In the popular news media, blockchain is often discussed in relation to cryptocurrencies or touted as a cure-all for anything and everything related to data. While a major player in the finance sector now, blockchain in health care is still in its infancy. Yet proponents say it has the potential to aid clinical research, help prevent counterfeit drugs and bolster health data security. You may begin to hear more about this technology in the coming years—both fact and fancy—so we spoke with experts to learn what blockchain is and how it could contribute to ophthalmology.


What Is Blockchain?

Blockchain is a form of distributed ledger technology that promotes trust through transparency and immutable data records. Experts say the technology could be used to safely transport patient data between various medical centers and labs, facilitate artificial intelligence development audits and aid clinical research by helping to identify potential participants and secure their data. (Images courtesy of Getty Images.)

Blockchain is a form of distributed ledger technology designed to engender trust through transparency, common access and unalterable data structures. “Transactions are recorded in ‘blocks’ which are cryptographically linked to the previous block using that block’s hash key, a type of unique identifier,” explains Daniel Shu Wei Ting, MD, an associate professor at the Duke-National University of Singapore Medical School, director of the Singapore Health Service’s AI Program and an ophthalmologist at the Singapore National Eye Centre, Singapore Eye Research Institute. “Every block is verified and approved by the blockchain’s participants through a consensus mechanism before it’s stored on the blockchain.”

In the world of finance and cryptocurrency, where blockchain has already found a foothold, it’s used to record transactions across many devices, including who owns currency, where it’s located and how it was spent over time. In health care, blockchains will help to manage and transport large amounts of medical data. 

“Help” is the key word here, according to Tim Mackey, MAS, PhD, a professor at UC San Diego in the Global Health Program and director of the Global Health and Data Policy Institute. “You never start off with blockchain as a solution,” he says. “There’s a lot of hype around blockchain, especially in the non-fungible token (NFT) market. We have to get around this idea that blockchain can solve everything and think of it more as just another facilitating technology that can enable trust in other systems.” 

 Blockchain networks must have the following four characteristics:1 

1. Consensus. All parties must agree on a transaction’s validity for it to be considered valid.

2. Provenance. Participants know where an asset came from and how its ownership changed over time.

3. Immutability. Transactions can’t be tampered with once they’ve been recorded to the ledger. If there’s a transaction error, a new transaction must be used to reverse the error, but both of these entries will remain visible as part of the record.

4. Finality. The ownership of an asset or completion of a transaction is recorded in one shared ledger.

Within blockchains, there are three types of architectures: private; public; and consortium. As you may guess, a private blockchain is akin to a private network, where the blockchain is held by a single authority. Public blockchains, such as those used for cryptocurrency, allow anyone access. Consortium blockchains are a hybrid of public and private blockchains and are permissioned through multiple authorities. Experts say private and consortium blockchains will be useful for health care’s high-security needs.


Uptake & Adoption

How soon can we expect blockchain to come to health care and the biomedical space? It may take years, Dr. Mackey says. “Health care is a unique and complex industry, and it’s highly regulated compared to industrial sectors,” he explains. “According to the Gartner Hype Cycle, [a five-stage graphical representation of a technology’s maturation and application] blockchain is at the ‘Peak of Inflated Expectations’ and it’s likely moving into the ‘Trough of Disillusionment,’ though I’m not sure I’d follow this curve as much for the health-care space.

“Much of blockchain adoption in health care will be centered on its money-saving potential,” he continues. “By keeping more transactions trustworthy and automating processes through smart contracts [coding programs that automatically self-execute the exchange of value once specific agreements are triggered],2  blockchain could save money—if people want to use it. They may not want to. Prescription benefit managers and billing companies that process reimbursements, for example, are the types of entities that blockchain is supposedly going to disintermediate. That means we may not use them as much, because one party will be able to talk to another party directly, in a more trusted manner.

“Choosing the right business model is another consideration,” he says. “Maybe consortium members—e.g., multiple health-care systems—all want to address CMS auditing or record validation. Maybe they all pay a membership fee and then some governance authority operates a blockchain on their behalf. In that case, every party might share in the cost of the overall blockchain environment and pay a transaction cost as a membership fee.

