Testing psychometric properties of Shared Decision Making Questionnaire – Physician Version (SDM-Q-Doc) in an Italian real-world psychiatric clinical sample

Renato de Filippis1, Matteo Aloi1,2, Salvatore Reina1, Antonia Cantavenara1, Luca Steardo jr1, Pasquale De Fazio1, Cristina Segura-Garcia3

1Psychiatry Unit, Department of Health Sciences, University Magna Graecia of Catanzaro, Italy; 2Department of Clinical and Experimental Medicine, University of Messina, Italy; 3Psychiatry Unit, Department of Medical and Surgical Sciences, University Magna Graecia of Catanzaro, Italy.

Summary. Objectives. The Shared Decision Making Questionnaire-Physician Version (SDM-Q-Doc) is the main tool assessing SDM relationship between patient and physician using the clinician viewpoint. It is reliable in all medical fields, and the validation of its Italian version was still missing. Our aim was to validate the Italian version of the SDM-Q-Doc in a clinical sample of patients suffering from severe mental illness. Methods. We approached 369 patients affected by major psychiatric disorders (including schizophrenia spectrum disorders, affective disorders and eating disorders) in a real-world outpatient clinical setting. We run the Confirmatory Factor Analysis (CFA) to test the SDM-Q-Doc structure. We calculated the correlations between the SDM-Q-Doc and the Observing Patient Involvement (OPTION) scale, used as comparing test, and McDonald ω coefficient to measure convergent validity and internal consistency respectively. Results. We reached a response rate of 93.2% (344 final participants). The CFA showed a very good fit compared of the Italian version of SDM-Q-Doc (χ2/df=3.2, CFI=.99, TLI=.99, RMSEA=.08, SRMR=.04). We found several correlations between the SDM-Q-Doc and OPTION scale supporting a robust SDM-Q-Doc construct validity, while internal consistency of the scale was McDonald ω coefficient .92. Further, inter-item correlations ranged from .390 to .703, with a mean of .556. Conclusions. This study confirms the suitability of the Italian version of SDM-Q-Doc, with good reliability and soundness even when compared to other languages validated versions and to OPTION scale. SDM-Q-Doc represents an easy-to-use physician-centered measure to assess patients’ involvement in medical decision-making, well performing in the Italian-speaking population.

Key words. Patient involvement, physicians’ perspective, psychometrics, questionnaires, shared decision making, validation study.

Valutazione delle proprietà psicometriche dello Shared Decision Making Questionnaire – Physician Version (SDM-Q-Doc) in un campione clinico psichiatrico italiano nel mondo reale.

Riassunto. Scopo. Lo Shared Decision Making Questionnaire - Physician Version (SDM-Q-Doc) è lo strumento psicometrico principale per valutare l’alleanza terapeutica dal punto di vista del clinico. Esso è utilizzabile in tutte le discipline mediche, ma la validazione della sua versione italiana non era ancora disponibile. Il nostro obiettivo è stato quello di validare la versione italiana dello SDM-Q-Doc in un campione clinico di pazienti affetti da gravi disturbi psichiatrici. Metodi. Abbiamo approcciato 369 pazienti ambulatoriali affetti da disturbi psichiatrici maggiori (inclusi disturbi dello spettro della schizofrenia, disturbi affettivi e disturbi alimentari). Abbiamo eseguito l’analisi fattoriale di conferma (CFA) per testare la struttura dello SDM-Q-Doc. Abbiamo inoltre calcolato le correlazioni esistenti tra la scala SDM-Q-Doc e l’Observing Patient Involvement (OPTION), utilizzata come test di confronto, e il coefficiente ω di McDonald per misurare rispettivamente la validità convergente e la coerenza interna. Risultati. Abbiamo ottenuto un tasso di risposta del 93,2% (344 partecipanti finali). Il CFA ha mostrato un ottimo adattamento rispetto alla versione italiana dello SDM-Q-Doc (χ2/df=3,2, CFI=,99, TLI=,99, RMSEA=,08, SRMR=,04). Abbiamo identificato diverse correlazioni tra lo SDM-Q-Doc e l’OPTION supportando una robusta validità della struttura dello SDM-Q-Doc, mentre la coerenza interna della scala ha ottenuto un coefficiente ω di McDonald di ,92. Inoltre, le correlazioni tra i quesiti variavano da ,390 a ,703, con una media di .556. Conclusioni. Questo studio conferma la validità della versione italiana dello SDM-Q-Doc, con buona affidabilità e solidità anche rispetto alle versioni validate in altre lingue e alla scala OPTION. Lo SDM-Q-Doc rappresenta una misura incentrata sul punto di vista del medico e di facile utilizzo per valutare il coinvolgimento dei pazienti nel processo decisionale clinico, ben performante anche nella popolazione di lingua italiana.

