甚麼是Basic-UDI-DI?
在2017/745 Annex VI, Part C中，關於Basic UDI-DI的定義如下：
The Basic UDI-DI is the primary identifier of a device model. It is the DI assigned at the level of the device unit of use. It is the main key for records in the UDI database and is referenced in relevant certificates and EU declarations of conformity.
不同於UDI-DI的性質為GTIN (Global Trade Item Number, 全球交易品項識別碼)，Basic UDI-DI的性質為GMN (Global Model Number，全球型號編碼)，其主要用途為「定義產品型號」，在MDR的管理系統中，Basic UDI-DI有以下的關鍵角色：
1. 產品在EUDAMED上註冊的單位
2. 指定機構(NB)評估抽樣和發證的單位
3. 授權代表(AR)管理產品項目的單位
在MDCG 2018-1 Rev. 4中，又再次對Basic UDI-DI的定義進行闡述：
The Basic UDI-DI is the main key in the database and relevant documentation (e.g. certificates, declaration of conformity, technical documentation and summary of safety and clinical performance) to connect devices with same intended purpose, risk class and essential design and manufacturing characteristics. It is independent/separate from the packaging/labelling of the device and it does not appear on any trade item. Any Basic UDI-DI shall identify the devices covered by that Basic UDI-DI in a unique manner.
從上述文字我們可以獲得以下資訊：
1. Basic UDI-DI應在證書、DoC、技術文件(TD)、SSCP上出現，並利用同樣的Basic UDI-DI將其串聯起來以進行追溯
2. 一個Basic UDI-DI可串聯的器材(device)，應該有相同的預期用途(Intended purpose)、同樣的風險等級以及同樣的基本設計(Essential Design)與製造特徵(Manufacturer Character)
3. Basic UDI-DI和UDI-DI是不同的，他不會出現在任何交易品項上
4. 每一個Basic UDI-DI都應該要定義其包含哪些器材
MDCG 2018-1 Rev. 4同時也進一步提示了Basic UDI-DI與證書和DoC之間的連結：
In accordance with Annex XII of the medical device Regulations, the scope of the certificates shall unambiguously identify the device or devices covered. The scope of EU technical documentation assessment certificates, EU type-examination certificates and EU product verification certificates shall include, together with the Basic UDI-DI, a clear identification, including the name, model and type, of the device or devices, the intended purpose, as included by the manufacturer in the instructions for use and in relation to which the device has been assessed in the conformity assessment procedure and the risk classification.
Each of the abovementioned certificates shall identify and cover all devices associated with the same Basic UDI-DI, that is referred to in that certificate. The association between different Basic UDI-DIs, where applicable, shall be identified through the technical dossiers.
In accordance with Annex IV of the two Regulations, the declaration of conformity shall contain the Basic UDI-DI and the product and trade name, product code, catalogue number or other unambiguous reference allowing identification and traceability of the device covered by the EU declaration of conformity.
不管是TD評估、形式檢驗或是產品驗證的證書，上面都應該要有Basic UDI-DI以及其明確的定義，包括名稱、型號或類別、預期用途、經過評核的IFU、風險等級等。
這些證書都應該要定義並涵蓋其提及的同一個Basic UDI-DI下的所有產品，如果有不同的Basic UDI-DI，就要在技術檔案中定義。
2017/745及2017/746的Annex IV都說明了DoC應呈現的內容，包含Basic UDI-DI、產品或商品名、分類號、目錄號或其他可以明確分類或追溯DoC上所提產品的明確參考。
後續在EUDAMED上登錄產品時，Basic UDI-DI也會是產品登錄及上傳相關上市後資訊的單位。
