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Development, Sensibility and Reliability of a New
Case-finding Questionnaire: the Toronto Axial
Spondyloarthritis Questionnaire (TASQ) in
Inflammatory Bowel Disease
by
Khalid Abdalla Ali Bin Yarouf Alnaqbi
MBBS, CCD, FRCPC, FACP, FACR
A thesis submitted in conformity with the requirements for the degree of
Master of Science
Graduate Department of The Institute of Medical Science University of
The TASQ self-administered questionnaire was designed to serve as a case finding
instrument that could facilitate referrals of IBD patients with suspected axSpA to
rheumatologists for further evaluation. Early diagnosis allows for earlier intervention, an
important concept especially since TNF inhibitors have been found to be efficacious in
early disease. Because focusing only on characteristics of IBP cannot be sufficient to
make a diagnosis of axSpA, additional features are required, such as other relevant
clinical information (family history, articular symptoms, extra-axial manifestations),
laboratory tests (HLA-B27, ESR, CRP), and imaging (X-ray, MRI).
Previous questionnaires focused on refining the characteristics of IBP and did not
specifically target IBD patients. TASQ is to be administered at a single point in time to
patients with IBD who have chronic back pain or stiffness that has ever lasted 3 months
or more. This cut-off time which was chosen to minimize the referrals of mechanical
back pain was also used in previous studies (93, 106, 121). TASQ is cheap, easy to
administer and easy to understand by an average student in the 5th
grade. Completion of
the questionnaire takes 5 minutes or less which is in accordance to the recommended
completion time between 5 and 15 minutes (122). This also facilitates its feasibility
especially when this questionnaire is handed to IBD patients in a busy gasteroenterology
clinic or even when used online.
Designing a new questionnaire requires multiple steps to ensure a proper methodology in
order to yield a reliable instrument. During the development stage, I included sensitive
and specific items to help capture different aspects of the construct being sought i.e.
axSpA in IBD. I organized it into 3 domains (IBD, inflammatory back symptoms, and
extra-axial features). I strove to simplify the words in order to achieve our aims.
Hypothetically these questions represent a wide spectrum of discriminatory features that
increase the likelihood of axSpA and, therefore, can help gastroenterologists refer those
patients in a timely fashion.
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The clinimetric method, as introduced by Feinstein, advocates for the use of clinical
judgment when developing a measuring instrument. The tools that I used for this
approach included sensibility and reliability. In 1993, Rowe and Oxman paved the road
shown by Feinstein and developed a questionnaire for sensibility assessment. Twelve
items were developed based on the principles of sensibility. The response options were
constructed on a 7-point Likert scale. Some of their questions appeared redundant, and
some contained double-barreled questions. This questionnaire was adapted during
development of recent measuring instruments such as the Pediatric Cardiopulmonary
Physiotherapy Discharge Tool (123), and HIV Disability Questionnaire (124). I also
adapted the sensibility questionnaire by modifying some of their questions and adding
new ones for feasibility. New items related to the concept of feasibility (ease of use)
consist of time to completion (in minutes), flow of questions, readability, typographical
errors, font size, and use of illustrations. I also changed the format of scaling responses
into dichotomous scale which goes along the theme of the scaling responses of TASQ.
The sensibility assessment proved to be a valuable and comprehensive approach during
selection of the items and pilot testing that enabled me to look at different facets of the
questionnaire and remedy its weaknesses. Using the sensibility assessment, the
questionnaire underwent 4 revisions incorporating feedback from the SpA team, general
rheumatologists, and patients before reaching the fourth and final version.
2 Clinimetric Measures in the Literature
Psychometric methods use classical test theory and item response theory. The former
involved the statistical analysis of the data to yield reliability (test retest reliability,
internal consistency, split half reliability) and validity. Item response theory uses other
statistical models with different assumptions and requires larger sample size. It is obvious
that these methods rely heavily on statistical analyses to select items of an index or
questionnaire. With regards to assessing the internal consistency of an instrument, it is
required to have high correlations between the items (inter-item correlation) and the
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whole instrument (items-total correlation). While having a high internal consistency
coefficient is preferred, it may give a false impression that items are homogenous. For
example, the coefficient can increase by only increasing the number of questions (even if
they are redundant). In this case, the sensitivity of the items may actually be low which
consequently lowers the discriminatory property of the items (125). Having a high
coefficient of internal consistency requires an appropriate, and usually large, sample size.