Parole chiave. Coinvolgimento del paziente, decisione clinica condivisa, prospettiva del medico, psicometria, questionari, studio di validazione.

Introduction

Shared decision making (SDM) refers to a complex interplay between patient and clinician, which occurs within the context of a composite environmental interaction aiming to reach a mutual medical decision1,2. The modern concept of SDM tries to overcome the old fashioned “paternalistic approach”, which dominated medical relationships for decades, with physicians ruling over patients regarding clinical choices. Only in recent years there has been a fresh and modern move toward increased patient involvement, implementing SDM in many specialties all over the world3.

Indeed, patients are more and more encouraged to communicate their medical preferences, consider the cost/benefit ratio of their choices, and select the option that best fits their personal predispositions4. In this context, SDM represents a joint process which helps to ensure that treatment decisions reflect patient inclinations with the goal to improve patient care experiences and overall treatment outcomes5,6. Therefore, SDM is becoming an essential point of health care quality and should be included into the principles of good clinical practice and international guidelines for all medical and surgery specialties7,8.

Measuring SDM may be challenging if considering it is not an objective evaluation9. Indeed, there are more actors’ opinions involved, and, therefore, it has been proposed to assess it from different perspectives: patient’s, physician’s, and independent observer’s one10. A combined triangulation of these three viewpoints is needed to optimize the result and reduce individual observation biases into the consultation process11. In this regard, even available assessment tools to evaluate SDM can be classified by preferred viewpoint, viz by an external observer, the patient, or the physician12.

To date, only a few validated psychometric measures are able to assess SDM from an external point of view, namely the dyadic OPTION (Observing Patient Involvement) scale13, and the MAPPIN’SDM measure14. On the other hand, the 9-item Shared Decision Making Questionnaire (SDM-Q-9)15,16 represents the patient-reported gold-standard tool to evaluate SDM, while its physician alter ego version is the Shared Decision Making Questionnaire - Physician Version (SDM-Q-Doc), which measures the same SDM features, but from the physician’s perspective17. Both instruments focus on the decisional process by rating physicians’ and patients’ behavior in medical encounters in a reliable and feasible administration with only nine items,12 within a valid and solid psychometric testing, and high acceptance rate16.

To date, the SMD-Q-Doc has been translated and validated in numerous languages18, including the Dutch version6, as well as German17, Japanese19, Persian20, and Spanish21, but, to the best of our knowledge, no validation study of the Italian version of SDM-Q-Doc has been conducted yet, thus severely limiting the analysis of SDM in this language18.

The aim of our study was to test and assess the psychometric properties of the Italian version of SDM-Q-Doc in a real-world outpatient clinical sample of patients suffering from major psychiatric disorders.

Materials and methods

Participants and procedure

Participants have been consecutively recruited at the psychiatric outpatient services of the University Hospital “Mater Domini” of Catanzaro (Italy) for 16 months (October 2020-February 2022) and have been evaluated by experienced clinicians according to the Mini International Neuropsychiatric Interview (MINI) with at least a previous 6-month follow-up time. The interviewers were expert clinicians who work in clinical practice and research, and were trained in the administration of the expected neuropsychiatric tests.

The study was carried out with a naturalistic design, without any influence with respect to the therapeutic choices that would have been implemented. We enrolled patients affected by any kind of psychiatric disease according to DSM-5 diagnostic criteria22, including schizophrenia spectrum disorders (SSD), bipolar disorder (BD), major depressive disorder (MDD), anxiety disorders, obsessive-compulsive disorder (OCD), personality disorders, and eating disorders (EDs).

