Blockchain

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A blockchain is a public distributed ledgers that maintains a growing list of ordered records (called "blocks") representing transactions that occurred among all interested participants. Each transaction is verified by a majority of the participants before it can be placed in the blockchain. This new transaction is securely linked to the rest of the blockchain. Once it is placed in the blockchain, it can never be erased. Block chain has been applied most famously in creating cryptocurrency, but its application can be extended to any field that values accurate and secured record keeping including banking, accounting, notary, health record keeping, etc. Multiple whitepapers have been published to discuss the application potential for blockchain in healthcare and research.

History of Blockchain

The Technology Behind Blockchain

Bitcoin

Blockchain was first introduced in 2008 by Satoshi Nakamoto (Nakamoto, 2008)as the underlying technology behind bitcoin, a type of virtual currency that uses cryptographic proof instead of a third-party verifier (such as a banking system) to confirm transaction[2]. The algorithm for how bitcoin works were explained by Nakamoto as followed:

Figure 1. How Blockchain works

Each user of Bitcoin is given a “public key” and a “private key.” When a transaction occurs, a digital signature created from the private key of the sender is sent to the public key of the receiver. This transaction is broadcasted to the entire network, and is verified by every node in the network (called “miner” node). The verification process includes confirming the sender’s identity by checking the digital signature, and making sure that the sender has sufficient fund by checking all of prior transactions involving the sender. To allow for all nodes to participate in the verification process, each miner node must go through a time-delay process that involves solving a mathematical puzzle before its work can be accepted. This is called “proof-of-work” since it takes computing power to solve the puzzles. The miner node is compensated for their work by a small amount of Bitcoin. The transaction is recognized when more than half (at least 51%) of the nodes agree that it is valid. This transaction is now recorded in a block, then added to the top of the ledger, linking to the last block in the ledger by adding to itself a hash made from the prior block. This is called the “blockchain.” All nodes in the network has a copy of the ledger, which will be updated simultaneously when transaction is confirmed. If a ledger differs from the majority, it will be updated to reflect the most up-to-date ledger. This is the blockchain concept of “distributed ledger.”


The technology of Bitcoin and blockchain has several advantages. The public key is cryptographically generated, allowing for anonymity. Because the ledger is widely distributed and updated based on consensus, it is extremely difficult to manipulate it outside of the verification process, preventing fraudulent transaction without the need of a third-party verifier. Furthermore, since every transaction is recorded in the ledger, the flow of currency is transparent and can be verified by anyone.

While the verification of Bitcoin involves simple calculations to adjust the balance of the sender and receiver after the transaction has been verified, there has been other cryptocurrencies such as Ethereum which take this further and run arbitrary user-defined programs on the blockchain (Wood, 2014), with the purpose of creating a “smart contracts.” The smart contract is an agreement between parties that is enforced automatically by the program. The person who requests the contract deposit currency into the program, which will wait until a certain condition is met before validating it and transfer the currency to the person who carried out the contract. If the condition is not met, the currency is refunded. This technology eliminates the need for a third party to enforce the contract.

New Innovations

Smart contract

Proof of Stake

Blockchain scaling

Application of Blockchain in Healthcare and Research

Blockchain has been proven to be a useful platform for financial transactions. However, its application goes beyond the financial system. Melanie Swan predicts three phases of blockchain adoption: Blockchain 1.0, 2.0, and 3.0 (Swan, 2015). Blockchain 1.0 manifested as online currency. Blockchain 2.0 is the near future, where blockchain is used to keep track of contracts, financial records, public records, and ownership of property. Blockchain 3.0 will be applied into science, medicine and education. Even though we are still at an early stage of applying blockchain into health care, there are multiple proposals for its application. The majority of these proposals leverage blockchain’s ability to maintain an immutable record to place control of patient’s health record into their hand by allowing them to grant and revoke access to their medical records according to their preference (Gordon & Catalini, 2018; Yue, Wang, Jin, Li, & Jiang, 2016). In a traditional system, patient’s health record is kept and maintained by a health care organization (e.g. hospital, clinic, etc.). Information can be freely shared between the organization and a Regional Health Information Organization (RHIO) or another organization that has a business agreement with the originating institution. If there is no business agreement between the institutions, one-off requests can be made, but this will take time and delay care (Figure 2A). As Meaningful Use Stage 3 is being implemented at health care organizations, there has been a push to create patient-facing application programming interfaces (APIs) that allow patient to directly retrieve their record from the institution and share it with the provider as needed (Figure 2B). Gordon et al. proposes a blockchain-enabled smart contracts controlled by the patient to authorize direct sharing of medical record between institutions (Figure 2C). Patient can specify the subset of the record to be shared or set an expiration date on the authorization.