“Consortium blockchains are prime candidates for health care, but getting all of the different consortium members to agree to the same governance principles is actually very hard,” Dr. Mackey adds. “That’s another thing that can slow adoption.” 

Evaluating Blockchain Projects

What are some ways to tell whether a blockchain proposal is more hype than practical? Tim Mackey, MAS, PhD, a professor at UC San Diego in the Global Health Program and director of the Global Health and Data Policy Institute, says he considers these three things when evaluating a blockchain project:


1. Good architecture. “We generally look for a correct architecture that’s fit for the purpose of the particular health-care problem,” Dr. Mackey says. “For example, if it’s a problem that relates to health-care records, what’s the structure? Private? Public? Hybrid? What’s the permission structure setup? What’s the consensus mechanism? Does it have a smart contract layer? Does it address a particular need?”


2. A diverse team. “We often look for teams that have both health-care people and engineers, not just one or the other,” he says. “We make sure there are people who understand what a blockchain can do, as well as understand the health-care angle.”


3. Boring is often better. “The most boring use cases tend to be the best ones, e.g., enabling better chargebacks or resalable returns for items,” he says. “In pharmaceuticals, when pharmaceutical products are sold to someone and then they’re brought back into inventory, blockchain would ensure you could track them so they could be resold again. Those types of use cases don’t sound super exciting, but they’re actually some of the best use cases.”


He says there are still some fundamental unanswered questions about blockchain in health care too. For instance, we don’t yet know how much it’ll cost to deploy at a health-care scale, and there may be issues of interoperability, such as the degree to which blockchain can interact with different health systems. “We also don’t know what the add-value is,” he says. “What can blockchain do that other systems such as cloud computing can’t already do with a permission structure?”

One early venture into health-care blockchain research comes from Mount Sinai, which launched the Center for Biomedical Blockchain Research in 2018 with the goal of leading Mount Sinai’s blockchain odyssey. The CBB’s aims are to identify real-world use cases for blockchain, separate hope from hype, evaluate and build new applications, and partner with industry.  


Patient Data 

Because of blockchain technology’s immutable nature, experts say it could assist with some newer needs that have cropped up during and since the COVID-19 pandemic, including contact-tracing, health/vaccination passports, tracking COVID-19 testing, disease reporting and ensuring the vaccine supply chain remains free of counterfeit vaccines.

A medical blockchain evaluation study reported that blockchain networks can preserve and exchange patient data through hospitals, diagnostic laboratories, pharmacy firms and physicians.3 The group also reported a potential for enhancing medical record analyses, handling deception in clinical trials and improving data efficiency and security in health care. 

Managing electronic health records is another potential blockchain space. There are several blockchain-based EHR companies today, but in these instances, blockchain is used to manage permissions and security, rather than serve as a repository for patient records. “There’s no time in the immediate future where blockchain would replace EHRs,” Dr. Mackey assures. “There are all sorts of challenges associated with putting EHR data on a blockchain. For example, storing patient records on blockchain may run into issues with HIPAA since it’s a distributed ledger.” 

Nevertheless, the next step in patient-centric care will require decentralized, encrypted data, Dr. Ting says. “Medical data, especially in the era of telehealth and the Medical Internet of Things,4 will need to be traceable and secure,” he says. “Traditional health-care databases are centrally managed, and that opens them up to vulnerability and limits the extent and efficiency of data exchange. The COVID-19 pandemic also prompted a space for blockchain. The technology could be used to assist with contact-tracing and immutable health passports,5 as well as keeping track of COVID-19 testing, disease reporting, and vaccine supply chain and distribution management.”


Health Insurance Claims

An estimated $2.6 billion loss in the United States is attributed to health-care fraud and abuse.6 Experts say blockchain may be able to improve patient, hospital and insurance provider communication, prevent duplicate claims and eliminate the multiple rounds of review required for claims approval.

Notably, in the insurance claim submission and reimbursement process, the patient isn’t included, Dr. Mackey points out. “This opens up the risk of fraud, but blockchain could mitigate that through secure data management and transparency,” he says. His group created a prototype blockchain framework to record claims data and transactions in an immutable format so that the patient could participate as a validating node in their insurance coverage.6 The prototype included consensus algorithms, smart contracts, tokens and governance based on digital identification on Ethereum, a blockchain-powered platform. They reported that their proposed framework would make the claims adjudication process more patient-centric and help to identify and prevent fraud and abuse.

