Ernst-Moritz-Arndt-University Greifswald, Institute of Epidemiology and Social Medicine, Greifswald and
1 Medical University of Lübeck, Department of Psychiatry and Psychotherapy, Research Group S:TEP (Substance Abuse: Treatment, Epidemiology, and Prevention), Lübeck, Germany
Received 24 August 2001; in revised form 15 December 2001; accepted 25 January 2002
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ABSTRACT |
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INTRODUCTION |
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The Readiness to Change Questionnaire (RCQ) (Rollnick et al., 1992) is a 12-item self-report questionnaire. Heather et al. (1993) proposed two methods of stage allocation, the quick and the refined method. The quick method assesses three stages of change: precontemplation (PC), contemplation (C) and action (A). The refined method of stage allocation also assesses preparation (P). An alternative allocation scheme using factor scores is described by Hapke (2000). The RCQ has been developed and applied in brief and opportunistic interventions among hazardous drinkers in general practices and wards of general hospitals. Reliability estimates from these settings were satisfactory (Rollnick et al., 1992
; Rodriguez Martos et al., 2000
). Applying the RCQ to clients undergoing alcohol-specific treatment (McMahon and Jones, 1996
; Gavin et al., 1998
) results in certain difficulties. Heather et al. (1999) addressed these with the treatment version of the RCQ. Evidence of predictive validity has also been gathered from clinical samples (Heather et al., 1993
; McMahon and Jones, 1996
; Hapke, 2000
). Construct validity has been investigated by analysing the factor structure of the RCQ. A three-factor structure, reflecting the stages PC, C and A, was found in different studies (Rollnick et al., 1992
; Wells Parker et al., 1998
; Hapke, 2000
; Rodriguez Martos et al., 2000
). Budd and Rollnick (1996) used a structural equation modelling technique and found that a model with correlating factors and a model with a second-order factor fit the data equally well.
The aims of the present study are: (1) to report item and scale properties (item difficulty, item selectivity, scale distributions and internal consistencies); (2) to investigate construct validity of the RCQ, when applied to subjects from the general population who show hazardous alcohol consumption, alcohol misuse or dependence.
Construct validity of the RCQ was investigated in two steps. In the first step, allocation to stage of change using the alternative allocation algorithms proposed by Heather et al. (1993) for subjects from the general population were compared with allocations resulting from studies using clinical samples. Since there are differences in prevalence rates of alcohol use and misuse between samples drawn from the general population and samples drawn from patient populations (Bronisch and Wittchen, 1992; Perkonigg et al., 1998
; Rumpf et al., 1999
, contradicting Cherpitel, 2000
), application of the instrument to subjects from the general population contributes to knowledge on strengths and limitations in utilization of the RCQ. Comparing samples from different studies is very difficult differences between studies may be attributable to a host of reasons and a detailed comparison of the samples is beyond the scope of this article. However, comparison of the allocation rates, with these limitations in mind, may be useful, in gauging what proportions of subjects may be expected from patient or general populations. In a second step, factor analysis was performed for the data under study. We investigated whether the three-factor structure found in patients on general hospital wards and general practices can be replicated with subjects from the general population.
Results from our analyses may serve as estimates for item and scale properties and provide information on validity of the RCQ if applied to hazardous consuming, alcohol-abusing or -dependent subjects from the general population. With regard to stages of change, we expect larger proportions of subjects to be in earlier stages of change, compared to subjects from patient samples. With regard to the three subgroups defined by different drinking patterns, we expect higher proportions of alcohol-abusing or -dependent subjects to be in later stages than hazardously consuming subjects.
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SUBJECTS AND METHODS |
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The survey assessed a representative sample of 4075 individuals, constituting a recruitment efficacy rate (Stang et al., 1999) of 70.2%. Meyer et al. (2000a) provided a detailed description of the population, sampling and response patterns. The main diagnostic tool in the survey was the computer-assisted MunichComposite International Diagnostic Interview (M-CIDI) (Wittchen et al., 1995
). The M-CIDI used for this survey comprises 14 sections containing questions relevant for diagnosis of psychological disorders according to ICD-10 (World Health Organization, 1993
) and DSM-IV (American Psychiatric Association, 1995
). A detailed description of procedures and quality assurance for the interviews is found in Meyer et al. (2000b). Depending on results from the M-CIDI, study staff handed out self-report questionnaires to respective subgroups of subjects. A detailed description of procedures and instruments may be found in Hapke et al. (1998) and in Hess et al. (1998).
