1. Introduction 
Clinical supervision (CS) has been a strategy for nursing practice in various forms for numerous years. Nurses can discuss patient care in a secure, supportive atmosphere with CS. During CS, nurses use reflective practice to identify and address their needs for professional development. This helps nurses provide a proof of their continued professional development for revalidation purposes (Brunero and Stein-Parbury, 2008; Butterworth, & Faugier, 2013; Driscoll et al., 2019). As part of improving the quality of care services, CS has become the standard method in all healthcare services (Snowdon, Leggat, & Taylo, 2017). CS is an activity for professional development. Less experienced healthcare practitioners may rely on their clinical supervisor’s knowledge and experience to fill knowledge or skill gaps which can ultimately enhance their clinical performance and patient care quality (Dawson, Phillips, & Leggat, 2013). 
The effect of CS on the quality of care is needed for improving the quality of services proposed by the World Health Organization (Cruz, 2011). CS allows nurses to discuss patient care in a safe and supportive environment. Nurses may also use CS to send feedback and advise their colleagues in order to improve their clinical issues (Brunero, & Stein-Parbury, 2008). However, CS in nursing is not just for controlling and supervising the nursing practice to achieve practical goals and efficient nursing care (Mohammadi et al., 2019). It enables nurses to increase the quality of patient care while still maintaining the current level of care. It also helps nurses show active support for one another as skilled associates, and provide comfort and affirmation (Mohamed, & Mohamed Ahmed, 2019). Recent studies have shown that CS has a positive effect on patient outcomes, such as reduced death or complications and increased treatment efficacy (Hyrkäs, 2005; Edwards et al., 2006; Addo, Stephen and Kirkpatrick, 2012; Farnan et al., 2012; Snowdon et al., 2016). 
Overall, CS provides assessment, counseling, and feedback on personal, professional, and educational development in the context of patient care (Mohamed, & Mohamed Ahmed, 2019). However, it remains challenging to ensure the effectiveness of its implementation across healthcare organizations. In this regard, the present study aims to investigate the effectiveness of CS in nursing practice and assess nurses’ attitudes and experiences regarding CS by using a mixed method and a systematic review approach. A mixed method may combine the findings related to CS efficacy and nurses’ CS experiences to understand better about how CS works and guide future procedures and policies related to professional support and development. This review study is based on the question: What are the effects of CS on nurses’ perceptions and performance? 

2. Materials and Methods
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was used to Report this systematic review. We used the PICO format (Population: nurses; Intervention: CS; Comparison: with routine program or other interventions; Outcome: nurses’ perceptions and performance) for construct a focused question. The search was conducted in PubMed, ScienceDirect, Cochrane library, Wiley Online Library, and ProQuest, and Google Scholar on relevant articles published from 2000 to 2021 using the keywords based on the Medical Subject Headings (MeSH). We used Boolean operators to combine the keywords, as follows: “Supervision OR Clinical Supervision” AND “Nurse Knowledge OR Nurse Perception OR Nurse Satisfaction” and “Nurse Performance OR Clinical Performance”. It is should be noted that the search was mostly conducted in PubMed database; Boolean operators do not work in Cochrane, ProQuest, and Google Scholar.
The following inclusion criteria were used for the selection of studies for this review: a) Relevance to specific group CS programs for nurses only, including registered nurses, associate nurses, and nursing assistants. A group CS program includes gathering one or more supervisors and two or more nurses to discuss their nursing practices, b) Being an empirical study on comparing group CS with routine programs or other interventions. Studies with randomized or non-randomized controlled design or pre-test/pos-ttest design were considered as comparative studies regardless of using quantitative or qualitative measurements, and c) Having information about the effects of CS on nurses. Studies conducted on other nurses, proposal papers, published non-English language, no available full-text, not being an original research such as letters to the editor, those with abstracts only, book chapters, case reports, dissertations, and editorials were excluded.
The McMaster Critical Review Form-Quantitative Studies v. 2.0 (Law et al., 1998) was used to assess quantitative studies, while the McMaster Critical Review Form-Qualitative Studies v. 2.0 (Letts et al., 2007) was used to evaluate qualitative studies. Two researchers worked independently on the procedure. Disagreements were handled in conversations until a consensus was established. One researcher extracted data from each study including design, sample size, key variables, equipment, CS models, and results. The remaining data were individually reviewed by the other researcher. The possible disagreements were resolved in discussions. The included studies were evaluated for risk of bias using the Cochrane Collaboration’ risk of bias assessment tool (Sterne et al., 2019) and the results were classified as “low risk of bias”, “some concerns” and “high risk of bias”. 
Qualitative data were synthesized thematically to comprehend the effectiveness of CS. It involves identifying, understanding, and reporting patterns and clusters of meaning across data (Thomas & Harden, 2008). The framework method was used to identify themes, and the included articles were read several times. Then, the topics were scrutinized for similarities, inconsistencies, and contradictions. The findings were categorized into qualitative themes. The integration of quantitative data with qualitative themes was accomplished by the first author. The matched concepts and quantitative findings were examined by the second author. Any disagreements were worked out in mutual dialogue. 