Psychometric methods are not concerned with face validity and sensibility (usefulness of
the instrument). In addition, they do not necessarily result in constructing an accurate
measure (125).
Feinstein emphasized that judgment (by physicians and/or patients) is an essential part
during development of an instrument measuring a complex clinical phenomenon and that
psychometric techniques may be used to aid this process. Assessing internal consistency
is of less relevance here because the aim of developing a measuring tool is to capture
different aspects of the same (uni-dimensional) construct. Therefore, the internal
consistency is likely to be low although this is not always the case (126). There are some
indices which fell out of favor because they were not sensible and were difficult to apply
such as the Norris prognostic index for myocardial infarction (110). The clinimetric
approach has been used in the literature to construct indices which can comprise
classification or diagnostic criteria, guidelines, prognostic criteria, and questionnaires.
Examples of clinimetric measures are the New York Heart Association Functional
Classification (127), the Jones criteria for rheumatic fever (128), the Apgar criteria to
score the health of a newborn immediately after birth (129), and the Pittsburgh Sleep
Quality Index (130).
Two independent studies compared 2 different versions of questionnaires (Quality of Life
After Myocardial Infarction and Asthma Quality of Life Questionnaire) using methods of
clinical judgment and statistical analysis for item reduction. In each study, the clinical
judgment method performed slightly better than the statistical method when both versions
were tested for concurrent validity and responsiveness.
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There are important issues that were raised for discussion during at the sensibility
assessment of TASQ. These will be discussed next.
3 Sensibility Assessment of TASQ
3.1 Comprehensibility (Transparency)
Assigning appropriate weighting to each item of the questionnaire is a challenge. There
are 4 methods that can shed some light on item weighting. The first method of scoring is
based on clinical judgment and intuition. For example, a total score can simply be the
sum of each item that is weighted equally with a score of 1. This gives the questionnaire
the advantages of being simple, easy to score and transparent. Pediatric Crohn’s Disease
Activity Index (PCDAI) was scored using this method (131). In addition, the contribution
of each item weight to the cumulative score will be clear as opposed to a questionnaire
that assigns different weights to each item. The disadvantage of this approach is the
implication that every item is of equal importance. The second method assigns a
weighted score for each domain e.g. double the total score of Domain 1 and half Domain
2. This indicates the greater significance of a domain and the lesser significance of
another. The third method uses a statistical test (factor analysis) where assigning weights
is based on factor loadings. However, this often requires large sample size i.e. 5 patients
for each item. In addition, the interpretation of factor analysis requires clinical judgment.
The fourth method relies on another statistical analysis i.e. multivariate logistic
regression analysis that quantifies each item depending on its importance in explaining
the outcome (dependent variable). This is the basis of scoring the Systemic Lupus
Erythromatosus Disease Activity Index (SLEDAI) and Crohn’s Disease Activity Index
(CDAI) (132, 133). While it may be scientifically appropriate to weight items based on
statistical analysis, the different statistical tests may give different final scores which also
depend on the characteristics of the population and the setting. Some scales were scored
using statistical models that resulted in assigning sophisticated scoring that requires a
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special calculator. A clear example is the scoring system for the case ascertainment
questionnaire.
A recent Canadian questionnaire for inflammatory back pain (for details, refer to Section
4 of the Discussion) compared 2 methods of weighting items: summative (adding a score
of 1 for each item) and weighted items based on multivariate regression analysis. The
sensitivity, specificity, positive LR and the area under the curve were similar when any
method was used (134).
Another recent Canadian study compared weighting of the Pediatric Ulcerative Colitis
Activity Index (PUCAI) using mathematical and judgmental models. The PUCAI has 8
items including 6 historical and 2 laboratory parameters. Judgmental approach was found
to be as good as the mathematical approach only if the 2 laboratory items were removed
(135).
In my questionnaire, although there were 2 questions which are not going to be scored
(type of IBD and previous diagnosis of AS), I retained them in the final version to
provide important descriptive data especially that their removal would slightly reduce the
length of the questionnaire.
In conclusion, I will explore the scoring of the questionnaire in the next validation phase
and will compare the different scoring methods.
