A Survey of Distributed Ledger Technologies in the Health Domain

This literature analysis was done in February 2024, and the search strategy and inclusion criteria were created to guarantee that pertinent, current, English language publications with reviews about blockchain in healthcare were chosen. The search was restricted to journal papers released from 2016 to 2024, and it used data from three reliable databases: Web of Science Core Collection, IEEEXplore, and Scopus. Duplicate articles were eliminated from the initial search results to preserve data integrity. Figure 1 shows the PRISMA workflow diagram. The search term was carefully selected to find articles that addressed blockchain in the context of electronic health records (EHR) or electronic medical records (EMR), emphasizing decentralization, DLT, and interoperability in healthcare. The ‘Healthcare’ industry was the population of interest, and the query added phrases like ‘Interoperability’ and ‘Decentralization’ as further filters to make sure the articles were relevant. ‘(“DLT”) AND(“Blockchain”) AND (“Electronic Medical Record” or ”EMR” or “Electronic Health Record” or “EHR”) AND (“Healthcare”) AND (“Interoperability” or “Decentralization”)” was the last search query that was used. The objective of our search approach was to locate an extensive range of current, relevant publications about the relationship between blockchain technology and healthcare, with a particular emphasis on decentralization and interoperability. Another search used the query ‘Distributed Ledger Technologies in the Health Domain,’ which produced about seventy-seven articles.

Figure 1.

PRISMA Workflow, n is the number of research articles

As mentioned earlier, the specified query is being applied to the Web of Science and Scopus databases, and 167 articles were found. Removing 21 duplicates and auto-ineligible articles. We were left with a total of 114 articles that were screened. The chosen publications were then subjected to a systematic analysis using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) technique, as stated in reference [12]. PRISMA is a well-respected methodology that guarantees the transparent and methodical analysis of research papers in systematic reviews and meta-analyses. This technique is intended to assist researchers in evaluating the quality and relevance of the papers they are examining by streamlining the review process and maintaining high standards. Figure 1 shows the PRISMA Workflow. After removing duplicates and screening, 41 articles were included in the study.

Zotero, Microsoft Excel, Scopus, and WoSCC web interfaces served as essential tools for managing and storing data pertinent to the articles during the systematic literature review conducted using the PRISMA method. This data encompassed various aspects, including article title, author, publication year, subject area, keywords, and abstract. A qualitative assessment was also performed using these criteria to facilitate a comprehensive data analysis.

Distributed Ledger Technology (DLT) is a progressive approach to storing records, transactions, contracts, and agreements within and between organizations [22]. Unlike conventional databases, DLT ensures data integrity through consensus mechanisms rather than centralized authority [1], making it more secure and decentralized. Figure 2. shows the DLT’s framework concept. Classification of DLT can be differentiated into the traditional ledger, Permissioned Private Ledger, Permissioned Public Ledger, and Un-permissioned Public Ledgers[23]. Permissioned Public ledgers enable open public participation in data contribution and consensus formation, ensuring universal ledger access without ownership by any single entity, thus facilitating unrestricted transaction injection into the ledger[23]. Public blockchains are more decentralized and inclusive than private blockchains. In a private blockchain, security and confidentiality are more important than decentralization. Security, scalability, and decentralization are intertwined, so enhancing one often diminishes another. This is also called the blockchain trilemma, the term coined by Ethereum founder Vitalik Buterin[24]. It facilitates fast, cost-effective, and secure data exchange processes while minimizing reliance on centralized authority for transaction management. Departing from traditional centralized models reliant on singular hubs for data integration, validation, and storage, DLT decentralizes these functions, with each interconnected node replicating, validating, and storing identical ledger copies. Subsequently, individual nodes independently update their respective ledgers, verifying alterations against updates from other network nodes [25]. Transactions are immutable, and the interconnected blocks are transmitted via a peer-to-peer network [26]. Attempts to tamper or modify records within these blocks undergo scrutiny by other nodes in the network; alterations are more challenging once a block is established and acknowledged. DLT improves trust between nodes in public (open) or private (closed) decentralized networks. Nodes connected in the network have a copy of the decentralized ledger with all the transactions within the network[27]. Its adoption within organizations reduces data manipulation, theft, and fraud.

