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Development and psychometric properties of the Verona Service Satisfaction Scale for methadone-treated opioid-dependent patients (VSSS-MT)
Drug and Alcohol Dependence 68 (2002) 209 /214 www.elsevier.com/locate/drugalcdep
Development and psychometric properties of the Verona Service Satisfaction Scale for methadone-treated opioid-dependent patients (VSSS-MT) Jose´ Pe´rez de los Cobos a,*, Sergi Valero a, Gonzalo Haro b, Guila Fidel a, Gemma Escuder a, Joan Trujols a, Juan Carlos Valderrama c a
Addictive Behaviours Unit, Department of Psychiatry, Hospital de la Santa Creu i Sant Pau, Auto´noma University of Barcelona School of Medicine, Sant Antoni Ma Claret, 167, 08025 Barcelona, Spain b Psychiatric Service, Hospital Clı´nico Universitario, Avda. Blasco Iban˜ez no. 17, 46010 Valencia, Spain c Fundacio´n de Ayuda contra la Drogadiccio´n, Valencian Regional Office, Isabel la Cato´lica no. 8, pta 35, 46007 Valencia, Spain Received 20 November 2001; accepted 24 June 2002
Abstract We adapted the 32-item Verona Service Satisfaction Scale (VSSS-32) to assess opioid-dependent patient satisfaction with services received from methadone treatment centres. The preliminary version of the VSSS for methadone treatment (VSSS-MT) was filled out anonymously and completed by 516 randomly recruited patients. After exploratory factor analysis and item refinement, the definitive 27-item VSSS-MT accounted for 58.8% of the total variance, comprising four factors: Basic Interventions, Specific Interventions, Social Worker Skills, and Psychologist Skills. These factors showed good to excellent internal reliabilities (Chronbach’s a : 0.91, 0.85, 0.87, and 0.92, respectively). At test /retest, intraclass correlation coefficients of VSSS-MT overall and factor scores were fair to good. The results of this study suggest that the VSSS-MT measures, briefly but also multidimensionally, opioid-dependent patient satisfaction with methadone treatment centres. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Satisfaction; Methadone; Opioid dependence; Psychometric properties
1. Introduction The assessment of opioid-dependent patient satisfaction with methadone treatment can provide useful data for improving its efficacy. The importance of this data lies in the fact that they reflect client opinions regarding the service at their treatment centres. Awareness of the patient’s point of view is a key factor, because the patient is the one who will finally decide whether to continue treatment or drop out.
Materials cited, but not presented, in the text, as well as the Spanish version of the VSSS-MT, are available at the journal’s website: http://www.elsevier.com/locate/drugalcdep under ‘Supplementary Materials’. * Corresponding author. Tel.: /34-93-291-9131; fax: /34-93-2919178 E-mail address: [email protected] (J. Pe´rez de los Cobos).
To our knowledge, there is currently no instrument designed to measure opioid-dependent patient satisfaction with methadone treatment centres. Given the lack of such a tool, methadone clients have been surveyed using isolated questions about overall satisfaction (QOS, Joe and Friend, 1989), or questionnaires for assessing satisfaction with mental health services (Trujols et al., 1999). According to these surveys, patients are highly satisfied with methadone treatment, but this result could be due to the fact that dissatisfaction is difficult to detect with non-dimensional assessment instruments (Ruggeri et al., 1994). We chose the 32-item Verona Service Satisfaction Scale (VSSS-32) (Ruggeri et al., 1996), the shortest version of the VSSS, as a starting point for creating an instrument able to specifically assess methadone-maintained patient satisfaction. There were several reasons for this choice. The VSSS-32 is a self-administered
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instrument designed to assess patient satisfaction with community-based mental health services, whose services and staff composition have much in common with methadone centres. In addition, the VSSS-32 enables investigators to assess satisfaction even when the centres being studied present a wide variety of material and human resources, as is the case with Spanish methadone centres (Domingo-Salvany et al., 1999). Another advantage of the VSSS-32 is that it has a well-tuned balance between brevity and multidimensionality. Brevity is indispensable to the feasibility of a survey involving methadone-treated patients, since they often suffer from substance intoxication. Multidimensionality facilitates detection of dissatisfaction, and elicits specific patient opinions on the services received. Lastly, we chose the VSSS-32 because a research group had previously translated different versions of the VSSS into Spanish (Gaite et al., 1998). The present paper describes how the VSSS for methadone-treated patients (VSSS-MT) was developed.
