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FACULTY OF ENGINEERING AND INFORMATION TECHNOLOGY Health Recommender System for Personalized Clinical Prescription Qian Zhang A thesis submitted for the Degree of Doctor of Philosophy University of Technology, Sydney July, 2018 i ABSTRACT General practitioners are faced with a great challenge of clinical prescription owing to the increase of new drugs and their complex functions to different diseases. A personalized recommender system can help practitioners discover mass of medical knowledge hidden in history medical records to deal with information overload problem in prescription. To support practitioner’s decision making in prescription, a literature review is conducted to find the research gaps and propose research questions in implementing health recommender system for prescription. Three research gaps are considered in this system framework: (1) to define a patient’s need by giving his/her symptom, (2) to mine features from free text in medical records and (3) to analyze temporal efficiency of drugs. The recommender system is expected to help general practitioners to improve their efficiency and reduce risks of making errors in daily clinical consultation with patients. Keywords: recommender systems, personalization, text mining ii case-based reasoning, healthcare ACKNOWLEDGEMENTS Insert acknowledgements here iii TABLE OF CONTENTS ABSTRACT ................................................................................................................. ii ACKNOWLEDGEMENTS ........................................................................................ iii TABLE OF CONTENTS ............................................................................................ iv LIST OF FIGURES ..................................................................................................... v LIST OF TABLES ...................................................................................................... vi Chapter 1 Introduction ................................................................................................. 1 1.1 Background ........................................................................................................ 1 Chapter 2 Literature Review ........................................................................................ 3 2.1 Recommender System........................................................................................ 3 2.2 Health Recommender System ............................................................................ 4 2.3 Application of RS techniques to HRS ................................................................ 5 2.4 Research Gap in Literature................................................................................. 7 2.4.1 The relationship between patient and drug ................................................. 7 2.4.2 Unstructured data in medical records .......................................................... 7 2.4.3 Temporal effectiveness of drug................................................................... 8 Chapter 3 A hybrid recommendation approach using feature mined from free text ... 9 Chapter 4 Temporal recommendation on drugs via long-and short-term efficiency . 10 Chapter 5 Multi-label classification based drug recommender system ..................... 11 Chapter 6 A hybrid recommender system for personalized clinical prescription ...... 12 Chapter 7 Conclusion and future study ...................................................................... 13 REFERENCES........................................................................................................... 14 APPENDIX A TITLE ................................................................................................ 20 APPENDIX B TITLE ................................................................................................ 21 iv LIST OF FIGURES v LIST OF TABLES vi CHAPTER 1 INTRODUCTION 1.1 Background Due to the large number of patients general practitioners (GPs) are meeting every day, efficiency and accuracy of decision making are quite crucial in clinical medicine. Prescription is an important element in every consultation with patient. Because of the fast variation of diseases, numerous new drugs are developed to deal with different situations occurred to patients. It is sometimes difficult to keep up to date with plenty and complex drug information even for an experienced GP, let alone the ones in internship. Moreover, contraindications of many drugs may bring chronic harm to unsuitable patients or what’s worse may cause lethal effect. Therefore, GPs are facing a big challenge in the information explosion era with many new drugs flooded into market every year. To reduce mistakes and cut off the time consumed in encounter with patients, there is a requirement of medical E-services to help GPs search and select drugs when they are making decisions on prescription. Some surveys show that GPs in clinics use an Electronic Medical Record System (EMRS) mainly for prescribing together with ordering laboratory tests and recording patient’s progress (McInnes, Saltman & Kidd 2006). Wildly used EMRS lead to fast