Figure 2.

Distributed ledger technology’s (DLT) framework concept

Efficient storage, interoperability, and accessibility of healthcare data are complex challenges. Emerging technologies, such as DLT, offer decentralized solutions for data transaction management [28]. The misuse of healthcare data is a prevalent concern, with numerous clinical data losses, unauthorized distribution to third parties, high patient cost burdens, and operational complexities for medical professionals. Implementing blockchain technology in healthcare systems is increasingly recognized to address data security and storage concerns, particularly regarding interoperability, data fragmentation reports, and retrieval difficulties. Leveraging DLT protocols, decentralized healthcare payment and insurance models are gaining momentum, offering investors transparency and trust while mitigating inefficiencies of the current system. By streamlining workflow communication and automating transactional services, blockchain and DLT innovations facilitate seamless processes, eliminating intermediaries and enhancing billing and claims procedures within the healthcare industry [6]. Moreover, these technologies hold promise in combating drug counterfeiting and improving healthcare data maintenance, addressing interoperability, data integrity, security, and cost management. Ultimately, the transformative potential of blockchain and DLT technologies underscores their pivotal role in revolutionizing healthcare operations, offering unprecedented advancements and value outcomes [29]. Table 1. shows different types of blockchain.

The healthcare blockchain ecosystem encompasses various stakeholders, including healthcare professionals and patients as data generators, the medical cloud for storage infrastructure, and the blockchain network comprising distributed ledger and Smart Contract functionalities for securing data access and interoperability. The healthcare industry demands strict security measures and protocols to safeguard sensitive patient information and ensure compliance with uncompromising data protection regulations. It requires security, interoperability, non-repudiation, access control, authentication, medical data sharing, and mobility. Blockchain technology offers distinct advantages tailored to the healthcare sector, including transparency, immutability, traceability, secure data exchange, decentralization, and cost-effectiveness. DLT applications within healthcare span diverse domains, including patient data management, drug traceability, cryptocurrency payment, clinical trials, data security, and the establishment of secure and decentralized healthcare setups [30]. Notably, EHR management facilitated by blockchain integration introduces features such as patient-controlled access, anonymous healthcare services, online EHR availability, confidentiality, integrity, access control delegation, zero-knowledge proof, emergency access, scalability, interoperability, and remote healthcare services [31]. Leveraging DLT enables the development of data protection-compliant solutions in trustless environments, ensuring data immutability, protection, and transparency as required [32].

Both paper-based and electronic traditional health record systems have security flaws and inefficiencies [33]. Blockchain has obstacles but has the potential to revolutionize healthcare data management. When implemented, data processing may be redesigned, improving privacy, security, and interoperability in clinical trials, EHRs, and drug supply chains. Scalability, compatibility with current systems, and adherence to laws like GDPR and HIPAA are among the problems. The main challenges include standardizing data, protecting privacy and security, and encouraging wider use. Challenges include dangers related to data loss, user education, and budgetary issues. Blockchain’s implementation in healthcare is further complicated by legal responsibility, the young age of the technology, and its smooth interaction with other cutting-edge technologies [34]. The use of blockchain technology in healthcare is hampered by significant financial limitations, particularly for smaller institutions, because of the high costs of system development, upkeep, and resource-intensive needs, which call for highly qualified staff and dependable infrastructure [35]. In addition, given the novelty and complexity of the technology, user education continues to be a major barrier that has to be overcome. In-depth training programs are needed to provide patients and healthcare professionals with the information they need to fully utilize blockchain’s advantages [36] [37].

The scalability of blockchain technology is a big issue, particularly for Ethereum and Bitcoin-based healthcare applications. The difficulty is managing large amounts of healthcare data and transactions effectively without incurring undue expenses or delays [38]. Medical data and patient information flow necessitate quick and safe processing. The limits of current blockchain technology, particularly on public networks, might result in slower processing times, higher costs, and inefficiencies, which reduce the technology’s usefulness for managing healthcare data. For blockchain to successfully satisfy the expectations of the healthcare industry, scalability is a critical issue [39].

