT monitoring and use of a wide-angle scope
results in a clinically relevant increase in number of lesions detected. Several studies
have demonstrated the positive association between ADR and/or APC and WT [4]
[12], but, to the best of our knowledge, this is the first study designed with the aim
of understanding whether use of the FUSE results in further diagnostic gain once WT
and withdrawal technique have been optimized.
Longer WT allows for more accurate visualization of the back of the folds and inner
curve of the flexures, which are usually not easily visible when using a SFVE. However,
even when used with an optimal withdrawal technique, SFVE is likely to be unable to
detect some polyps. Evidence from colonoscopy tandem studies indicates that SFVE may
have a higher adenoma miss rate when compared with systems that potentially enable
visualization of mucosa behind the folds, such as the FUSE and EndoRing [9]
[13].
Moreover, some studies have demonstrated that prospective institution of an optimal
WT of at least 7 minutes may have no impact on polyp detection rates [8]; similarly, a prospective cohort study determined that WT, using 6 minutes as the
threshold, was not a strong predictor of likelihood of finding a polyp [14]. All these data are likely to suggest that SFVE may have intrinsic limitations in
visualizing the entire colonic mucosa that cannot be overcome by prolonging inspection
time.
The FUSE system has been recently introduced to overcome intrinsic limitations in
the SFVE. In phase 1 of our study, when both the FUSE and SFVE were used at a suboptimal
WT, the FUSE enabled an increase in ADR from 27.3 % to 33 % in comparison with SFVE;
in phase 2, accuracy of both SFVE and FUSE increased, but the FUSE again allowed detection
of more adenomas, increasing ADR from 33.6 % to 41.8 %. That means that the vast majority
of lesions can be detected by SFVE using a slow and very accurate withdrawal technique,
but a few lesions can be recognized only using a scope able to visualize the back
of the folds and of the flexures. Our data also suggest that a correct WT, i. e. withdrawal
technique, is a fundamental requisite when performing colonoscopy, independent of
which endoscope is used, because when using the FUSE, it is also necessary to perform
up and down tip movements to cover the mucosal surface in the vertical plane (the
wide angle of view of FUSE pertains only to the lateral direction); moreover, effectively
monitoring the three screens for exposed polyps can be difficult and time-consuming.
Interestingly, ADR achieved by the FUSE in the preintervention phase did not differ
from the postinterventional ADR obtained with the SFVE, a result that is likely to
be important because the FUSE, exposing all the colonic mucosa faster and more efficiently
than the SFVE, would potentially reduce WT duration without affecting accuracy.
This is not the first time that the FUSE has demonstrated promising results in comparison
with a
SFVE. In a previous tandem-colonoscopy study by Gralnek et al. [9],
use of the FUSE resulted in a significantly lower adenoma miss rate in comparison
to the SFVE.
More recently, a randomized multicenter Italian study performed in the setting of
the national CRC screening program was not able to demonstrate any statistically significant
differences in ADR and advanced ADR between FUSE and SFVE in FIT-positive individuals
[15]. This study was, however, performed on a very select population with an expected
very high prevalence of neoplastic lesions, and endoscopists were likely to have maximized
the diagnostic accuracy of each single technique to avoid relevant false-negative
results. That fact may have minimized advantages of the FUSE over the SFVE. In addition,
the detection rate for advanced neoplasia rather than ADR was the primary endpoint
of the study.
Gralnek et al. found that most of the lesions missed by colonoscopy are diminutive
polyps of the right colon [9]. A more accurate inspection of the right colon using retroflexion of the scope or
segmental repetition of the withdrawal phase has been suggested to reduce the polyp
miss rate [16]. These data are in accordance with our finding that optimizing WT may result in
a significant increase in number of lesions detected in the right colon with the SFVE,
while use of the FUSE is likely to offer only a very small (about 2 %) further increase
in detection rate; conversely, in the left colon, optimization of WT is likely to
carry a limited benefit when a SFVE is used, while use of the FUSE seemed to increase
the detection rate. It is plausible that in a quite straight colon, such as the proximal
one, rotation of the tip of the scope combined with in-out movements of tube insertion
would allow a standard narrow view scope to cover the colon mucosa, while in the sigmoid
colon, the very narrow curves and flexures would create several hidden areas that
can be exposed only using a wider-angle view scope or a system able to flatten the
folds and straighten the curvatures.
A recent study has demonstrated that unmonitored endoscopists may have poor adherence
to the WT protocol, but that their WT increases (and also their ADR) when they are
aware of being monitored [10]. This information has been reproduced in our study and has allowed to us to evaluate
the effectiveness of instituting an adequate WT in improving accuracy of colonoscopy.
Reduced adherence to WT recommendations seems to be a real problem in the real world
[17], and some centers systematically monitor WT to increase endoscopists’ adherence
[18]. The physicians performing our study are all very expert endoscopists, who had performed
more than 1000 investigations; they all were aware of the value of WT in improving
accuracy of colonoscopy, and in previous monitored sessions, they showed a high adherence
to the 6-minute withdrawal protocol. In spite of this, in the first part of the study,
only about 22.9 % of procedures were performed with a WT > 6 minutes.
We have demonstrated that WT, i. e. attention that the endoscopists pay during scope
retraction, was strictly related to the subjective perceived chance of finding a significant
lesion at endoscopy. As a consequence, in phase 1, when endoscopists were unaware
of being monitored, WT was longer when a first adenoma was detected during the procedure,
as well as in patients undergoing colonoscopy for CRC screening; conversely, WT was
shorter in cases of overt bleeding, an indication for which endoscopy is performed
to look for grossly bleeding lesions. The clinical impact of such behavior has yet
to be evaluated, but it is likely to be minimized by use of the FUSE.
Our study design deserves some consideration. As a real-life study, patients were
not randomized and assignment to undergo colonoscopy with one or the other scope was
only determined by scope availability. The two groups were, however, comparable for
demographic and clinical characteristics, which would have minimized risk of bias.
In addition, randomization would not have ensured any blind comparison, as the endoscopist
could not be masked to the type of scope used.
The study design allowed recruitment of patients undergoing colonoscopy for different
indications. Thus, only 30 % of patients were screened for colonoscopy, whereas the
values of ADR are strictly defined. Instead, in our setting, heterogeneity of indications
for colonoscopy makes it difficult to compare our results with ADRs of other studies,
which may be a limitation of this study.
Overall in this study, both introduction and retraction times were longer for the
FUSE in comparison with the SFVE, a fact that would suggest that endoscopists were
not completely confident with using the FUSE. Prior to the study’s start, a formal
training was done and every endoscopist performed 10 investigations with the new instrument
to get familiar with it. We could hypothesize that the learning curve for the FUSE
may be longer even for expert endoscopists, but because insertion time for the FUSE
was similar in the two phases of the study, it is more likely that characteristics
of the FUSE system may be associated with some difficulties related to maneuverability
and that the need to monitor three screens may result in expenditure of more time.
Conclusion
In conclusion, we have demonstrated that unmonitored endoscopists have suboptimal
WT, and that WT increases when they are aware of being monitored. Optimizing WT is
a fundamental requisite when performing colonoscopy, whichever endoscope is used.
Even if used with adequate WT, standard scopes may be unable to visualize all lesions,
and use of the FUSE may increase the number of lesions detected. While detection of
proximal adenomas is more strictly related to application of a correct WT protocol,
use of the FUSE may represent an important aid in detection of lesions in the distal
colon.
