Construction and Validation of a Questionnaire to Measure the Health Beliefs of General Practice Patients

Family Practice Oxford University Press 1987 Vol. 4, No. 2 Printed in Great Britain Construction and Validation of a Questionnaire to Measure the Health Beliefs of General Practice Patients JILL COCKBURN, PAUL FAHEY AND R W SANSON-F1SHER Cockburn J, Fahey P and Sanson-Fisher R W. Construction and validation of a questionnaire to measure the health beliefs of general practice patients. Family Practice 1987; 4: 18 116. The health belief model has been widely used as a conceptual framework for understanding and explaining compliance behaviour. A weakness characterizing work in the area has been lack of standardization of measurement of the components of the health belief model. This paper describes the development and validation of a questionnaire to measure these components. The questionnaire was designed for use with general practice patients who have a wide range of different illnesses, therefore the nature of the patients' illness is not mentioned in the content of the items. Principal components analysis was used to determine the dimensions underlying patients' beliefs. Principal components analysis and application of Cronbach's alpha statistic identified four reliable sub-scales of the questionnaire. The sub-scales measured patient's beliefs about: the threat caused by illness, the efficacy of traditional medical care, the way illness is dealt with and the barriers to taking medications. The health belief model, a theoretical framework for explaining and understanding individuals' responses to health related matters, has been the focus pf considerable attention in health research. The model was originally developed to explain and predict patients' participation in preventive health activities such as immunization and attendance at screenings. 1-2 It has since been used to explain compliance with prescribed medications, dietary and other types of medical advice. M The original health belief model'- 2 argued that an individual's decision about undertaking a recommended health action was a function of the individual's beliefs on three subjective dimensions: 1. The threat posed by an index condition. This dimension comprises the individual's perception of the likelihood of the occurrence or recurrence of the condition (perceived susceptibility) and its potential for causing physi- Disciplinc of Behavioural Science in Relation to Medicine. Faculty of Medicine. The University of Newcastle. NSW 238. Australia. Correspondence to Professor R. W. Sanson-Fisher. 18 cal harm and interference with social roles (perceived severity). 2. The individual's beliefs in the efficacy or the value of the recommended action in reducing the threat (perceived benefits). 3. The individual's estimates of the physical, psychological, financial or other costs involved in the proposed action (perceived barriers).'- 2 As research investigating the ability of the model to explain health related behaviours has progressed, the original model has been reformulated and expanded to incorporate new findings. In its early form, the model focused on specific disease-avoidance interactions, but an increasing body of evidence suggested that a person's general motivation towards health related matters influenced compliant behaviour. 1 " 12 The category of 'general health concerns' was added in an effort to describe an individual's degree of interest in, and concern about, health practices and preventive activities. Similarly, the original model focused exclusively on beliefs about one index condition. General categories of vulnerability to disease and worry about illnesses were added to the model to tap broader nonspecific perceptions of health threat. Other cate-

gories which have been added have included 'feeling of control over health matters', and 'faith in doctors and medical care'. l In addition, demographic, structural and enabling factors, which had been found to be predictive in other compliance research, were included as mediating variables in the revised model. 113 The adequacy of a theory for explaining behaviour can be judged onfive criteria proposed by Gergen. l4 These are that a theory should have: heuristic value for a discipline or field of study; parsimony of statement; operationally defined terms; predictive capability; and a strong data base. Fisher 15 has pointed out that the health belief model fits most, but not all, of the above criteria. Its heuristic value for health research is shown by the plethora of studies which have used the conceptual framework. 91M4 It is beyond doubt that the model has had a major influence on the thinking of those studying non-compliance. The model is parsimonious, with only a limited number of major variables which together provide a simple statement concerning health-related behaviours. A major weakness of the health belief model, however, is uncovered when the third criterion is considered. Despite its widespread use, the constructs of the health belief model are operationalized in different ways by various investigators attempting to measure the same beliefs. The final two criteria are related to these changing operational definitions. The data base supporting the model has expanded considerably since its formulation. The predictive capability has been tested, and support for the predictive capability of the model has been found in some instances. 9 However, research is often plagued by methodological problems in the measurement of the model. As early as 1974, Rosenstock 2 pointed out that no two studies had used identical questionnaires to determine the presence of absence of each belief. This raised the possibility that the concepts being measured may also have varied from study to study. Rosenstock recommended that standardized methods of asking questions and the reliability of measures be examined, so that the utility of the model could be examined without the confounding influence of different, and perhaps inaccurate, measurement procedures. Becker and Maiman 1 reiterated the points of Rosenstock stressing that consensus was needed on ways to standardize measurement, including CONSTRUCTION QUESTIONNAIRE HEALTH BELIEFS 19 the sharing of operational and conceptual definitions, so thatfindingscould be compared across studies. They also pointed to the need for more sensitive measures of dimensions of the health belief model, using interval or ratio scales. Such scales enable individuals to be placed on a continuum according to the strength of belief, rather than to be classified into one of only two groups according to whether the belief is held or not. Continuous scores allow noteworthy differences between individuals to be assessed. Green 25 summarized the situation by describing the health belief model as 'the most documented set of health beliefs, but nonetheless without standardization, or tests of reliability or validity'. Though several studies since the remarks of Green have reported the reliability of the scales used, 18-24 - 26 there have been few attempts at assessing the validity of these scales. This is an obvious and major problem. Though items which appear in current scales are usually chosen with some theoretical basis and therefore have face validity, there is little evidence that the scales have construct validity. Factor analysis is a potentially useful tool for examining this dimension of validity as it determines which groups of items cluster to form scales in the questionnaire. 