2. Method 2.1. Participants Two separate samples of methadone-maintained opioid-dependent patients (DSM-IV: 304.02; American Psychiatric Association, 1994) were assessed. Both samples were randomly recruited in Spain, one nationwide and the other in a single Spanish region (Valencia). These groups participated in two surveys (one nationwide, the other in Valencia) of patient satisfaction with state-funded methadone centres. The results of these surveys will be analysed in later publications. The same methodology was used in both studies. First, we estimated the total of patients being treated with methadone in each catchment area, and then listed all of the methadone dispensing centres involved, specifying the number of clients treated at each one. We did not list those centres that only prescribed methadone but did not dispense it, because the study method was to conduct the survey when patients were leaving the centre where they had taken methadone or picked up their doses. When patients were being treated by a combination of prescribing-only and dispensingonly centres, the survey instructions clarified that the expression ‘methadone treatment centre’ referred to the dispensing centre and the prescribing centre together. We randomly selected the methadone-dispensing centres where the surveys were to be carried out, and then determined the proportional number of patients to be surveyed at each centre. Participation in the survey was proposed consecutively to those patients who had received methadone at this centre for at least 3 months, and who signed an informed consent form. Those
patients who presented clear signs of substance intoxication were not asked to participate. Patients were not compensated for their participation in the surveys. 2.2. VSSS-MT development We adapted the VSSS-32 to assess opioid-dependent patient satisfaction with services received from methadone treatment centres. The VSSS-32 is a self-reported instrument, in which the following conceptual dimensions are considered: Overall Satisfaction, Professionals’ Skills and Behaviours, Information, Access, Efficacy, and Types of Intervention. All of these items, except those included in Types of Intervention, have a fivepoint Likert scale response option ((1) terrible; (2) mostly dissatisfied; (3) mixed; (4) mostly satisfied; (5) excellent) presented with alternate directionality (Ruggeri et al., 1996). On items from the subscale Types of Intervention, patients are first asked if they have received intervention. In the case of a ‘yes’ answer, satisfaction is rated in the same way as other items on the scale. If the answer is ‘no’, patients are asked if they would have liked to receive intervention ((6) no; (7) do not know; (8) not applicable; (9) yes). Thus, the VSSS-32 has the advantage of valuing satisfaction not only with services received, but also with the provision of services designed by the staff. The assessment period for satisfaction, which is 1 year on the VSSS-32, was reduced to 3 months on our adaptation. We decided to do this in order to enable patients to participate in the survey who had dropped out of their methadone treatment programme before completion, perhaps due to feeling dissatisfied with the services they were receiving. Three months was considered enough time for patients to have acquired sufficient experience with the centre’s capacity for initiating and maintaining methadone treatment. The text of the VSSS-32 was modified, adapting it specifically for methadone maintenance treatment (process not presented). This VSSS-MT preliminary version comprised 36 items. 2.3. Questions about overall satisfaction (QOS) To assess concurrent validity of the preliminary version of the VSSS-MT, we asked the patients three QOS adapted from the client satisfaction questionnaire (CSQ-8) (Larsen et al., 1979). The first QOS was, ‘‘What is your overall feeling about the quality of the service you have received from the centre where methadone treatment was conducted?’’ For this question, satisfaction ratings were the same five-point Likert scale as the VSSS-32 items. The other two questions were: ‘‘Would you recommend, to a friend who needed it, the centre were you are currently receiving methadone maintenance treatment?’’ and ‘‘Suppose that you could now
J. Pe´rez de los Cobos et al. / Drug and Alcohol Dependence 68 (2002) 209 /214
choose a methadone treatment centre, would you ask for this treatment again at the same centre where your are being treated now?’’ The satisfaction rating on these two questions was the following: (1) no, definitely not; (2) no, but with reservations; (3) it would not matter either way; (4) yes, but with reservations; (5) yes, definitely.
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interpreted according to the ranges of clinical significance recommended by Ciccheti and Sparrow (1990), Ciccheti (1994), respectively. Tests of significance employed were always two-tailed. All analyses were performed using the SPSS 7.5 statistical package.
3. Results 2.4. Procedures and testing conditions 3.1. Sample characteristics Four research assistants, three psychologists and one physician were trained during 1 week on how to administer the survey. All of them had at least 6 months of clinical experience with patients suffering from drug dependence disorders. These research assistants visited the selected centres to propose and supervise both surveys. Participants filled out the preliminary version of the VSSS-MT and QOS. Research workers assisted low-literacy participants by reading the items with them. Both surveys were conducted without the presence of staff from the different centres. Anonymity was also guaranteed by instructing the patients not to put their names on the questionnaires. A subgroup of patients from both surveys participated in a retest of the preliminary version of the VSSSMT. These patients were recruited consecutively at centres chosen according to the feasibility of the following procedure. The day of the test, the research assistants gave retest participants an envelope containing a new copy of the preliminary version of the VSSSMT. This copy was identified only by the patient’s key number. Participants received two more instructions: to fill in the scale a second time exactly 7 days after taking the test, and to hand in the closed envelope at their respective centres. Staff at these centres were asked to send the envelopes to the institute that co-ordinated both surveys (Addictive Behaviours Unit, Sant Pau Hospital, Barcelona). 2.5. Data analysis Exploratory factor analysis of the preliminary version of the VSSS-MT was conducted, using principal component analysis. The Scree test (Cattell, 1961), Kaiser’s eigenvalues-greater-than-one rule (Kaiser, 1960), and the interpretability of simple structure were used to determine the number of components to retain. A varimax rotation was performed on the resulting component pattern. The items that had a loading greater than 0.4 in one factor were chosen to construct the components. The internal consistency of the components resulting from the previous analysis was estimated using Cronbach’s a coefficient (Cronbach, 1951). Test / retest reliability of the preliminary version of the VSSSMT was calculated with the intraclass correlation coefficient (ICC). Cronbach’s a and ICC results were