We settled the following inclusion criteria for patients: 1) absence of any diagnoses of substance abuse or dependence for a continuative time of more than 6 months; 2) aged between 18 and 65 years; 3) ability to read and understand the study informed consent; 4) chart diagnosis of SSD, BD type I, BD type II, cyclothymia, MDD, dysthymia, anxiety disorders, OCD, personality disorders or EDs according to the DSM-5 criteria22; and 5) in clinical remission at the time of the assessment according to a Clinical Global Impression (CGI) score ≤223.

We excluded all patients who met the following exclusion criteria: 1) clinical diagnosis of pervasive developmental disorder or autism spectrum disorder according to the DSM-5; 2) difficulty in understanding the research protocol; 3) estimated premorbid IQ <70; 4) personal history of a severe medical or neurological disease that could affect cognitive or social functioning; and 5) medical and psychiatric history that was recent, implausible, or undocumented. No specific inclusion/exclusion criteria were settled for clinicians involved in the study and conducting the visits.

All eligible candidates were informed about the aims and procedures of the study, the voluntariness of participation, anonymity, and safety of personal data, and that no clinical or economic benefits would be given for the participation. A written informed consent was signed before any further step took place. The study protocol was submitted and approved by the local Ethical Committee of University Hospital Mater Domini at Catanzaro (Italy) “Regione Calabria, sezione Area Centro” before collecting any data. A complete description of the aims and methods was given to each of them before signing the informed consent. The study protocol and procedures complied with the ethical principles set out in the revised version of Helsinki Declaration24.

Measures

All participants underwent a comprehensive assessment and clinical evaluation at their follow-up in person visits by means of the following tests: 1) The nine-item physician version of the shared decision making questionnaire (SDM-Q-Doc), filled-up by physicians conducting the visits, and 2) the OPTION Scale, already validated in Italian25. Clinicians completed by themselves the SDM-Q-Doc assessment, after the consultation.

The following assessment tools were administrated to clinicians and patients respectively, respectively:

The nine-item Shared Decision-Making Questionnaire physician version (SDM-Q-Doc) is a self-reported questionnaire designed to assess physicians’ point of view on SDM17. The assessment encloses two open-ended questions: [‘Please indicate which health complaint/problem/illness the consultation was about’ and ‘Please indicate which decision was made’] followed by nine multiple-choice questions. Each multiple-choice question describes various aspects of SDM through a statement, and they rate on a 6-point balanced scale ranging from 0 (= ‘completely disagree’) to 5 (= ‘completely agree’). The total score is calculated by summing the score of all nine items, and it is synthetized on a scale ranging between 0 and 45, and a higher score denotes a greater level of perceived SDM from the clinician. Following earlier studies, we rescaled the raw total scores to a 0-100 range15. The original version of the SDM-Q-9 was translated into English and Italian, permitting its use in international research15.

The OPTION Scale26: is a 12 item five-point scale [from 0 (behavior not observed) to 4 (high standard)], so the raw total score ranges from 0 to 48. Scores are normally transformed into a 0-100 score25.

In addition, socio-demographic and clinical data were collected for all participants as per chart.

Statistical analysis

The Confirmatory Factor Analysis (CFA) was run through the open-source software JASP (JASP, Version 0.16.1, University of Amsterdam, The Netherlands) to better examine the structure of the Italian version of SDM-Q-Doc. Diagonal Weighted Least Squares (DWLS) estimator was used to estimate the parameters since it provides the best option for categorical or ordered data27.

The Tucker-Lewis Index (TLI), the Comparative Fit Index (CFI), the Root Mean Square Error of Approximation (RMSEA), Standardized Root Mean Squared Residual (SRMR) and its chi-square (χ2/df) were used to evaluate the goodness of adaptation of the data to the proposed model.

For TLI and CFI, values of .90 and above are considered adequate, while values of .95 or above are considered excellent; for RMSEA values of .08 and below are considered adequate and values of .05 or below are considered excellent; for SRMR a cut-off value close to .08 are considered adequate. Values of χ2/df <3.0 are considered good, while values <2.0 are excellent. The levels of these indices were assessed according to the recommendations of Hu and Bentler28.

Regarding the internal consistency, given the renown limitations to the use of the Cronbach’s α29,30 due to the very restrictive assumptions it relies on, we assessed it through the McDonald’ ω total31.

