Background
Illicit drug use has long been recognized as a major global public health issue. It causes a lot of psychological and physical health consequences, such as depression, anxiety, psychosocial dysfunction, fatal and nonfatal overdose, and increases the risk of HIV transmission and other blood-borne diseases [
1,
2]. There were 250 million drug users worldwide in 2015, with 29.5 million suffered from substance use disorders, approximately 1.6 million living with HIV and more than 6.1 million infected with hepatitis C [
3]. Vietnam is a developing country located in the South-East Asia, in an area of 331,210 km
2 and has the population of 92.7 million people [
4]. In Vietnam, people who inject drugs have been found to be the primary drivers of the HIV epidemic, accounting for 34% of new HIV cases [
5] and approximately 65% of all people living with HIV [
6].
To address this issue, the methadone treatment has been considered as a priority in Vietnam due to its high degree of effectiveness not only in reducing the frequency of illicit drug use, HIV-related risk behaviors and illegal activities, but also in improving the general health and quality of life among drug users [
7‐
10]. Since its first introduction in 2008, there are 280 methadone clinics to date, treating for 51,318 patients in the country, 95% were male [
11]. However, since MMT involves long-term medication, patients are likely to have the risk of suffering withdrawal symptoms, drug relapse and drop out from MMT [
12‐
14].
A large body of literature has demonstrated that social support is a significant predictor of success in methadone treatment and in the recovery process of drug users [
15‐
17]. Data on social support is necessary to optimize the effectiveness of MMT. However, there is a lack of appropriate tools to measure this important component among Vietnamese patients undergoing MMT.
The Medical Outcome Study: Social Support Survey (MOS-SSS) [
18] is one of the most widely used instruments. It is a brief, multi-dimensional scale developed to assess the functional aspects of perceived social support. The instrument is composed of 19 main items to measure four aspects of social support, including tangible support, emotional-informational support, positive social interactions and affectionate support. One additional item assesses the structural dimension of social support (i.e. the number of close relatives and friends) [
18]. The high level of reliability and validity of the original MOS-SSS was demonstrated in a sample of 2987 chronic patients [
18]. The MOS-SSS has been translated and adapted to different languages including Chinese [
19,
20], Malay [
21], French [
22], Portuguese [
23], Italian [
24]. Since the questionnaires may be affected by the context in which they are used and differences in ethnicity and culture are likely to influence the way people understand and respond to the questionnaires [
25], validation of the MOS-SSS is a crucial need.
The MOS-SSS has not been validated in Vietnam. The lack of such validated scale may result in the limited understanding of the social support levels among patients in MMT programs. This study was conducted to investigate the psychometric properties of the Vietnamese version of the MOS-SSS, including internal consistency, test-retest reliability, construct validity and concurrent validity among patients undergoing MMT in Vietnam.
Discussion
Although social support plays an important role in the treatment and recovery process of patients undergoing MMT, there has been no linguistically relevant instrument for measuring social support among this increasing population in Vietnam. The results of our study indicate that the MOS-SSS is a reliable and valid instrument for MMT patients in Ho Chi Minh City, Vietnam.
The MOS-SSS has good internal consistency and test-retest stability. The Cronbach’s alpha coefficients for the overall scale and four subscales were greater than 0.8, the threshold that is considered as a reasonable benchmark indicating good internal consistency. This result was similar to that reported for the original version, where Cronbach’s alpha ranged from 0.91 to 0.97 [
18]. The value of the Cronbach’s alpha exceeding 0.95 might indicate the need for item redundancy [
39]. However, given social support is a complex and multidimensional concept, the higher number of items is likely to correctly measure its various aspects [
18,
40]. The high Cronbach’s alpha was also found in other validation studies, such as the Chinese version (α = 0.98) [
19], Malay version (α = 0.96) [
21], French version (α = 0.90–0.96) [
22], Brazilian version (α = 0.95) [
23]. Moreover, the high correlations between each item with the overall MOS-SSS provided evidence that all items were homogeneous in measuring the same construct and fulfilled the scaling assumption of internal consistency.