accumulation of medical data where potential medical knowledge is to be extracted to guide GPs in prescription (Jensen, Jensen & Brunak 2012). Prescription decision support to GPs is to supply them with personalized drug list based on patients’ medical symptoms, test results and other characteristics collected by EMRS. Similarly, to find appropriate item for specific customers in E-commerce is a problem solved by personalized recommendation (Lu 2004). Recommender systems (RS) aim to predict users’ potential interests on items they haven’t bought according to users’ preferences (explicitly as ratings on historical item and implicitly as social relations) thus making a personalized product list for customers to choose (Lu et al. 2015). RS is broadly adopted to different areas both in academia and in industry in the past two decades (Huang et al. 2012). Some RSs have been developed to support medical prescription (Wiesner & Pfeifer 2010). Collaborative filtering (CF) is used together with a trust-based relationship among clinicians using drug frequency in prescribing to represent its rating of a clinician (Begum et al. 2011). Moreover, since clinicians often solve a new problem based on previous medical experience (solved case) with some adjustments implemented (Ting et al. 2010), application of knowledge based technique in RS or specifically, case-based reasoning (CBR) method is applied in this problem. CBR is refined by association rule mining and Bayesian reasoning to integrate general knowledge from relationship between clinical manifestation and prescribed medicine into cases (Sesen et al. 2014; Ting et al. 2011). However, due to the patient privacy in medicine, implementation of recommender system techniques in drug recommendation has gained less attention (Ricci, Rokach & Shapira 2011). Accordingly, a health recommender system (HRS) is ‘a specialization of a RS’ (Wiesner & Pfeifer 2014, p. 2582). Similarly, HRSs make predictions based on patients’ medical records the same as RSs do based on user’s profile. But in the context of medicine, HRS assists clinicians in decision making according to the practical condition of a patient rather than user’s interest. The decision support for clinicians can be presented in three ways. Chiefly, it helps clinicians to save time 1 when making diagnosis and prescribing medicines if the system can give proper recommendation based on the similar history records in the database. Also, it reduces the probability of false diagnosis if the system can acquire knowledge related to the clinical case based on other clinician’s experience. Last but not least, this system may help discover latent patterns that may be significant in medicine after analysis of different patients’ cases. Consequently, exploiting a health recommender system is a good way to help clinicians reduce irrelevant information. Although these systems mentioned above filtered some unrelated drugs and achieved good performance on test, some questions are remained to be solved. First, unlike the items recommendation which depend on user’s preference in E-commerce, drugs prescribed by GP are corresponding to patient’s symptoms. How to define a patient’s need given a patient’s symptom is a primary problem in prescription recommendation. Existing method choose CBR to evade this issue or simplify it to a single one-to-one symptom-drug relationship. However, the relationship between symptom and drug is complex to deal with but seriously influence the final recommendation accuracy. Second, free text message in EMRS is not taken into consideration. Free text written by GP is the most flexible part containing latent characteristics of different patients, where distinguishable feature extracted are valuable for personalization. Third, since numerous new drugs are developed each year to improve therapy performance, analysing temporal efficiency of drugs will help GP grasp the trend in the leading edge. The three aspects mentioned above will affect the accuracy and practical utility of the prescription recommender system, which are not well developed in previous research. To solve the identified issues, a new hybrid recommender system which uses artificial neural network and case-based reasoning to personalize prescriptions in a comprehensive way, should be exploited. This system relates patient’s need to different drug clusters includes meticulous patient features in free text and mines upto-date drug trends to support GP in drug decision making. And my research will focus on developing methods based on RS techniques for clinical environment, especially in personalized prescription. 2 CHAPTER 2 LITERATURE REVIEW In this part, it begins with the detailed description of formulated recommendation and categorization of different methods used in RSs. Then the differences between RS and HRS will be provided based on the content of RS. At last, recent applications of RS techniques used in HRS will be reviewed to give a light on how to exploit a hybrid recommender system for in health service and why it is significant. 