Table 1.

Blockchain features that could enable patient-driven interoperability, with examples.

Blockchain Feature	Example of Application to Patient-Driven Interoperability
Digital access rules	Clinical data—stored off-chain or on-chain—is linked to the public key of a patient. The patient can use properties of the blockchain, like smart contracts, to assign access rules for the data. For example, authorizing release to a research patient registry for a fixed period of time.
Data aggregation	A patient connects to different institutional interfaces with institution-specific logins (like a patient portal), and provides that institution with their blockchain public key, along with permission to securely transmit data (or metadata) to the blockchain. Done across multiple institutions, clinical data (or references towards clinical data) can thus be aggregated using the technology.
Data liquidity	Highly time sensitive clinical data—for example, advanced care planning “code status” or medication allergies, can be published on a public blockchain, ensuring ready, liquid access to this information as appropriate.
Patient identity	Patients can manage their public keys—perhaps through a multi-sig wallet or mobile device—and use the public-key infrastructure (PKI) to establish their identity for retrieving clinical data from the blockchain, as well as adding new information (like home monitoring devices). PKI ensures providers and institutions can trust that the patient is generating the data.
Data immutability	Clinical data (or metadata) is securely distributed across multiple entities, ensuring integrity, lowering the risk of loss, and offering an audit trail (in case of malicious actor). Append-only model of blockchain ensures all providers with access to information have complete clinical picture.