Towards a patient journey perspective on causes of unplanned readmissions using a classification framework: results of a systematic review with narrative synthesis

Background Several literature reviews have been published focusing on the prevalence and/or preventability of hospital readmissions. To our knowledge, none focused on the different causes which have been used to evaluate the preventability of readmissions. Insight into the range of causes is crucial to understand the complex nature of readmissions. With this review we aim to: 1) evaluate the range of causes of unplanned readmissions in a patient journey, and 2) present a cause classification framework that can support future readmission studies. Methods A literature search was conducted in PUBMED and EMBASE using “readmission” and “avoidability” or “preventability” as key terms. Studies that specified causes of unplanned readmissions were included. The causes were classified into eight preliminary root causes: Technical, Organization (integrated care), Organization (hospital department level), Human (care provider), Human (informal caregiver), Patient (self-management), Patient (disease), and Other. The root causes were based on expert opinions and the root cause analysis tool of PRISMA (Prevention and Recovery Information System for Monitoring and Analysis). The range of different causes were analyzed using Microsoft Excel. Results Forty-five studies that reported 381 causes of readmissions were included. All studies reported causes related to organization of care at the hospital department level. These causes were often reported as preventable. Twenty-two studies included causes related to patient’s self-management and 19 studies reported causes related to patient’s disease. Studies differed in which causes were seen as preventable or unpreventable. None reported causes related to technical failures and causes due to integrated care issues were reported in 18 studies. Conclusions This review showed that causes for readmissions were mainly evaluated from a hospital perspective. However, causes beyond the scope of the hospital can also play a major role in unplanned readmissions. Opinions regarding preventability seem to depend on contextual factors of the readmission. This study presents a cause classification framework that could help future readmission studies to gain insight into a broad range of causes for readmissions in a patient journey. In conclusion, we aimed to: 1) evaluate the range of causes for unplanned readmissions, and 2) present a cause classification framework for causes related to readmissions. Electronic supplementary material The online version of this article (10.1186/s12874-019-0822-9) contains supplementary material, which is available to authorized users.


Background
The definition of unplanned readmissions varies among countries, but it is most often defined as an urgent readmission within 30 days from a previous admission [1][2][3]. In many cases, unplanned readmissions result in potential health risks for patients, an increased workload for caregivers and excessive healthcare expenditure [4]. Reducing readmission rates is therefore considered to be of great importance. Many countries use readmission rates as a quality indicator of hospital care. However, previous research shows that unplanned readmissions are not only caused by suboptimal care provided by the hospital [5,6]. In fact, unplanned readmissions that are considered to be potentially preventable due to suboptimal hospital care (~20-25% of the unplanned readmissions) often also have other underlying causes which are not related to hospital care [6,7]. This suggests that hospitals are being held accountable for unplanned readmissions, while they may not always be able to prevent them [8].
In the previous decades, studies have been performed on the prevalence and preventability of readmissions. Existing assessment tools with predefined causes (such as State Action on Avoidable Rehospitalizations (STAAR), Root-Cause Analysis Tool (PRISMA: Prevention and Recovery Information System for Monitoring and Analysis) [9] and Research Electronic Database Capture (REDcap tool) are often applied or adapted in readmission studies. The variation in different sets of causes used makes comparison between studies difficult. Comparison between studies is crucial to fully understand the complex nature of readmissions.
To date, it is unclear which causes are considered in unplanned readmission studies. In particular, the causes which are not related to hospital care have not been given much emphasis so far. Hence, this systematic review focuses on evaluating the different causes that have been taken into consideration in studies on unplanned readmissions using patient record review. With this review we aim to: [1] evaluate the range of causes of unplanned readmissions in a patient journey, and [2] present a cause classification framework that can support future readmission studies.

Methods
In 2017, we conducted a systematic review on (the implications of) the different methods used to assess the preventability of unplanned readmissions by use of patient record review [10]. Previous studies demonstrated that health administrative databases often lack extensive information (e.g. functional status and social support) [11]. Therefore, we focused on studies which used patient record review to assess preventability of unplanned readmissions. The current systematic review provides an in-depth insight on the causes that have been used by the studies in the previous review.

Literature search
The literature search was applied in Web of Science, Scopus, Pubmed and Embase in December 2016, using "readmission and avoidability or preventability" as key terms (Additional file 1). A medical information specialist was consulted for the search. All citations were imported into Endnote × 7.3.1TM.

