ABSTRACT
Background:Treatment of diabetes mellitus (DM) is complex, requiring multifaceted lifestyle change or reg-ulation and, for many, self-regreg-ulation of insulin levels in the blood. Historically, daily insulin treatment has been viewed as burdensome to patients, prompting newer formulations and improved delivery methods.
Objective: This multicenter, clinical study was designed to develop a conceptually sound, clinically meaning-ful, and psychometrically valid measure of insulin treatment satisfaction, applicable to a wide range of insulin therapies.
Methods:A 3-phase iterative process was employed to develop and validate the Insulin Treatment Satisfaction Questionnaire (ITSQ): (1) conceptual development of items, (2) preliminary validation among patients with DM, and (3) confirmatory validation among patients with DM.
Results:The ITSQ was validated with 170 patients in phase 2 and 402 patients in phase 3. Confirmatory fac-tor analysis produced a 5-facfac-tor, 22-item instrument assessing regimen inconvenience, lifestyle flexibility, glycemic control, hypoglycemic control, and satisfaction with the insulin delivery device. Results for reliability and construct validity of the final version were consistent in both samples of patients treated with insulin, with different data collection methods. Internal consistency (using Cronbach α coefficient) of the subscales ranged from 0.79 to 0.91. Test–retest reliability (using Spearman rank correlation coefficients) ranged from 0.63 to 0.94. ITSQ scores showed moderate to high correlation with related measures of treatment burden. The ITSQ differ-entiated among insulin delivery methods, glycosylated hemoglobin values, the number of times the patient required assistance administering insulin, and insulin adherence.
Conclusion: In our study samples, the ITSQ appeared to be conceptually and psychometrically sound and applicable to a wide range of insulin therapies. (Clin Ther. 2004;26:565–578) Copyright © 2004 Excerpta Medica, Inc.
Key words: treatment satisfaction, insulin, diabetes mellitus.
CLINICALTHERAPEUTICS®/ VOL. 26, NO. 4, 2004
Accepted for publication February 5, 2004.
Printed in the USA. Reproduction in whole or part is not permitted. 0149-2918/04/$19.00
Development and Validation of the Insulin Treatment Satisfaction
Questionnaire
Roger T. Anderson, PhD,
1Soren E. Skovlund, MSc, BSc,
2David Marrero, PhD,
3Douglas W. Levine, PhD,
4Keith Meadows, DrPhil,
5Meryl Brod, PhD,
6and
Rajesh Balkrishnan, PhD
71Wake Forest University School of Medicine, Winston-Salem, North Carolina, 2Novo Nordisk, Bagsvaerd, Denmark, 3Indiana University School of Medicine, Indianapolis, Indiana, 4University of South Carolina, Columbus, South Carolina, 5City University, London, United Kingdom, 6The Brod Group, Mill Valley, California, and 7University of Texas Health Sciences Center School of Public Health, Houston, Texas
INTRODUCTION
The incidence of diabetes mellitus (DM), a leading cause of disability and health care costs in most Western countries, is increasing at epidemic propor-tions.1,2 Among the various pharmacologic
treat-ments, insulin is among the most widely used, encom-passing all cases of type 1 DM and between 20% and 30% of adult cases of type 2 DM.3Insulin treatment of
DM is complex, involving the self-regulation of insulin levels in the blood. Successful glycemic control is the primary clinical outcome. Most insulin regimens require that the patient self-administer doses on a daily basis according to a prescribed treatment plan. This need for self-care, coupled with the lifestyle restrictions imposed by insulin regimens, may play an important role in the patient’s success in following treatment recommendations and achieving good glycemic control.
Patients who are satisfied with their treatment in terms of low burden and easy integration with daily activities will likely manage their home treatment bet-ter and consequently could be expected to maintain positive physical and psychological health, whereas poor self-management of DM can lead to serious, dis-abling complications. With the emergence of new short-, medium-, and long-acting insulin analogues delivered by both pen and pump devices,4there is a
complementary need to quantify the impact of these treatment options in terms of individual patients’ treatment burden. Currently, few well-tested surveys are available for describing and comparing patient experiences across a wide range of insulin treatment regimens. Measures are needed that have sufficient breadth of scope to characterize key patient experi-ences and features of insulin therapies that substan-tially affect daily life with DM. This includes identify-ing specific problem areas requiridentify-ing attention from patient DM counselors and educators, to maximize the fit between insulin therapy and patient preference and lifestyle, and ultimately to enhance glycemic con-trol through optimal patient adherence. The latter objectives bring treatment satisfaction to the fore.