Subjects
For this study, a subgroup of 302 subjects was analysed in more detail. Of these, 202 subjects met criteria for hazardous drinking behaviour at the time of assessment. Hazardous drinking was defined according to the criteria proposed by the British Medical Association (Bradley et al., 1993) (i.e. 20 g alcohol per day for women and 30 g of alcohol per day for men). Of the remaining subjects, 46 met criteria for alcohol misuse and 55 subjects met criteria for alcohol dependence. One of the 55 alcohol-dependent subjects did not complete the RCQ and was dropped from analyses, leaving 54 subjects who met the criteria for alcohol dependence. Allocation to one of these three classes was mutually exclusive. Compared to other prevalence estimates for alcohol misuse and dependence in Germany (Bronisch and Wittchen, 1992
; Nelson and Wittchen, 1998
; Bühringer et al., 2000
), these rates are lower. However, this estimate is in accordance with regional differences in alcohol consumption in Germany (Meyer et al., 1998
), where per capita consumption rates in the southern regions of Germany are higher than in northern Germany. Table 1
provides a brief description of the subjects under study.
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All differences between subgroups under study (hazardous consumers, alcohol misusers and alcohol dependants) were significant (sex: 2 = 11.8, d.f. = 2, P = 0.003; employment status: Fisher's exact test = 17.9, P = 0.026; marital status: Fisher's exact test = 18.9, P = 0.007). Age differed significantly between groups (F = 20.4, d.f. = 2, P < 0.001).
Assessments
The RCQ consists of 12 items on a 5-point rating scale ranging from strongly disagree (2) to strongly agree (2). The respective four items comprising one subscale (Rollnick et al., 1992) are summed. This results in three subscales PC, C and A, ranging from 8 to + 8. Since the RCQ was designed to assign subjects to motivational stages, emphasis has been put on techniques of stage allocation (Heather et al., 1993
). The two methods used contemporaneously are the quick method and the refined method of stage allocation. The quick method assigns subjects according to the highest subscale score. In the case of a tie, the stage chosen is the furthest stage of change reached. Assignment becomes arbitrary when subjects score high or equal on more than just one subscale and/or show only gradual differences in scale scores.
On closer inspection of profiles in scale scores, Heather et al. (1993) found that, if distinctiveness of stages was taken strictly (only positive scores on one subscale with scores of zero or negative scores on the remaining two subscales), a consistent classification was possible in only 40% of subjects investigated. This, along with logical inconsistencies in interpretation of scale profiles, led to the refined method of stage allocation (Heather et al., 1993). The refined method analyses the relationship of positive and negative scale scores as a profile of three scores. The P stage of change may be allocated. The allocation scheme is as follows: (1) subjects scoring positive on PC and negative on both C and A are classified as being in PC; (2) subjects scoring positive on C and negative on both PC and A are classified as being in C; (3) subjects with negative scores in PC and positive scores in both C and A, and with a higher score in C than A, are allocated to P; (4) subjects with negative scores in PC and positive scores in both C and A, and a C score lower or equal to the A score are allocated to A. The refined method leads to a logically more consistent assignment, but results in a certain proportion of cases that cannot be allocated. In a sample of 174 excessive drinkers in general practices or on a general hospital ward, 40 subjects (23% of the total sample) could not consistently be assigned to one of the four stages (Heather et al., 1993
).
Translation
RCQ items were translated into German. Items resulting in double negative phrases, if rated, were adapted. The translation was checked and translated back into English by a native speaker. Resulting differences due to adaptation were inspected and discussed in terms of item content. The phrasing which best captured the original content of the item, without rendering double negative phrases, was retained for the survey.
Statistical analysis
Proportions were complemented with 95% confidence bands of the estimates (the assumption that proportions distribute normally is made throughout for confidence estimates). Reliability was estimated via internal consistency (Cronbach's alpha). Factors were extracted using principal components analysis with the KaiserGuttman criterion and were subsequently varimax-rotated. Between-group comparisons were made according to scaling and distributional shape of variables either using analysis of variance or KruskalWallis rank-sum test. Analyses were performed using SPSS Version 10.0.7 for Windows and S-Plus 2000© for Windows.
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RESULTS |
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Stage allocation
The RCQ's relevant information in order to allocate subjects to stages of change lies in the relationship between scores, rather than in the magnitude of scores. Allocation to stage of change using the quick method results in 67 ± 5% being allocated to PC, 24 ± 5% to C and 8 ± 3% to A. Using the refined method results in 58 ± 5% being allocated to PC, 15 ± 4% to C and 4 ± 2% to A; 12 subjects (4 ± 2%) were allocated to P and 56 subjects (19 ± 4%) did not show scores conforming to the model and could not therefore be allocated to any stage. Table 3 shows a cross-tabulation of allocations resulting from the quick and refined methods.
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Table 4 shows stage allocation according to the quick and refined method, from this study, and compares the results with those of Hapke (2000)
, Heather et al. (1993) and Rodriguez Martos et al. (2000).
