Development of an instrument to assess expectations of and preference for an insulin injection pen compared with the vial and syringe.
BACKGROUND
Before using a product, patients form expectations regarding the extent of a product's desirable attributes. These expectations can be used to understand their preference and anticipate potential satisfaction with the product.


OBJECTIVE
The aim of this study was to produce a valid and reliable data collection instrument (the Insulin Injection Preference questionnaire [IIP-q]) to measure expectations of and preference for the insulin injection pen compared with the vial and syringe.


METHODS
This study was initiated at the University of Mississippi (University, Mississippi). The IIP-q was developed to determine the extent to which respondents' prepurchase expectations of a product's attributes relate to preference for an insulin injection pen compared with the vial and syringe. Instrument development began with item generation related to product attributes important to patients who inject insulin. Items originated from an extensive search of the peer-reviewed Internet-based literature, marketing reports, clinical studies, and existing instruments. Content validity also was assessed using expert panel and focus group review. The resultant instrument (the IIP-q) was mailed to 1200 patients known to have type 1 or type 2 diabetes mellitus who either did or did not use insulin. Subscales were identified through exploratory factor analysis. Reliability and validity were assessed using Cronbach alpha for subscale items. Product-moment correlations between subscale dimensions and 2 global measures of preference were used to test the relationship between attribute expectations and preference.


RESULTS
Seventeen of the questionnaires were returned as undeliverable, leaving 1183 in the sample population. Questionnaires were received from 302 individuals, 55 of whom failed to complete > or = 85% of the items and thus were not included in the final analysis. Of the 247 respondents (135 women, 112 men; mean [SD] age, 52.4 [13.2] years (range, 18-83 years]), 99 (40.1%) were current insulin users and 143 (57.9%) were not using insulin. Exploratory factor analysis resulted in a 13-item solution (Cronbach alpha = 0.92), accounting for 73.6% of the total explained variance. Ease of use, activity interference, and social acceptability emerged as expectation subscales from exploratory factor analysis. Cronbach alpha for items comprising the subscales ranged from 0.82 to 0.92. The 3 subscales were significantly correlated with patient preference (ease of use, r = 0.520, P < 0.001; activity interference, r = 0.570, p < 0.001; social acceptability, r = 0.602, p < 0.001).


CONCLUSIONS
The results of the present study provide support for the IIP-q as a reliable and valid instrument to assess patient expectations of product attributes and preference. This instrument can be modified for use in clinical trials to determine the role of patient expectations and preference in their judgments regarding satisfaction with insulin delivery devices.
Szeinbach
Sheryl L
SL
Department of Pharmacy Practice and Administration, College of Pharmacy, The Ohio State University, 500 West 12th Avenue, Room 136A, Columbus, OH 43210, USA. Szeinbach.1@osu.edu
Barnes
James H
JH
Summers
Kent H
KH
Lenox
Sheila M
SM
D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy; D004209:Disposable Equipment; D005260:Female; D006801:Humans; D007279:Injections, Subcutaneous; D007328:Insulin / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013594:Syringes
D007328:Insulin