3. Results 
Initial search yielded 1041 articles. After removing duplicates, 804 potentially relevant articles remained. Due to irrelevance, being a review/report, no available full-text, being a book chapter, thesis/dissertation, 785 articles were excluded. Out of 19 remaining articles, 8 were removed due to unclear methodology, and 11 articles were finally included in the review process. To enhance the interpretation of the results, we first clarified the methodology, name of authors, and CS characteristics for the selected papers. PRISMA flowchart for literature search is plotted in Figure 1 and the characteristics of the selected articles are shown in Table 1. 


Characteristics of the included studies 
A total of 11 articles met the inclusion criteria. The included studies were conducted in different countries including: Sweden (n=4), UK (n=3), Indonesia (n=2), Norway (n=1), and Canada (n=1). In terms of the study design, 5 articles were correlational studies (Magnusson, Lützén, & Severinsson, 2002; Hyrkäs, 2005; Edwards et al., 2006; Amsrud, Lyberg, & Severinsson, 2015; Sundler et al., 2019), 4 articles were experimental studies (Heaven, et al., 2006; Bradshaw, Butterworth, & Mairs, 2007; Santoso, Sari, & Anggorowati, 2017; Yuswanto, & Ernawati, 2018) and 2 articles were qualitative studies (Berggren and Severinsson, 2000; Lantz and Severinsson, 2001). The sample size in these studies ranged from 8 to 660 nurses.

Results of the studies
There was significant methodological heterogeneity in the studies; therefore, data from the included studies could not be pooled for meta-analysis.

Variables and instruments
Various variables were determined in the studies, including knowledge, attitude, service users (Bradshaw, et al., 2007), satisfaction (Hyrkäs, 2005; Santoso et al., 2017; Sundler et al., 2019), nurse-patient relationship (Magnusson,et al, 2002), decision making (Berggren, & Severinsson, 2000; Magnusson, et al., 2002), perception, response, self-insight, reflection, creativity (Lantz and Severinsson, 2001), patient safety (Amsrud et al., 2015), communication skills (Heaven, et al. 2006), burnout (Hyrkäs, 2005; Edwards et al., 2006), and nursing documentation (Yuswanto and Ernawati, 2018). Variables were measured by Multiple-Choice Questions, the Krawiecka, Goldberg and Vaughan’s Symptom Scale, Social Functioning Scale (Bradshaw et al., 2007), questionnaire (Lantz, & Severinsson, 2001; Magnusson et al., 2002; Amsrud et al., 2015; Santoso et al., 2017; Sundler et al., 2019), interview (Berggren and Severinsson, 2000; Lantz and Severinsson, 2001; Heaven et al., 2006; Sundler et al., 2019), Manchester Clinical Supervision Scale (Hyrkäs, 2005; Edwards et al., 2006; Amsrud et al., 2015; Yuswanto and Ernawati, 2018), the Effects of Supervision Scale (ESS), the Focus on Empowerment Scale (Amsrud et al., 2015), Maslach Burnout Inventory (Hyrkäs, 2005; Edwards et al., 2006), and the Minnesota Job Satisfaction Scale (Hyrkäs, 2005). 

