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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 10  |  Issue : 2  |  Page : 117-124

Psychometric properties and validation of the Arabic Maslach Burnout Inventory-Student Survey in Saudi dental students


1 Department of Pedodontics and Orthodontic Dental Sciences, College of Dentistry, King Khalid University, Abha, Saudi Arabia
2 Department of Periodontics and Community Dental Sciences, College of Dentistry, King Khalid University, Abha, Saudi Arabia
3 Department of Diagnostic Sciences and Oral Biology, College of Dentistry, King Khalid University, Abha, Saudi Arabia
4 Department of Public Health Dentistry, Manipal College of Dentistry, Manipal, Karnataka, India

Date of Submission14-Feb-2021
Date of Decision20-Oct-2021
Date of Acceptance23-Feb-2022
Date of Web Publication15-Apr-2022

Correspondence Address:
Alezi Braimoh Ifindon Eroje
Department of Periodontics and Community Dental Sciences, College of Dentistry, King Khalid University, PO Box No 3263, Abha
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjmms.sjmms_116_21

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  Abstract 


Background: Few studies have studied burnout among dental students worldwide, and no such study is available from Saudi Arabia. In addition, an Arabic version of the Maslach Burnout Inventory-Student Survey (MBI-SS) has not yet been validated for use among students.
Objectives: This study aimed to translate and validate an Arabic version of the MBI-SS questionnaire and to examine the psychometric properties of burnout among dental college students at a university in Saudi Arabia.
Materials and Methods: This cross-sectional questionnaire study included all dental students at King Khalid University, Saudi Arabia, and was conducted between December 2019 and January 2020. After the MBI-SS questionnaire was translated, its face validity was determined and the test–retest reliability was assessed. Confirmatory factor analysis and reliability analysis were performed following the full-scale study to validate the Arabic MBI-SS.
Results: A total of 433 dental students responded in the full-scale study (mean age: 21.9 ± 1.6 years). Emotional exhaustion was present in 32.3% (95% confidence interval: 28%–36.9%), cynicism in 33.7% (29.3%–38.4%), and poor academic efficacy in 34.2% (29.8%–38.9%) of the dental students. Emotional exhaustion and cynicism were significantly associated with academic level, a history of medication due to academic stress, and thoughts of quitting the course (for all, P < 0.05). The reliability of MBI-SS was found to be adequate for all three subscales: Emotional exhaustion, Cronbach's α = 0.827; cynicism, α = 0.855; academic efficacy, α = 0.704.
Conclusions: All three subscales of burnout were highly prevalent in the study cohort. The Arabic version of the MBI-SS inventory was shown to be a valid and reliable tool for assessing the psychometric properties of burnout among dental students, and its use may aid in identifying burnout in the early stages.

Keywords: Arabic, dental students, health-care evaluation, Maslach Burnout Inventory, student burnout, validation


How to cite this article:
AlShahrani I, Eroje AB, Tikare S, Togoo RA, Soliman AE, Rao G R. Psychometric properties and validation of the Arabic Maslach Burnout Inventory-Student Survey in Saudi dental students. Saudi J Med Med Sci 2022;10:117-24

How to cite this URL:
AlShahrani I, Eroje AB, Tikare S, Togoo RA, Soliman AE, Rao G R. Psychometric properties and validation of the Arabic Maslach Burnout Inventory-Student Survey in Saudi dental students. Saudi J Med Med Sci [serial online] 2022 [cited 2022 May 16];10:117-24. Available from: https://www.sjmms.net/text.asp?2022/10/2/117/343331




  Introduction Top


Chronic stress at workplace coupled with inadequate coping mechanisms can result in burnout or work environment syndrome, which can negatively affect the personal and professional lives of individuals.[1],[2] The physical, social, and mental implications of burnout syndrome on the well-being of individuals make it a public health problem.[3],[4] Burnout syndrome has three main subcategorization: Exhaustion, which is emotional draining resulting in not being able to work; cynicism, which is distancing behaviors toward work, customers, and co-workers; and inefficiency, which is feeling of incompetence/inadequacy in performing a task at work.[5],[6]

In the medical domain, burnout is not only prevalent among doctors and nurses but also among students.[7],[8],[9] Among students, trainees in medicine and nursing are vulnerable groups.[9],[10] Specifically, in dentistry, dental students have been found to experience considerable levels of stress during their academic and clinical aspects of dental training,[11] which in turn can result in burnout.[12],[13] However, to the best of the authors' knowledge, the overall breadth of evidence regarding burnout among dental students is not sufficient, and no such studies are available from Saudi Arabia.