Conceptually, treatment satisfaction is a recipient’s rating of the salient aspects of the process and results of the treatment.5 To formulate an assessment, each
individual weighs the relevant aspects of treatment and determines his or her overall degree of satisfaction through a cognitive process that reflects personal
pref-erences for treatment, experiences during treatment, and the importance of each outcome relative to desired goals. In the context of DM, it is possible for a patient to be dissatisfied despite the clinical effectiveness of a therapy. A treatment plan of decreasing glycosylated hemoglobin (HbA1c) to stringent parameters (eg, <6%) with an intensive insulin treatment therapy may have intended negative consequences on a patient’s daily life or well-being (eg, hypoglycemia) that may be per-ceived by the patient as outweighing the goal of opti-mal control and long-term health protection.
Tools to measure patient satisfaction with insulin regimens are available in the literature.6,7 However,
most of these instruments have been developed for a specific delivery method (eg, pen systems) or formu-lation, potentially limiting their usefulness across various insulin treatments. Instruments that assess generic characteristics of DM treatments may be inconclusive or insensitive to unique differences in burden concerning insulin therapies.
The purpose of this research program was to devel-op a conceptually sound, clinically meaningful, and psychometrically valid treatment satisfaction measure applicable for modern insulin therapies.
METHODS
Development of the Insulin Treatment Satisfaction Questionnaire (ITSQ) was conducted in 3 distinct phases: (1) conceptual development of the items, (2) preliminary psychometric validation, and (3) con-firmatory psychometric validation.
Phase I: Conceptual Development
The conceptual basis for the ITSQ and its items were developed through a literature review, consulta-tion with clinicians, and interviews with patients with DM. Focus groups were conducted to generate and revise an initial item pool. Four groups were formed of patients with either type 1 or type 2 DM from low-income community health clinics and from a DM care clinic in an academic medical center. English-language MEDLINE listings (last 10 years) were searched using the following key words: diabetes care, insulin, burden, and satisfaction. Published reports and relevant questionnaires in the literature were examined to yield lists of general content clusters. The latter lists were given to DM health care providers for review to add or further specify the content. An initial CLINICALTHERAPEUTICS®
patient focus group was held (comprising patients using syringe, pen, and pump methods of insulin delivery) to discuss general issues of treatment burden and to refine the list. A list of draft items was pro-duced (based on this feedback) and discussed, and 3 iterative patient focus groups were held to develop the items in terms of concept clarity, conciseness, and rele-vance. All focus groups were audiotaped, transcribed, and content coded by trained experts.
Phase II: Preliminary Validation
Following item development, a prototype ITSQ instrument was tested in a sample of patients treated with insulin. A validation battery comprised ques-tions on patients’ demographics, treatment history, and the following related instruments: the 12-Item Short-Form (SF-12, version 2) Health Survey,8which
assesses general health and well-being; and the Insulin Management Self-Efficacy Scale,9 which
measures patients’ confidence in their ability to care for themselves with insulin.
Other items assessed history of symptoms known to occur with insulin treatment and glycemic control adapted from Whitty el al.10 The Problem Areas in
Diabetes (PAID) Scale11measured the extent of
prob-lems perceived by the patient regarding different aspects of having DM. The World Health Organ-ization Diabetes Treatment Satisfaction Question-naire (WHO-DTSQ)6measured overall DM treatment
satisfaction.*
Items assessing global satisfaction with insulin developed for this study and subjected to cognitive testing during patient interviews for clarity, concise-ness of meaning, and ease of response. The items assessed patients’ experiences during the past 4 weeks: “In general, how satisfied are you with your insulin regimen?”; “In general, how satisfied have you been with the type of insulin you use?”; “In general, how satisfied have you been with the device or method you use to give yourself insulin?”; and “In general, how satisfied have you been with your over-all diabetes treatment (think about over-all aspects of your treatment including diet, exercise, tablets, insulin, etc)?” The response scale was ordinal, ranging from 1 (extremely satisfied) to 6 (extremely dissatisfied).
Construct validity of the ITSQ total score, the pri-mary score of this tool, would be affirmed if the score demonstrated moderate correlations (eg, r > 0.30) with measures of related concepts such as general DM treatment satisfaction (eg, WHO-DTSQ), problems with DM management (eg, PAID), and somatic symptoms relevant to DM. Thus, we hypothesized that respondents who reported regi-men problems or symptoms or who give low ratings for general aspects of their insulin treatment would also report lower satisfaction on the ITSQ. Fur-thermore, we expected that global measures of health status (eg, SF-12) would demonstrate consis-tency between poorer health and lower satisfaction, reflecting inadequate DM control. As a measure of treatment burden, the ITSQ was expected to show relatively low correlations with physical well-being, a distinctly different concept than treatment satis-faction. Construct validity of the ITSQ subscale domains, representing core content areas of the sur-vey, would be affirmed if each ITSQ subscale corre-lated more highly with pertinent measures than with the other less relevant subscales. Thus, scales assessing inconvenience and flexibility would corre-late highest with measures of regimen problems (eg, PAID); a subscale assessing satisfaction with glycemic control would correlate highest with glob-al ratings of satisfaction with insulin and treatment; and the subscale assessing satisfaction with devices would correlate highest with a global item on satis-faction with method of insulin delivery. Finally, we expected that because treatment satisfaction is intended as a core indicator of treatment quality, it would correspond to clinical outcomes of HbA1c value and medication adherence.