Clinical supervision
In general, CS can be carried out in a variety of ways. This review included studies that presented CS in the forms of psychosocial interventions in groups of 3 (two students and one supervisor) (Bradshaw et al., 2007), a reflective supervision model (Santoso et al., 2017), process-oriented supervision in psychiatric care, clinical nursing supervision, psychotherapeutic oriented supervision (Magnusson et al., 2002), weekly supervision for an hour (Berggren, & Severinsson, 2000), focus group-oriented supervision (Lantz and Severinsson, 2001), individual and group supervision (Hyrkäs, 2005; Edwards et al., 2006; Amsrud et al., 2015; Sundler et al., 2019), based on Bandura’s theory (Heaven et al., 2006), and based on Proctor Theory (Yuswanto, & Ernawati, 2018). 
All the included studies reported positive changes or improvement in knowledge, attitude, social functioning (Bradshaw et al., 2007), job satisfaction (Hyrkäs, 2005; Santoso et al., 2017; Sundler et al., 2019), security in decision making (Berggren and Severinsson, 2000; Magnusson et al., 2002), safer relationship with the patient (Magnusson et al., 2002), perception of and response to the family members’ need, self-insight (Lantz, & Severinsson, 2001), awareness, interpersonal, professional, and communication skills (Heaven et al., 2006; Amsrud et al., 2015), reduced burnout (Hyrkäs, 2005; Edwards et al., 2006), learning experience and satisfaction (Sundler et al., 2019), and quality of nursing documentation (Yuswanto and Ernawati, 2018).

Critical appraisal
The critical evaluations of quantitative and qualitative studies are shown in Tables 2 and 3, respectively.

As can be seen from Tables 2, the quantitative studies had a clear objectives and related literature review. However, lack of sample size legitimation, lack of measurement, and lack of a control group were their weaknesses. All studies reported reasonable conclusions, considering the purpose of the study. As shown in Table 3, the two qualitative studies had an explicit purpose, a literature review, targeted sampling, and overall certainty. However, their data acquisition methods were weak, and the sampling problem was obvious. The results of studies were transferable. All studies had rational conclusions by taking into account the study purpose.