27 If the factor-based groupings correspond to the a priori theoretical grouping of items then empirical support is given for the construct validity of the questionnaire. Factor analysis has been used to develop instruments based on the health belief model to measure the beliefs of women regarding breast self-examination, 23 the health beliefs of diabetics 17 and the more general health beliefs of a community sample. 28 All of these questionnaires have demonstrable construct validity and analysis has confirmed that distinct dimensions of beliefs exist in people's perceptions of health related matters. However, the specificity of the content of items in the questionnaires of Given and colleagues 17 and Champion and colleagues 23 limit their applicability to the groups for which they were designed. The questionnaire of Jette and colleagues 28 is more general in its application, but has as yet only been tested on a 'healthy' population; 78% of the sample in Jette's study considered themselves to be in excellent health at the time the questionnaire was administered. It is possible that people's beliefs about health may be different when they are faced with

11 FAMILY PRACTICE AN INTERNATIONAL JOURNAL actual illness. For example, Jette's group 28 found that beliefs about severity of potential illnesses were distinct from perceptions about susceptibility. This is contrary to the traditional grouping of the dimensions under the concept of 'threat posed by illness' in the theoretical literature. A standardized questionnaire which can be used to examine the health beliefs of different patient groups is important, so that comparisons between studies can be made without the confounding factor of different measurements and operationally defined terms. The aim of the present study was to develop and field test a questionnaire of individuals' health beliefs which would meet standard psychometric criteria, and have an application for primary care patients. METHOD Study Setting and Design The data were collected as part of a large-scale direct observational study (the primary care study) which was examining the processes of general practice and relating these processes to a number of outcomes. The primary care study was conducted in the surgeries of randomly selected general practitioners from Newcastle, Australia and data were collected over an 18-month period from November 1982 to April 1984. The patient sample was recruited in the waiting rooms of the general practice surgeries. Patients were eligible for inclusion if they were aged 18 years or more, were literate in English and were not too ill or in too much pain to complete questionnaires. After consultation with their doctor, consenting patients were given a questionnaire package, which included the health belief questionnaire. Instructions were given to patients to take the questionnaire home to complete, and to return it using a reply-paid envelope. A reminder letter was sent to patients on the day after the consultation, and if the questionnaire had not been returned within one week of distribution, a reminder phone call was made. Instrument Development The revised expanded version of the health belief model 113 was used as the conceptual framework for the construction of the questionnaire. The initial pool of items to reflect these dimensions came from three sources: (1) review of the theoretical literature pertaining to health beliefs; (2) revision of past scales, with particular attention to items shown to be valid and reliable and (3) structured interviews with groups of medical students, general practice patients and colleagues to determine the appropriate content and wording of items within specific areas. In these interviews people were asked to describe how they dealt with illness, their attitudes to medications and to traditional medical care. Thirty-five items were derived by these means. These were edited to exclude repetitions and ambiguities, resulting in 22 items being included in the pilot form. The number of items in each hypothesized dimension were: general health threats, 3 items; general health concern, 2 items; specific threat level factors, 6 items; control over illness, 4 items; medical motivation, 3 items; and barriers to medication, 4 items. Items were structured in the form of a complete statement, for example 'Doctors know best for you when you are ill.' A seven-point Likert 29 response scale, ranging from strongly agree to strongly disagree, was used for all items. The uniformity of response format works on the premise that once respondents become familiar with the response choices, statements can be read and responses indicated quickly. Differing item response formats increase the time and effort needed to understand and complete questionnaires. 3 A seven-point scale was used as it allows more information about the varying strengths of a patient's beliefs to be obtained and yields more reliable data than response choices with fewer alternatives. 31 Items from each content area were randomly distributed throughout the questionnaire and patients marked responses directly on to the questionnaire. The pilot form of the questionnaire was tested on a sample of 115 patients from three general practitioners who were participating in the primary care study. Analyses for the pilot study were confined to calculations of means and standard deviations, the sample size being too small for factor analysis. 32 The examination focused particularly on comparability of item score distributions. Roughly symmetrical response distributions with a mean of 4 and a standard deviation near 2.6 are desirable characteristics for items to be combined in summated rating scales. 33 Careful note was also made of items which were frequently missed an indication that the items were either not relevant to general practice patients or that the wording of items caused problems with interpretation.