Participants were recruited from 3 medical centers in the United States by using patient lists of DM care centers at each location. The settings were primary care practices that offer comprehensive DM care to both publicly and privately insured patients. Eligible patients were aged ≥18 years, had no apparent cogni-tive impairment, had a diagnosis of DM, were treated with insulin therapy, and were able to read English. To ensure sample heterogeneity for patients’ treat-ment exposures and experiences, we drew a conve-nience sample of patients, overselecting type 1 DM and alternative insulin delivery methods such as pump and pen (versus syringe). From this group, *Permission to use the WHO-DTSQ was granted by the World Health
participants were randomly selected for a substudy to complete the questionnaire again 1 week later in the physician’s office to assess test–retest reliability. Clinical information recorded from the patients’ charts included type of DM, HbA1c value, whether the patient was prescribed insulin or insulin/oral hypoglycemic agents, and the number of bolus and basal injections per day. We also assessed self-reported adherence with insulin doses, operationalized as self-reported frequency (often to not at all) in the last 4 weeks of “skipping an insulin dose because you forgot to take it.”
Exploratory factor analysis with orthogonal trans-formation was used to identify the ITSQ item struc-ture for subsequent testing. Construct validity of the initial ITSQ factors was checked from correlations with related measures in the battery. An intermediate version of the ITSQ was produced for refinement.
Phase III: Confirmatory Validation
In the final step, the item structure of the ITSQ was retested in an independent sample with confirmatory factor analysis and refined to maximize model fit to produce a final ITSQ version. The confirmatory validation battery consisted of the revised ITSQ, questions on patients’ demographics and insulin treatment, and self-reported clinical information including most recent HbA1cvalue, duration and type of DM, insulin product and regimen, and time taking insulin. The battery was administered via the Internet to patients treated for DM in a national Internet con-sumer panel. Patients with DM were contacted by e-mail, and only those matching the inclusion criteria were asked to participate. To ensure that the survey respondents had the required characteristics, we veri-fied the original panel registration data with personal data on the questionnaire.
Confirmatory factor analysis was performed with structural equation modeling to evaluate the model developed in the preliminary validation phase. Model fit was assessed using the chi-square test. Because it is well known that the chi-square test of significance is sensitive to sample size,12model fit was also
evaluat-ed in light of 3 other common fit indices: the normevaluat-ed chi-square (χ2/df), the comparative fit index (CFI),13
and the root-mean-square error of approximation (RMSEA).14Values of the normed chi-square close to
2 represent good fit.12,15,16Internal consistency
relia-bility of the ITSQ total score and subscales was assessed using the Cronbach α coefficient.17
Test–retest reliability was examined using Spearman rank correlation coefficients. Known-groups validity was examined by comparing adjusted means of ITSQ factors for insulin delivery assistance (none vs some help), HbA1c value (≤7.5% vs >7.5%), and insulin delivery method (syringe vs pen). The clinical mean-ingfulness of the ITSQ was assessed during the con-firmatory study by correlating ITSQ scores with patients’ blood glucose levels and by assessing the ITSQ to discriminate patients by their HbA1cvalues. Spearman rank correlation coefficients were used to mea-sure the association of ITSQ total scores and subscale scores with related measures (PAID, WHO-DTSQ, Insulin Management of Diabetes, Self-Efficacy Scale, and DM symptoms) and with global ratings of satis-faction. Known-groups validity was assessed by tests of least square means (adjusted for age and sex) for ITSQ subscale and total scores between HbA1cvalues (≤8% vs >8%), method of insulin delivery (syringe and vial vs pen, pump), and self-reported frequency of need for assistance taking insulin (never vs any need).
ITSQ subscale scores were calculated by imputing the missing values based on the mean of the nonmiss-ing items. All subscales were transformed to a scale of 0 to 100, with higher scores indicating better treat-ment satisfaction.
RESULTS
Phase I: Conceptual Development
A total of twenty-five patients with DM participat-ed in 4 focus groups. Participants were diverse in terms of age, sex, ethnicity, length of time and method of taking insulin, and type of DM. Findings from patient interviews, clinical expert review, and the literature were synthesized to generate a prelimi-nary set of 32 items covering 6 general aspects of insulin treatment (ease of regimen, glycemic control, treatment burden or distress, interference in meal planning, lifestyle, and symptoms) and method of insulin delivery.