Several assessment tools are available for measuring burnout. However, Maslach Burnout Inventory (MBI) developed by Maslach and Jackson in 1981 remains the most frequently used standardized tool to evaluate the burnout syndrome.[6] The 22-item MBI Human Services Survey (HSS) scale has been translated into several languages and validated.[14],[15],[16] The MBI–Student Survey (MBI-SS) is an adaptation of the original MBI scale to make it applicable specifically to students.[17] The psychometric domains of the student's scale refer to feeling exhausted because of academic stress, cynicism related to one's study, and feeling professionally incompetent as a student. However, to the best of the authors' knowledge, an Arabic version of the MBI-SS questionnaire has not been validated for use among students in Saudi Arabia, which is important because variability in interpretation can result in lower quality data collection. Therefore, to address the current gaps in literature, this study aimed to translate and validate an Arabic version of the MBI-SS questionnaire as well as examine the psychometric properties of burnout among dental college students at a university from Saudi Arabia.


  Materials and Methods Top


Study design, setting, and participants

This cross-sectional analytical study was conducted among dental students at King Khalid University (KKU), Saudi Arabia, from December 01, 2019, to January 31, 2020. Assuming the prevalence of burnout syndrome as 17%,[18] with an absolute precision of 3.5% at 95% confidence level, the minimum sample size was estimated to be 231 dental students. The sampling frame included all dental undergraduate students attending the College of Dentistry at KKU (n = 480). Students in internship and those included in the pilot study were excluded from the main analysis.

The study was conducted after obtaining ethical approval from the Scientific Research Committee at College of Dentistry, KKU. Participants were included only after they provided an informed consent.

Study tool and data collection

A three-part questionnaire in Arabic language was used for this study. The first two parts elicited data regarding sociodemographic characteristics and academic performance, while the third part was the Arabic translated MBI-SS.[6],[17] MBI-SS is a 15-item tool assessed using a 7-point Likert scale, ranging from 0 (never) to 6 (everyday). The instrument has three dimensions: Emotional exhaustion (five items), cynicism (four items), and academic efficacy (six items). The presence of burnout syndrome was determined according to the criteria used by Maslach and Jackson.[19] Cutoff values for exhaustion and cynicism were individuals above the 66th percentile, while for academic efficacy, it was individuals below the 33rd percentile. The academic performance-based questions elicited data regarding variables such as performance in the course, medication intake due to academic stress, and thoughts of quitting the course. The questionnaire did not collect any identifying information.

Prospective participants were directly approached at the end of lectures and the study purpose was explained. In addition, the students were informed that participation is voluntary, and that the data collected would only be used for this study. A Google Form link was shared through E-mail with those who consented to participate. Participants were provided 20 min to complete the questionnaire, which was estimated to be adequate based on the pilot study, and the investigators were available for any clarifications required. Response to all questions was made mandatory to be considered in the final analysis. No financial incentives were offered for participation in the study.

Questionnaire translation and validity assessment

The questionnaire was forward translated from English to Arabic language by two independent native Arabic speakers (one had a PhD in Arabic language and the other in Dentistry and both of their academic rank were Full Professor). Then, the Arabic version was back-translated by a professional English language expert who is also an Arabic speaker. No discrepancy was noted in the back-translated and original versions. The native independent Arabic speakers again verified the final translation, but no further changes were deemed necessary.