Of the 783 clients who were invited to participate in the two surveys, 536 (68.5%) accepted. The analysis included only the answers of those 516 patients who completed at least 80% of the items on the scale. Of these 516 patients, 76% were male, the mean age was 33.1 (S.D. /6.5) years, and the mean period of education 8.3 (S.D. /3.1) years. Fifty-seven percent had never been married. Patients took methadone in conventional centres (71.1%), buses (20.5%), and prisons (8.3%). 3.2. Factor analysis of the preliminary version of the VSSS-MT The correlation matrix was considered suitable for factor analytical modelling because the Kaiser /Meyer / Olkin measure was high (0.801) and Barlett’s Test of Sphericity was statistically significant (P /0.0005). After conducting the principal component analysis of the 36 items, the criteria used to determine the number of factors to retain revealed four factors as the best solution. This initial solution explained 49.7% of total variance. An iterative refinement process was then carried out, with the deletion of six items that attenuated the internal consistency of their respective factors. These deleted items addressed the following issues: living in a sheltered institution, help in obtaining welfare benefits, admission to a hospital for substance use problems, changes in methadone treatment, costs of the service, and prescriptions of medication other than methadone. The items about helping patients with relationships outside their families, or to deal with problems, loaded comparably on the first and third factor (Table 1). These two complex items did not attenuate internal consistency on the first factor, but they did on the third factor. For this reason, these items were maintained as part of the first factor and excluded as constituents of the third factor. Three items whose deletion was not associated with a reduction in internal factor consistency were deleted. These redundant items addressed assistance in seeking open employment, response of the service to emergencies, and the appearance of the centre. The item related to ‘nurses manner’ could also have been eliminated using the same criteria. However, this item was retained, because it was not considered theoretically coherent for
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Table 1 Factor analysis of the VSSS-MT: rotated factor loadings VSSS-MT item descriptiona
7. Improving relationship between patient and relatives 9. Nurses’ knowledge of patient’s medical history 8. Helping family members to understand patient’s problems 14a. Nurses’ ability to listen 4. Referring to other specialists 13. Helping patient to look after himself 15. Help received for methadone side effects 2a. Doctors’ ability to listen 10. Information on addiction 12. Instructions between visits 6a. Nurses’ manner 3a. Doctors’ manner 11. Helping patient in relationships outside the familyd 1. Helping patient deal with problemsd 5. Overall satisfaction 19. Activities organised by centre 17. Individual psychotherapy 22. Help by the centre at home 23. Help to join in activities separate from the centre 21. Sheltered work 20. Group psychotherapy 16. Individual rehabilitation 18. Family therapy 6b. Social workers’ manner 14b. Social workers’ ability to listen 3b. Psychologists’ manner 2b. Psychologists’ ability to listen a b c d
Componentsb,c 1
2
3
4
0.753 0.732 0.717 0.699 0.682 0.625 0.615 0.613 0.596 0.573 0.573 0.565 0.533 0.500 0.467 / / / / / / / / / / / /
/ / / / / / / / / / / / / / / 0.735 0.728 0.725 0.717 0.679 0.636 0.594 0.558 / / / /
/ / / / / / / / / / / / 0.469 0.476 / / / / / / / / / 0.821 0.796 / /
/ / / / / / / / / / / / / / / / / / / / / / / / / 0.832 0.802
Item description is based on Ruggeri et al. (2000). Number of each item in the definitive VSSS-MT is included. The names of components are ‘Basic Interventions’ (1), ‘Specific Interventions’ (2), ‘Social Worker Skills’ (3), and ‘Psychologist Skills’ (4). Component loadings lower than 0.40 were eliminated. Items 1 and 11 were excluded from the third component because they attenuated this factor’s internal consistency.
the VSSS-MT to assess satisfaction with doctors’, psychologists’, and social workers’ manner, but not with nurses’ manner. As a result of these refinements, the final version of the scale includes only 27 items. All subsequent results refer to the definitive 27-item VSSS for methadone treatment (VSSS-MT). The definitive VSSS-MT accounted for 58.8% of the total variance. The names we gave to factors 1 through 4 were (each followed in brackets by the percentage of total variance explained by each factor): ‘Basic Interventions’ (23.0%), ‘Specific Interventions’ (15.6%), ‘Social Worker Skills’ (11.0%) and ‘Psychologist Skills’ (9.2%), respectively. The rotated item loadings onto each factor are presented in Table 1.
3.3. Internal consistency of VSSS-MT subscales Cronbach’s a for the four subscales were good to excellent: 0.91 for Basic Interventions (15 items), 0.85 for Specific Interventions (eight items), 0.87 for Social
Worker Skills (two items), and 0.92 for Psychologist Skills (two items).
3.4. Test /retest reliability of VSSS-MT scores A retest was proposed to 96 participants, but only 83 filled out the VSSS-MT for a second time. The retest group (n /83) and the no-retest group (n /433) differed in terms of gender, years of education, and type of treatment centre. Compared with patients from the test group, members of the retest group included more women (34.9 vs. 27.4%; x2(1) /5.47, P /0.019), and had more years of education (9.19/3.2 vs. 8.19/3.3; t97 /2.88; P /0.005). In the retest group, 89.0% were treated in conventional centres, 3.7% in a bus, and 7.3% in prisons, while in the no-retest group, these percentages were 67.7, 23.7, and 8.5%, respectively, (x2(1) / 18.04, P /0.0005). The number of patients included to calculate the test/ retest reliability of each one of the VSSS-MT subscale scores was notably different (Table 2), due to the fact that the reply ‘not applicable’ was used with different
J. Pe´rez de los Cobos et al. / Drug and Alcohol Dependence 68 (2002) 209 /214 Table 2 Test /retest of VSSS-MT ICC (95% CI)a, * VSSS-MT, overall (n 82) Basic interventions (n 81) Specific interventions (n 77) Social worker skills (n 50) Psychologist skills (n 49)
0.73 0.58 0.60 0.69 0.55
(0.61 /0.82) (0.42 /0.71) (0.44 /0.73) (0.51 /0.81) (0.33 /0.72)
a
ICC, intraclass correlation coefficient. CI, confidence intervals. * P B 0.0005 in all ICC obtained.
frequency on the subscales. The case exclusion criteria applied before analysing test /retest data are listed below. In the analysis of the VSSS-MT overall scores, and Basic or Specific Intervention scores, those cases were excluded on which, for the test or the retest, the number of ‘not applicable’ or unanswered items was as follows: VSSS-MT overall /five items, Basic Interventions /three items, and Specific Interventions /two items. Each one of these cut-offs corresponds to the value closest to 20% of the items on the scale or subscale. Test /retest analysis of the Social Worker Skills and Psychologist Skills subscales were not carried out if the items were not applicable, or there was a missing answer. Table 2 presents the results of the test/retest reliability of VSSS-MT scores. All ICC were statistically significant. The VSSS-MT overall, Specific Interventions, and Social Worker Skills scores showed good reliability, while Basic Interventions and Psychologist Skills reliability was only fair. Gender and years of education, which showed different values in the retest group and the no-retest group, were not related to the consistency of VSSS-MT scores over time (data not presented). 3.5. Concurrent validity of the VSSS-MT Table 3 shows Pearson correlations between QOS and the VSSS-MT overall and subscale scores. All correlations were statistically significant. An exploratory factor
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analysis was then performed on the set of the three QOS, as well as the 27 items on the VSSS-MT. All three QOS loaded onto the Basic Intervention subscale. QOS orthogonal rotated factor loadings on this first factor were as follows: ‘asking for treatment at the same centre again’ (0.638), ‘overall feeling about the service’ (0.607), and ‘recommending the centre to a friend’ (0.434). On the other three VSSS-MT dimensions, factor loadings of the QOS were B/0.40. A stepwise multiple regression analysis was used to verify the results regarding concurrent validity of the VSSS-MT (data not presented).