4. Discussion
The main objective of the current review was to systematically review the literature relevant to the effectiveness of CS on nursing practice in various fields of care. After a comprehensive database searching, 1041 potential studies were identified; by screening their titles and abstracts, 804 were selected for examining the full-texts. In the end, only 11 studies met the inclusion criteria and were finally included in the data synthesis. These studies varied widely in terms of background, scope, and quality, making it difficult to compare and summarize the findings. In general, the results obtained from this review study showed that CS had a significant effect on nursing practice. However, it should be acknowledged that these studies did not cover all areas of nursing practice due to their conformity with the exclusion criteria. These findings support the results of previous review studies which reported that CS provides peer support and stress relief for nurses (restorative function), and promotes professional accountability (normative function), skills, and knowledge (formative function) based on Proctor’s theory (Brunero and Stein-Parbury, 2008). Another review study showed that CS by health professionals is associated with care improvement, and found a significant improvement in the care process that may improve processes related to improving patient outcomes (Snowdon et al., 2016).
A study by Bradshaw et al. (2007) showed that nursing students in the experimental group showed a powerful increase in knowledge of psychological interventions compared to the control group. Moreover, service users seen by the students in the experimental group showed significantly more reductions in psychotic symptoms and total symptoms than those seen by students in the control group. The authors reported that CS in the workplace may have benefits for nurses attending in psychosocial interventions. In their study, CS was conducted in small groups led by a member of the program team. A review study believe that CS by mental health professionals may reduce psychological symptoms of patients diagnosed with a mental illness (Snowdon et al. 2017). Another study conducted by Santoso et al. (2017) provided a 7 day reflective CS training model focusing on job satisfaction. This model improved the nurses’ job satisfaction measured by a questionnaire consisting of autonomy in work, task variation, job identity, job importance, and feedback. Studies of reflective CS in early childhood care have indicated that it stimulates emotional well-being dimensions, including emotional comprehension, compassion, and self-efficacy. These skills are essential to boost early childhood professionals to manage job stress and maintain a sense of balance and capability. Emotional perception, self-efficacy, empathy, and compassion are associated with mental health, job satisfaction, and resilience to job stress (Susman-stillman et al., 2020). 
Regarding the nursing documentation, CS model based on Proctor theory and interpersonal relationship cycle may enhance nurses’ performance in improving the quality of nursing care documentation (Yuswanto and Ernawati, 2018). The CS is not only for monitoring the task performance of nurses in the best possible way in accordance with the instructions or conditions, but also helps to know how to improve the ongoing nursing process. Supervision in nursing is done to ensure the operations are carried out based on the vision, mission, and objectives of the organization and following predetermined standards (Yuswanto and Ernawati, 2018). Nursing documentation can improve the ability of nurses and the quality of provided services (Urquhart et al., 2018). It helps nurses understand their shortcomings and strive to improve their performance (Madlabana et al., 2020). CS balances the perceptions of the ward manager and nurses regarding the quality of care and documentation. Therefore, in each guidance and situation, new ideas, suggestions, knowledge and skills are expected (Yulianita et al., 2020).
Berggren and Severinsson's (2000) hermeneutic interpretation analysis showed four themes: greater self-assurance, increased ability to help the patient, increased ability to be in relationship with the patient, and increased ability to accept responsibility. In their qualitative study, the most notable effect of CS was increased self-assurance in decision making. Nurses had different decision-making strategies. Some observed the patient directly, while others gathered information in other ways. They reflected the data they collected and prioritized the decisions needed to support the patient. Understanding the patient’s wishes is important nurse’s decision-making. The ability of nurses to observe the needs of patients is needed for their decision-making. Through observation, nurses identify problems and continue the decision-making process (Nibbelink and Brewer, 2018). Another qualitative study found that the ability to exchange work experiences was a factor that affected the nurses’ development in CS (Lantz and Severinsson, 2001). In their working environments, the nurses expressed feelings of loneliness. This was replaced by a sense of comfort stated as “others think and feel the same way I do.” Other study believed that the ablility to convey this profound sense of confirmation is the result of CS (Francis, & Bulman, 2019). It was observed that sharing supervisory experiences was significant since it prompted thought on how one’s colleagues feel and think about their work environment (Francis, & Bulman, 2019).

5. Conclusion
CS is significantly effective in nursing practice. There is a growing need in the future for more experimental studies, taking into account the use of more appropriate methodologies. We have identified several limitations in this study, including limited access to high quality databases, which are expected to provide broader search results. Moreover, there were fewer studies that met our inclusion criteria with respect to the aspects of nursing practice. Most of focus in this study was on the mental health care. The risk of bias in the reviewed studies was low or had some concern of bias; therefore, it should be cautious when using the results of the current review.

Ethical Considerations
Compliance with ethical guidelines
There was no need for ethical approval in this study, since no any experiment on animal or human models were conducted.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors' contributions
Writing-original draft: All authors; Data collection: Ernawati Ernawati and Dam M Damris; Data analysis and Writing – review & editing: Ernawati Ernawati, Asra Revis, and Solha Elrifda.

Conflict of interest
The author declared no conflict of interest.

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