What is the FDA UDI System?
The UDI system is designed to provide a standardized way to identify medical devices across all healthcare systems. By scanning a single barcode, hospital inventory systems can immediately verify what the device is, when it was made, and if it has been subject to a recall.
A complete UDI is composed of two distinct parts: the Device Identifier (DI) and the Production Identifier (PI). Together, they form a unified string of data that travels with the device from the manufacturer to the patient.
Device Identifier (DI) vs. Production Identifier (PI)
The Device Identifier (DI) is the mandatory, fixed portion of a UDI. It identifies the specific labeler (manufacturer) and the specific version or model of the device. In the GS1 system, the DI is represented by the Global Trade Item Number (GTIN).
The Production Identifier (PI) is the conditional, variable portion of a UDI. Depending on how the device is manufactured and tracked, the PI may include the lot or batch number, the serial number, the expiration date, and the date of manufacture. Not all devices require all PI attributes.
- DI (Device Identifier): Static GTIN denoting the exact model.
- PI (Production Identifier): Dynamic data like lot number or expiration date.
Decoding GS1 Application Identifiers (AIs)
To pack multiple pieces of information (like a GTIN, lot number, and expiry date) into a single GS1-128 barcode or DataMatrix, the GS1 system uses Application Identifiers (AIs). These are 2 to 4-digit prefixes in parentheses that tell the scanning software exactly what kind of data immediately follows.
For example, the AI (01) always precedes a 14-digit GTIN. The AI (17) precedes an expiration date in YYMMDD format. The AI (10) denotes a lot or batch number, which can be alphanumeric and variable in length. The AI (21) denotes a serial number.
- (01) = Global Trade Item Number (GTIN)
- (10) = Batch / Lot Number
- (17) = Expiration Date (YYMMDD)
- (21) = Serial Number
GUDID Database Submission
Assigning a barcode is only half of the UDI requirement. Manufacturers must also upload the static Device Identifier (DI) information into the FDA's Global Unique Device Identification Database (GUDID).
This public database stores the attributes of the device, such as its MRI safety status, whether it contains latex, and whether it requires sterilization. The GUDID does not store the dynamic PI data (like specific lot numbers), as that changes with every production run.
Frequently asked questions
Do all medical devices require a UDI?
Most do, but there are exemptions. Class I devices often have less stringent requirements, and some highly specialized or custom-made devices may be exempt from UDI labeling entirely.
What barcode formats are acceptable for FDA UDI?
The FDA does not mandate a specific barcode symbology, only an 'automatic identification and data capture' (AIDC) technology. Manufacturers commonly use GS1-128 linear barcodes or GS1 DataMatrix 2D barcodes.
How is the GTIN check digit validated?
Like the SSCC, the 14th digit of a GTIN is a Modulo 10 check digit calculated based on the preceding 13 digits to prevent scanning errors.
Is the UDI required on the device itself?
Direct Part Marking (DPM) is required for devices that are intended to be reused and reprocessed before each use (like surgical instruments), ensuring the identifier survives the sterilization process.