Interoperability and broad acceptability are the two most important conditions for blockchain integration in healthcare. Blockchain adoption for data management is necessary for the healthcare ecosystem to succeed. Building an innovative and trusting culture while overcoming organizational and technical constraints is hard. For effective patient data transmission, interoperability necessitates smooth cooperation between blockchain systems and healthcare organizations. Different blockchain designs and data types provide obstacles, requiring protocols to establish communication. Establishing interoperability standards and closing these gaps would need cooperation between government agencies, digital companies, and the healthcare industry. This would enhance patient care [13] [40]. Integrating blockchain into antiquated healthcare systems that handle patient data is difficult. These systems need a lot of effort, money, and system upgrades to make them seamlessly compatible with blockchain technology since they do not have the necessary interfaces [41]. Fundamental modifications to data processing and storage techniques must align with blockchain, which may require new software interfaces. Hardware, network, and security protocol re-configurations may also be required. Healthcare organizations strive to surmount these obstacles to enhance data security, facilitate interoperability, and reap the rewards of sharing [42]. A searchable blockchain-based HIE system is suggested by L. Sigong et al. to address the trade-off between data usefulness and security. The system processes EHRs using a granular manner based on attributes. As a result, it permits effective EHR search and utilization without needless decryption procedures. The suggested approach improves data usability by enabling users to run targeted queries and statistical analyses on particular healthcare data. It uses the immutability and decentralization of blockchain technology to protect EHRs from potential privacy risks associated with HIE systems [43].

BC-UADS framework implements blockchain-based user authentication and a data sharing scheme. It uses a consortium blockchain to provide a distributed and decentralized data-sharing platform in a permission network using the PoR consensus algorithm. This framework protects the authenticity, immutability, and transparency of patient HER data which are transferred online between different hospitals [44]. T. Wang et al. propose a mechanism for exchanging health data HSHB, which is built on a hybrid blockchain, that separates data sharing into two categories: alliance chain and private chain. To ensure the security and privacy of health data sharing, sensitive data is managed through Smart Contracts before being shared with outside organizations [45]. Healthcare is obligated by laws such as GDPR and HIPAA to protect patient data. Notwithstanding its advantages, blockchain’s decentralization makes it difficult to adhere to these requirements [33]. Dispersed data complicates management and auditing and makes privacy compliance difficult. It is imperative to do a privacy legislation analysis of blockchain technology before implementing healthcare data systems. It could be necessary to use anonymization procedures to safeguard patient identities. Adherence is essential, necessitating blockchain solutions prioritizing data security and privacy [46][41].

Healthcare organizations and blockchain developers must collaborate to build solutions that make it easier for standardized healthcare data to be translated and compatible with blockchain systems to overcome this obstacle [47]. This may entail developing middleware or data transformation procedures to bridge the gap between current data formats and blockchain needs. Data standards and blockchain compatibility must be achieved to guarantee that blockchain-based healthcare solutions can successfully communicate and exchange data with traditional healthcare systems and providers [48]. It is essential to maximize blockchain’s benefits while preserving healthcare data management continuity and enhancing interoperability. Blockchain improves data security but raises privacy issues for the medical field. It is still challenging to strike a balance between data interchange and privacy, particularly when it comes to patient data. Blockchain’s immutability and openness raise the possibility of a patient data vulnerability, necessitating strict access control even in the face of cryptographic security [49]. Smart Contracts provide an open data interchange, automate permission, and give patients control over data access within prescribed bounds. Developing blockchain-based healthcare systems that guarantee data sharing and privacy is complex. For patient privacy, compliance with data protection rules such as GDPR and HIPAA is essential [50] [51].

Cryptographic keys are used in blockchain systems to restrict access to data, and their loss can render data permanently inaccessible. This issue highlights the importance of safely handling and saving private keys to prevent the irrevocable loss of crucial medical data. A blockchain-based healthcare setting emphasizes the necessity of vital key management techniques and user education to reduce the danger of data loss [49] [52]. Blockchain networks use consensus protocols to verify transactions and the chain’s current state [49]. Although blockchain technology is still in its infancy, it has the potential to solve concerns about patient privacy, interoperability, and data security in the healthcare industry [36]. Present concerns include less understandable user interfaces, complicated implementations, and scalability issues. As technology advances, these early difficulties should disappear and make it easier to employ for healthcare. Healthcare blockchain integration with AI and IOT needs compatibility and collaboration. IoT collects real-time medical data, AI improves processing, and blockchain guarantees security. Expert cooperation is essential to building a smooth IT environment [53] [54]. There are protocols, such as Proof of Work (PoW) and Proof of Stake (PoS), each with pros and cons. Careful consideration of security, energy efficiency, scalability, and decentralization is necessary when choosing the best approach for healthcare. Adapting the consensus process to healthcare requirements avoids inefficiencies, excessive energy use, and security threats [55].