2.1 Recommender System Recommender system (RS) is first applied in E-commerce to solve information overload problem brought by Web 2.0 and quickly expanded to personalization of egovernment, e-learning, e-tourism etc. (Lu et al. 2015). They gave an overall summarization on the development of RSs in the last two decades. Basically, recommendation is to be formulated as follows (Adomavicius & Tuzhilin 2005): 𝑢: 𝐶 × 𝑆 → 𝑅 This is a utility function about how to define the preference of a user c ∈ C on a specific item s ∈ S. Usually, the preference of a user is presented as ratings on items. RS is to find the item for the user to maximize the utility function, formulated as follows (Adomavicius & Tuzhilin 2005): ∀𝑐 ∈ 𝐶, 𝑎𝑟𝑔𝑚𝑎𝑥 𝑢(𝑐, 𝑠) 𝑠∈𝑆 Classification of RSs are different in papers, but here it is categorised in 4 types according to methods used in the system: content-based, collaborative filtering (CF)based, knowledge-based and hybrid approaches (Adomavicius & Tuzhilin 2005; Burke 2002; Ekstrand, Riedl & Konstan 2011; Trewin 2000). Different methods have its own advantages and drawbacks, detailed information were summarised in table 1. Hybrid method combines two or more techniques to overcome the limitation of any individual one. There are seven different types of hybrids: ‘weighted, switching, mixed, feature combination, feature augmentation, cascade and meta-level’ (Burke 2002, p. 340). 3 Table 1 Comparison of different methods used in RSs Method Basic Description Content based Recommendations were based on the content of the item user preferred before. CF based Recommendations were based on other users who have similar tastes. Knowledge based Recommendations were based on user's needs and item's function. Hybrid Method Combination of the above methods. Representative Techniques Heuristic method: Keyword-based Vector Space Model, TF-IDF Statistical model and machine learning method Advantages Drawbacks 1. New item can be recommended 2. User independent 3. Transparency 1. New user problem 2. Overspecialization (lack of serendipity) Memory-based: Neighbour-based CF Top-N CF Model-based: Dimension reduction Latent semantic Hybrid CF methods Case-based reasoning Ontology-based semantic web 1. No need to consider the content 2. Easy implementation 1. Cold-start problem 2. Scalability 3. Sparsity 1. New item and user can be recommended 2. Reasonable recommendation and specific needs can be meet Overcome the limitations of each single method 1. Complex knowledge database management 2. monotonous recommendation Knowledge-based CF Content-based CF Implementation expense is relatively high 2.2 Health Recommender System Accordingly, a health recommender system (HRS) is ‘a specialization of a RS’ (Wiesner & Pfeifer 2014, p. 2582). Similarly, HRSs make predictions based on patients’ medical records the same as RSs do based on user’s profile. But in the context of medicine, HRS assists clinicians in decision making according to the practical condition of a patient rather than user’s interest. The decision support for clinicians can be presented in three ways. Chiefly, it helps clinicians to save time when making diagnosis and prescribing medicines if the system can give proper recommendation based on the similar history records in the database (Lu, Huang & Duan 2012). Also, it reduces the probability of false diagnosis if the system can acquire knowledge related to the clinical case based on other clinician’s experience (Huang et al. 2012). Last but not least, this system may help discover latent patterns that may be significant in medicine after analysis of different patients’ cases (Huang, Lu & Duan 2012). 4 Unlike the user-item matrix in RS, medical record is the primary information in health recommender system. Recommendations are based on user’s medical history. Before applying the techniques used in RS to the medical context, it is necessary to conduct analogy between RS and HRS. A classical e-commerce RS in most of research papers is to recommend a movie to a customer based on the customer’s rating to movies he has already seen. Besides, other information beyond the useritem rating matrix like user social network/demographic feature, movie genre/tag/taxonomy can be considered as user’s profile and item’s profile. All the factors mentioned in the scenario above can be matched in HRS. In HRS (Komkhao, Lu & Zhang 2012), 1. Users are corresponding to patients; 2. Items are corresponding to medicines; 3. User’s profile is corresponding to patient’s disease history, age, weight and other attribute in PHRS; 4. Item’s profile is corresponding to medicine’s attribute such as ADR(adverse drug reaction) and dose; 5. Rating is corresponding to the frequency of a specific medicine found in the database containing all the prescriptions. Although the analogy of RS and HRS indicate the two systems to be quite similar, there are still some different aspects between the two systems. For instance, in the context of medicine, features extracted from patient’s medical history or from medicine attribute have its own special meaning in clinic. Whether these features will lead to final decision made by clinicians or they were chosen in coincidence should be estimated by clinicians. The whole process should be under surveillance of a professional expert like a general practitioner so that the risk of misjudgement by the