Validation of a measure of knowledge about human papillomavirus (HPV) using item response theory and classical test theory

Waller, Jo, Ostini, Remo, Marlow, Laura A. V., McCaffery, Kirsten and Zimet, Gregory (2013) Validation of a measure of knowledge about human papillomavirus (HPV) using item response theory and classical test theory. Preventive Medicine, 56 1: 35-40. doi:10.1016/j.ypmed.2012.10.028

Author Waller, Jo
Ostini, Remo
Marlow, Laura A. V.
McCaffery, Kirsten
Zimet, Gregory
Title Validation of a measure of knowledge about human papillomavirus (HPV) using item response theory and classical test theory
Journal name Preventive Medicine   Check publisher's open access policy
ISSN 0091-7435
Publication date 2013-01-01
Year available 2012
Sub-type Article (original research)
DOI 10.1016/j.ypmed.2012.10.028
Open Access Status Not Open Access
Volume 56
Issue 1
Start page 35
End page 40
Total pages 6
Place of publication Maryland Heights, MO, United States
Publisher Academic Press
Language eng
Subject 2713 Epidemiology
2739 Public Health, Environmental and Occupational Health
Abstract As the human papillomavirus (HPV) vaccine is now recommended for males, a reliable, comprehensive HPV knowledge measurement tool which addresses issues relevant to males is needed. We aimed to replicate, validate and test the comprehensiveness of an existing general HPV and an HPV vaccination knowledge scale in English and French. We also measured parental HPV knowledge and changes over time. An online questionnaire was administered in February (Time 1; T1) and November 2014 (Time 2; T2) to a nationally representative sample of Canadian parents of boys. Dimensionality, internal consistency and model fit were evaluated at both time points and separately in English and French sub-samples. Differences in knowledge scores were measured. Analyses were performed on 3117 participants at T1 and 1427 at T2. The 25-item HPV general knowledge and an 11-item HPV vaccination scale were unidimensional, showed high internal consistency (α>0.87, α>0.73) and had good model fit. Both general HPV and vaccine-specific knowledge significantly increased over time in both languages, but remained low at T2, with only about half of the items being answered correctly. Correct responses at T2 are best explained by correct responses at T1, with some small changes from 'Don't know' at T1 to correct at T2. The extended general and vaccine-specific knowledge scales are valid, reliable and comprehensive, and could be used among parents of boys, in both English and French. Educational interventions could target specific knowledge gaps and focus on providing information rather than correcting misconceptions.
Formatted abstract
Objective: Public understanding of HPV is important to ensure informed participation in cervical cancer prevention programmes. While many studies have measured HPV knowledge, none has developed a validated measure for use across countries. We aimed to develop and validate such a measure.

Method: Items tapping knowledge of HPV, HPV testing and HPV vaccination were developed from previous literature and with expert consultation. The 29-item measure was administered via the internet to 2409 adults in the UK, US and Australia in 2011. Classical test theory and item response theory were used to establish the measure's psychometric properties.

Results: Total scale reliability was very good (α=0.838), as was internal consistency for a 16-item general HPV knowledge subset (α=0.849). Subsets of HPV testing and vaccination items showed reasonable test-retest reliability (rtest-retest=0.62 and 0.69) but moderate internal consistency (α=0.52 and 0.56). Dimensionality analyses suggested that one item was not measuring the same construct as the remainder of the questionnaire. A 2-parameter logistic item response theory (IRT) model was fitted to the remaining 28 scale items.

Conclusions: A structurally coherent set of items covering a range of important HPV knowledge was developed. Responses indicated a reliable questionnaire, which allowed the fitting of an IRT model.
Keyword IRT
HPV vaccination
Scale development
HPV knowledge
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 14134
Institutional Status UQ
Additional Notes Available online: 8 November 2012.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Healthy Communities Research Centre Publications
Official 2013 Collection
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Citation counts: TR Web of Science Citation Count  Cited 31 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 34 times in Scopus Article | Citations
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