While implementing blockchain in healthcare, legal and liability considerations are crucial. The decentralized nature of blockchain presents issues for health data management in terms of accountability [56]. It becomes difficult to assign blame for mistakes or disagreements because of decentralized networks and cryptographic keys. To resolve this, specific legal frameworks and contracts outlining responsibilities and liabilities are required, guaranteeing that all parties understand and abide by the legal protections designed for blockchain-based healthcare systems [35]. For blockchain systems to operate well, a vital network infrastructure is essential. In rural or remote places, limited access to reliable networks reduces the device’s efficacy. Investments in network infrastructure and enhanced internet connectivity are necessary to realize blockchain’s promise in these environments [57].

MedRec uses Ethereum’s Smart Contracts to generate intelligent representations of medical records on separate network nodes. It creates contracts with data integrity, permissions, and record ownership metadata. The blockchain transactions provide cryptographically signed instructions for maintaining specific attributes. The state-transition features of the contract implement policies requiring data alteration only through authorized transactions [58]. The blockchain Smart Contract record contains information about permissions and reclaiming data access. This is to create a fresh, minimally functioning patient record for a physician or administrator. An ID, such as a name or SSN, can identify each patient record. A public-key cryptographic ID is assigned to every patient record.

The architecture contains the registrar contract, summary contract, and patient-provider relationship. The summary contract must maintain the patient’s medical record history on file. The document includes references to patients–provider relationship contracts (PPRs) and reflects the current and former participants in the various nodes of the system. Almost always, the patient gets recommendations from the doctor, and they also have the right to provide authorized users access to their medical records. It notifies users from the EMR manager with acknowledgment from the patient for consent and provides updates. The patient can accept, delete, or reject connections, and the provider decides each one’s status. This patient can leave the dispersed network and return to it several times.

The contract structures and relationships of the MedRec framework implementation are designed as follows. This design has four parts: the client, manager, library, and database. Each user has a distinct ID and address, and the registrar’s contract address makes it simple to identify the summary contract. The services immediately reported any modifications to the summary contract. After taking note of the user, the EHR Manager established an automated connection to the local database. The client sends the cryptographically signed request, which is sent to the issuer to verify IDs to the Gatekeeper. The customer must receive their data back if the address was supplied. With the aid of the registrar contract, the patient chooses which data to share with other users utilizing his address. When all the elements are merged with the EHR program, it offers the user update, view, data sharing, and retrieval options.

By enabling physicians and specialists to access medical information from anywhere in the EHR, medical data is kept within the appropriate geographic area. The blockchain describes how the patient’s health data may be accessed over the cloud. Other medical professionals can access the patient’s medical records using this manner. Research and pharmaceutical departments can access the data. The Business Network Archive (BNA), utilized to ascertain the physiognomies and capabilities of MediChain, is created using Hyperledger Composer [65]. The composer created the script, access control, and model files. Any user may be a caretaker, physician, or patient. Every user registering for one of the three roles receives a unique ID number. The health record is solely accessible to the owner. The owner and the caretaker have the right to exchange information.

The Medichain framework manages various types of patient health data, including prescriptions, bills, test results, and diagnostic images. Hashes of these assets are stored on the blockchain. Through their Smart Contract, the patient may access their electronic medical record. The script file (Smart Contract) controls access to the health record. The Smart Contract stores the patient log data and viewing authorization. Essentially, it gives us limited access to the data. The access control list keeps track of all access regulations, including role-based, unconstrained, and mandatory access control.