The stability of the MOS-SSS over a 2-week period was generally satisfactory with ICCs at moderate to good levels. This finding was consistent with that found in the original study where the stability of the scale was confirmed over a one year period [
18]. Compared to other validation studies, the ICCs for the overall and four subscales of the MOS-SSS in our study were lower than those reported by Yu et al. (ICC = 0.84) [
19], and Wang et al. (ICC = 0.74–0.89) [
20] over a 2-week period. Since these two studies were conducted among inpatients with physical health problems, the condition of inpatients might facilitate the presence of higher stable level of support, such as the regular visits and informative support by physicians, or other support from relatives and friends. In contrast, drug users in Vietnam are still discriminated and stigmatized [
13].
In terms of construct validity, although the Chi-squared test indicated that the model did not fit the data well, the other fit indices including CFI, TLI, SRMR and RMSEA revealed that the MOS-SSS was a good fit to a four-factor model. This four-factor solution was consistent with the original factor structure [
18]. Other validation studies also reported the results that the Chi-squared test was unsatisfactory with the four-factor model but other fit indices showed a good fit [
19,
20,
24]. Furthermore, the correlation among the four factors and high standardized factor loadings in the model were similar to those reported by Sherbourne & Stewart, where the correlation coefficients ranged from 0.69 to 0.82 and factor loadings ranged from 0.76 to 0.93 [
18].
As expected, the MOS-SSS had good concurrent validity since it had positive correlation with MSPSS score (
r = 0.77) and negative correlation with PSAS score (
r = − 0.76). These findings were similar with the results reported by Yu et al. [
19] where the correlation coefficients between the MOS-SSS subscale and MSPSS scale were high (
r = 0.76–0.85).
Vietnam has shown intense efforts to reduce the number of drug users as well as the incidence of drug injection-related blood-borne diseases at both national and international levels, such as the plan to extend MMT service to 80,000 drug users [
41]. Since social support highly affects the treatment success and recovery process of MMT patients [
15‐
17], measurement of social support will yield important information to the relevant stakeholders in improving the quality of methadone treatment outcomes and ultimately respond to the epidemic of opioids abuse as well as its consequences. Researchers and health professional can use the Vietnamese version of MOS-SSS as screening tool for routine clinical care for methadone patients. This scale has been shown to be simple, cover the broad functional aspects of social support and have high level of reliability and validity. Such applications can help to fulfill the gaps in the paucity of information about social support and to improve quality of life in this vulnerable population in Vietnam.
The present findings should be interpreted in the context of a number of potential limitations. Since the validated scales for measuring social support are limited in literature, the MSPSS and the PSAS have not been validated in Vietnamese MMT patients and thus the concurrent validity found in this study might be potentially biased. Second, social support may be different and be specific to certain types of co-mordibility and health conditions such as HIV status and depression. Further studies investigating the psychometric properties of the MOS-SSS among MMT patients with different health conditions are needed. Third, although the characteristics of the MMT patients involved in this study were similar to previous studies in Vietnam and in Ho Chi Minh City in particular, including the high percentage of males of 90% - 95% [
7,
9,
10,
42], all the patients in our study were from a methadone clinic in a large city and might not be generalizable to all MMT patients in other areas of Vietnam.
Acknowledgements
The authors would like to thank all MMT patients who participated in this study, as well as the individuals and institutions that made this research possible: Dr. Dang Van Anh, Ms. Chung Hong Ngoc Tu, Ms. Nguyen Ha Van An, Mr. Ho Binh Minh, Mr. Tran Dang Khoa from District 6 Methadone Clinic; Associate Professor Do Van Dung, Dr. Trinh Thi Kim Thao from Ho Chi Minh city University of Medicine and Pharmacy; Ms. Thoa, Mr. Tra from Khoa Tri English Center.