Case study | From kit discontinuation to an IVDR-ready LDT: securing diagnostic continuity for Legionella testing
What happens when the qPCR diagnostic kit you rely on is discontinued? Discover how a french National Reference Center responded by rapidly developing
a custom Legionella LDT and partnering with us for standardized manufacturing and documentation, supporting ISO 15189 and IVDR requirements.
How to secure diagnostic continuity after a qPCR kit discontinuation?
When a long-used diagnostic kit is suddenly discontinued, the impact can be harsh, especially for reference laboratories with national public health responsibilities.
This was exactly the situation faced by the Legionella National Reference Center (NRC) in Lyon, France, when the supplier of its qPCR kit decided to discontinue the product in July 2022.
A critical challenge for a National Reference Center (NRC) laboratory
For more than a decade, the Legionella NRC had relied on a commercial kit to support routine Legionella detection and nationwide surveillance activities. When the kit was abruptly discontinued, the laboratory had to react quickly to ensure diagnostic continuity, while still complying with ISO 15189 and IVDR requirements for LDTs.
At the same time, the market offered very few qPCR assays capable of detecting all Legionella species, making a directit replacement impossible. Leveraging its strong internal expertise, the NRC therefore decided to set up its own Laboratory-Developed Test (LDT), an in-house diagnostic assay designed and validated within the laboratory.
However, assay development was only the first step. The NRC still needed to validate the LDT for diagnostic use, ensure robust traceability, and standardize reagent formulation in line with ISO 15189 and IVDR Article 5.5 requirements.
Why standardization matters for LDT validation?
Formulating LDT reagents fully in-house can quickly become complex as consistency, documentation, and traceability are critical. For the Legionella NRC, the challenge was not assay design itself, but rather the need to:
- standardize reagent formulation
- simplify day-to-day handling
- secure batch-to-batch consistency
- strengthening documentation to support LDT validation in a diagnostic setting.
To address these challenges, NRC partnered with Eurogentec for its custom qPCR assay preparation service.
How Eurogentec supported the Legionella NRC
Based on the NRC’s specifications, Eurogentec prepared a custom oligonucleotide premix targeting Legionella spp. and an internal control, formulated and dispensed under cleanroom conditions. The service included:
- cleanroom formulation of a custom premix (6 primers + 3 probes)
- robotic dispensing into 8-tube qPCR strips
- centralized, lot-specific documentation & QC
- targeted technical guidance, notably for probe selection
This approach helped standardize production, reduce hands-on time and accelerate LDT validation steps.
Measurable benefits in routine Legionella diagnostics
Switching to Eurogentec’s pre-filled strip format delivered immediate and tangible benefits.
According to Dr. Laetitia Béraud, Biologist in Legionella National Reference Center, the simplified workflow had a direct impact on daily laboratory operations. She first highlighted the ease of use of pre-filled strips:
“The main advantage is the technical easiness.”
By eliminating daily reagent preparation and hands-on mixing, the new format allowed operators to focus on higher-value tasks that are essential in a reference laboratory environment. As Dr. Béraud explained, workflow efficiency is critical for routine diagnostics:
“Routine screening has to be fast and cause no technical issues. The pre-filled strips are easy to use and let our operators spend more time on typing or epidemiological techniques, which are more demanding.”
She also emphasized how documentation and traceability, often complex with fully in-house assays, became significantly easier to manage. Instead of handling primers and probes as separate components replaced at different times, all reagents are now linked to a single strip lot:
“We now change all reagents together with each strip lot. That greatly simplifies reagent follow-up and traceability.”
Standardized cleanroom manufacturing and robotic dispensing further strengthened assay robustness, notably by addressing fluorescence variability between wells, sometimes observed with in-house homogenization. Dr Béraud noted:
“In-house homogenization and distribution can lead to initial fluorescence variability. With pre-filled strips, this issue is resolved.”
Finally, she underlined the importance of responsive technical support throughout assay setup and optimization:
“You provided valuable guidance, notably in selecting the probes. We relied on your expertise, which helped us save time,” she added, highlighting how technical expert support was especially valuable and helped her save time.
From commercial kit discontinuation to long-term LDT optimization
What began as a kit supply disruption ultimately became an opportunity for the Legionella NRC to streamline its diagnostic workflow, strengthen regulatory readiness, and build a scalable custom Legionella testing solution.
Next steps
Encouraged by the success of the first outsourced assay preparation, the NRC is willing to outsource a second primer/probe premix into distinctly labeled pre-filled strips, allowing easy differentiation between assays while maintaining standardized production.
Supporting LDT production with confidence
This case study illustrates how Eurogentec supports diagnostic laboratories in securing testing continuity, simplifying LDT preparation and validation, in line with IVDR requirements. Without compromising flexibility or assay design control.
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