system can be lowest. Another difference is that patient’s privacy must be considered in HRS. Despite privacy problem also exists in classical RS, the security level of HRS is much higher since the data is related to patient’s medical history. Data from hospital must be de-identified before they come to research or practical application. This, from an aspect, explains the reason why the development of HRS is not fast. It is because the research is restrained by the availability of data from clinical area (Ricci, Rokach & Shapira 2011). Relevant information or items can be recommended to users scale from clinicians who are domain experts and need the system to keep them up-to-date to patients who are laymen but care about their own health and want a better explanation to their current health status (Kashfi 2011). Here, we focus on the HRS for clinicians considering that decision making in medicine is crucial to human life so that trust a machine may not be reasonable. Therefore, HRS is a tool to support clinicians to improve their efficiency in diagnosis and prescription rather than to replace them. 2.3 Application of RS techniques to HRS In recent years, different data mining techniques of recommender system are applied in medical data to acquire medical knowledge to support diagnosis, treatment or prognosis (Hassan & Syed 2010). Wiesner & Pfeifer (2010) proposed a framework of how HRS can be implemented in electronic medical system. This is a first approach showing how the system can be put into practical use in medicine. And it is about how to use free-texted encyclopedia and Wikipedia to manage medical 5 information and transform it to features that can be used in recommender system techniques. Rodríguez et al. (2009) applied semantic web and ontology in HRS and a hierarchy of ontology is given. Although these papers are among the first applications of RS in the health area, their development is insufficient and no experiment is implemented, thus making the conclusions to be doubted. CF is the classical method used in RS and its performance is quite well during the test from both academia and industry (Hassan & Syed 2010). According to the analogies in Section 3.2, user-item matrix can be identified in HRS so that a CFmethod can be applied. Wiesner & Pfeifer (2014) argued CF is ‘an inappropriate approach’ because the confidential health record should not be used in the system to protect patients’ privacy. However, problem caused by privacy can be solved by deidentify the medical records or by other privacy friendly frameworks which are proved effective in (Hoens et al. 2013). Besides, some research about CF techniques used in HRS proved that CF is a suitable method in the context of medicine. Hassan & Syed (2010) predicted the risks in heart attacks using CF and compared this method with traditional classification methods like SVM or LR. Huang et al. (2012) implemented CF algorithm together with a trust-based relationship among clinicians into the medical knowledge recommender system. Concretely, one of the case studies uses drug frequency in prescribing to represent its rating of a clinician. The performance of the proposed method is good, suggesting that the assumption above is valid and CF algorithm performs well in practical use. Komkhao, Lu & Zhang (2012) adopted an incremental CF algorithm, W-InCF, with Mahalanobis distance and fuzzy membership and compares it with classical K-NN and K-means algorithm. Davis et al. (2010) proposed a system named iCARE based on CF and ensemble learning to make predictions of patient’s disease risks according to their disease history. All the evidence above have proved the feasibility of CF application in HRS. Except CF techniques, other techniques are also considered by researchers. Since clinicians will solve a new problem based on the previous medical experience(solved case) with some adjustments implemented (Begum et al. 2011). And a medical case not only contains the medicine ‘ratings’ but also other kinds of knowledge such as severity of a symptom or special health condition of a patient related to the diagnosis and medicine prescription. The application of knowledge based technique in RS or specifically, a case-based reasoning method in HRS seems reasonable. Case based reasoning has been used in clinical problems in (Kolodner & Kolodner 1987). That is the first time to propose a framework based on CBS and test this method by medical data. Many systems are developed since then based on CBS and they are reviewed by(Bichindaritz & Marling 2006). Particularly, some recent research also proved this method is applicable to decision making in clinical area. A recommendation system to predict treatment to different diabetes cases according to different features selected using rough set feature reduction (Lu, Huang & Duan 2012). A CBR method is also applied to determine radial dose in cancer treatment and weights of features are optimized by Bee Colony Optimization (Teodorović, Šelmić & Mijatović-Teodorović 2013). 