Patients’ response options were based on an ordered scale. For example, for the question, “How convenient is it for you to take all your daily insulin doses as prescribed?” patients indicated their responses on a 7-point scale from “extremely conve-CLINICALTHERAPEUTICS®
nient” (score of 1) to “not at all convenient” (score of 7). We did not test importance or preference weight-ing in the development and scorweight-ing of the ITSQ instrument because recent research suggests that assigning preference weights does not improve sensi-tivity to change.18,19
Phase II: Preliminary Validation
The preliminary validation sample included 170 patients (Table I). Respondents had a mean (SD) age of 48.7 (13.2) years, and 107 (62.9%) were women. Many had completed high school (83 [48.8%]); 44 (25.9%) had completed college and 36 (21.2%) had not completed high school. Of these 170 patients, 63 (37.1%) had type 1 DM, and their primary method of taking insulin was syringe and vial (120 [70.6%]), followed by pen injection (22 [12.9%]), pump (22 [12.9%]), and inhaler 4 (2.4%). In 55 respondents (32.4%), HbA1c values were categorized as low (<7.5%), 36 (21.2%) were moderate (7.5%–8.5%), and 55 (32.4%) were high (>8.5%); 17 respondents (10.0%) took insulin QD, 73 (42.9%) BID, 32 (18.8%) TID, 29 (17.1%) QID, and 15 (8.8%) >4 times daily. Most respondents (95 [55.9%]) had had DM for >10 years, 31 (18.2%) for 6 to 10 years, and 19 (11.2%) for 3 to 5 years. Few respondents (24 [14.1%]) had had DM for ≤2 years. Likewise, the largest group of respondents (69 [40.6%]) had been taking insulin for >10 years, followed by 16.0% for 6 to 10 years, 31 (18.2%) for 3 to 5 years, and 41 (24.1%) for ≤2 years.
Exploratory factor analysis of questionnaire responses in this sample identified a parsimonious 5-factor structure including ease and convenience of regimen, burden of regimen, lifestyle flexibility, glycemic control, and satisfaction with the insulin delivery device, with a total of 16 items. This struc-ture was highly consistent with content areas identi-fied in the focus groups. Internal consistency (Cronbach αcoefficient) of the subscales ranged from 0.78 (lifestyle) to 0.92 (glycemic control), and for all ITSQ questions, it was 0.92. Test–retest reliability (Spearman rank correlation coefficient) in a random-ly selected sample was moderate to high for all sub-scales, ranging from 0.63 to 0.94 (Table II). Based on the psychometric findings, 5 items were added to cre-ate a separcre-ate domain of hypoglycemia as distinct from overall glycemic control. An additional item was
added to form an inconvenience subscale, collapsed from the burdenand easesubscales. These procedures resulted in a 22-item ITSQ, which was submitted for confirmatory validation.
Phase III: Confirmatory Validation
Approximately 60% of patients contacted by e-mail agreed to participate in the study. The confirmatory validation sample included 402 respondents (Table I). They had a mean (SD) age of 55.6 (9.4) years, and 174 (43.3%) were women. Nearly equal proportions of the patients had completed high school (193 [48.0%]) and had completed college (199 [49.5%]). All had type 2 DM, and 328 (81.6%) used insulin delivered by syringe and vial, followed by pen injec-tion (55 [13.7%]), pump (5 [1.2%]), and inhaler (1 [0.2%]). Among the respondents, 127 (31.6%) had HbA1c characterized as low (<7.5%), 125 (31.1%) had moderate values (7.5%–8.5%), and 72 (17.9%) had high values (>8.5%). Insulin administration QD was most common (207 [51.5%]), followed by BID (45 [11.2%]) and ≥3 times per day (150 [37.3%]). Most patients (233 [48.0%]) had had DM for >10 years, 114 (38.4%) for 6 to 10 years, 34 (8.5%) for 3 to 5 years, and 21 (5.2%) for ≤2 years. A total of 87 patients (21.6%) had been taking insulin for >10 years, 129 (32.1%) for 6 to 10 years, 54 (13.4%) for 3 to 5 years, and 132 (32.9%) for ≤2 years.
Confirmatory factor analysis of the 22-item ITSQ reproduced the original item structure and the pro-posed factor of hypoglycemia items (Appendix). Three of the 4 fit indices indicated that the model fit the data20,21: normed χ2 = 2.35, CFI = 0.96, and
RMSEA = 0.06. The χ2
184 was 431.78 (P < 0.001),
reflecting the sensitivity of the latter test to sample size. Thus, the final ITSQ contained 22 items among 5 content clusters, forming a total ITSQ score trans-formed as 0 to 100 where 100 indicates complete sat-isfaction with insulin treatment.