The format of thefinalform of the health belief questionnaire was identical to that described for the pilot form. The reading ease of the questionnaire was calculated using the Flesch formula. 34 The score of 91 indicates that the questionnaire could be understood by 9% of the general population (those with an IQ of 81+). Field Test of Questionnaire The data for the main study were obtained from patients of the remaining 53 general practitioners who were participating in the primary care study. Procedures for gaining consent and distribution of the questionnaire were similar to those described previously. The analysis of the health belief questionnaire took place in four stages: factor analysis, index score derivation, reliability analysis and validity analysis. Factor analysis. The principal components method was used to extract factors from a matrix of correlations among pairs of the 22 health belief items. The analysis was done using the statistical package BMDP, programme P4M. (University of California, 1982.) The initial unrotated component was evaluated against four criteria to determine how many factors should be retained for rotation. The criteria used were the Scree test, 35 the 5% guideline, 36 consideration of eigenvalues 27 and use of trial rotations. 27 Factors were rotated so as to maximize 'simple structure', a criteria proposed by Thurstone 37 as a means of providing a parsimonious description of the observed relationships. Varimax orthogonal rotation, which does not allow correlations among the factors, was used. Items with loadings of.4 or above within factors were grouped together in an index. Index score derivation. A score for each patient for each of the derived factor-based scales was computed by adding up the scores on items with significant loadings on the factor. 29 Scoring of negatively worded items was reversed prior to scale computation, so that a low score represented a strongly held belief about the particular health related matter being examined. Reliability. The internal consistency of items contributing to each factor-based scale was estimated using Cronbach's alpha. 38 In keeping with the recommendations of Helmstadter 39 and Nunally, 4 a coefficient of.5 was considered CONSTRUCTION QUESTIONNAIRE HEALTH BELIEFS 111 adequate indication of internal consistency for a questionnaire in the early stages of construction. Validity. Empirical evidence for the construct validity of the health belief questionnaire was provided by the results of the principal components analysis. These results were compared with the a priori theoretical grouping of items, the rationale being that if the factor-based scales were in accordance with hypothesized groupings, then confirmatory evidence would be given for the theoretical constructs being measured. 41 The discriminant validity of the derived health belief scales, and support for the independence of different beliefs was provided by 'reliability of difference' scores. 42 These scores determine the amount of overlap shared by all possible pairs of scales within an instrument. The reliability of difference between two scales is based on the reliability of each scale and the correlation between them. The higher the reliability of difference score the more likely it is that separate dimensions are being measured. A standard of.5 and greater has been used in previous research as an indication that distinct dimensions are being assessed. 42 " 44 RESULTS AND DISCUSSION Patient Sample In all 821 questionnaires were distributed, of which 621 were returned, a return rate of 75%. Of those returned, 59 had every question answered. As the principal components analysis programme works only on complete data sets these 59 respondents were the sample for the current study. Sixty per cent of the sample were male, 4% were female. The mean age of the sample was 41 years. Eight per cent of the sample had received no secondary schooling, 75% had completed lower secondary school, and 17% had full secondary education; 7% of the sample also had tertiary qualifications. In order to determine the representativeness of the sample, and therefore the generalizability of obtained results, the demographic characteristics of respondents in the sample have been compared with those of patients who were given a questionnaire and failed to return it. No significant differences were found on any of the comparisons made. Principal Components Analysis Principal components anaylsis identified seven factors with eigenvalues greater than 1. These

112 FAMILY PRACTICE AN INTERNATIONAL JOURNAL seven factors accounted for 18%, 9%, 7%, 7%, 5%, 5%, and 4% respectively of the total variance. Therefore, using the 5% guideline, six factors would be appropriate for rotation. Scree test results, however, suggested that four important factors were defined by items in the questionnaire. Thus, depending on the criterion used, between four and seven factors are deemed suitable for rotation. Trial rotations of four, five, six and seven factors were compared. The clearest information about the dimensionality of the health belief questionnaire was given when six factors were rotated. These six factors accounted for 53% of the total variance, a proportion which has been deemed acceptable in previous research. 