We also calculated the SDM-Q-Doc inter-item correlations for each of 9 items. In details, the inter-item correlations provide an estimation of the item redundancy, or rather the degree to which the tool items estimate the same content. Still, inter-item correlations appraise how much scores on one item are related to scores on all other item in the same scale.

Construct validity was determined by correlations between the single items and total scores of the SDM-Q-Doc and the OPTION, considering that correlation coefficients (r) greater than .30 are recommended32. A p<.05 was considered statistically significant.

Results

We recruited a total of 369 consecutive patients fulfilling the protocol inclusion/exclusion criteria, with their respective 7 clinical psychiatrists. Of these, 25 patients refused to participate in the study because they did not have the time to complete the assessment (n=15); did not sign the informed consent (n=8); or for other reasons (n=2). Therefore, we reached a 93.2% participation rate, and the final sample was made up of 344 patients, with an average age of 39.7 ± 17.9 years, and a majority of female (n=221; 64.2%), non-smoker (n=242; 70.3%), single (n=193; 56.1%), students (n=94; 27.3%), mostly suffering from MDD (n=61; 17.7%) and SSD (n=59; 21.8%) (table 1).




The CFA showed a very good fit: relative chi-square (χ2/df) = 3.2, CFI = .99, TLI = .99, RMSEA = .08, and SRMR = .04, suggesting the suitability of the Italian version of SDM-Q-Doc model (figure 1).




The McDonald ω coefficient was .92 for the total score indicating an excellent reliability of the questionnaire. Further, inter-item correlations ranged from .390 to .703, with a mean of .556 (table 2).

Finally, regarding convergent validity, low and moderate correlations emerged between the items and the total scores of OPTION and SDM-Q-Doc (table 3).




Discussion

In this cross-sectional study, we enrolled a large clinical sample aiming to validate the Italian version of the SDM-Q-Doc, a psychometrically solid tool which assesses the SDM process from the physician’s perspective. We tested the psychometric properties of the scale, already validated and used in several languages17,19, demonstrating excellent reliability, sound internal consistency, and good and acceptable-to-good convergent validity for the Italian translation of the scale as well. Moreover, we found an elevated level of acceptance by the physicians who were approached for the study. Finally, we also confirmed the hypothesized factorial structure of one dimension, supporting factorial validity, whereas several low loadings and residual correlations simultaneously suggest substantial construct heterogeneity.

Overall, our results are in line with previous findings from the original German version of SDM-Q-Doc by Scholl et al., who developed and validated the physician’s perception of the SDM process adapting the already largely used SDM-Q-917. The decision to develop and validate an assessment tool that focuses on the doctor’s point of view in SDM arises from the deep nature of the therapeutic relationship and the shared clinical decision33. In fact, since it is a two-actor relationship, the involvement of the patient’s point of view alone appears to be lacking in one component, which is therefore filled with the SDM-Q-Doc. For instance, the availability of the double-side instruments in Italian language to comprehensively clinically assess the SDM finally fills the gap on the topic, and such eventuality should be encouraged in other languages as well18,34.

As already applied in our previous work16, in this study we excluded patients suffering from substance abuse or dependence, severe medical or neurological diseases potentially affecting affect cognitive or social functioning, and recent or unclear psychiatric history, in order to avoiding possible bias and confounding factors with respect to the doctor-patient relationship and therefore make the results implausible34,35. Certainly, in the future, it will be interesting to explore SDM also in patients suffering from these disorders, with recent access to psychiatric services, or following them over time to evaluate the evolution of the SDM in their therapeutic path.

Regarding the enrolled sample size, our final sample is larger than similar validation studies of the SDM-Q-Doc in German17, Japanese19, Dutch6, and other languages18. This point strengthens our results, but the data is even more interesting when compared to the number of clinicians involved. In fact, our large sample foresees the involvement of only 7 clinicians, greatly reducing the inter-rater variability. If on the one hand the reduced number of evaluators could be seen as a limitation potentially able to invalidate the variability of the answers collected, on the other hand it increases the internal consistency and inter-rater reliability, guaranteeing greater uniformity of training and clinical judgment, overall balanced by patients’ OPTION scale assessments. Notably, we touched a 93.2% acceptance rate, thus confirming a high level of completion rate for all items, and in line with what has been reached in other languages6,17,36.