Table II shows the ITSQ subscale and total score means, percentage at ceiling (most satisfied), and internal consistency reliability (Cronbach α coeffi-cient) of the final item set. Consistent with the results for the exploratory sample, the confirmatory sample showed high reliability, ranging from 0.79 (lifestyle flexibility) to 0.91 (glycemic control), and 0.93 for all ITSQ questions. Ceiling effects were relatively low, ranging from 16.2% (inconvenience of regimen) to
CLINICALTHERAPEUTICS®
Table I. Characteristics of preliminary and confirmatory validation samples (n = 170 and n = 402, respectively).*
Characteristic Preliminary Sample Confirmatory Sample
Age, mean (SD), y 48.7 (13.2) 55.6 (9.4)
Sex, no. (%)
Women 107 (62.9) 174 (43.3)
Men 61 (35.9) 228 (56.7)
Highest level of education, no. (%)
Did not complete high school 37 (21.2) 10 (2.5)
Completed high school or equivalent 83 (48.8) 193 (48.0)
Completed college 44 (25.9) 199 (49.5)
DM type, no. (%)
Type 1 63 (37.1) 0 (0.0)
Type 2 92 (54.1) 402 (100.0)
HbA1cvalue, no. (%)
Low (<7.5%) 55 (32.4) 127 (31.6)
Moderate (7.5%–8.5%) 36 (21.2) 125 (31.1)
High (>8.5%) 55 (32.4) 72 (17.9)
No. of times insulin taken per day, no. (%)
1 17 (10.0) 207 (51.5)
2 73 (42.9) 45 (11.2)
3 32 (18.8) 141 (35.1)
4 29 (17.1) 7 (1.7)
>4 15 (8.8) 2 (0.5)
Time with DM, no. (%)
<6 mo 7 (4.1) 2 (0.5) 6 mo–1 y 2 (1.2) 2 (0.5) 1–2 y 15 (8.8) 17 (4.2) 3–5 y 19 (11.2) 34 (8.5) 6–10 y 31 (18.2) 114 (28.4) >10 y 95 (55.9) 233 (58.0)
Time taking insulin, no. (%)
<6 mo 10 (5.9) 34 (8.5) 6 mo–1 y 13 (7.6) 25 (6.2) 1–2 y 18 (10.6) 73 (18.2) 3–5 y 32 (18.8) 54 (13.4) 6–10 y 27 (15.9) 129 (32.1) >10 y 69 (40.6) 87 (21.6)
Primary method of taking insulin, no. (%)
Syringe and vial 120 (70.6) 328 (81.6)
Pen injection 22 (12.9) 55 (13.7)
Pump 22 (12.9) 5 (1.2)
Inhaler 4 (2.4) 1 (0.2)
Other 0 (0.0) 13 (3.2)
DM = diabetes mellitus; HbA1c= glycosylated hemoglobin.
7.5% (hypoglycemic control), and 1.2% for the total score.
Construct validity of the ITSQ subscales and total score, summarized in Table III, showed moderate correlation with the PAID (r = –0.43 to –0.69), WHO-DTSQ (r = –0.42 to –0.74), DM symptoms (r = –0.28 to –0.54), and Insulin Self-Efficacy Scale (r = – 0.24 to –0.67). Relatively low correlations were found between ITSQ subscales and SF-12 Health Survey physical component score as the ITSQ is not a measure of physical well-being; however, the moderate correla-tion with mental component score is evidence that the ITSQ overlaps with emotional distress.
Table IVpresents the known-groups validity of the ITSQ subscales and total score. Adjusted mean ITSQ total scores differentiated among insulin delivery groups: insulin delivery method (70.4 vs 76.7, P < 0.01), HbA1cvalues (75.5 vs 69.6, P= 0.01), and less burden in terms of needing help with insulin regimen (73.1 vs 64.9, P < 0.01). The ITSQ subscales dis-played targeted sensitivity to their intended concepts, with ITSQ lifestyle and flexibility discerning insulin delivery method (P = 0.01), ITSQ glycemic control discerning HbA1c value (P= 0.01), and ITSQ hypo-glycemic control and inconvenience discerning the need for help taking insulin (P= 0.03).
Finally, as shown in Table V, patients reporting high compliance (ie, no skipped doses of insulin in the last 4 weeks) had lower HbA1cvalues than those with partial compliance (ie, some skipped doses), as
well as fewer symptoms and higher ITSQ satisfaction scores (P= 0.05, P = 0.001, and P= 0.003, respec-tively). Predictors of insulin adherence (data not shown) were number of prescribed doses and older age, consistent with the literature on medication adherence in general.22
DISCUSSION
Insulin treatment of DM is a complex regimen that requires self-regulating insulin levels to match physio-logic needs. Although successful glycemic control is the primary outcome, adoption and maintenance of the requisite behaviors depend on the patient’s expecta-tions, self-efficacy, and day-to-day experiences with treatment.23Health care providers recognize that
psy-chosocial issues play an important role in how effective-ly patients manage their DM. Insulin regimens that best fit patients’ expectations and lifestyle demands may promote adherence and effective HbA1ccontrol. Comparison of insulin therapies with different insulin profiles, different formulations, or different modes of delivery requires a comprehensive instrument that is clinically meaningful and psychometrically sound.
