Critical appraisal:Viana Freitas BR, Kibune Nagasako C, Pavan CR, Silva Lorena SL, Guerrazzi F, Saddy Rodrigues Coy C, et al 2013 2

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Risk of bias assessment: diagnostic accuracy study

Patient Selection
Prior tests and any referral filters
Condition that defined entry into study
All patients who underwent

colonoscopy and provided the stool sample were initially
included in the study. Those with incomplete colonoscopy
(which did not reach the cecum) and noncancerous bleeding
lesions at the time of colonoscopy, such as inflammatory
bowel disease or bleeding hemorrhoids, were excluded from
the analysis.
The study

Setting
university hospital endoscopy unit
Was a diagnostic case-control design avoided?
Yes
Consecutive or random sample?
Yes
Did the study avoid inappropriate exclusions?
Yes
Reasons
All consecutive patients scheduled for elective colonoscopy at our university hospital endoscopy unit from July 2009 to July 2010 were invited
If comparing more than one index test was the design fully paired or paired randomly?
Not applicable
If a paired randomised design was used, was allocation to groups concealed and was the generation of allocation sequence adequate?
Not applicable
What is the risk that the selection of participants introduced bias?
Low
Comments
Index test 1
Describe index test and how it was conducted and interpreted
Feca-Cult One Step Test (Alamar Tecno

Cient´ıfica Ltda)which is an immunochromatographic test for
the qualitative determination of human hemoglobin in feces. Interpreted via manufacturer's instructions. FIT was performed in a single sample taken
from a bowel movement one week before colonoscopy. All
tests were performed by the same investigator, and borderline
positive results (faint bands) were interpreted as positive.

Were the index test results interpreted without knowledge of the results of the reference standard?
Unclear
If a threshold was used, was it pre-specified?
Yes
If two tests are being compared, have they been assessed independently / blind to each other?
Not applicable
What is the risk that the conduct or interpretation of the index test introduced bias?
Unclear
Comments
Under FIT 2.2 "All

tests were performed by the same investigator" - unclear if this refers just to FIT or to reference as well.

Index test 2
Describe index test and how it was conducted and interpreted, if applicable
Were the index test results interpreted without knowledge of the results of the reference standard?
Not applicable
If a threshold was used, was it pre-specified?
Not applicable
What is the risk that the conduct or interpretation of the index test introduced bias?
Not applicable
Comments
Reference Standard
Describe the reference standard and how it was conducted and interpreted
Before colonoscopy

a questionnaire containing clinical and epidemiological
data of the patientwas completed.Colonoscopieswere
performed or supervised by experienced endoscopists who
were blinded to the FIT results.

Polyps identified at the time of the exam were characterized
by number, size, colonic location (proximal or distal to
the splenic flexure), and endoscopic appearance. All polyps
were removed and sent for histological analysis. Adenomas
were classified by number, size, location, and histologic
characteristics (tubular, tubulovillous, or villous).

Patients with diverticular diseases or nonbleeding
hemorrhoids were considered as having normal
colonoscopic findings.

Is the reference standard likely to correctly classify the target condition?
Yes
Were the reference standard results interpreted without knowedge of the results of the index test/s?
Yes
Was the reference test standard independent of the index test?
(i.e. the index test did not form part of the reference standard)
Yes
What is the risk that the reference standard, its conduct or interpretation introduced bias?
Low
Comments
Flow and timing
Describe any patients who did not receive the index test(s) and/or reference standard or who were excluded from the 2x2 table
All exclusions justified (Figure 1).
Describe the time interval and any interventions between index test(s) and reference standard
FIT was performed in a single sample taken

from a bowel movement one week before colonoscopy. Patients invited to bring a stool sample on the day
of the educational session about colonoscopy, which takes
place one week before the exam.

If a predictive test (the reference standard is a later event that the test aims to predict) were any subsequent interventions between test and later event blind to test result?
Not applicable
Was there an appropriate interval between index test(s) and reference standard?
Yes
Did either all participants or a random sample of participants receive a reference standard test?
Yes
Did all patients receive the same reference standard irrespective of index test result?
Yes
Were all test results including unclear results reported?
Yes
Were all patients included in the analysis?
Yes
What is the risk that the patient flow introduced bias?
Low
Comments
Overall risk of bias
At risk of bias Additional comments: Unclear if index test was conducted blind to reference findings or an appropriate interval beteween tests.


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Article
Viana Freitas BR, Kibune Nagasako C, Pavan CR, Silva Lorena SL, Guerrazzi F, Saddy Rodrigues Coy C, et al. Immunochemical fecal occult blood test for detection of advanced colonic adenomas and colorectal cancer: comparison with colonoscopy results. Gastroenterol Res Pract 2013;2013:384561 Available from: http://www.ncbi.nlm.nih.gov/pubmed/24319453.
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User:Melissa.chow
Topic area
Guidelines:Colorectal cancer
Clinical question
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