4. Discussion The results of this study suggest that the VSSS-MT measures, briefly but multidimensionally, opioid-dependent patient satisfaction with methadone treatment centres. The VSSS-MT is brief, its factorial structure is easily interpretable, and it has good psychometric properties. Its only drawback is that, according to our findings, the VSSS-MT test /retest reliability is fair to good. Exploratory factor analysis revealed a four-factor structure of the VSSS-MT that accounted for 59% of total variance, approximately. In keeping with the items included on each factor, we named the VSSS-MT subscales ‘Basic Interventions’, ‘Specific Interventions’, ‘Social Worker Skills’, and ‘Psychologist Skills’. The Basic Interventions subscale accounted for 23% of total variance. This factor contains all items on the following VSSS-32 theoretical subscales: family members’ involvement, efficacy, information, and overall satisfaction. It also contains the items referring to nurses and doctors on the VSSS-32 subscale ‘Professionals’ Skills and Behaviour’. Our interpretation is that this subscale (Table 1) includes the activity of those professionals who are essential in carrying out methadone treatment, together with the help received in two areas that are especially deteriorated in heroin-dependent patients:
Table 3 Pearson correlations between VSSS-MT scores and QOS VSSS-MT
QOS Overall feeling about the service
Recommending the centre to a friend
Asking for treatment at the same centre again
Overall
0.47b**
0.38**
0.38**
Components Basic interventions Specific interventions Social worker skills Psychologist skills
0.47** 0.33** 0.24** 0.23**
0.38** 0.24** 0.18* 0.21**
0.39** 0.25** 0.15* 0.21**
*, P B 0.01, two-tailed. **, P B 0.001, two-tailed.
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interpersonal relationships and self-care. QOS were related, above all, to Basic Interventions, which was expected, because this subscale includes the only VSSS32 item about overall satisfaction. The Specific Intervention subscale accounted for 16% of total variance, approximately. All of the items on this subscale belong to the VSSS-32 conceptual factor ‘Types of Intervention’. In addition, no Types of Intervention items (VSSS-32) were retained on another VSSS-MT subscale. Social Worker Skills and Psychologist Skills subscales accounted for 11 and 9% of total variance, respectively. Both subscales contained the two items referring to these professionals’ manner and ability to listen. These items belong to the Professionals’ Skills and Behaviour factor of the VSSS-32. Specific Interventions, and Social Worker or Psychologist Skills, are not essential to methadone administration. However, together, these satisfaction components accounted for 36% of total variance, whereas Basic Interventions accounted for only 23%. This finding takes on considerable weight if patient satisfaction is considered an important criterion for determining staff composition and the activities to be carried out by the centre. Internal consistency appears to be the outstanding psychometric property of the VSSS-MT; for all the subscales, including those comprising only two items, the Cronbach’s a was ]/0.85. However, the test /retest reliability of the VSSS-MT was merely fair to good, a result suggesting that consistency over time is this scale’s weakest property. However, this result could be due to retest limitations. Unlike the test, and for reasons related to the study’s feasibility, the retest was conducted on a convenience sample of patients, and without our supervision. The study’s other noteworthy limitations were the fairly high rate of refusal to participate in the surveys, and the consecutive recruitment of participants, a method which does not ensure a representative sample of methadone centres’ clients. The VSSS-MT provides different measures of patient satisfaction which are potentially useful for evaluating methadone centres and assessing their activities. However, more work is needed to further develop this instrument. The answers to VSSS-MT items given by opioid-dependent patients who have dropped out from programmes at methadone centres should also be analysed. Moreover, the scale’s structure needs to be confirmed, since it was obtained using an exploratory factor analysis.
Acknowledgements The present study was supported by the Spanish Ministry of the Interior’s National Drugs Plan, and the Department of Drug Dependencies of the Valencian Regional Government’s Social Welfare Council. We thank Luis Gaite, from the Clinical and Social Psychiatry Research Unit, Marque´s de Valdeeilla Hospital (University of Cantabria, Spain), for providing us with the Spanish versions of the VSSS, and for his technical comments regarding this manuscript.