Study selection
The 77 studies which were included in the previous review [10] were checked for eligibility for this review by two researchers (CB and RS) (see Additional file 2). Studies were included if they fulfilled to the following criteria: original data, primary focus on preventable readmissions, clear description of preventable readmissions and potential causes of preventable readmissions (the cause classification) (see Additional file 3). We defined a cause classification as the description of at least three causes or synonyms for causes (e.g. (contributing) factors and reasons). Studies that described the causes of preventable readmissions (≥3) were further reviewed. Studies that made no distinction in readmissions and (primary) admissions, or preventable readmissions and non-preventable readmissions, were excluded from further analysis. In case of disagreement, a senior researcher was consulted to reach a final selection of studies.

Critical appraisal of individual studies
We applied a validated approach to evaluate and compare the studies. This approach was developed by the Cochrane Consumers and Communication Review Group with the aim to perform a structured and transparent analysis for systematic reviews that rely primarily on the use of words and text to summarize and explain the findings of the synthesis. The approach can be described as 'narrative' analysis or synthesis [12]. We used this approach because of the large heterogeneity in study designs, and because other quality appraisal approaches and tools were less appropriate to apply. Prior to the narrative analysis a data-charting form was jointly developed by the authors to determine which variables to extract (including defining these variables). Subsequently, the authors independently charted the data, discussed the results and continuously updated the data-charting form in an iterative process. The data-charting form included variables such as: study design characteristics, sources of information to assess preventability, definition of preventability and percentage of preventable readmissions. After extracting the data the authors critically evaluated the applicability of the data and tabulated the results in order to identify patterns across the included studies.

Data collection and classification Preventability
Two researchers (RS and CB) collected all the causes described by the studies. Each cause was classified as preventable or unpreventable. In our previous review, we found that the definition of preventability varied widely among studies. Many studies did not provide a clear definition, but referred to a cause classification with causes that were pre-defined as preventable [10]. For instance, Williams et al. defined potential areas to avoid readmissions; 'It was noted that readmission could have been avoided if more effective action had been taken in one or more of five areas: preparation for and timing of discharge, attention to the needs of the carer, timely and adequate information to the general practitioner and subsequent action by the general practitioner, sufficient and prompt nursing and social services support, and management of medication' [13]. Other studies such as Ryan et al. provided a broad definition of preventability; 'Providers were given no specific guidelines for deciding whether a readmission was preventable. This allowed use of their different backgrounds in choosing which elements of the clinical record to focus on' [14].
In this study, the researchers coded whether a cause was preventable as stated by the study authors. When the study was unclear regarding the preventability of a cause, the researchers classified the cause as neutral. Causes that studies considered both preventable and unpreventable, were coded as both.

Root cause
The root causes were based on the PRISMA classification scheme of Schaaf & Habraken [9]. PRISMA is an abbreviation of Prevention and Recovery Information System for Monitoring and Analysis, and is often applied for root cause analyses in healthcare. Schaaf & Habraken defined four root causes: technical, organizational, human behavior and patient. We adapted these categories prior to the start of the data collection based on our experience with patient record reviewing in several Dutch hospitals [91]. We sub-divided the root causes "organization, human and patient" in organization (integrated care), organization (hospital department level), human (care provider), human (informal caregiver), patient (self-management) and patient (disease). In addition, we provided examples of causes for the settings: hospital care, ambulatory care and home (care). Hospital care was defined as the complete care process from admission until discharge, including outpatient visits after discharge. Ambulatory care was defined as medical care provided in an outpatient setting. Care at home was defined as informal care provided at home after discharge.
Two researchers (RS, MdB, CB, FK independently) allocated each cause to the root causes mentioned above. A third senior researcher performed a double check on the final cause classification. Disagreements between researchers were resolved during meetings (RS, CB, FK, MdB) until consensus was reached.
A few studies combined multiple types of causes within one single cause. We separated these different causes in order to allocate each of them to the most appropriate root cause. This resulted in a higher number of causes than there were originally present in the study. Furthermore, we were not able to allocate all causes to one root cause because some causes lacked a clear description of the context. We classified these causes as Unclassifiable. Specific categories of causes such as planned readmissions or unrelated readmissions were not considered for further analysis as these were not root causes for a readmission. After allocating all the causes, a final cause classification framework was constructed. Data collection and analyses were documented in Microsoft Excel 2016.

Results
After applying the detailed inclusion and exclusion criteria 32 studies were excluded for this review, leaving 45 studies for further analysis (see Additional file 2b). The 32 studies were excluded because of at least one of the following reasons: no original data [16][17][18], no primary focus on preventable readmissions [15,[19][20][21][22], no clear description of methods and results (e.g. no distinction in preventability or type of admission  and no description of causes [45]. An overview of the excluded studies is shown in Additional file 4.