The face validity of the Arabic version was checked by two authors who are native Arabic speakers. A pilot study was conducted with randomly chosen dental students (N = 23) to determine the reliability and feasibility of the questionnaire; for the test–retest reliability, the questionnaire was distributed twice with a 1-week interval. These students were not included in the full-scale study. Cronbach's α was used for assessing the internal consistency: ≥0.90 was considered as excellent reliability, ≤0.90–0.70 as high reliability, ≤0.70–0.50 as moderate reliability, and ≤0.50 as low reliability.[20]

Statistical analysis

Data were analyzed using STATA version 13 (StataCorp LP, College Station, TX, USA) after checking for completeness and consistency. Continuous variables such as age are presented as mean ± standard deviation, and categorical variables are presented as frequency/percentage. Comparison of sociodemographic and other variables of interest by each psychometric domain of MBI-SS was performed by Student's t-test and analysis of variance test. The level of significance for decision-making was 5%. The prevalence of psychometric properties was presented as percentage with a 95% Confidence Interval (95% CI). Marco's guidelines were followed in analyzing the psychometric qualities of the MBI-SS.[21] Confirmatory factor analysis was used to assess the construct's validity and reliability. Chi-square/df, root mean square error of approximation (RMSEA), goodness-of-fit index (GFI), comparative fit index (CFI) were used to assess the model fit. The model was considered valid if: Factorial validity Chi-square/df values ranged between 1 and 2, GFI and CFI values were <0.9, and RMSEA was <0.08. Average variance extracted (AVE) for each factor was analyzed to assess the convergent validity of the factors. The AVE values for factors >0.5 were considered to present convergent validity. Finally, the construct's reliability was assessed through internal consistency (Cronbach's α), with values >0.7 indicating good reliability.


  Results Top


In the pilot test, the internal consistency of MBI-SS was found to be high for emotional exhaustion (α = 0.75) and cynicism (α = 0.73) but moderate for academic performance (α = 0.618). For the full-scale study, of the available 457 dental students, 436 responded (95.4%). Three responses were discarded due to errors such as incomplete filling of sociodemographic information, and thus, 433 responses were used for all further analyses.

Sociodemographic and academic characteristics

The mean age of the participants was 21.9 ± 1.6 years, with the majority being female (58.7%). About three-fourths of the students (76.2%) had dentistry as their first course choice. The distribution of the students according to other sociodemographic and academic characteristics is shown in [Table 1]. About a quarter (24.5%) of the respondents took medication due to academic stress and almost half (49%) considered quitting.
Table 1: Sociodemographic and other characteristics of the dental students (N=433)

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Maslach Burnout Inventory-Student Survey

[Table 2] shows the scale-wise distribution of study participants for each MBI-SS question. In terms of burnout across the three subscales, emotional exhaustion was present in 32.3% (95% CI: 28%–36.9%), cynicism in 33.7% (95% CI: 29.3%–38.4%), and poor academic efficacy in 34.2% (95% CI: 29.8%–38.9%) of the dental students. However, all the three domains were not concurrently positive in any participant [Table 3].
Table 2: Distribution of participant's responses to Maslach Burnout Inventory-Student Survey (N=433)

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Table 3: Prevalence of psychometric properties of burnout among the dental students by percentile basis (N=433)

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The mean scores in emotional exhaustion and cynicism significantly increased with the academic level (P < 0.05). In students with a history of medication due to academic stress, the emotional exhaustion and cynicism mean scores were significantly higher than other students (for all, P = 0.0001). Similarly, students who considered quitting the course also had significantly higher emotional exhaustion and cynicism mean scores (P = 0.0001) and lower academic efficacy (P = 0.0001) [Table 4].
Table 4: Comparison of sociodemographic and other variables of interest by each psychometric domains of MBI-SS (N=433)

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Reliability and model fit

The reliability of the MBI-SS by confirmatory factor analysis was found to be adequate for all three subscales: For emotional exhaustion, Cronbach's α = 0.827; cynicism, α = 0.855; academic efficacy, α = 0.704. The level of fit was acceptable (RMSEA = 0.069). Moreover, CFI and Tucker–Lewis Index were found to be 0.923 and 0.907, respectively, which indicates good model fit. The standardized root mean square residual was 0.050, also indicating a good model fit [Table 5]. The results of the confirmatory factor analysis model with factor loadings are presented in [Figure 1].
Figure 1: Maslach Burnout Inventory-Student Survey confirmatory factor analysis for the sample under study

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Table 5: Goodness-of-fit of Maslach Burnout Inventory-Student Survey

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  Discussion Top


This study found that in this dental student cohort from Saudi Arabia, burnout across all three subscales were >30%. Further, emotional exhaustion and cynicism increased with academic level and were higher among those with a history of medication due to academic stress and those who considered quitting the course. The current study also provides a validated Arabic version of the MBI-SS inventory, which can be used to identify burnout among Arabic-speaking students. This is particularly important given that burnout syndrome is now included within occupational diseases and recognized as a public health problem.