References American Psychiatric Association, 1994. Diagnostic and Statistical Manual of Mental Disorders, fourth ed.. American Psychiatric Association, Washington, DC. Cattell, R.B., 1961. The scree test for the number of factors. Multivariate Behav. Res. 1, 245 /276. Ciccheti, D.V., 1994. Guidelines, criteria, and rules of thumb for evaluating normed and standardised assessment instruments in psychology. Psychol. Assess 6, 284 /290. Ciccheti, D.V., Sparrow, S.S., 1990. Assessment of adaptive behavior in young children. In: Johnson, J.J., Goldman, J. (Eds.), Developmental Assessment in Clinical Child Psychology: a Handbook. Pergamon Press, New York, pp. 173 /196. Domingo-Salvany, A., Pe´rez, K., Torrens, M., Bravo, M.J., Anto´, J.M., Alonso, J., 1999. Methadone treatment in Spain, 1994. Drug Alcohol Depend. 56, 61 /66. Gaite, L., Ramı´rez, N., Artal, J., Rodrı´guez Pulido, F., Arriaga, A., Va´zquez-Barquero, J.L., 1998. Estudio de la satisfaccio´n con los servicios de salud mental en pacientes psiquia´tricos ambulatorios. Arch. Neurobiol. (Madr.) 61, 153 /168. Joe, G.W., Friend, H.J., 1989. Treatment process factors and satisfaction with drug abuse treatment. Psychol. Addict Behav. 2, 53 /64. Kaiser, H.F., 1960. The application of electronic computers to factor analysis. Educational Psychol. Measurement 20, 141 /151. Larsen, D.L., Attkisson, C.C., Hargreaves, W.A., Nguyen, T.D., 1979. Assessment of client/patient satisfaction: development of a general scale. Eval. Program Plann. 2, 197 /207. Ruggeri, M., Dall’Agnola, R., Agostini, C., Bisoffi, G., 1994. Acceptability, sensitivity and content validity of the VECS and VSSS in measuring expectations and satisfaction in psychiatric patients and their relatives. Soc. Psychiatry Psychiatr. Epidemiol. 29, 265 /276. Ruggeri, M., Dall’Agnola, R., Bisoffi, G., 1996. Factor analysis of the Verona Service Satisfaction Scale-82 and development of reduced versions. Int. J. Methods Psychiatric Res. 6, 23 /38. Ruggeri, M., Lasalvia, A., Dall’Agnola, R., Van Winja Arden, B., Knudsen, H.C., Leese, M., Gaite, L., Tansella, M., and Epsilon Study Group, 2000. Development, internal consistency and reliability of the Verona Service Satisfaction Scale-European Version. Br. J. Psychiatry 177 (Suppl. 39) s41 /s48. Trujols, J., Tejero, A., Duro, P., Casas, M., 1999. Users’ satisfaction with methadone maintenance treatment. Tenth International Conference on the Reduction of Drug Related Harm (Abstract), p. 128.
Development and psychometric properties of the Verona Service Satisfaction Scale for methadone-treated opioid-dependent patients (VSSS-MT) Jose´ Pe´rez de los Cobos a,*, Sergi Valero a, Gonzalo Haro b, Guila Fidel a, Gemma Escuder a, Joan Trujols a, Juan Carlos Valderrama c a
Addictive Behaviours Unit, Department of Psychiatry, Hospital de la Santa Creu i Sant Pau, Auto´noma University of Barcelona School of Medicine, Sant Antoni Ma Claret, 167, 08025 Barcelona, Spain b Psychiatric Service, Hospital Clı´nico Universitario, Avda. Blasco Iban˜ez no. 17, 46010 Valencia, Spain c Fundacio´n de Ayuda contra la Drogadiccio´n, Valencian Regional Office, Isabel la Cato´lica no. 8, pta 35, 46007 Valencia, Spain Received 20 November 2001; accepted 24 June 2002
Abstract We adapted the 32-item Verona Service Satisfaction Scale (VSSS-32) to assess opioid-dependent patient satisfaction with services received from methadone treatment centres. The preliminary version of the VSSS for methadone treatment (VSSS-MT) was filled out anonymously and completed by 516 randomly recruited patients. After exploratory factor analysis and item refinement, the definitive 27-item VSSS-MT accounted for 58.8% of the total variance, comprising four factors: Basic Interventions, Specific Interventions, Social Worker Skills, and Psychologist Skills. These factors showed good to excellent internal reliabilities (Chronbach’s a : 0.91, 0.85, 0.87, and 0.92, respectively). At test /retest, intraclass correlation coefficients of VSSS-MT overall and factor scores were fair to good. The results of this study suggest that the VSSS-MT measures, briefly but also multidimensionally, opioid-dependent patient satisfaction with methadone treatment centres. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Satisfaction; Methadone; Opioid dependence; Psychometric properties
1. Introduction The assessment of opioid-dependent patient satisfaction with methadone treatment can provide useful data for improving its efficacy. The importance of this data lies in the fact that they reflect client opinions regarding the service at their treatment centres. Awareness of the patient’s point of view is a key factor, because the patient is the one who will finally decide whether to continue treatment or drop out.
Materials cited, but not presented, in the text, as well as the Spanish version of the VSSS-MT, are available at the journal’s website: http://www.elsevier.com/locate/drugalcdep under ‘Supplementary Materials’. * Corresponding author. Tel.: /34-93-291-9131; fax: /34-93-2919178 E-mail address: [email protected] (J. Pe´rez de los Cobos).
To our knowledge, there is currently no instrument designed to measure opioid-dependent patient satisfaction with methadone treatment centres. Given the lack of such a tool, methadone clients have been surveyed using isolated questions about overall satisfaction (QOS, Joe and Friend, 1989), or questionnaires for assessing satisfaction with mental health services (Trujols et al., 1999). According to these surveys, patients are highly satisfied with methadone treatment, but this result could be due to the fact that dissatisfaction is difficult to detect with non-dimensional assessment instruments (Ruggeri et al., 1994). We chose the 32-item Verona Service Satisfaction Scale (VSSS-32) (Ruggeri et al., 1996), the shortest version of the VSSS, as a starting point for creating an instrument able to specifically assess methadone-maintained patient satisfaction. There were several reasons for this choice. The VSSS-32 is a self-administered
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instrument designed to assess patient satisfaction with community-based mental health services, whose services and staff composition have much in common with methadone centres. In addition, the VSSS-32 enables investigators to assess satisfaction even when the centres being studied present a wide variety of material and human resources, as is the case with Spanish methadone centres (Domingo-Salvany et al., 1999). Another advantage of the VSSS-32 is that it has a well-tuned balance between brevity and multidimensionality. Brevity is indispensable to the feasibility of a survey involving methadone-treated patients, since they often suffer from substance intoxication. Multidimensionality facilitates detection of dissatisfaction, and elicits specific patient opinions on the services received. Lastly, we chose the VSSS-32 because a research group had previously translated different versions of the VSSS into Spanish (Gaite et al., 1998). The present paper describes how the VSSS for methadone-treated patients (VSSS-MT) was developed.