Patientory eliminates the need for third-party middlemen. It is most frequently used for health information exchange (HIE). Improved integrity, reduced transaction costs, and eliminating middlemen are all advantages of a decentralized system such as blockchain technology. Using the HIE enhances the continuity of the care cycle and reduces pointless administrations with repeated tests. Every rule and regulation under the Health Insurance Portability and Accountability Act (HIPAA) is adhered to, including those concerning security and privacy [61]. Patient-related outcome measures (PROMs) are maintained by this system, which primarily allows customers to examine a patient profile to keep track of their medical history. PROMs can include a patient’s side effects and personal satisfaction with the treatment. The system can facilitate communication between patients and doctors on the importance of treatment-related diseases by providing a comprehensive and detailed evaluation of drugs for individual conditions. The system uses simple methods such as visits, hospital charges, personalized therapy data, protection, and prescriptions from the pharmacy to assist the patient.

A data provenance architecture based solely on blockchain and cloud technology. The data that are kept on the blockchain are accessible to any peer. Without the help of a third party, Prov-Chain automatically creates an open timestamped history of all client activities on cloud data. While the data are accessible, the provenance auditor can never identify the original user. The final one is data validation, where records are accessible via the blockchain network, and numerous nodes verify each block. The transmission of provenance information is approved by Prov-Chain using a blockchain receipt.

The blockchain network, provenance database, provenance auditor, and cloud user are the elements that make up the Prov-chain architecture. Access to the user’s data on the blockchain and permission to share them with others are granted. Then, blockchain nodes verify the data modifications. The next component is the cloud service provider, which offers user registration and storage benefits. It keeps track of any modifications to the data and can gather a great deal of information about activities carried out by each client to improve management. It also detects intrusions. Mainly, this precaution protects their computerized health records. Provenance database entries were kept on the blockchain network, which was utilized by the malicious system.

The administration and access control of medical records and data are intended to be revolutionized by blockchain implementation in IBM Blockchain for Healthcare. Fundamentally, the blockchain indexes all user health records and data, acting as an access-control manager. The blockchain indexes contain transaction timestamps, encrypted linkages to health records, unique user identities, and metadata for quick and easy access to data, much like a library’s card catalog. This method guarantees the safe monitoring of personal health information for the duration of an individual’s life, including information gleaned via wearable sensors, mobile apps, and formal medical records. A separate data lake, scalable and able to hold a variety of data kinds, including documents, images, and key-value stores, is also included in the architecture[62].

IBM Healthcare implements blockchain technology to change medical records data management and access control. The blockchain serves as an access-control manager and index of all user health information and data. Similar to a library’s card catalog, the blockchain indexes comprise timestamps for transactions, encrypted connections to medical records, distinct user identities, and metadata for rapid and simple data retrieval. This approach ensures that personal health data, including that obtained from official medical records, wearable sensors, and mobile apps, is safely monitored throughout an individual’s life.

With personal genomics becoming increasingly popular, the proposed blockchain system solves essential concerns about the security and privacy of genomics data. Notably, issues have surfaced about the possibility of government access to genomics databases, the transparency of data utilization by personal genomics companies, and the dangers of discrimination based on genetic information. The framework prioritizes privacy by supporting pseudo-anonymous transactions made possible by cryptocurrencies such as Bitcoin, promoting user anonymity. This lowers the risk of security breaches and data misuse by enabling people to purchase genetic testing services while minimizing the acquisition of personally identifiable information. Furthermore, the framework recognizes the limitations of blockchain anonymity and suggests using cryptographic methods to improve user privacy and confidentiality in blockchain transactions, including genetic data, such as zero-knowledge proofs[64].

The framework for the genomics blockchain promotes user-centric data access control, enabling people to own the encryption keys for their genomics data. Using a decentralized method reduces the risk of data breaches and unauthorized access as there is less reliance on centralized genomics databases managed by genomics companies. By dispersing data access control, delegated access control improves security and transparency. It involves several independent organizations holding shares of encryption keys. The framework also highlights how crucial record auditability is and how blockchain technology makes this possible by allowing for clear communication of user consent, data sharing permissions, and requests for access to data. The framework utilizes blockchain technology to create unchangeable records, which fosters trust, encourages data exchange, and guarantees accountability in the handling and examining of genetic data.