Background:
; External Quality Assessment (EQA) for myelogram interpretation traditionally relies on the distribution of physical slides, which poses significant logistical challenges when large numbers of laboratories are involved. At Sciensano, a strategic decision was made to transition to virtual samples for the myelogram EQA programme.

Objective:
; To describe Sciensano’s workflow for preparing virtual myelogram samples and to present the final digital format delivered to participants.

Methods:
; Clinical cases and corresponding smears are provided by external experts, as Sciensano is not a hospital. Slide scanning is performed in‑house using an Olympus VS120 microscope. Multiple MGG staining protocols and microscope settings were evaluated to obtain optimal image quality. The microscope software generates proprietary image files and allows JPG export, but with a 2‑GB limit—insufficient for whole‑slide images that may exceed 100 GB and result in quality loss due to compression. To preserve full resolution and compatibility with image‑processing software, raw image files were extracted and used for further processing.

Images were then prepared for integration into a portable application. Three types of images are provided to participants:

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1. a large blood smear image,
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2. a gallery of white blood cells for indicative differential counting,
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3. a large bone marrow smear image for diagnostic orientation.
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Results:
; The application displays clinical information, complete blood count data, and high‑resolution smear images with full zoom functionality. Participants may perform indicative counts on blood and marrow smears; only blast percentage is considered for evaluation when relevant to the diagnosis. Additional tests (e.g., Perls staining, lymph node cytology) are included when appropriate. Participants can print their results and submit them through Sciensano’s web platform.

Conclusion:
; Sciensano successfully implemented a fully digital workflow for myelogram EQA, enabling high‑quality virtual slide distribution without the logistical constraints of physical slide shipment. This approach supports consistent diagnostic evaluation while improving accessibility for participating laboratories.