2. Method 2.1. Participants Two separate samples of methadone-maintained opioid-dependent patients (DSM-IV: 304.02; American Psychiatric Association, 1994) were assessed. Both samples were randomly recruited in Spain, one nationwide and the other in a single Spanish region (Valencia). These groups participated in two surveys (one nationwide, the other in Valencia) of patient satisfaction with state-funded methadone centres. The results of these surveys will be analysed in later publications. The same methodology was used in both studies. First, we estimated the total of patients being treated with methadone in each catchment area, and then listed all of the methadone dispensing centres involved, specifying the number of clients treated at each one. We did not list those centres that only prescribed methadone but did not dispense it, because the study method was to conduct the survey when patients were leaving the centre where they had taken methadone or picked up their doses. When patients were being treated by a combination of prescribing-only and dispensingonly centres, the survey instructions clarified that the expression ‘methadone treatment centre’ referred to the dispensing centre and the prescribing centre together. We randomly selected the methadone-dispensing centres where the surveys were to be carried out, and then determined the proportional number of patients to be surveyed at each centre. Participation in the survey was proposed consecutively to those patients who had received methadone at this centre for at least 3 months, and who signed an informed consent form. Those
patients who presented clear signs of substance intoxication were not asked to participate. Patients were not compensated for their participation in the surveys. 2.2. VSSS-MT development We adapted the VSSS-32 to assess opioid-dependent patient satisfaction with services received from methadone treatment centres. The VSSS-32 is a self-reported instrument, in which the following conceptual dimensions are considered: Overall Satisfaction, Professionals’ Skills and Behaviours, Information, Access, Efficacy, and Types of Intervention. All of these items, except those included in Types of Intervention, have a fivepoint Likert scale response option ((1) terrible; (2) mostly dissatisfied; (3) mixed; (4) mostly satisfied; (5) excellent) presented with alternate directionality (Ruggeri et al., 1996). On items from the subscale Types of Intervention, patients are first asked if they have received intervention. In the case of a ‘yes’ answer, satisfaction is rated in the same way as other items on the scale. If the answer is ‘no’, patients are asked if they would have liked to receive intervention ((6) no; (7) do not know; (8) not applicable; (9) yes). Thus, the VSSS-32 has the advantage of valuing satisfaction not only with services received, but also with the provision of services designed by the staff. The assessment period for satisfaction, which is 1 year on the VSSS-32, was reduced to 3 months on our adaptation. We decided to do this in order to enable patients to participate in the survey who had dropped out of their methadone treatment programme before completion, perhaps due to feeling dissatisfied with the services they were receiving. Three months was considered enough time for patients to have acquired sufficient experience with the centre’s capacity for initiating and maintaining methadone treatment. The text of the VSSS-32 was modified, adapting it specifically for methadone maintenance treatment (process not presented). This VSSS-MT preliminary version comprised 36 items. 2.3. Questions about overall satisfaction (QOS) To assess concurrent validity of the preliminary version of the VSSS-MT, we asked the patients three QOS adapted from the client satisfaction questionnaire (CSQ-8) (Larsen et al., 1979). The first QOS was, ‘‘What is your overall feeling about the quality of the service you have received from the centre where methadone treatment was conducted?’’ For this question, satisfaction ratings were the same five-point Likert scale as the VSSS-32 items. The other two questions were: ‘‘Would you recommend, to a friend who needed it, the centre were you are currently receiving methadone maintenance treatment?’’ and ‘‘Suppose that you could now
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choose a methadone treatment centre, would you ask for this treatment again at the same centre where your are being treated now?’’ The satisfaction rating on these two questions was the following: (1) no, definitely not; (2) no, but with reservations; (3) it would not matter either way; (4) yes, but with reservations; (5) yes, definitely.
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interpreted according to the ranges of clinical significance recommended by Ciccheti and Sparrow (1990), Ciccheti (1994), respectively. Tests of significance employed were always two-tailed. All analyses were performed using the SPSS 7.5 statistical package.
3. Results 2.4. Procedures and testing conditions 3.1. Sample characteristics Four research assistants, three psychologists and one physician were trained during 1 week on how to administer the survey. All of them had at least 6 months of clinical experience with patients suffering from drug dependence disorders. These research assistants visited the selected centres to propose and supervise both surveys. Participants filled out the preliminary version of the VSSS-MT and QOS. Research workers assisted low-literacy participants by reading the items with them. Both surveys were conducted without the presence of staff from the different centres. Anonymity was also guaranteed by instructing the patients not to put their names on the questionnaires. A subgroup of patients from both surveys participated in a retest of the preliminary version of the VSSSMT. These patients were recruited consecutively at centres chosen according to the feasibility of the following procedure. The day of the test, the research assistants gave retest participants an envelope containing a new copy of the preliminary version of the VSSSMT. This copy was identified only by the patient’s key number. Participants received two more instructions: to fill in the scale a second time exactly 7 days after taking the test, and to hand in the closed envelope at their respective centres. Staff at these centres were asked to send the envelopes to the institute that co-ordinated both surveys (Addictive Behaviours Unit, Sant Pau Hospital, Barcelona). 2.5. Data analysis Exploratory factor analysis of the preliminary version of the VSSS-MT was conducted, using principal component analysis. The Scree test (Cattell, 1961), Kaiser’s eigenvalues-greater-than-one rule (Kaiser, 1960), and the interpretability of simple structure were used to determine the number of components to retain. A varimax rotation was performed on the resulting component pattern. The items that had a loading greater than 0.4 in one factor were chosen to construct the components. The internal consistency of the components resulting from the previous analysis was estimated using Cronbach’s a coefficient (Cronbach, 1951). Test / retest reliability of the preliminary version of the VSSSMT was calculated with the intraclass correlation coefficient (ICC). Cronbach’s a and ICC results were