44 These six factors were rotated to simple orthogonal structure. The rotated orthogonal factor loadings for items are shown in Table 1. Communality estimates are shown in the far right hand column. The first factor contained items which related to perceived severity of the current condition, the perceived severity of illness in general, and perceived susceptibility to illnesses in general. These TABLE 1 Correlations between health belief items and rotated principal components No. Item I II Rotated component III IV V VI Commun- _ uslitv h 17. 19. 11. 2. 8. 4. 16. 7. 6. 14. 22. 1. 3 21. 13. 12. 18. 1. 9. 15. 2. 5. My current condition will lead to serious long-term health problems. My current condition is causing me a lot of worry and concern. The illnesses I get worry me a great deal. Whenever I get sick it seems to be serious. My current condition will interfere a great deal with my normal activities. I will become very sick as a result of my current condition. I get sick more easily than other people my age. I am concerned about the possibility of becoming seriously ill. I worry that taking tablets may cause problems. The trouble with tablets is that you can get too dependent on them. Often the side-effects from tablets are worse than the illness. Doctors know best for you when you are ill. When I follow my doctor's advice I usually feel better. I trust my own feelings about my health rather than a doctor's advice. When I get sick, I just keep going as usual. I do not let illness interfere with my life. When I think I am going to be sick I fight it. Often remembering to take tablets is more trouble than its worth. Looking after my health is one of my major concerns. It's likely that my current condition will happen again. Good health is largely a matter of good luck. Compared to other illnesses, my condition is not serious..73.72.72.67.6.59.58.57.7.4.16 -.9.7 -.19.32.18.2 -.4 -.4.2.3.6 - -.2.25.75.75.66 - -.1.18.3 -.7.11.18.17 -.11 -.5.21 -.6 -.4.1 -.3.1 -.1 -.12 -.3 -.12.8.8 -.6.5.2.3 -.13.9 -.6.3 -.5 -.5 -.17.2.1 -.19.5 -.13.6.12.11.76.66.62.11.2 -.5.9 -.18 -.15.26.47 -.11.15.14.6 -.1.16.2.9 -.16.64 -.58.47.14 -.15 - -.4.17 -.14 -.15.28.11 -.13.7.3.18.2 -.2.4 -.2 -.2.77.56.55.59.56.5.45.6.46.4.62.61.5.68.66.48.59.49.43.48.49.28.66.55

items were originally hypothesized to fall into the specific threat level and general health threat content areas. This finding is contrary to that of Jette and colleagues. 28 Whereas their work suggested that condition-specific threat level factors were distinct from general threat level factors, the results from the present study do not support this distinction. Patients in this study saw all illnesses, including the specific condition for which advice was being sought, in the same way. This discrepancy may be due to the different samples used. In the present study, the beliefs of patients concerning a real illness episode were explored. Jette and colleagues asked healthy subjects about hypothesized situations. It seems that when people are genuinely ill, the threat caused by all illnesses, potential or real, are perceived in the same way. This first factor has therefore been labelled 'perceived threat to health caused by illness'. Items which related to beliefs about medication made up the second factor, labelled 'perceived barriers to taking medication'. These questions were all concerned with general attitudes to taking tablets. Items loading significantly on the third factor 'medical motivation', were concerned with trust in doctors and traditional medical care. Items of the fourth factor reflected people's beliefs about the way they deal with illness. This factor has been labelled 'perceived control over illness'. A patient who would endorse the beliefs measured by this subscale would be one with a stoic approach when faced with ill-health. The fifth factor extracted contained three items, one of which was originally hypothesized to fall into 'barriers to taking medication' dimension, one from the 'general health threat' domain and the other which related to the 'general health concern' domain. The content of these items showed little in common. Therefore no label was attached to this factor. This also holds true for factor 6. The two items with significant loadings TABLE 2 Cronbach's alpha for factor-based scales Scale Label Alpha 1 2 3 4 5 6 Illness threat Barriers Medical motivation Control over illness CONSTRUCTION QUESTIONNAIRE HEALTH BELIEFS 113.82.63.56.49.27.14 were from the 'general health concern' and 'perceived severity' of the presenting condition domains. Reliability Cronbach's alpha coefficients for the six factorbased scales are shown in Table 2. These ranged from.14 for items loading on the sixth factor to.82 for the first factor-based scale. The low reliabilities of the fifth and sixth scales were a further indication that these derived scales were more a reflection of factor analytic techniques than an indication of patients' perceptions. These scales were therefore not considered to be valid reflectors of underlying health beliefs. The alpha of.49 for the 'belief about illness' scale was just below that recommended by Helmstader 39 and Nunually, 4 but it was decided to retain the scale, as the questionnaire was in the early stages of development. However, if this scale were to be used in future research, further examination of its reliability should be obtained. The reliability of