Table 1.

Overview of blockchain-based health care applications in the research literature.

Article, author (year)	Research method	Focus	Key findings
Maslove et al (2018) [22]	Proof-of-concept	Clinical trials data management	A web-based interface, BlockTrial, allowed patients to grant researchers access to their data and allowed researchers to submit queries for data that are stored off-chain. The proposed system increased the trustworthiness of data collected during clinical research, with benefits to researchers, regulators, and drug companies alike.
Zhou et al (2018) [2]	Proof-of-concept	Medical insurance storage system	A blockchain-based medical insurance system, MIStore, deployed on Ethereum was proposed to serve as a medium for accountable record keeping. Medical insurance data were better managed in a distributed way.
Chen et al (2018) [36]	System design	Secure medical data storage and service framework	A storage scheme to manage personal medical data based on blockchain and cloud storage was proposed without third parties. No single party would have absolute power to affect the processing; better and more secure medical storage could be achieved.
Ali et al (2020) [37]	Proof-of-concept	Remote health monitoring and data sharing	A solution for patients to share biomedical data with their doctors was proposed without manipulation by trusted third parties. In various health monitoring scenarios, three use cases—cardiac monitoring, sleep apnea testing, and electroencephalogram following epileptic seizures—were tested for system feasibility.
Hau et al (2019) [23]	Survey	Attitudes on information sharing	Medical doctors reported significantly more negative attitudes than patients. Furthermore, self-employed doctors reported more negative attitudes than employed doctors and university professors.
Esmaeilzadeh and Mirzaei (2019) [18]	Experimental study	Medical information exchange	Significant differences existed in patients’ perceptions of various exchange mechanisms with regard to patient privacy concern, trust in competency and integrity, opt-in intention, and willingness to share information. Participants held a favorable attitude toward the implementation of blockchain-based exchange mechanisms for privacy protection, coordination, and information exchange purposes. This study proposed the potential strengths and limitations of a blockchain-based attempt within a health information exchange context.
McGhin et al (2019) [38]	Literature survey and case study	Research challenges and opportunities	The survey presented a careful examination of specific blockchain issues and how they affect the health care industry. Health care industry requirements and blockchain potential effects in supporting these requirements were discussed.
Vazirani et al (2019) [39]	Systematic review	Blockchain implementation	Of the 71 included studies, the majority discussed potential benefits and limitations without evaluation of their effectiveness, although some systems were tested on live data.
Bouras et al (2020) [28]	Literature review	Identity management	This study presented state-of-art decentralized identity management using blockchain and highlighted the possible opportunities for future adoption. Decentralized models and pilot projects were presented to give implications.
Zhang et al (2019) [40]	Framework construction	Development of balanced scorecard evaluation framework	A framework was proposed to holistically assess the performance of blockchain initiatives in providing value-based care. By extending the concept of existing balanced scorecard evaluation, both the financial and nonfinancial benefits of blockchain initiatives were evaluated.
Shuaib et al (2019) [41]	Literature review	Blockchain potential in improving secured digitized medicine	The digital ledger technology could be used to improve current systems. Data are distributed and decentralized, preventing loss and allowing recovery in the event of an attack. Audit trails keep track of what transactions and modifications are made to patient records, while notifying all users on the network. Patients will be given more control over who has access to their data by selecting who carries the cryptographic keys required to decrypt and view them. In addition, issues such as scalability need more research efforts.
Guo et al (2018) [42]	System design	Secure signature authentication	An attribute-based signature scheme with multiple authorities, in which a patient endorses a message according to the attribute while disclosing no information other than the attested evidence, was proposed. By sharing the secret pseudorandom function seeds among authorities, this protocol resists collusion attack out of N from N–1 corrupt authorities.
Kadam et al (2019) [43]	System design	Patient data privacy	Patient data were secured by applying the Secure Hash Algorithm for the generation of hash values and the Paillier algorithm to re-encrypt the same information regarding patient data that is divided among a number of different servers. This approach increases the difficulty of hacker access and attack and maintains the security principles (ie, availability, integrity, and confidentiality).
Al Omar et al (2019) [44]	System design	Health care data privacy	A patient-centric health care data management system was proposed by using blockchain technology for storage, which helped to attain privacy. Cryptographic functions were used to encrypt patients’ data and to ensure pseudonymity.
Yue et al (2016) [45]	System design	Health care data privacy	The Healthcare Data Gateway architecture, using blockchain, enabled patient-centric data management (ie, own, control, and share patient data) in a secure way without violating privacy, which improves the intelligence of health care systems. The proposed access model ensures better manipulation of health care data and enables untrusted third parties to conduct computation with patient data without violating privacy.