Of the 783 clients who were invited to participate in the two surveys, 536 (68.5%) accepted. The analysis included only the answers of those 516 patients who completed at least 80% of the items on the scale. Of these 516 patients, 76% were male, the mean age was 33.1 (S.D. /6.5) years, and the mean period of education 8.3 (S.D. /3.1) years. Fifty-seven percent had never been married. Patients took methadone in conventional centres (71.1%), buses (20.5%), and prisons (8.3%). 3.2. Factor analysis of the preliminary version of the VSSS-MT The correlation matrix was considered suitable for factor analytical modelling because the Kaiser /Meyer / Olkin measure was high (0.801) and Barlett’s Test of Sphericity was statistically significant (P /0.0005). After conducting the principal component analysis of the 36 items, the criteria used to determine the number of factors to retain revealed four factors as the best solution. This initial solution explained 49.7% of total variance. An iterative refinement process was then carried out, with the deletion of six items that attenuated the internal consistency of their respective factors. These deleted items addressed the following issues: living in a sheltered institution, help in obtaining welfare benefits, admission to a hospital for substance use problems, changes in methadone treatment, costs of the service, and prescriptions of medication other than methadone. The items about helping patients with relationships outside their families, or to deal with problems, loaded comparably on the first and third factor (Table 1). These two complex items did not attenuate internal consistency on the first factor, but they did on the third factor. For this reason, these items were maintained as part of the first factor and excluded as constituents of the third factor. Three items whose deletion was not associated with a reduction in internal factor consistency were deleted. These redundant items addressed assistance in seeking open employment, response of the service to emergencies, and the appearance of the centre. The item related to ‘nurses manner’ could also have been eliminated using the same criteria. However, this item was retained, because it was not considered theoretically coherent for
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Table 1 Factor analysis of the VSSS-MT: rotated factor loadings VSSS-MT item descriptiona
7. Improving relationship between patient and relatives 9. Nurses’ knowledge of patient’s medical history 8. Helping family members to understand patient’s problems 14a. Nurses’ ability to listen 4. Referring to other specialists 13. Helping patient to look after himself 15. Help received for methadone side effects 2a. Doctors’ ability to listen 10. Information on addiction 12. Instructions between visits 6a. Nurses’ manner 3a. Doctors’ manner 11. Helping patient in relationships outside the familyd 1. Helping patient deal with problemsd 5. Overall satisfaction 19. Activities organised by centre 17. Individual psychotherapy 22. Help by the centre at home 23. Help to join in activities separate from the centre 21. Sheltered work 20. Group psychotherapy 16. Individual rehabilitation 18. Family therapy 6b. Social workers’ manner 14b. Social workers’ ability to listen 3b. Psychologists’ manner 2b. Psychologists’ ability to listen a b c d
Componentsb,c 1
2
3
4
0.753 0.732 0.717 0.699 0.682 0.625 0.615 0.613 0.596 0.573 0.573 0.565 0.533 0.500 0.467 / / / / / / / / / / / /
/ / / / / / / / / / / / / / / 0.735 0.728 0.725 0.717 0.679 0.636 0.594 0.558 / / / /
/ / / / / / / / / / / / 0.469 0.476 / / / / / / / / / 0.821 0.796 / /
/ / / / / / / / / / / / / / / / / / / / / / / / / 0.832 0.802
Item description is based on Ruggeri et al. (2000). Number of each item in the definitive VSSS-MT is included. The names of components are ‘Basic Interventions’ (1), ‘Specific Interventions’ (2), ‘Social Worker Skills’ (3), and ‘Psychologist Skills’ (4). Component loadings lower than 0.40 were eliminated. Items 1 and 11 were excluded from the third component because they attenuated this factor’s internal consistency.
the VSSS-MT to assess satisfaction with doctors’, psychologists’, and social workers’ manner, but not with nurses’ manner. As a result of these refinements, the final version of the scale includes only 27 items. All subsequent results refer to the definitive 27-item VSSS for methadone treatment (VSSS-MT). The definitive VSSS-MT accounted for 58.8% of the total variance. The names we gave to factors 1 through 4 were (each followed in brackets by the percentage of total variance explained by each factor): ‘Basic Interventions’ (23.0%), ‘Specific Interventions’ (15.6%), ‘Social Worker Skills’ (11.0%) and ‘Psychologist Skills’ (9.2%), respectively. The rotated item loadings onto each factor are presented in Table 1.
3.3. Internal consistency of VSSS-MT subscales Cronbach’s a for the four subscales were good to excellent: 0.91 for Basic Interventions (15 items), 0.85 for Specific Interventions (eight items), 0.87 for Social
Worker Skills (two items), and 0.92 for Psychologist Skills (two items).
3.4. Test /retest reliability of VSSS-MT scores A retest was proposed to 96 participants, but only 83 filled out the VSSS-MT for a second time. The retest group (n /83) and the no-retest group (n /433) differed in terms of gender, years of education, and type of treatment centre. Compared with patients from the test group, members of the retest group included more women (34.9 vs. 27.4%; x2(1) /5.47, P /0.019), and had more years of education (9.19/3.2 vs. 8.19/3.3; t97 /2.88; P /0.005). In the retest group, 89.0% were treated in conventional centres, 3.7% in a bus, and 7.3% in prisons, while in the no-retest group, these percentages were 67.7, 23.7, and 8.5%, respectively, (x2(1) / 18.04, P /0.0005). The number of patients included to calculate the test/ retest reliability of each one of the VSSS-MT subscale scores was notably different (Table 2), due to the fact that the reply ‘not applicable’ was used with different
J. Pe´rez de los Cobos et al. / Drug and Alcohol Dependence 68 (2002) 209 /214 Table 2 Test /retest of VSSS-MT ICC (95% CI)a, * VSSS-MT, overall (n 82) Basic interventions (n 81) Specific interventions (n 77) Social worker skills (n 50) Psychologist skills (n 49)
0.73 0.58 0.60 0.69 0.55
(0.61 /0.82) (0.42 /0.71) (0.44 /0.73) (0.51 /0.81) (0.33 /0.72)
a
ICC, intraclass correlation coefficient. CI, confidence intervals. * P B 0.0005 in all ICC obtained.