The internal consistency of the Arabic MBI-SS inventory was found to be adequate overall, with Cronbach's α values of >0.8 for exhaustion and cynicism. The Cronbach's α for academic efficacy (0.704) was slightly lower. However, these results are in line with studies conducted by Campos et al.[18] in Brazil, Simancas-Pallares et al.[22] in Colombia, and other studies across different parts of the world.[23],[24],[25] The confirmatory factor analysis showed that the tri-factorial model is an adequate fit and thus further supported the construct validity of the MBI-SS inventory.

The three burnout subtypes were not concurrently present in any of the respondents in this study, which was also the case in the study conducted by Carlotto et al.[26] Similarly, both studies found high levels of exhaustion, which is understandable given the high levels of stress faced by dental students during their dental training.[11],[27] According to Maslach's model, higher levels of emotional exhaustion could be the first signal toward the potential development of burnout. However, Campos et al.[18] showed that cynicism was more prevalent than the other two sub-categories of burnout.

In our study, no significant gender-based differences were noted in the scores, which is consistent with the findings of Kwak et al.[13] However, another study found that the scores were higher among male students in all psychometric domains of the burnout scale. The lower scores in female students were attributed to them seeking the support of family more frequently than males.[27]

Students at higher academic levels were found to have significantly higher scores of exhaustion and cynicism. This could be due to higher curriculum requirements and workload demands at later years of an academic program. In line with this, Kwak et al.[13] had found a significant association between academic workload (i.e., actual working hours) and exhaustion and cynicism. In contrast, few studies found higher emotional exhaustion and cynicism at lower levels of the academic programs,[25],[26],[27],[28] likely because at the time of intake, undergraduate students may lack the autonomy and responsibility required for professional graduate programs. However, these differences indicate the need for studies to better understand factors influencing higher emotional exhaustion and cynicism, which would help design appropriate interventional programs.

The current study found a statistically significant association between the thought of quitting the course with all dimensions of the MBI-SS. These findings were found similar to studies conducted by Campos et al. and Carlotto et al.[18],[26] Future studies should aim to determine if possible strategies such as positive reinforcement are helpful in overcoming this problem.

Similarly, a significant association was noted across the three subscales of MBI-SS and students on medications due to academic stress, who feel that their teachers are incompetent and who have poor academic performance. In Saudi Arabia, the practice of self-medication due to academic stress has been reported among undergraduate female health cluster students.[29] When considered with the findings of almost a quarter of the respondents in the current study using medication due to academic stress, there is a clear need for a call to action from policymakers to reduce stressors and, in turn, such practices. It should be noted that in our study, the causal effect could not be established because of the possibility of reverse causal association. For example, the students could indeed have been taking the medications because of burnout and not the contrary. The academic performance could have been poor in those students with burnout as a result of stress due to the heavy academic load, which in turn could have resulted in their skeptical attitude. A similar study conducted in Brazil also found comparable results.[18] Longitudinal studies would help establish the relationship with many other sources of stress among dental students and thus in developing robust preventive strategies.

A strength of this study is that it included an adequate sample size and used a standard questionnaire that has been found to be effective in assessing burnout and is easy to administer. In addition, to the best of our knowledge, this is the first study that has assessed of validity and reliability of an Arabic version of this scale in dental students from Saudi Arabia. However, as the included students belonged to a single institution, the study has a few limitations such as limited representativeness and risk of sampling bias, although this was minimized due to the high response rate. Finally, the study had inherent limitations of cross-sectional studies, wherein there is a possibility of reversing causal association.