3.2 Content Validity
Many items had to be dropped because I wanted to keep the questionnaire simple and
concise (on 2 pages). A recent Cochrane systematic review found that the response rates
of patients in clinical trials increased when shorter self-reported questionnaires were
mailed (136). For example, the odds ratios (ORs) per page increase were 0.90 (95% CI
0.83–0.98) for one page compared with ≥ 4 pages, and 0.98 (95% CI 0.96–0.99) for one
page compared with ≥ 2 pages.
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During the pilot testing, the item “fibromyalgia” was removed for 3 reasons related to
low discriminatory property: 1) patients with true axSpA may have enthesitis that could
have been misdiagnosed with fibromyalgia, 2) enthesitis may overlap with tender points
of fibromyalgia, and 3) fibromyalgia can co-exist independently in both axSpA and IBD
as part of its association with some chronic diseases (137, 138). In addition, patients did
not endorse this item in the pilot study.
3.3 Feasibility
3.3.1 Acceptability
An item on “race” was included in the Phase 2 (item generation) since axSpA is more
common in Caucasian people of European extraction. Therefore, I considered ethnicity in
this instance a risk factor for axSpA. During Stage 3 of the development of TASQ, one
member of our team pointed towards the inappropriate inclusion of an item about race. In
a recent Cochrane systematic review, the likelihood of not responding to mailed
questionnaires was shown to increase when they asked about sensitive questions (139). I
then removed this item in order to increase the response rate.
3.3.2 Readability
Clarity of Questions
Constructing a clear questionnaire proved to be a challenge. Patients may not necessarily
read and understand what health care workers perceive as a straightforward question
since each comes from different backgrounds. In this study, I had to rephrase certain
questions a few times and even drop certain items because they were unclear to patients,
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even thought they were relevant to the complex construct of axSpA. I will elaborate more
on this in the following sections.
Insidious onset of back pain: The item has long been considered vague, as previous
studies did not agree on its exact definition. It is intended to measure the mode of onset of
back pain. However, does it mean slow onset or gradual onset? Can it be measured that in
weeks or months or even years? As a result of this unclear definition, studies showed an
overlap between mechanical low back pain and IBP when the poorly defined terms
“chronic” or “insidious onset” were used (93, 94). In the case ascertainment questionnaire
of Weisman and colleagues, the questionnaire developers defined “insidious onset” by
asking about the length of time (in months) since patients started to have back pain or
stiffness. At the end, I decided to keep the question as “When your back pain first began,
did it develop quickly (over hours or days) or slowly (over weeks or months). All patients
during the pilot and reliability studies were able to answer it easily.
Sleep disturbance at the second half of the night: Rudwaleit and colleagues found this
item an important characteristic of IBP when they administered their questionnaire (in
German) by an interviewer (93). I am unaware of any published cross-cultural adaptation
of their questionnaire. However, I used this item during the pilot testing phase but
decided to drop it because some patients found it difficult to define a cut-off for the
second half of the night.
Hip arthritis: Hip joint is localized in a deep-seated site, which may prevent patients
from expressing their pain clearly. The diagnosis of hip arthritis is often based on clinical
(history and physical examination) and radiographic evidence. There is a strong
association between hip arthritis and AS (37). A study showed that hip arthritis is
significantly associated with primary AS compared to IBD-associated AS (36). However,
I believe that this item is important and merits asking in a questionnaire. The problem
was how to ask about it properly using a single and relatively short question to fit in a
case-finding questionnaire. In clinical practice, rheumatologists ask patients different
questions about hip pain to increase the pre-test probability of hip arthritis. For example,
they may ask whether patients have pain or stiffness in the upper frontal side of the thigh
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that radiates to the groin. Some ask whether patients feel or even hear a click during hip
joint movements. Some patients point towards the painful area by cupping their thumb
and index fingers around the hip joint, which can also be seen in other conditions such as
trochanteric bursitis or fibroacetabular impingement syndrome. In the pilot study, some
patients drew a line (without being asked) to point towards hip pain but they directed the
line at either the buttock or sacroiliac joint. At the end, I could not include this item in our
questionnaire due to lack of a standardized definition and its susceptibility to
misinterpretation. A recent study attempted to describe hip pain for patients by using of a
diagram with pre-shaded area for localizing the hip pain and compare it with a
standardized question asking, “In the past month have you had any pain in the hip lasting
one day or longer?” This study concluded that the use of combined methods was
associated with signs of hip disease (abnormal physical examination and radiographic
changes). However, if these combined methods were used to exclusively define hip pain,
the sensitivity of capturing those patients would be low which does not go in the same
direction of our questionnaire (140). Future studies are needed to best describe hip pain to
patients.