frequency on the subscales. The case exclusion criteria applied before analysing test /retest data are listed below. In the analysis of the VSSS-MT overall scores, and Basic or Specific Intervention scores, those cases were excluded on which, for the test or the retest, the number of ‘not applicable’ or unanswered items was as follows: VSSS-MT overall /five items, Basic Interventions /three items, and Specific Interventions /two items. Each one of these cut-offs corresponds to the value closest to 20% of the items on the scale or subscale. Test /retest analysis of the Social Worker Skills and Psychologist Skills subscales were not carried out if the items were not applicable, or there was a missing answer. Table 2 presents the results of the test/retest reliability of VSSS-MT scores. All ICC were statistically significant. The VSSS-MT overall, Specific Interventions, and Social Worker Skills scores showed good reliability, while Basic Interventions and Psychologist Skills reliability was only fair. Gender and years of education, which showed different values in the retest group and the no-retest group, were not related to the consistency of VSSS-MT scores over time (data not presented). 3.5. Concurrent validity of the VSSS-MT Table 3 shows Pearson correlations between QOS and the VSSS-MT overall and subscale scores. All correlations were statistically significant. An exploratory factor
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analysis was then performed on the set of the three QOS, as well as the 27 items on the VSSS-MT. All three QOS loaded onto the Basic Intervention subscale. QOS orthogonal rotated factor loadings on this first factor were as follows: ‘asking for treatment at the same centre again’ (0.638), ‘overall feeling about the service’ (0.607), and ‘recommending the centre to a friend’ (0.434). On the other three VSSS-MT dimensions, factor loadings of the QOS were B/0.40. A stepwise multiple regression analysis was used to verify the results regarding concurrent validity of the VSSS-MT (data not presented).
4. Discussion The results of this study suggest that the VSSS-MT measures, briefly but multidimensionally, opioid-dependent patient satisfaction with methadone treatment centres. The VSSS-MT is brief, its factorial structure is easily interpretable, and it has good psychometric properties. Its only drawback is that, according to our findings, the VSSS-MT test /retest reliability is fair to good. Exploratory factor analysis revealed a four-factor structure of the VSSS-MT that accounted for 59% of total variance, approximately. In keeping with the items included on each factor, we named the VSSS-MT subscales ‘Basic Interventions’, ‘Specific Interventions’, ‘Social Worker Skills’, and ‘Psychologist Skills’. The Basic Interventions subscale accounted for 23% of total variance. This factor contains all items on the following VSSS-32 theoretical subscales: family members’ involvement, efficacy, information, and overall satisfaction. It also contains the items referring to nurses and doctors on the VSSS-32 subscale ‘Professionals’ Skills and Behaviour’. Our interpretation is that this subscale (Table 1) includes the activity of those professionals who are essential in carrying out methadone treatment, together with the help received in two areas that are especially deteriorated in heroin-dependent patients:
Table 3 Pearson correlations between VSSS-MT scores and QOS VSSS-MT
QOS Overall feeling about the service
Recommending the centre to a friend
Asking for treatment at the same centre again
Overall
0.47b**
0.38**
0.38**
Components Basic interventions Specific interventions Social worker skills Psychologist skills
0.47** 0.33** 0.24** 0.23**
0.38** 0.24** 0.18* 0.21**
0.39** 0.25** 0.15* 0.21**
*, P B 0.01, two-tailed. **, P B 0.001, two-tailed.
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interpersonal relationships and self-care. QOS were related, above all, to Basic Interventions, which was expected, because this subscale includes the only VSSS32 item about overall satisfaction. The Specific Intervention subscale accounted for 16% of total variance, approximately. All of the items on this subscale belong to the VSSS-32 conceptual factor ‘Types of Intervention’. In addition, no Types of Intervention items (VSSS-32) were retained on another VSSS-MT subscale. Social Worker Skills and Psychologist Skills subscales accounted for 11 and 9% of total variance, respectively. Both subscales contained the two items referring to these professionals’ manner and ability to listen. These items belong to the Professionals’ Skills and Behaviour factor of the VSSS-32. Specific Interventions, and Social Worker or Psychologist Skills, are not essential to methadone administration. However, together, these satisfaction components accounted for 36% of total variance, whereas Basic Interventions accounted for only 23%. This finding takes on considerable weight if patient satisfaction is considered an important criterion for determining staff composition and the activities to be carried out by the centre. Internal consistency appears to be the outstanding psychometric property of the VSSS-MT; for all the subscales, including those comprising only two items, the Cronbach’s a was ]/0.85. However, the test /retest reliability of the VSSS-MT was merely fair to good, a result suggesting that consistency over time is this scale’s weakest property. However, this result could be due to retest limitations. Unlike the test, and for reasons related to the study’s feasibility, the retest was conducted on a convenience sample of patients, and without our supervision. The study’s other noteworthy limitations were the fairly high rate of refusal to participate in the surveys, and the consecutive recruitment of participants, a method which does not ensure a representative sample of methadone centres’ clients. The VSSS-MT provides different measures of patient satisfaction which are potentially useful for evaluating methadone centres and assessing their activities. However, more work is needed to further develop this instrument. The answers to VSSS-MT items given by opioid-dependent patients who have dropped out from programmes at methadone centres should also be analysed. Moreover, the scale’s structure needs to be confirmed, since it was obtained using an exploratory factor analysis.
Acknowledgements The present study was supported by the Spanish Ministry of the Interior’s National Drugs Plan, and the Department of Drug Dependencies of the Valencian Regional Government’s Social Welfare Council. We thank Luis Gaite, from the Clinical and Social Psychiatry Research Unit, Marque´s de Valdeeilla Hospital (University of Cantabria, Spain), for providing us with the Spanish versions of the VSSS, and for his technical comments regarding this manuscript.
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