The ITSQ proved to be conceptually sound and clinically relevant to important goals of glycemic con-trol and adherence. In addition, its practicality was evident from the low incidence (<5%) of missing val-ues in both preliminary and confirmatory samples. From the qualitative work based on patient inter-views through the results of the quantitative analysis
Table II. Comparison of results from the preliminary and confirmatory validation samples (n = 170 and n = 402, respectively).
Preliminary Sample Confirmatory Sample
No. of Ceiling, Cronbach α Test–Retest No. of Ceiling, Cronbach α
ITSQ Subscale Items Mean*(SD) % Reliability Reliability† Items Mean* (SD) % Reliability Inconvenience of regimen 4 76.36 (22.87) 20.5 0.88 0.83 5 78.38 (20.33) 16.2 0.90 Lifestyle flexibility 3 67.47 (25.30) 13.3 0.78 0.75 3 65.27 (22.54) 9.0 0.79 Glycemic control 3 60.41 (28.54) 9.6 0.92 0.63 3 65.58 (24.34) 8.7 0.91
Hypoglycemic control – – – – – 5 73.39 (20.06) 7.5 0.87
Insulin delivery device
satisfaction 6 73.08 (22.39) 10.9 0.88 0.94 6 74.38 (20.17) 7.7 0.86 ITSQ total 16 67.68 (20.85) 2.4 0.92 0.90 22 71.40 (16.53) 1.2 0.93
ITSQ = Insulin Treatment Satisfaction Questionnaire.
*Scores range from 0 to 100 (lower score indicates less treatment satisfaction). †Test–retest period was ~2 weeks (n = 27).
and final item reduction, we found 5 core dimensions of patients’ satisfaction with insulin treatment: incon-venience, lifestyle interference, glycemic control, hypoglycemia, and insulin delivery device. The treat-ment inconveniencefactor is a composite of treatment ease, burden, and quality, graded along a continuum. We followed a rigorous process for the development of the ITSQ, involving content review by experts in
the United States, Europe, and Japan, multiple focus-group discussions, and use of 2 samples to test and confirm the results.
The iterative approach of preliminary validation and confirmatory validation allowed improvement of the ITSQ and yielded a final 22-item version with a reliable internal structure and good construct validity of its subscales and total score. In addition, the ITSQ CLINICALTHERAPEUTICS®
Table III. Construct validity of Insulin Treatment Satisfaction Questionnaire (ITSQ) subscales in testing sample (n = 170).*
Global Satisfaction
Insulin SF-12 Health Satisfied Satisfied Satisfied Satisfied ITSQ WHO- DM Self-Efficacy Survey,8|| with DM with Insulin with Type with Device/ Subscale PAID11† DTSQ6‡ Symptoms§ Scale9 MCS/PCS Treatment|| Regimen¶ of Insulin¶ Method¶ Inconvenience of regimen – 0.69 – 0.68 – 0.45 – 0.49 0.54/0.03 (NS) – 0.49 – 0.61 – 0.55 – 0.52 Lifestyle flexibility – 0.45 – 0.42 – 0.28 – 0.24 0.33/0.12 (NS) – 0.22 – 0.35 – 0.33 – 0.37 Glycemic control – 0.43 – 0.50 – 0.48 – 0.40 0.35/0.20 (NS) – 0.57 – 0.58 – 0.47 – 0.38 Insulin delivery device satisfaction – 0.67 – 0.74 – 0.53 – 0.67 0.50/0.16 (NS) – 0.54 – 0.74 – 0.67 – 0.77 ITSQ total – 0.67 – 0.69 – 0.54 – 0.54 0.43/0.06 (NS) – 0.55 – 0.68 – 0.60 – 0.64
PAID = Problem Areas in Diabetes; WHO-DTSQ = World Health Organization Diabetes Treatment Satisfaction Questionnaire; DM = diabetes mellitus; SF-12 = 12-Item Short-Form Health Survey (version 2); MCS = mental component score domain; PCS = physical component score domain.
*Spearman rank correlation coefficients are shown. All coefficients in table have statistical significance of P< 0.01 unless noted as NS (not significant;P> 0.05).
Scores range from 0 to 100 (lower score indicates less treatment satisfaction).
†Higher score indicates higher burden. ‡Higher score indicates less satisfaction. §Higher score indicates higher symptom burden. ||Higher score indicates better health status.
¶Satisfaction during the past 4 weeks (higher score indicates more satisfied).
Table IV. Known-groups validity of the Insulin Treatment Satisfaction Questionnaire (ITSQ) subscales, grouped by clinical status according to least squares means.