all the other scales in the present research appears adequate. Construct Validity Factor analysis provided empirical evidence for the validity of health belief constructs which were measured in this study. With few exceptions, items hypothesized a priori to be measuring the same underlying construct were found to be statistically related. All items from the medical motivation grouping factored together, as did items measuring the 'control over illness' dimension. Three of the four items which were hypothesized to be measuring the 'barriers to taking medication' dimension also factored together. Support was therefore given for the construct validity of these scales. The first factor to emerge 'threat caused by illness' was a composite of specific severity, general severity and general susceptibility. Theory has suggested that 'perceived severity' and 'perceived suseptibility' be grouped together under 'threat of illness'. 113 The appropriateness of this grouping was confirmed by factor analysis and support given for the contention that the 'threat' elements of the health belief model be considered together conceptually. The data also susbstantiated the independence of the four perceptual dimensions measured in this questionnaire. Examination of the reliability of difference scores between pairs of subscales

114 FAMILY PRACTICE AN INTERNATIONAL JOURNAL TABLE 3 Correlations (shown above the diagonal), Cronbach's alpha (shown in bold) and reliability of difference scores (shown below the diagonal) of health belief subscales 'Threat' 'Barriers' 'Medical' 'Control' 'Threat' 'Barriers' 'Medical' 'Control'.82.65.72.69.21.62.68.53 - -.25.58.5O -.11.5.49 showed that all six pair-wise comparisons met the minimum standard for subscale distinctness (Table 3). The data suggested that clear and different belief dimensions exist, helping to substantiate the model as presently formulated. The item measuring resusceptibility for the presenting condition, however, did not factor as expected with the other threat level items. Only one such item was included, as it was thought that it would be conceptually linked with other threat level factors, such as perceived severity. Perhaps if more items in this specific area had been included a separate, distinct factor for 'specific vulnerability' may have emerged in the general practice sample. This finding will need to be explored as refinement of the scale continues. Descriptive Statistics of Health Belief Subscales A score was obtained from each patient on each of the four retained subscales by the method of summated ratings. 29 In order to facilitate visual comparisons, the ranges of the summated ratings have been standardized to lie between (indicating the belief is strongly held) and 1 (indicating the least belief strength). The distributions of the standardized scores are shown in Figure 1. From Figure 1 it can be seen that the scores on the 'perceived threat caused by illness' subscale were skewed towards the lower end of belief strength. The general practice patients in this study tended to believe that any illness, including the one for which they were seeing a doctor, was not a major threat to them. Figure 1 also shows that people's beliefs measured by the 'perceived 2 4 6 8 1 STANDARDIZED SCORE a) Threat posed by illness 2 4 6 8 1 STANDARDIZED SCORE b) Barriers 2 4 6 8 1 STANDARDIZED SCORE c) Medical Motivation 2 to 6 8 1 STANDARDIZED SCORE d) Control over illness FIGURE 1 Distribution of standardized scores on subscales of the health belief questionnaire

barriers to taking medications' subscale were fairly evenly distributed. The distribution of scores on the third subscale 'Medical motiviation', is skewed towards the end of the scale which indicated a more strongly held belief. This would be expected for a general practice sample who were completing questionnaires after a visit to a doctor to seek medical advice. The scores on the fourth subscale were also skewed towards the end of the scale indicating a more strongly held belief. People in this sample tended to endorse 'stoicism' as a means of dealing with illness. This may reflect a cultural trait noted in other studies, 45 which causes Australians, even in adversity, not to complain. CONCLUSIONS The health belief questionnaire in the present research must be seen to be in the early phases of development. However, the results of the analysis reported here suggested that the derived scales reliably and validly measured the health belief constructs which were included in the questionnaire. The composition of the indices support the theoretical assumption that the health belief model dimensions are sufficiently distinct to be considered different beliefs in the sample under study. One problem with the existing questionnaire is that there is no subscale to measure perceived benefits of undertaking recommended health actions. Testing and refinement of items to measure the 'benefits' dimension of the health belief model is needed so that all major dimensions are represented in the questionnaire. It should be noted too that the validity analyses described in this paper are based on internal criteria features of the relationships among and between scale items. Further validation procedures based on external criteria are currently being examined. 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