“Theoretically, blockchain creates an auditable data log agreed upon by the parties,” Dr. Mackey says. “CMS audits are one use case for blockchain. If everyone has agreed to a record being written to the blockchain, and it’s validated across multiple parties, and it’s transparent, then you wouldn’t necessarily have to go through a full process of an audit to look for those documents and try to validate billing. 

“Now, a lot of times the people authorizing or validating that information aren’t CMS or a payer, but a payer could come and look at that information,” he continues. “On a blockchain, it can’t be changed and it’s cryptographically hashed. As long as the parties were in good faith, then you have a record that’s much more trustworthy than, say, public records. In our paper, we proposed that the patient come in and also validate the insurance information, so if there’s fraud, the patient would be able to verify whether they got the medical equipment or the prescription that was prescribed. You can do additional validation by adding notes to the blockchain.”


Fighting Counterfeit Drugs

“A supply chain use case basically tracks a product across multiple parties, and everyone involved has a single source of information they can trust about where the product was shipped to and from, and so on,” Dr. Mackey says. 

As you may recall, in February 2012, the American Society of Retina Specialists was notified by Genentech that a counterfeit drug labeled as Avastin had been distributed in the United States by a foreign supplier. Vials of the counterfeit drug had been found in oncology practices in the United States. In the following years, the FDA issued more than 1,000 warning letters to physicians and medical practices as more counterfeit batches were discovered.7

Environmental Impact

“A lot of people talk about the environmental impact of Bitcoin because it uses a consensus algorithm that’s called Proof of Work,” says Tim Mackey, MAS, PhD, a professor at UC San Diego in the Global Health Program and director of the Global Health and Data Policy Institute. “Essentially, this requires a lot of machines to randomly solve problems, and users mine Bitcoin by solving these random mathematical problems.

“However,” he continues, “in most business blockchains, you wouldn’t adopt a Proof-of-Work algorithm. So, if you use a different type of consensus mechanism, the computing power required to do that would probably not be any more than that of cloud computing or anything like that, depending on your type of consensus. There are other much simpler ways of doing consensus. 

“Much of the environmental impact concern relates to cryptocurrencies and financial technologies like FinTech,” he continues. “There are environmental impacts because of the computing time it takes, but those things can be mitigated to a certain extent with just a different design of a blockchain.” 


An outbreak of intraocular inflammation later found to have been caused by endotoxin-contaminated counterfeit bevacizumab was reported in China in 2013.8 In 2015, ophthalmologists reported 15 cases of intraocular inflammation following injections of counterfeit bevacizumab in Gujarat, India. 

The counterfeit drug problem is a very complex social, economic and public-health issue. 

While not a solution in and of itself, blockchain has the potential to shore up the supply chain against counterfeits by acting as an architecture for sharing and validating trustworthy data across multiple parties. 

“The pharmaceutical supply chain has many actors,” Dr. Mackey explains. “We’d like to validate data that’s coming from those different actors and identify where there’s a potential for drug diversion or drug counterfeiting. In a traditional supply-chain model, we could have all of these different parties feeding information into the blockchain. If the parties don’t agree that a trader is providing legitimate information, then that anomaly can be detected quickly. Because of shared information and visibility, blockchain could support much earlier identification of exploitation.

“But when it comes to counterfeit Avastin, there were illegitimate supply chain actors such as online pharmacies or unregistered distributors,” he continues. “It may be harder to detect these types of actors since they’re outside of the controlled supply chain. The Drug Supply Chain Security Act is in place in the United States now, and it requires track-and-trace across the whole supply chain. Blockchain has been explored as one potential technology that could facilitate better implementation of the DSCSA, but it’s not the only one. It’s an additive technology. We’ll still need technology that’s able to detect counterfeits and test them quantitatively through analytical chemistry. We’ll need barcodes and other anti-counterfeiting packaging approaches.”