Alternating buttock pain: This item was found to be one of the specific characteristics of
IBP (although not sensitive) and was therefore incorporated in Amor criteria and in
Rudwaleit’s study (93, 102). However, we had to drop it for 3 reasons: 1) some patients
had difficulty understanding the question, 2) buttock pain can still be a complaint in some
patients with AS and mechanical back pain, and 3) this particular item was not included
in the description of IBP of the ASAS classification criteria for axSpA (105).
Illustrations
TASQ is unique compared to the previous questionnaires in that it shows for the first
time a diagram of the back to allow patients to identify the locations of their back pain or
stiffness. I initially wanted to include a location for the ribcage since this has been noted
in some studies. But I decided against this idea because it will make the diagram cluttered
with too many arrows.
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The decision to remove the colored pictures of peripheral arthritis and dactylitis was
reached by consensus from the committee members and from the feedback of patients.
These pictures could be mutually misinterpreted. The picture of iritis was also removed
during selection of the items because it may be misinterpreted as conjunctivitis. However,
a future study is required to refine symptoms of iritis particularly if associated with
axSpA in IBD patients. A disadvantage of using colored pictures is the expense which
may limit the questionnaire feasibility. Questionnaires with colored pictures can be used
on the website but can only be used by patients who have access to the internet.
Recently, Gladman and colleagues developed a screening questionnaire for psoriatic
arthritis among patients with psoriasis and in general population; the Toronto Psoriatic
Arthritis Screening (ToPAS) (141). ToPAS has 3 domains, namely skin, joint and nail.
Among all the screening questionnaires for psoriatic arthritis, ToPAS was the first to
include colored pictures of the skin rash, and nail changes. A Dutch study found that
ToPAS performed slightly better compared to the Psoriatic Arthritis Screening and
Evaluation (PASE) questionnaire which could be partly related to the use of illustrations
(142). An update of ToPAS with more colored pictures is underway (143).
4 Reliability
4.1 Rating Responses of the Questionnaire Items
Upon looking at the responses of TASQ in the reliability study, all but one patient started
to have back pain or stiffness below the age of 45 years. The most prominent items
among patients with established IBD and axSpA were as follows: male gender, age of
onset of back pain ≤ 45 years, slow development of back pain initially (over weeks or
months), current morning stiffness of the back, current morning stiffness of the back
lasting 30 minutes or more, pain or stiffness in the neck, lower back and the buttock,
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improvement of back pain or stiffness at all with daily physical activities, and history of
peripheral arthritis.
4.2 Test-Retest Reliability
I chose test-retest (intra-rater) reliability to assess the stability of the items over time in
order to quantify measurement error rather than true change in disease activity. I provided
detailed information on the reliability and agreement using coefficients of reliability
(along with statistical uncertainty) and percentage agreement as per the recent
recommendations of the 2011 Guidelines for Reporting Reliability and Agreement
Studies (GRRAS) (115).
There are various criteria for the interpretation of coefficients. These include the
criteria of Landis and Koch, Cicchetti and Sparrow, and Fleiss (118, 144, 145). It is
important to note that all these criteria are arbitrary. In our study, I chose the criteria of
Landis and Koch. My a priori hypothesis was that the reliability coefficient (kappa or )
would be estimated as 0.90. The coefficient for each item was more than 0.80
indicating almost perfect agreement. Similarly, the absolute agreement for each item was
more than 91%. Although it may seem that some items had reliability coefficients (range
0.81 – 0.88) of less than the hypothesized reliability of 0.90, the minimally accepted
reliability for this study was 0.80. Therefore, those items are still within acceptable range
of reliability i.e. > 0.80 indicating almost perfect agreement.
I observed that the 95% CIs of coefficients for some items were wide and that may be
due to our small sample size. If we used a larger sample size, we may improve the
precision around the k statistics.
The sub-question “Prior diagnosis of psoriatic arthritis” was removed after the reliability
study for 2 reasons. First, this item was rarity endorsed by patients (only 1 patient).