Need for Help with Insulin Delivery Method* HbA
1c* Taking Insulin†
Syringe and Vial Pen/Pump Low High No Yes
ITSQ Subscale (n = 328) (n = 74) P (n = 127) (n = 197) P (n = 358) (n = 44) P
Inconvenience of regimen 77.99 80.84 0.33 81.24 77.16 0.08 80.04 71.66 0.01 Lifestyle flexibility 63.59 72.28 0.01 66.44 64.58 0.48 65.70 60.43 0.14 Hypoglycemic control 72.44 77.17 0.15 75.69 72.04 0.12 74.30 67.12 0.03
Glycemic control 65.19 70.13 0.18 74.95 61.65 0.00 66.58 58.89 0.05
Insulin delivery device satisfaction 72.55 83.54 0.00 79.31 72.40 0.00 75.78 64.57 0.00
ITSQ total 70.37 76.72 0.01 75.53 69.57 0.00 73.13 64.95 0.00
HbA1c= glycosylated hemoglobin.
*Analysis of variance adjusted for age and sex.
was reproducible (test–retest) and had convergent validity with instruments that overlap the content areas assessed. Based on our investigation, the ITSQ appears to be clinically meaningful because it is able to discriminate between methods of taking insulin, difficulty with the regimen, recent HbA1cvalues, and patients’ adherence to insulin therapy. Notably, patients with poor adherence to insulin had signifi-cantly lower treatment satisfaction and higher HbA1c values, demonstrating that difficult or demanding treatment regimens may appreciably lower treatment effectiveness, which may be possible to achieve with less burdensome treatment.
This study documented the validity and reliability of the ITSQ; it did not investigate relative perfor-mance of the ITSQ compared with other candidate measures in discriminating among various levels of insulin treatment satisfaction or other clinical out-comes. Future studies are needed to contrast and compare the benefits of treatment-specific versus generic instruments. Since the completion of validity testing, the ITSQ has been translated successfully into 8 other languages (Danish, Dutch, Finnish, French, German, Norwegian, Polish, and Swedish). Assess-ment of the burden of blood sugar monitoring and weight gain with therapy were outside the scope of this development, but may need to be assessed sepa-rately, depending on study focus.
The ITSQ was developed specifically for use with insulin treatment and does not address satisfaction with noninsulin (tablet) medications, for which other instruments are needed. Another limitation of the ITSQ is that although its development included considerable input from researchers in Europe, Japan, and the United States, the primary validation involved samples obtained in the United States.
Therefore, the validity of the ITSQ in international settings is unknown and must be tested. Although the ITSQ validation results were obtained from sam-ples diverse in terms of DM type, age, and race/ ethnicity, the extent to which the ITSQ subscale scores perform equivalently among subgroups of patients is not certain. We did not find statistically significant interactions with patient characteristics; however, additional research is needed to address the question of structural invariance by group. Our study was cross sectional and was not capable of examining casual influences of low treatment satis-faction on clinically relevant outcomes. For exam-ple, patients taking more complicated regimens may have experienced more difficulty controlling their DM and therefore may have been less satisfied with their regimen. In the absence of a randomized con-trolled trial to test this, the data presented in this analysis could be limited by confounding. The use of the Internet to find patients could also have con-tributed to selection bias because Internet users may be better educated, wealthier, and potentially have better glycemic control. The global measures of sat-isfaction with diabetes treatment, insulin device, and adherence used in this study to validate the ITSQ produced results that are highly consistent with their underlying concepts. However, these measures were developed and pretested for this study and have not been formally validated. Therefore, the measurement error of the latter items is uncertain. A final limitation is that despite the strong construct validity and sensitivity to clinical indices, responsiveness to change (eg, changes in HbA1cvalues) of the ITSQ was not examined in this cross-sectional study. Prospective studies are planned to address this issue.
Table V. Mean patient outcomes (n = 130) by insulin treatment compliance group.
Outcome High Compliance* Partial Compliance† P‡
HbA1cvalue 8.15 8.87 0.05
Symptom score 17.89 24.32 0.001
ITSQ total score 73.69 63.10 0.003
HbA1c= glycosylated hemoglobin; ITSQ = Insulin Treatment Satisfaction Questionnaire.
*No skipped doses. †Some skipped doses. ‡Student ttest of group means.
CONCLUSION
This study has described the development and vali-dation of a 22-item instrument designed to assess treatment satisfaction with a wide range of insulin therapies. Results from our 2 samples indicate the ITSQ is a conceptually and psychometrically sound measure of treatment satisfaction for conventional and modern insulin regimens.
ACKNOWLEDGMENTS
This study was supported by Novo Nordisk. The authors acknowledge the valuable contributions of Dr. Annabel Bowden, Quintiles, for assistance with manuscript preparation; Dr. Hitoshi Ishii, Tenri Hospital, for advice, adaptation, and testing of the ITSQ in Japanese; Dr. Sherwyn L. Schwartz for help-ing with data collection; and Kathleen Dziak, BA, Fabian Camacho, MA, and Vanessa Duren-Winfield at Wake Forest University School of Medicine for help with data collection.
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R.T. Anderson et al.