6 2.4 Research Gap in Literature Evidence shows that CF-based and knowledge-based techniques are feasible in HRS. In addition, because medical cases and treatment plans in clinical context can be quite complex and no simple and direct rules can be traced, a hybrid method could be an advisable choice since this combination performs well in RS for restaurants (Burke 2002). Therefore, a hybrid method of knowledge-based CF algorithm specific to medical environment is to be exploited. And this is the whole view of what I will do in my research. 2.4.1 The relationship between patient and drug Literatures reviewed previously take lab test results in numerical form as patient feature to retrieve most similar case in predicting the unknown case. The prediction made in these literatures are quite simple either a binary yes-or-no decision or a choice from less than 10 candidates. Usually, the suggested decisions are made from treatments in broad categories like tablet/injection/surgery (Lu, Huang & Duan 2012; Sesen et al. 2014). However, medical cases and treatment plans in clinical context can be quite complex and no simple and direct rules can be traced. Decision making in prescription is to be made among hundreds or thousands of drugs. Moreover, combinations and relationships between different drugs will increase the difficulty of the choice. Till now, no adequate system to support decision making of GP’s prescription has been provided. Therefore, how to deal with the relationship between patient feature space and drug he/she needs is the question to be answered. This issue is worth researching because the accuracy of recommender system for personalized prescription depends on how to mine this relationship. To get a more reasonable and accurate recommendation list to guide GP, the relationship is the most crucial and dispensable question to be solved. 2.4.2 Unstructured data in medical records Unstructured data are totally un-predefined. Unlike structured data which have unified standards and are easy to select and compare, unstructured data are usually not easy to deal with. In medical records, lab test and patient’s demographic features are structured data that have a range of values like the blood glucose concentration or a binary option like gender. These features can be directly used as patient features and used in data mining and machine learning methods. At the same time, clinicians like to write free text to describe patient’s symptom or other issues to keep patients’ diversiform characters in record. However, unstructured data is not well explored and most literatures focus on structured data and classical classification methods (Esfandiari et al. 2014). As a consequence, how to mine useful features from free text written by GP is another research question in this research area. Some literatures study free text in medical records, but they either focused on text classification or named entity recognition (e.g. finding keywords to classify the records or finding the terms of disease or syndrome). Free text information is seldom used in personalized prescription. Since clinicians are keen to use free text and much dynamic information about patients are to be mined, it is important to dig up free text to provide GPs with dynamic and personalized recommendation service. 7 2.4.3 Temporal effectiveness of drug The amount of information is increasing nowadays, so user’s interests are changing rapidly. The challenge of recommender systems in e-commerce is to keep up with the changing of user’s preferences. This leads to a lot of research in recommender system in temporal dynamics(Ding & Li 2005; Koren 2010). Same situation occurs to health recommender system. The effectiveness of a drug is changing with the fast development of medical research. For instance, a drug can be eliminated once patients develop resistance to a certain drug; a drug can be substituted by new drugs which have better therapy performance or less side effects. With the changing of a curative effect of a drug, the frequency of this drug prescribed by GP will be reduced once its clinical effect is not as good as new drugs. This is time drifting data widely known as concept drift. Referred to literature review, personalized recommender system for prescription is not well developed, let alone to take temporal effectiveness of drugs into consideration. Still, this problem is practical in medial prescription, especially for patients with severe diseases such as cancer or AIDS. 8 CHAPTER 3 A HYBRID RECOMMENDATION APPROACH USING FEATURE MINED FROM FREE TEXT 9 CHAPTER 4 TEMPORAL RECOMMENDATION ON DRUGS VIA LONG-AND SHORT-TERM EFFICIENCY 10 CHAPTER 5 MULTI-LABEL CLASSIFICATION BASED DRUG RECOMMENDER SYSTEM 11 CHAPTER 6 A HYBRID RECOMMENDER SYSTEM FOR PERSONALIZED CLINICAL PRESCRIPTION 12 CHAPTER 7 CONCLUSION AND FUTURE STUDY 13 REFERENCES Adomavicius, G. & Tuzhilin, A. 2005, 'Toward the next generation of recommender systems: a survey of the state-of-the-art and possible extensions', IEEE Transactions on Knowledge and Data Engineering, vol. 17, no. 6, pp. 73449. Begum, S., Ahmed, M.U., Funk, P., Xiong, N. & Folke, M. 2011, 'Case-based reasoning systems in the health sciences: a survey of recent trends and developments', IEEE Transactions on Systems, Man, and Cybernetics, Part C: Applications and Reviews, vol. 41, no 4, pp. 421-34. 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