  Conclusions Top


All three subscales of burnout were highly prevalent among the studied dental student population from Saudi Arabia. Emotional exhaustion and cynicism increased with academic level and were higher among those with a history of medication due to academic stress and those who considered quitting the course. The developed Arabic version of the MBI-SS inventory was shown to be a valid and reliable tool for assessing psychometric properties of burnout among dental students.

Ethical considerations

This study was approved by the Scientific Research Committee at College of Dentistry, King Khalid University, Abha, Saudi Arabia, (Ref. no.: SRC/ETH/2017-18/023) on November 11, 2017. The study adhered to the Declaration of Helsinki, 2013, and all participants provided consent before inclusion.

Data availability statement

The datasets generated and/or analyzed during the current study are not publicly available due to privacy and confidentiality agreements as well as other restrictions but are available from the corresponding author on reasonable request.

Peer review

This article was peer-reviewed by four independent and anonymous reviewers.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Maslach C, Jackson SE. The measurement of experienced burnout. J Occup Behav 1981;2:99-113.  Back to cited text no. 1
    
2.
Maslach C, Schaufeli WB, Leiter MP. Job burnout. Annu Rev Psychol 2001;52:397-422.  Back to cited text no. 2
    
3.
Montoya NP, Glaz LC, Pereira LA, Loturco I. Prevalence of burnout syndrome for public schoolteachers in the Brazilian context: A systematic review. Int J Environ Res Public Health 2021;18:1606.  Back to cited text no. 3
    
4.
Petrelli F, Scuri S, Tanzi E, Nguyen C, Grappasonni I. Public health and burnout: A survey on lifestyle changes among workers in the healthcare sector. Acta Biomed 2018;90:24-30.  Back to cited text no. 4
    
5.
World Health Organization. Burn-Out an “Occupational Phenomenon”: International Classification of Diseases; 2019. Available from: https://www.who.int/mental_health/evidence/burn-out/en/. [Last accessed on 2021 Oct 12].  Back to cited text no. 5
    
6.
Maslach C, Jackson SE, Leiter MP. Maslach Burnout Inventory. Palo Alto, CA: Consulting Psychologist Press; 1996.  Back to cited text no. 6
    
7.
Levert T, Lucas M, Ortlepp K. Burnout in psychiatric nurses: Contributions of the work environment and a sense of coherence. S Afr J Psychol 2000;30:36-43.  Back to cited text no. 7
    
8.
Garrosa E, Moreno-Jiménez B, Liang Y, González JL. The relationship between socio-demographic variables, job stressors, burnout, and hardy personality in nurses: An exploratory study. Int J Nurs Stud 2008;45:418-27.  Back to cited text no. 8
    
9.
Erschens R, Keifenheim KE, Herrmann-Werner A, Loda T, Schwille-Kiuntke J, Bugaj TJ, et al. Professional burnout among medical students: Systematic literature review and meta-analysis. Med Teach 2019;41:172-83.  Back to cited text no. 9
    
10.
Njim T, Mbanga C, Mouemba D, Makebe H, Toukam L, Kika B, et al. Determinants of burnout syndrome among nursing students in Cameroon: Cross-sectional study. BMC Res Notes 2018;11:450.  Back to cited text no. 10
    
11.
Elani HW, Allison PJ, Kumar RA, Mancini L, Lambrou A, Bedos C. A systematic review of stress in dental students. J Dent Educ 2014;78:226-42.  Back to cited text no. 11
    
12.
Jiménez-Ortiz JL, Islas-Valle RM, Jiménez-Ortiz JD, Pérez-Lizárraga E, Hernández-García ME, González-Salazar F. Emotional exhaustion, burnout, and perceived stress in dental students. J Int Med Res 2019;47:4251-9.  Back to cited text no. 12
    
13.
Kwak EJ, Ji YA, Baek SH, Baek YS. High levels of burnout and depression in a population of senior dental students in a school of dentistry in Korea. J Dent Sci 2021;16:65-70.  Back to cited text no. 13
    
14.
Amri A, Abidli Z, Bouzaaboul M, Rabea Z, Ahami AO, Soulaymani A. Psychometric validation of the Maslach Burnout Inventory (MBI) adapted to Moroccan teachers. Medico Legal Update 2021;21:1-6.  Back to cited text no. 14
    