Gordon et al. suggested five features of block chain that allow for successful patient-driven interoperability: digital access rules, data aggregation, data liquidity, patient identity, and data immutability. The blockchain-enabled digital access rule is centralized, which makes it accessible by multiple institutions, while facilitating editing of the rules by the patient at any moment via a smart phone-based or web-based application. Patient could also aggregate their data (or metadata) across institutions to a blockchain or another secured location using the digital access rule, thus creating a complete record of their health. Because the change in digital access rules will take effect as soon as the patient (or legal representative) approves it, data can be share rapidly to the requesting institution, allowing access to time-sensitive information such as allergies, “code status,” etc. Even though there is no national patient identifier, institutions can use the blockchain-assigned individual’s public key and match it with their local identifier to start sharing data across systems. Finally, since all changes made to the blockchain is recorded and immutable, the risk of loss is minimized, and the record can be audited at any time.

Another application for blockchain is in clinical research. A problem that has plagued research is the lack of reproducibility (Ioannidis, 2005), which could be from multiple types of errors, misconduct or fraud. Blockchain offers a solution to this problem by providing an ability to track, share and care for data (Benchoufi & Ravaud, 2017). A recent study has shown that 80% of US employees would share their medical data provided privacy and security can be ensured (Chu). With blockchain-enabled data access rules, patient can easily allow researchers to gain access to their anonymized data, thus increasing the scope and sample size of the clinical research. The integrity of the clinical trial phase can also be maintained by entering each step of the trial with a time stamp into a blockchain and, using smart contract, only allow the next step to be validated after the preceding steps has been fully validated (Figure 3). This will avoid post-hoc data manipulation and posteriori calculus bias. Upon completion of the trial, the publication can be sent along with the link to the block chain which verifies that the study protocol has been followed as it was designed. The blockchain is also readily available to anyone who wants to evaluate validity of the study.

Limitations and Proposed Solution

As exciting as the potential for application of blockchain in healthcare is, there remains a number of limitations of blockchain that prevents its widespread use. This section will discuss the different challenges inherent in the first iteration of blockchain and provide possible solutions to them.

The first concern with block chain is its inability to handle the transaction volume of clinical data. Blockchain is great at keeping a record of changes to a small amount of data (such as account balance, owner’s identity, etc.). However, it is not economically practical to store a large amount of data on the blockchain due to cost associated with creating a very large ledger to store this information and to perform proof-of-work on this ledger. One way to overcome this barrier is to validate data using a different approach to consensus such as proof-of-stake (Siim). Another proposed solution is to store a summary of, instead of a complete clinical report (Gordon & Catalini, 2018). Alternatively, patient’s data can be stored on a permissioned (private) regional blockchains that are built to handle large transaction volumes without time-intensive validation.

A second limitation of blockchain is the lack of privacy and security. Even though the identifier on the blockchain is the cryptographically generated public key, this is only pseudonymous, as patient can still be identified by matching for other basic demographic information, and once the public key has been linked to the patient, their activity on the blockchain can be tracked. A proposed solution is to use permissioned (member-only) blockchain to avoid public exposure. Basic demographic information stored on a block chain can be encrypted to prevent access as well. Another way to minimize exposure is to store sensitive data off-chain, with on-chain data focusing on granting permission to access requested data using pointers and metadata. This would also allow patients to assign different access rule for different users of their data

Since the focus of many blockchain-based projects is on patient-controlled health care data, it necessitates more patient participation than the traditional, institution-based paradigm. They must be able to assign certain permissions for different institutions that request access. Having a patient-friendly “app” to manage public keys and permissions will become very important to get more buy-in from patients. Furthermore, patient will also need to keep track of their password to gain access to their private key in order to make changes to the block chain. There will need to be a mechanism for recovering lost password when this occurs.

Finally, the largest barrier to widespread adoption of blockchain in healthcare deals with the issue of incentives. Meaningful Use stage 3 requires implementation of patient-facing API, but this does not entail handling access control of healthcare record to patient. Institution has little incentive to pay for the cost of setting up a blockchain just to give patient more control even though this will improve interoperability. One solution is expanding federal incentives to patient-controlled medical record. Alternatively, researchers can be incentivized to pay for the setup of these blockchains by gaining access to patient anonymized data for research purposes.


References

1. Gupta, Vinay. “A Brief History of Blockchain.” Harvard Business Review, 5 Apr. 2017, hbr.org/2017/02/a-brief-history-of-blockchain.

2. Crosby, Michael, et al. "Blockchain technology: Beyond bitcoin." Applied Innovation 2 (2016): 6-10.

3. Marr, Bernard. “A Very Brief History Of Blockchain Technology Everyone Should Read.” Forbes, Forbes Magazine, 20 Mar. 2018, www.forbes.com/sites/bernardmarr/2018/02/16/a-very-brief-history-of-blockchain-technology-everyone-should-read/#5bde14d57bc4.