The Italian version of SDM-Q-Doc showed a high internal consistency value (McDonald ω coefficient was .92), elevated items discrimination, and an adequate inter-item correlation, thus confirming a good consistency of the translated tool. Indeed, our findings are similar and even better if compared to other SDM-Q-Doc translated versions including Dutch (Cronbach’s α of 0.88)6, German (Cronbach’s a of .88)17, and Japanese (Cronbach’s α= 0.87, ω= 0.88)19 versions, highlighting a similar scale reliability for our version. We also found low and moderate correlations between the single items and the total scores of SDM-Q-Doc and OPTION scale, strengthening the data in favor of convergent validity between the instruments.

Consistently to the original German version of the scale17, also we reached satisfactory results testing all the items of the scale without the need to test different single-factor models excluding specific SDM-Q-Doc items. The same factor analysis was also confirmed by the Japanese translation with the enrollment of 130 patients and 23 doctors19, while the Dutch version, with 43 psychiatrists and 201 patients, obtained a better index excluding items 1 and 96, shining light on the hypothesis that the result may be influenced by the sample size, and even more by the number of raters involved.

Compared to different neurocognitive or psychological assessment, the SDM evaluation scale provide both a theoretical research value and a concrete application into everyday clinical practice. Indeed, the concurrent use of both SDM-Q-9 and SDM-Q-Doc allows the global assessment of the perspectives of both shareholders in the SDM process. Moreover, in the light of the feasibility and quick-filling of the instruments, they can easily be used in trials as well as in clinical practice for a real-time analysis of the effectiveness of different interventions on the implementation of SDM and as a quality indicator of health service assessments17.

Limitations and strengths

Interpreting our results, we acknowledge both some limitations and strengths. First, the cross-sectional study design does not allow to draw longitudinal and prospective conclusions. Indeed, considering the SDM as a lively and moving process based on personal relationships and human interactions, it should be desirable to conduct dynamic follow-up studies to explore its evolution over time. Second, the huge sample size diagnostic variability carries on a broad spectrum of clinical severity, duration of disease and treatment management choices which could influence SDM making, making the final results very heterogeneous. However, this wide variability did not affect the validations results, neither the inter-item correlations, thus demonstrating the tool’s applicability and reproducibility even in each setting of a real-world clinical sample. This consideration stands in line with current literature data reporting a wide clinical area application for SDM-Q-Doc and a range of its use in different health care settings to evaluate different interventions36. Finally, we did not provide a test-retest reliability calculation. Nonetheless, we must consider that the reproducibility over time, also known as test-retest reliability, is one of several statistical approaches to evaluate and measure reliability, which embrace also internal consistency, inter-rater reliability and convergent validity compared to the gold-standard tool (i.e., the OPTION scale), that we run. Certainly, internal consistency estimates how the single items results correlate with each other37, that we demonstrated to be more than acceptable in our findings.

On the other hand, we highlight some important and peculiar strengths in our study. First, we reached a large and satisfactory final sample size, enrolling 344 participants and recording a very high participation rate (93.2%). This value is much higher than similar studies6,16,17,36, and, even superior to the minimal recommended limit to validate an assessment tool. On this regard, indeed, most used recommendations for minimum sample size suggest ranging from 2 to 20 subjects per tool item38, with a total minimum number of 100 to 250 subjects anyway39. Furthermore, we also followed guidance proposed by Comrey and Lee (1992)40: 100 participants=poor, 200=fair, 300=good, 500=very good, ≥1000=excellent. Thus, with a total of 344 participants with a 9-items tool, according to the described recommendations, the enrolled sample can be considered more than adequate to validate the scale.

Second, we used the OPTION scale, widely recognized as gold-standard instrument to explore SDM from external viewpoint, as a proper assessment to test the convergent validity41. Indeed, considering the lack of an alternative self-assessment to measure SDM by clinicians, we applied an already validated technique to overcome this limitation16,42. Finally, we run the study in a real-world outpatients clinical setting, enrolling consecutive patients without any specific exclusion criteria, thus presenting an easily reproducible trial with a large sample made up of patients suffering from a range of severe psychiatric disorders, with the aim of making the results generalizable.