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Using the refined method, without taking the P stage into account, classification to stages of change results in 36 ± 7% of subjects who could not be classified in the study from Heather et al., and 23 ± 5% in this study. If classification to the additional P stage is taken into account, the rate of subjects who cannot be classified is reduced to 37 (22 ± 6%) in the study from Heather et al. and to 56 (19 ± 4%) in the present study. In the other two studies on patient samples, allocation according to the refined method is not reported.
Comparing allocation methods for the three subgroups under inspection (hazardous consumption, alcohol misuse and dependence) (Table 5) revealed that allocation to stage of change differed considerably between subgroups and also between methods. Differences are due to allocation to P and those subjects who could not be allocated. Regardless of the allocation method, subjects with hazardous consumption or those meeting criteria for alcohol misuse were mostly allocated to PC, with the smallest number of subjects allocated to A. The majority of alcohol-dependent subjects was allocated to C, with second most subjects being allocated to PC, and more allocated to A compared with the other two groups.
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DISCUSSION |
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Analyses of standard psychometric properties, such as item selectivity, item difficulty and internal consistency in this study support the item selection. As was expected, item difficulty scores differed between the three subgroups. While items from PC had the highest difficulty scores for hazardous consumers, items from C and A had the highest difficulty scores for alcohol-dependent subjects. Internal consistencies from different translations and different groups of subjects produced estimates similar to those for hazardous drinkers, alcohol misusers and alcohol dependants from the general population. These results speak in favour of the item selection, their translations and their organization in three subscales corresponding to the three stages of change. In this study, distribution of raw scores was very flat for the PC and very skewed for the C and A scales. Since allocation to stage of change is the main objective of administration, rather than interpretation of raw scores, distributional qualities do not interfere with interpretation of test results.
Allocation to stage of change showed the expected distribution, given the subjects under inspection. In contrast to the patient samples, the majority of subjects was allocated to PC. Differential inspection showed that the majority of subjects showing either hazardous drinking behaviour or alcohol misuse were allocated to PC. A larger proportion of alcohol-dependent subjects was allocated to C. These results are also in accordance with predictions from the Transtheoretical Model and may be taken as further aspects of construct validity. The comparison between patient and non-patient samples, however, has to be put into perspective. While the overall comparison between patients and the group in this study differed markedly in allocations to stages of change, this difference decreased noticeably if only alcohol-misusing and alcohol-dependent subjects from this study are compared with the subjects from the patient groups. However, neither subgroup in this study showed a consistently similar pattern in stage allocation comparable to the patient samples. This may be taken as an indicator that differences in motivational stages of change between general hospital or general practice patients and subjects from the general population are not only due to drinking behaviour. Rather, being confronted with their health status as prompting a visit with a healthcare expert may have served as a trigger for the patients to re-evaluate their alcohol consumption behaviour. The higher proportions of patients allocated to the A stage also supports this interpretation.
Allocation to stage of change did not show strict model conformity in 22% of subjects. If the refined method was used and P as stage of change was taken into account, this rate was reduced to 19%. Compared to the patient sample, this rate is considerably lower, indicating that it is easier to allocate subjects to stages of change if they are sampled from the general population. Nevertheless, a classification scheme that conflicts in every fifth to every third subject with the underlying model or results in an inconclusive classification leaves room for further improvement. Allocation methods produced comparable results for the three subgroups under inspection (hazardous consumption, alcohol misuse, alcohol dependence). This reflects a general shortcoming of the allocation scheme, rather than a differential incompatibility between method and subjects under inspection.
Principal component analysis produced inconclusive results. In contrast to the theoretical formulation and background, only two components with eigenvalues of >1 could be extracted. At a first glance, it looks inviting to interpret the first factor as a bipolar representation of a continuum with PC on one end, and C on the other, and the second factor as a unipolar representation of A. However, items from PC and C showed similar loadings on both factors. Nor did analysing subgroups result in an interpretable structure; and indications for a single factor solution were not found. It looks likely that these results derive from the item distributions that do not agree with distribution assumptions necessary for factor analyses. Thus, no conclusions concerning the factor structure of the RCQ may be drawn from this study.
In conclusion, the RCQ is a brief instrument with satisfying psychometric properties, that enables quick allocation to stages of change of subjects with at least high-risk drinking behaviour, if sampled from the general population. Classification results are in accordance with predictions from the Transtheoretical Model for behaviour change and may be taken as valuable hints for construct validity of the instrument. Results from factor analysis, however, are jeopardized by item distribution characteristics and do not allow a conclusion about the factor structure of the RCQ, thus weighing against the instrument's construct validity. Finally, another methodological shortcoming may be seen in the rate of subjects who showed scores without strict model conformity.
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ACKNOWLEDGEMENTS |
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FOOTNOTES |
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