Cause classification
The frequencies of each root cause are listed in Additional file 5. A total of 381 causes were found of which 275 were reported as preventable and 44 as unpreventable (see Additional file 5). Twenty-six causes were reported as both preventable and unpreventable in a single study, and these causes were coded as both. Examples of causes that were considered differently among studies are listed in Table 2. Other causes that were not explicitly defined as preventable or unpreventable (n = 36) were coded as neutral. The final cause classification framework is listed in Table 3.

Technical
None of the studies reported technical failures as a cause for preventable readmissions.

Humancare provider
Seven studies reported causes related to the care provider [2,67,68,72,74,84,86], such as inadequate decision making, inadequate (clinical) skills and knowledge, or lack of experience. In all cases, these causes were considered to be preventable. Examples of these causes include: 'Failure resulting from faulty task planning or performance' and 'Failure of an individual to apply their knowledge to a new clinical situation' [2].

Humaninformal caregiver
Six studies described causes related to the informal caregiver [13,71,77,[84][85][86]. All these causes were seen as preventable. For example, Harhay and Vinson described inadequate support at home as a cause for preventable readmissions.

Patientself-management
Twenty-one studies included causes related to self-management of the patient [ Non-adherence was also frequently reported as a preventable cause [14,51,54,59,61,67,71,74,77,82]. For example, Yam described adherence problems and patient coping as causes for preventable readmissions. In six studies, causes related to self-management were seen as unpreventable [58,59,61,64,79,81]. For example, Burke considered causes such as adherence to discharge plan, refusal of discharge plan and substance use as unpreventable.

Unclassifiable
Twelve studies reported some causes that could not be classified into root causes [13,14,47,59,65,69,71,74,75,78,82,85]. Causes such as problems with services can apply to institutions, departments or individuals. For example, patient assessment was mentioned as a cause for readmission, but it was not specified who performed the patient assessment or what was exactly meant with it.

Purpose of study and significant conclusions
The main objective of this systematic review was to summarize the range of causes described for unplanned readmissions and to present a cause classification framework for causes of readmissions. The findings of this review show that many studies primarily focus on causes related to organization of care at the department level. The causes were mainly evaluated from a hospital perspective. None reported technical failures as one of the causes of (preventable) readmissions. We succeeded in classifying the majority of the causes according to the adapted PRISMA scheme and to distinguish between levels of care. We were not able to allocate causes that were ambiguous.

Key results compared to other studies
The results of this review indicate that the causes of readmissions depend on the context of the study, e.g. the inclusion of department/healthcare organization, case-mix, assessor of preventability, and definition of preventability. All studies were conducted in the hospital and several studies included causes beyond the setting of the hospital. The latter studies often identified other causes for readmissions in addition to hospital care (e.g. social support [13,71,77,[84][85][86]). This finding is in line with the existing literature [6,11,[88][89][90]. Zhou et al.
(2017) reviewed studies which used prediction models for (preventable) unplanned readmissions. They identified that health insurance and overall prognosis should be considered as contributors in addition to the clinical factors which are normally included in the statistical models. We also found that factors such as self-management, social support, and type of healthcare organization can play a role. Other factors beyond the scope of the hospital should be assessed in more detail to gain a better insight into the complexity behind unplanned readmission and to understand where interventions can have the most impact. In addition, gaining more understanding on these factors is necessary in order to optimize the applicability of unplanned readmissions as a quality indicator of integrated care [11,88]. Decreasing unplanned readmissions needs a holistic approach, because health care is a complex dynamic system in which patients, professionals, health care organization are acting within the regulations of their national health care system. Furthermore, this review highlights that studies differ in which causes are considered to be preventable. In particular, complications, adherence and disease progression were seen as both preventable and unpreventable. For example, 'foreseen complications' were seen as preventable [61,79]. Complications of surgical procedures were also reported as preventable in many studies [48,49,81]. Greenberg et al. reported complications related to neurological impairment and immobility as an unpreventable cause [70]. Shah et al. considered complications as preventable and unpreventable. They defined the following complications: complications occurring in spite of best practices being followed, complications due to progression of natural history of certain chronic neurosurgical disease, post-procedure complications and complications related to medication use. The first two were reported as unpreventable, and the latter two as preventable [63]. These findings highlight that preventability can differ depending on many contextual factors and what the authors of studies regard as adequate care.
The proposed classification allows researchers and policymakers to further consider the complex nature of readmissions. Differences in cause classifications can be problematic for fair comparison of studies. Therefore, it is essential that studies describe the context of the research setting/research population and elaborate on what they regard as preventable.
In addition, this review indicates that the assessment of readmissions is mainly based on data that is inputted in the hospital information system. Some studies included interviews and were thereby able to capture the patients' experience. However, the transcripts were not available and therefore not included in this review. Furthermore, studies indicated that interviews with patients and/or caregivers can provide additional information on factors beyond the hospital setting which cannot be found in medical records [85]. For instance, Sutherland et al. (2016) found that the combination of patient interviews and chart review revealed additional gaps in care [75]. In addition, Toomey et al. (2014) found in 31.2% of cases that interviews with patients and primary care providers provided new information. These findings support other studies stating that increased involvement of patients and other stakeholders are crucial for assessing the cause of the readmission and may contribute to the prevention of readmissions and to better quality of care [89].