Conclusions

Our results confirm a very good fit, a high reliability, and excellent psychometric properties of the Italian version of SDM-Q-Doc, largely equivalent to the original and other language validation versions. Indeed, the Italian version of SDM-Q-Doc showed a robust internal consistency, even when compared to OPTION scale and tested in a clinical a sample of patients affected by major psychiatric disorders. Therefore, we can assume that SDM-Q-Doc demonstrated to be a feasible, reliable, and easy-to-use tool to assess SDM in Italian clinical settings.

Conflict of interests: the authors have no conflict of interests to declare.

References

1. Makoul G, Clayman ML. An integrative model of shared decision making in medical encounters. 2006; 60: 301-12.

2. Berger Z, Galasinski D, Scalia P, Dong K, Blunt HB, Elwyn G. The submissive silence of others: examining definitions of shared decision making. Patient Educ Couns 2022; 105: 1980-7.

3. Kon AA. The shared decision-making continuum. JAMA 2010; 304: 903.

4. Elwyn G, Laitner S, Coulter A, Walker E, Watson P, Thomson R. Implementing shared decision making in the NHS. BMJ 2010; 341: c5146-c5146.

5. Chewning B, Bylund CL, Shah B, Arora NK, Gueguen JA, Makoul G. Patient preferences for shared decisions: a systematic review. Patient Educ Couns 2012; 86: 9-18.

6. Rodenburg-Vandenbussche S, Pieterse AH, Kroonenberg PM, et al. Dutch translation and psychometric testing of the 9-Item Shared Decision Making Questionnaire (SDM-Q-9) and Shared Decision Making Questionnaire-Physician Version (SDM-Q-Doc) in primary and secondary care. PLoS One 2015; 10: e0132158.

7. Stiggelbout AM, Van der Weijden T, De Wit MPT, et al. Shared decision making: really putting patients at the centre of healthcare. BMJ 2012; 344: e256.

8. de Filippis R, De Fazio P, Gaetano R, et al. Current and emerging long-acting antipsychotics for the treatment of schizophrenia. Expert Opin Drug Saf 2021; 20: 771-90.

9. Charles C, Gafni A, Whelan T. Shared decision-making in the medical encounter: what does it mean? (or it takes at least two to tango). Soc Sci Med 1997; 44: 681-92.

10. Légaré F, Ratté S, Stacey D, et al. Interventions for improving the adoption of shared decision making by healthcare professionals. Cochrane Database Syst Rev 2010; (5): CD006732.

11. Mead N, Bower P. Patient-centredness: a conceptual framework and review of the empirical literature. Soc Sci Med 2000; 51: 1087-110.

12. Scholl I, Koelewijn-van Loon M, Sepucha K, et al. Measurement of shared decision making. A review of instruments. Z Evid Fortbild Qual Gesundhwes 2011; 105: 313-24.

13. Melbourne E, Roberts S, Durand M, Newcombe R, Légaré F, Elwyn G. Dyadic OPTION: measuring perceptions of shared decision-making in practice. Patient Educ Couns 2011; 83: 55-7.

14. Kasper J, Hoffmann F, Heesen C, Köpke S, Geiger F. MAPPIN’SDM--the multifocal approach to sharing in shared decision making. PLoS One 2012; 7: e34849.

15. Kriston L, Scholl I, Hölzel L, Simon D, Loh A, Härter M. The 9-item Shared Decision Making Questionnaire (SDM-Q-9). Development and psychometric properties in a primary care sample. Patient Educ Couns 2010; 80: 94-9.

16. de Filippis R, Aloi M, Pilieci AM, et al. Psychometric properties of the 9-item Shared Decision-Making Questionnaire (SDM-Q-9): validation of the Italian version in a large psychiatric clinical sample. Clin Neuropsychiatry J Treat Eval 2022; 19: 264-71.

17. Scholl I, Kriston L, Dirmaier J, Buchholz A, Härter M. Development and psychometric properties of the Shared Decision Making Questionnaire--physician version (SDM-Q-Doc). Patient Educ Couns 2012; 88: 284-90.

18. SDM-Q-9 / SDM-Q-Doc. The 9-item Shared Decision Making Questionnaire. Available from: https://bit.ly/3Is9jES [last accessed 19 May 2023].

19. Goto Y, Miura H, Son D, et al. Association between physicians’ and patients’ perspectives of shared decision making in primary care settings in Japan: the impact of environmental factors. PLoS One 2021; 16: e0246518.