Second, during the validation phase of the case ascertainment questionnaire, this item did
not help differentiating AS from chronic back pain (107). We considered psoriasis
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adequate for this questionnaire, as previous studies found it co-exist in 10-25% of AS
patients. Furthermore, psoriasis was recently shown to be more associated with non-
radiographic axSpA (OR 3.6) compared to classic AS (146). This additional item
reduction led to version 5 (dated May 1st, 2012).
5 Recent Questionnaire for Back Pain (April 2012)
A newly self-reported questionnaire has been published this year (April 2012). It is a
screening questionnaire for IBP developed by the Edmonton group of SPARCC. It
consists of 6 items with 3 branching questions. Items address morning stiffness of the
back and/or hip (branching question asked about the most noticeable time), nocturnal
pain (branching question asked about time of nocturnal awakening), diurnal variation of
pain in the back and/or hip, peripheral arthritis, response to exercise, and response to rest.
The questionnaire was administered to patients with established AS and mechanical back
pain (MBP).
In univariate analysis, 4 items distinguished IBP from MBP: morning stiffness, diurnal
variation, response to exercise and response to rest. In multivariate logistic regression
analysis, the last 3 items were independently associated with IBP, especially diurnal
variation (p = 0.0001). The “diurnal variation” item asked, “At what time of day your
back and/or hip symptoms the worse? Morning, Afternoon, Evening, Night, or Not
Applicable.” Using all the 6 items, the questionnaire outperformed Calin criteria and the
IBP criteria of ASAS in identifying patients with IBP. In my opinion, the way in which
the item “diurnal variation” was asked seems easier to understand than asking about
nocturnal pain at the second half of the night as suggested from Rudwaleit’s study (93).
In addition, this item showed the strongest association with IBP (OR 11.2, CI 3.7 – 34.2),
with a specificity of 92% and a sensitivity of 49%. As in the case of the previously
published questionnaires (Calin and case ascertainment questionnaire), the 6-item
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questionnaire is not targeted to IBD patients, and focused on features of IBP with one
question on peripheral arthritis.
As discussed earlier, investigators, who are interested in early diagnosis of axSpA, have
long been searching for the optimal characteristics of IBP which can improve the current
increase in post-test probability from 5 to 14%. Further, the interpretation of IBP needs
some clinical experience. Therefore, IBP cannot be used solely as a referral criterion. The
recommendation is to combine IBP with other features of the complex disease (axSpA) in
order to achieve a high post-test probability of axSpA (more than 90%) (17, 104, 146).
Indeed, IBP is no longer considered by ASAS to be a mandatory element in the definition
of axSpA. My questionnaire is in agreement with this, since other elements in addition to
characteristics of the back pain, are given equal importance.
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Chapter 6
Conclusions
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TASQ is a newly developed self-reported instrument to be administered to patients with
IBD who have ever had chronic back pain or stiffness that has lasted 3 months or more. It
consists of 3 domains (inflammatory bowel disease, inflammatory back symptoms, and
extra-axial features) and 16 items. The items were chosen based on their high sensitivity
(i.e. found in most patients with axSpA) and reasonable specificity which is in
accordance with a purpose of case-finding questionnaire. I have demonstrated that TASQ
is sensible, reliable, and inexpensive. It is easy-to-apply and requires 5 minutes of less to
complete. It is suitable for a student in the 5th
grade.
TASQ is a very promising questionnaire that might facilitate early patients’ referral to
rheumatologists and avoid delay in diagnosis of axSpA.
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Chapter 7
Limitations and Future
Directions
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While the project achieved it primary goals, there are some limitations to point out. The
following sections will discuss the limitations of this research and future directions.
1 Development
The pilot study was conducted at the Spondylitis clinic using a convenience sample of
patients with axSpA. Ideally, a sample of the target patients should be used i.e. patients
with IBD and axSpA. However, we only had 2 questions specific to IBD patients (type of
IBD, response of back pain or stiffness to biologic drugs). In addition, patients in the pilot
study provided their feedback on the sensibility of the IBD items. Ideally, a random
sample of axSpA patients would be representative as it should include a mixture of
patients with different levels of disease severity and levels of education. The sampled
patients represented a wide spectrum of axSpA disease activity. The questionnaire is
limited to patients who have finished grade 5. It could potentially be too sophisticated for
patients who have lower educational levels. If this were truly shown in a future study, one
solution would be to use more illustrations.