Strengths and limitations
This review provides insight into the range of causes reported in unplanned readmission studies. The insights gained from this review may help others in conducting readmission studies. However, this review has some limitations. Firstly, the studies included were based on a set of articles which were collected for a previous review [10]. As a consequence, we may have missed studies which also examined the causes of unplanned readmissions, but did not provide information on the rate of preventable readmissions. This might have limited the number of causes reported in this study and consequently the number of root causes/categories in our cause classification framework. However, we performed a cross reference checking in Scopus and Web-of-Science and did not find additional studies. Secondly, we allocated a single cause to only one root cause. Thus, causes which consisted of multiple sub-causes were disentangled into separate causes. This might have influenced the frequency of the themes and subthemes that were found. Thirdly, studies which did not explicitly specify the context of a specific cause (ambiguous causes) were considered "Unclassifiable". As a result, the number of causes related to other root causes may be underestimated. Lastly, all phases were either consensus based-driven and/or performed by at least two independent data extractors. However, using this procedure can not preclude that some amount of interpretation bias occurs during data collection, synthesis and interpretation.

Recommendations for policy
Since 2016, unplanned readmissions have been used as a quality indicator for hospital care in the Netherlands. To increase the comparability of causes between readmission studies, we advise that the use of a standardized cause classification framework should be stimulated. The framework proposed in this review provides a broad range of causes which are most frequently observed. Regarding hospital care at the department and institutional level this overview is rather complete, although technical causes are lacking and are becoming more relevant due to development of eHealth, mHealth and ICT supported long distance care. Causes at the patient and health care system level are still of limited detail. For example, more information on the patient experience can be collected using interviews. Insight into these causes is crucial for developing improvement opportunities.
In addition, the proposed framework may contribute to a transparent development of prediction models. Information on how data sources are used to calculate the readmission indicator are often lacking [11]. Current prediction models depend on a limited range of data documented in the hospital information system. Information on what happens after discharge is (often) not documented. Hence, policy makers should be careful in holding hospitals accountable for unplanned readmissions as long as it is unclear which percentage of these readmissions is truly preventable by preventive actions of the hospital itself. Unplanned readmission should be viewed as adverse events occurring in a complex dynamic system, in which patients, professionals and organizations all play a crucial role, regulated by the healthcare system.

Recommendations for research
This review indicates that the causes of unplanned readmissions which are examined by the studies differ between studies and are often limited to causes focused on hospital care. As a result, the multifactorial nature of readmissions is not well understood and certain contributing causes might be overlooked. This limits the potential impact of (patient-centered) interventions to prevent readmissions [88]. To improve our understanding of readmissions, all actors involved in the patient journey should be considered. The suggested framework may provide direction on which causes to include in a readmission study and prediction models. In the future, we hope that with the use of prediction models, highrisk patients can be more easily identified and targeted for alternative management [90]. In addition, future research should take into account the interdependency of causes. For instance, when a patient gets readmitted due to an incorrect assessment by a physician at discharge, this readmission might be the result of how readmissions are handled at a department/organization. Physicians might not be effectively trained to ask the patient if they are ready to be discharged. Lack of skills can thus also be considered a result of suboptimal organization of care (organization department level care). Failure on organization level (e.g. missed opportunity to train physicians) or care-provider level (lack of skills) are important to consider. In addition, it is also possible that failure on one level might be mitigated by other levels. Each level must be considered in the study of readmissions. Multiple causes of readmissions -in and beyond the hospital -play a role. All these causes should be assessed to capture the complex nature of readmissions and should be considered interdependently.

Conclusion
In conclusion, we aimed to: [1] evaluate the range of causes for unplanned readmissions, and [2] present a cause classification framework for causes related to readmissions. The results show that the causes of readmissions used differ considerably among the studies. The current use of different causes limits the opportunity to compare studies and to learn from unplanned readmissions. A shared vision on unplanned readmissions is necessary to improve the uniformity and transparency on the causes of readmissions. This can be achieved by ordering all causes in the new cause classification framework based on the PRISMA cause classification. The new cause classification framework may contribute to