20. Nejati B, Lin C-C, Imani V, et al. Validating patient and physician versions of the shared decision making questionnaire in oncology setting. Heal Promot Perspect 2019; 9: 105-14.

21. Calderón C, Ferrando PJ, Carmona-Bayonas A, et al. Validation of SDM-Q-Doc Questionnaire to measure shared decision-making physician’s perspective in oncology practice. Clin Transl Oncol 2017; 19: 1312-9.

22. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Washington, DC: American Psychiatric Association Publishing, 2013.

23. Guy W. Clinical Global Impression (CGI). Guy W, editor. ECDEU Assessment Manual for Psychopharmacology. Rockville, Maryland: Department of Health, Education, and Welfare, 1976.

24. World Medical Association. World Medical Association Declaration of Helsinki: ethical principles for medical research involving human subjects. JAMA 2013; 310: 2191.

25. Goss C, Fontanesi S, Mazzi M, et al. Shared decision making: the reliability of the OPTION Scale in Italy. Patient Educ Couns 2007; 66: 296-302.

26. Elwyn G, Hutchings H, Edwards A, et al. The OPTION Scale: measuring the extent that clinicians involve patients in decision-making tasks. Health Expect 2005; 8: 34-42.

27. Buck B, Browne J, Gagen EC, Penn DL. Hostile attribution bias in schizophrenia-spectrum disorders: narrative review of the literature and persisting questions. J Ment Heal 2023; 32: 132-49.

28. Hu L, Bentler PM. Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct Equ Model A Multidiscip J 1999; 6: 1-55.

29. McNeish D. Thanks coefficient alpha, we’ll take it from here. Psychol Methods 2018; 23: 412-33.

30. Trizano-Hermosilla I, Alvarado JM. Best alternatives to Cronbach’s Alpha Reliability in realistic conditions: congeneric and asymmetrical measurements. Front Psychol 2016; 7: 769.

31. Revelle W, Zinbarg RE. Coefficients Alpha, Beta, Omega, and the glb: comments on Sijtsma. Psychometrika 2009; 74: 145-54.

32. McGraw KO, Wong SP. Forming inferences about some intraclass correlation coefficients. Psychol Methods 1996; 1: 30-46.

33. Ortiz SE, Rosenthal MB. Medical marketing, trust, and the patient-physician relationship. JAMA 2019; 321: 40.

34. Luciano M, Sampogna G, Del Vecchio V, et al. When does shared decision making is adopted in psychiatric clinical practice? Results from a European multicentric study. Eur Arch Psychiatry Clin Neurosci 2020; 270: 645-53.

35. Carrà G, Johnson S, Crocamo C, et al. Psychosocial functioning, quality of life and clinical correlates of comorbid alcohol and drug dependence syndromes in people with schizophrenia across Europe. Psychiatry Res 2016; 239: 301-7.

36. Doherr H, Christalle E, Kriston L, Härter M, Scholl I. Use of the 9-item Shared Decision Making Questionnaire (SDM-Q-9 and SDM-Q-Doc) in Intervention studies. A systematic review. PLoS One 2017; 12: e0173904.

37. Cook DA, Beckman TJ. Current concepts in validity and reliability for psychometric instruments: theory and application. Am J Med 2006; 119: 166.e7-166.e16.

38. Hair J, Anderson R, Tatham R, Black W. Multivariate data analysis: with readings. London: Pearson College, 1995.

39. Anthoine E, Moret L, Regnault A, Sébille V, Hardouin J-B. Sample size used to validate a scale: a review of publications on newly-developed patient reported outcomes measures. Health Qual Life Outcomes 2014; 12: 2.

40. Comrey AL, Lee HB. A first course in factor analysis. 2nd ed. Mahwah, NJ: Lawrence Erlbaum Associates, 1992.

41. Melbourne E, Sinclair K, Durand M-A, Légaré F, Elwyn G. Developing a dyadic OPTION scale to measure perceptions of shared decision making. Patient Educ Couns 2010; 78: 177-83.

42. Scholl I, Kriston L, Dirmaier J, Härter M. Comparing the nine-item Shared Decision-Making Questionnaire to the OPTION Scale - an attempt to establish convergent validity. Heal Expect 2015; 18: 137-50.