This questionnaire is only applicable to English-speaking and literate patients. Therefore,
future research is needed for cross-cultural adaptation and validation to different
languages.
Some features of IBP need to be clarified in future studies. As described in the Results,
defining “alternating buttock pain” using simple words was challenging and led to
dropping this item from the final version. On the same token, finding an accurate
definition for “hip pain” needs to be studied in the future since hip arthritis is a feature of
axSpA. The classic item of Calin criteria “improvement of back pain or stiffness with
exercise” remains to be further clarified. It should be noted that this item is also observed
in patients with mechanical back pain. Does improvement of IBP imply any degree of
exercise? Is the improvement expected to occur after a certain period of time?
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Future modifications for this questionnaire may emphasize shoulder involvement in
axSpA patients. Chronic rotator cuff and enthesitis at the insertion of the supraspinatus
muscle to the bone are common manifestations of axSpA. Inclusion of this item can be
achieved with the use of a diagram.
2 Future Validation Studies
The TASQ was demonstrated to be reliable in patients who had IBD and axSpA and
attended a hospital-based rheumatology clinic. An important next step is validation is this
questionnaire in gastroenterology clinics. We are currently in the process of validating
the TASQ through collaboration with the gastroenterologists at the University Health
Network including Mt. Sinai, Toronto General and Toronto Western Hospitals. Inclusion
criteria for the study include age ≥ 18 years, fluency in English, established IBD
diagnosis, chronic back pain or stiffness ever present ≥ 3 months in duration, and
competency to consent. Patients will be recruited and referred to the Spondylitis Clinic
for a thorough assessment according to a standardized protocol. They will complete the
TASQ in the waiting area. An advanced practice physiotherapist, who will be blinded to
the patients’ answers of the questionnaire, will then assess them. The diagnosis of back
symptoms will be determined. The ideal situation for validation of the questionnaire
requires 2 groups of IBD patients: patients with mechanical back pain and patients with
axSpA. Finally, the type of validity will be assessed such as concurrent construct validity.
Another validation of TASQ is underway in which we have collaborated with
gastroenterologists at a hospital-based IBD clinic in the US. This validation is based on a
case-control study. IBD patients have undergone CT scans of the abdomen and pelvis at
some point of time as part of investigations for their IBD. We determined that the clinic
has on file a bank over 900 CT scans of which approximately 130 patients were found to
have definite sacroiliitis on CT scan. These patients likely have IBD-associated AS. The
controls will consist of 200 IBD patients with no sacroiliitis on CT scan. After having just
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recently obtained approval of the institutional research board at that hospital, my new
questionnaire will be administered to those patients either via email or mail. The scores
of the questionnaire will be determined using the receiver operator curve with the aim of
having high sensitivity.
A third future study is to validate the TASQ in the primary care setting in patients who
have IBD. This will involve approaching the Family Practice Units of the University of
Toronto affiliated teaching hospitals.
The reliability study of this questionnaire was conducted in patients with established IBD
and axSpA. This questionnaire applies to a subset of seronegative SpA patients who have
IBD and undetected axSpA. With the exception of IBD domain, there is no reason to
assume that this questionnaire cannot be applied to any patient at risk for axSpA such as
patients with reactive arthritis or uveitis. However, this would require future validation.
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Appendix A: Consent to participate in a research study
Date: 13 July 2011
Dear Ms. / Mrs. / Mr.,
Many patients with inflammatory bowel disease such as Crohn’s disease, ulcerative colitis, or
indeterminate (unclassified) colitis are at high risk for developing inflammatory back disease which
is the main symptom of a group of chronic back diseases called spondyloarthritis. We have developed
a new questionnaire that could help in earlier detection of inflammatory back disease in patients
with inflammatory bowel disease in order to facilitate early treatment, with the aim to improve their
quality of life. Our goal now is to make sure this questionnaire is reliable.
We are asking you to complete a questionnaire (marked as 1), and then mail it back to us. After
about 1 week, fill out the same questionnaire (marked as 2) and send it back to us by 25th July 2011.
Two stamped, self-addressed envelopes have been provided.
We appreciate you time and cooperation with our request.
Sincerely,
Dr. Robert D. Inman, MD
Director of the Spondylitis Program
Director of the Arthritis Centre of Excellence
Professor of Medicine and Immunology University of Toronto