15.
Matejić B, Milenović M, Kisić Tepavčević D, Simić D, Pekmezović T, Worley JA. Psychometric properties of the Serbian version of the Maslach Burnout Inventory-Human Services Survey: A validation study among anesthesiologists from Belgrade teaching hospitals. ScientificWorldJournal 2015;2015:903597.  Back to cited text no. 15
    
16.
Ghali R, Boulos D, Alorabi M. Cross-sectional study of burnout among a group of Egyptian Oncologists at Ain Shams University. Res Oncol 2019;15:26-30.  Back to cited text no. 16
    
17.
Portoghese I, Leiter MP, Maslach C, Galletta M, Porru F, D'Aloja E, et al. Measuring burnout among university students: Factorial validity, invariance, and latent profiles of the Italian version of the Maslach Burnout Inventory Student Survey (MBI-SS). Front Psychol 2018;9:2105.  Back to cited text no. 17
    
18.
Campos JA, Jordani PC, Zucoloto ML, Bonafé FS, Maroco J. Burnout syndrome among dental students. Rev Bras Epidemiol 2012;15:155-65.  Back to cited text no. 18
    
19.
Maslach C, Jackson SE. Maslach Burnout Inventory Manual. Palo Alto: University of California, Consulting Psychologist Press; 1986.  Back to cited text no. 19
    
20.
Taherdoost H. Validity and reliability of the research instrument; how to test the validation of a questionnaire/survey in a research. Int J Acad Res Manag 2016;5:28-36.  Back to cited text no. 20
    
21.
Maroco J, Maroco AL, Campos JA. Student's academic efficacy or inefficacy? An example on how to evaluate the psychometric properties of a measuring instrument and evaluate the effects of item wording. Open J Stat 2014;4:484-93.  Back to cited text no. 21
    
22.
Simancas-Pallares MA, Fortich Mesa N, González Martínez FD. Validity and internal consistency of the Maslach Burnout Inventory in Dental Students from Cartagena, Colombia. Rev Colomb Psiquiatr 2017;46:103-9.  Back to cited text no. 22
    
23.
Puranitee P, Saetang S, Sumrithe S, Busari JO, van Mook WN, Heeneman S. Exploring burnout and depression of Thai medical students: The psychometric properties of the Maslach Burnout Inventory. Int J Med Educ 2019;10:223-9.  Back to cited text no. 23
    
24.
Janatolmakan M, Torabi Y, Rezaeian S, Andayeshgar B, Dabiry A, Khatony A. The relationship between resilience and academic burnout among nursing and midwifery students in Kermanshah, Iran. Educ Res Int 2021;2021:6647012.  Back to cited text no. 24
    
25.
Liu H, Yansane AI, Zhang Y, Fu H, Hong N, Kalenderian E. Burnout and study engagement among medical students at Sun Yat-sen University, China: A cross-sectional study. Medicine (Baltimore) 2018;97:e0326.  Back to cited text no. 25
    
26.
Carlotto MS, Nakamura AP, Camara SG. Síndrome de Burnout emestudantes universitários da área da saúde. Psico USF 2006;37:6-11.  Back to cited text no. 26
    
27.
Alhajj MN, Khader Y, Murad AH, Celebic A, Halboub E, Márquez JR, et al. Perceived sources of stress amongst dental students: A multicountry study. Eur J Dent Educ 2018;22:258-71.  Back to cited text no. 27
    
28.
Alemany Martínez A, Berini Aytés L, Gay Escoda C. The burnout syndrome and associated personality disturbances. The study in three graduate programs in Dentistry at the University of Barcelona. Med Oral Patol Oral Cir Bucal 2008;13:E444-50.  Back to cited text no. 28
    
29.
Al Rasheed F, Naqvi AA, Ahmad R, Ahmad N. Academic stress and prevalence of stress-related self-medication among undergraduate female students of health and non-health cluster colleges of a public sector university in Dammam, Saudi Arabia. J Pharm Bioallied Sci 2017;9:251-8.  Back to cited text no. 29
    


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