Appendix. The 22-item Insulin Treatment Satisfaction Questionnaire (ITSQ).
People who take insulin can have many different experiences with their treatment. Some people who take insulin may find it difficult and burdensome, whereas others feel that it is not much of a bother at all.
The following questions are about your perceptions of your current insulin treatment and how it affects you in your daily life. When you think of your insulin treatment, please keep in mind the type of insulin you take, the dose or amount of insulin, your schedule for taking insulin, and the device or method you use to give yourself insulin.
Please think about your experiences during the past 4 weekswhen you answer the questions.
Please answer each question by circling the number 1 that best represents your answer. If you are unsure about how to answer a ques-tion, please give the best answer you can.
1. How much of a bother is it for you to take all your daily insulin doses as prescribed?
No bother A tremendous
at all bother
1 2 3 4 5 6 7
2. How much does your current insulin treatment interfere with your ability to enjoy social or leisure activities?
Does not Interferes
interfere at all tremendously
1 2 3 4 5 6 7
3. How much does your current insulin treatment interfere with your work or school activities? (If you do not work or attend school, think about your regular daily activities.)
Does not Interferes
interfere at all tremendously
1 2 3 4 5 6 7
4. How much do you have to plan the timing of your meals or snacks around the insulin you currently use?
No planning A tremendous
at all amount of planning
1 2 3 4 5 6 7
Appendix. (Continued)
5. How much do you have to plan what you eatwith your current insulin treatment?
No planning A tremendous
at all amount of planning
1 2 3 4 5 6 7
6. How much do you have to plan your physical activities (such as exercise or strenuous household chores) around your current insulin treatment?
No planning A tremendous
at all amount of planning
1 2 3 4 5 6 7
7. How confident are you that you can avoid symptoms of low blood sugar(such as sweating, trembling, dizziness, blurred vision) with your current insulin treatment?
Extremely Not at all
confident confident
1 2 3 4 5 6 7
8. How confident are you that you can avoid severe episodes of low blood sugar that result in loss of consciousness (fainting or passing out) with the insulin you currently use?
Extremely Not at all
confident confident
1 2 3 4 5 6 7
9. In general, how bothered are you by symptoms of low blood sugar (such as sweating, trembling, dizziness, blurred vision) with the insulin you currently use?
Not at all Extremely
bothered bothered
1 2 3 4 5 6 7
10. How much do you feel that the insulin you are currently using increases the chances that you will experience low blood sugar?
Not at all Extremely
1 2 3 4 5 6 7
11. How worried are you about experiencing low blood sugar during the night with the insulin you currently use?
Not at all worried Extremely worried
1 2 3 4 5 6 7
CLINICALTHERAPEUTICS®
R.T. Anderson et al.
Appendix. (Continued)
12. How confident are you that you can avoid symptoms of high blood sugar(such as dry mouth, thirst, frequent urination, fatigue, increased appetite) with your current insulin treatment?
Extremely Not at all
confident confident
1 2 3 4 5 6 7
13. How satisfied are you with the stability of your blood sugar levels with your current insulin treatment?
Extremely satisfied Not at all satisfied
1 2 3 4 5 6 7
14. Overall, how pleased are you with the blood sugar control you achieve with your current insulin treatment?
Extremely pleased Not at all pleased
1 2 3 4 5 6 7
15. In general, how stressful is it for you to manage your current insulin treatment?
Not at all stressful Extremely stressful
1 2 3 4 5 6 7
16. How burdensome is it for you to manage your current insulin treatment?
Not at all Extremely
burdensome burdensome
1 2 3 4 5 6 7
The following questions are about your perceptions of your current method of taking insulinand how it affects your daily life. For these questions, you should only think about the device or method you use to give yourself insulin.
17. How easy is it for you to take the correct amount of insulin each time with your current method of taking insulin?
Extremely easy Not at all easy
1 2 3 4 5 6 7
18. How convenient is your current method of taking insulin when you are away from home?
Extremely Not at all
convenient convenient
1 2 3 4 5 6 7
Appendix. (Continued)
19. How much pain or other physical discomfort do you experience with your current method of taking insulin?
No pain or A tremendous amount
discomfort of pain or discomfort
1 2 3 4 5 6 7
20. How comfortable are you taking insulin in a public place (where people might see you) with your current method of taking insulin?
Extremely Not at all
comfortable comfortable
1 2 3 4 5 6 7
21. How much emotional distress or anxiety do you experience from your method of taking insulin?
No distress A tremendous amount
or anxiety of distress or anxiety
1 2 3 4 5 6 7
22. Overall, how satisfied are you with your current method of taking insulin?
Extremely satisfied Not at all satisfied
1 2 3 4 5 6 7
CLINICALTHERAPEUTICS®
Address correspondence to:Roger T. Anderson, PhD, Department of Public Health Sciences, Wake Forest Uni-versity School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157. E-mail:[email protected]