Clinical Trials

There are several blockchain use cases for clinical trials. Blockchain may make it easier to obtain participant consent and to update consent protocols, for example. “You could use blockchain to recruit patients based upon validated information about their health status and to better match patients to trials regarding inclusion and exclusion criteria,” Dr. Mackey says. “It may expand the pool of potential clinical trial candidates. It may also help to coordinate the different parties involved in clinical trials—whether it be data monitoring, data safety, the board, study sites, the investigators—they’ll all have the validated ledger of every transaction going on. 

“As I noted before, blockchain may disintermediate aspects such as a clinical research organization that currently manages many of these processes,” he says. “There may be less work with blockchain and smart contracts automating some of these processes. We could also have more decentralized or distributed trials—e.g., trials done in a home care setting, not at the site itself. Blockchain would help to validate the information from all those different sources.”


Remote Monitoring

More and more companies are developing remote-monitoring technology, from at-home OCT and IOP monitoring to the many types of wearable tech from giants such as Apple, Google and Samsung. “Blockchain can aggregate and validate data across multiple sources, and that has a lot of potential for decentralized clinical trials,” Dr. Mackey says.  

“Many patients want to access and have ownership over their health data, and potentially share it with other parties outside the closed software systems,” he continues. “Many of these remote patient monitoring devices collect data for clinical trials, but the portability of that data still isn’t there. That portability could potentially be facilitated by blockchain or a digital wallet.”


Artificial Intelligence

Artificial intelligence is poised to shape the future of health care, but it’s somewhat limited by a lack of access to data. “Data privacy laws such as HIPAA and the General Data Protection Regulation prevent proper data sharing and make global collaboration difficult,” Dr. Ting says. “Data could be managed through smart contracts and node authentication. Additionally, privacy-preserving processes such as federated learning could facilitate peer-to-peer sharing.”

Transparency in the development process is another concern that blockchain could address. Dr. Ting says he sometimes has difficulty verifying AI papers he receives as a journal editor because he’s unable to access the original dataset or because some of the development details are in the black box. By preserving each step of development immutably on the blockchain, he says auditing and verifying AI development would be simpler and more transparent.


The Future Landscape

Though it’s a disruptive technology, Dr. Mackey says the impact of blockchain on your clinical practice is something you won’t see. “Hopefully, a lot of the blockchain technology we’re talking about will operate in the background,” he says. “There may also be a wave of consumer health applications that are blockchain-based, where people generate their own health information from wearables and other consumer health information sources. Genomic data is now available to the consumer too, with direct-to-consumer testing.

“So, what you may see in the future is a bifurcation of the market: the clinical blockchain applications you’ll never see that just make things run smoother, versus the consumer health applications,” he concludes. “Blockchain applications could give patients more access to their own data, let them be more active in their health-care decisions and share that data actively or even potentially monetize it. We’ll see how those two areas grow, but these are two likely spaces in health care where we’ll see blockchain emerge.”

1. Kuo T, Kim H, Ohno-Machado L. Blockchain distributed ledger technologies for biomedical and health care applications. J Am Med Inform Assoc 2017;24:6:1211-1220.

2. Yun D, Chen W, Wu X, et al. Blockchain: Chaining digital health to a new era. Annals Transl Med 2020;8:11:696-698.

3. Haleem A, Javaid M, Singh RP, et al. Blockchain technology applications in health care: An overview. Int J Intel Networks 2021;2:130-139.

4. Dwivedi AD, Srivastava G, Dhar S, Singh R. A decentralized privacy-preserving health care blockchain for IoT. Sensors 2019;19:2.

5. Abid A, Cheikhrouhou S, Kallel S, Jmaiel M. NovidChain: Blockchain-based privacy-preserving platform for COVID-19 test/vaccine certificates. Software: Practice & Experience 2021. [Epub May 18, 2021].

6. Mackey TK, Miyachi K, Fung D, Qian S, Short J. Combating health care fraud and abuse: Conceptualization and prototyping study of a blockchain antifraud framework. Journal of Medical Internet Research 2020;22:9:e18623.

7. Mackey TK, Cuomo R, Guerra C, et al. After counterfeit Avastin—What have we learned and what can be done? Nature Rev Clin Oncology 2015;12:302-08.

8. Wang F, Yu S, Chen F, et al. Acute intraocular inflammation caused by endotoxin after intravitreal injection of counterfeit bevacizumab in Shanghai, China. Ophthalmol 2013;120:2:355-61.