Lab-developed tests (LDTs) are a vital part of modern diagnostics, allowing clinical laboratories to innovate and adapt to meet specialist patient needs. Each year, approximately 10,000 new LDTs are developed in US alone, building on the latest research insights to deliver fast results and tailored solutions.1
In this post, we’ll explain how LDTs differ from in vitro diagnostic products, why they offer several advantages for some applications, how the regulations are changing and what assay developers should look for in a supplier.
LDTs vs IVDs
An LDT is a diagnostic test that is developed and validated by a single laboratory. As it is created in-house, it can only be used by that lab’s testing service. This is in contrast to an in vitro diagnostic (IVD) product, which is manufactured for broad distribution.
The vast majority of tests ordered in hospitals are IVDs.2 However, LDTs play an important role in filling the gap for specialised diagnostics that can adapt to rare, emerging or complex diseases. If no commercial test is available, it’s vital for clinicians to get reliable results through LDTs.
For rare diseases, it might not be financially feasible to mass-produce an IVD kit. Similarly, at the start of an outbreak of a new virus, LDTs can be developed more quickly than a commercial test.
LDTs also offer a way for innovative approaches to reach clinics. This allows clinicians to take advantage of the latest technology to deliver more valuable insights to the patients in their care.
Because of these different use cases, LDTs and IVDs have been regulated differently. LDTs have previously had much less regulatory oversight, however this has come under scrutiny in major markets like the US and the EU. Below, we’ll go into more detail about how regulators have changed their approach and what this may mean for assay developers.
Advantages and applications of LDTs
LDTs have become a popular tool for many hospitals and diagnostic labs because of the flexibility they can offer. Below, we run through some of the key advantages of LDTs and how they have been used to improve patient care.
Develop new tests quickly and affordably
LDTs can be developed at lower cost, which makes it more feasible to meet the demands for rare disease diagnostics. The cost of gaining FDA approval for an NGS test of a rare childhood genetic condition has been described as “prohibitive”.3
IVDs typically also take much longer to develop before they can be used in the clinic. One group of researchers estimated that a proteomic LDT using mass spectrometry could be developed and validated in weeks, compared to at least two years for development and FDA approval of an equivalent immunoassay.4
During the early stages of the COVID-19 pandemic, LDTs were essential in tracking the rapidly growing outbreak. Just days after the SARS-CoV-2 virus genome was sequenced, labs had developed and validated PCR tests for use as LDTs, providing a vital tool at a time of crisis.
Control of supply chain
Once approved, IVDs are constrained in their ability to change reagents and so users are dependent on the stability of the provider’s supply chain. LDTs are not restricted in the same way and allow developers to avoid being locked into using reagents from a single vendor.
Eric Chow, Associate Professor at UCSF, spoke to us during the pandemic about purposefully choosing to develop LDTs instead of IVDs to have more control over the supply chain.
Discover our range of reagents for qPCR assays, including oligos, extraction kits, enzymes, controls and master mixes.
Tailor to patient groups
LDTs are more easily tailored than IVDs, allowing labs to tweak their design to suit the patient population or research question.
These adjustments can help tests benefit a broader set of patients. For example, with no FDA-approved IVDs for human papillomavirus (HPV) in head and neck cancer, clinical laboratories developed new assays or modified IVDs for cervical cancer to fill this gap in patient care.3
These tests provided valuable prognostic insights and informed treatment decisions for head and neck cancer patients. They also allowed clinical trials to recruit patients for personalised treatment approaches.3
Guide use of novel treatments
Quantifying genetic mutations using qPCR can help to predict and monitor treatment outcomes. For example, LDTs were used to identify the BCR-ABL1 fusion gene in patients with chronic myeloid leukaemia (CML).3
These tests could predict the effectiveness of treatment with the drug imatinib, as well as guide dosage and indicate the need to switch therapies. The LDTs were used for more than 15 years before regulators cleared IVD versions of these tests.3,5 Now, there is a mass-produced digital PCR test available that provides absolute measures of BCR-ABL1 mRNA.
Deliver fast results
LDTs are advantageous when turnaround time is critical to patient management. For example, a mass spectrometry-based LDT can accurately measure levels of immunosuppressants in-house, allowing clinicians to adjust the dosage to avoid organ rejection or toxic side effects.6 This avoids needing to send samples away for testing or rely on less accurate tests.
Adapt to new research
LDTs can be more easily updated to keep up with the latest scientific findings. In fast-moving fields, like epigenetic profiling of cancer cells, LDTs can incorporate new knowledge by adding or changing markers that deliver better performance.
This agility means that LDTs can offer greater complexity and breadth that might not be feasible for IVDs. Specialists can develop LDTs that are cutting-edge or feature a broad panel to detect multiple pathogens or genetic variants. These can be regularly updated as new markers are discovered.
New types of tests that start out as LDTs can evolve to become IVDs. For example, FoundationOne CDx is an NGS device that can identify mutations to select personalised treatments for cancers. This developed from an original LDT to become the first FDA-approved broad companion diagnostic for solid tumours.7
The evolving landscape of regulations
In the US, LDTs have been primarily governed by the Clinical Laboratory Improvement Amendments (CLIA) regulations. These require LDTs to undergo analytical validation, i.e. that they successfully detect the biomarker that they aim to, however they don’t include clinical validation, i.e. the accuracy of identifying a patient’s condition or predisposition.
By contrast, the FDA classify IVDs as medical devices, which have more stringent requirements, including pre-market approval, manufacturing controls and post-approval surveillance of adverse events.
The FDA attempted to bring in rules to regulate LDTs as medical devices that would be phased in from 2025 through 2028. These changes would have introduced many of the same restrictions that are already in place for IVDs. However, a legal challenge blocked the plans for the FDA to have oversight of LDTs, and the FDA updated its regulations accordingly in September 2025.
In the EU, the 2022 IVDR regulation means that labs can only use an LDT (also known as an in-house test or in-house IVD) if there is no equivalent CE-marked (declaration of European conformity) IVD on the market. This is now in place for all new diagnostics, with transition periods for many existing LDTs. After the transition period, EU labs will have to stop offering existing LDTs if an equivalent IVD has become available (unless they get market approval for their LDT to become an IVD).
The two types of tests also come under different ISO standards. Best practices for the quality, safety, performance and documentation of LDTs are described in ISO 5649.
ISO 20916 lays out the standards for designing, conducting and reporting clinical performance studies for IVD devices. It was updated in 2024 to be in line the IVDR requirements. As medical devices, IVDs also come under ISO 13485, which covers quality and safety standards.
What to look for in a supplier
LDT developers need to ensure they have suppliers who are reliable partners. From the initial design through to scaling up reagents, having a trusted supplier will give your assay the best chance of success.
Here are four key factors to consider when choosing a supplier for a qPCR LDT and how LGC Biosearch Technologies™ can help:
- Quick implementation: With our Assay Design and Development team, we take a consultative approach to ensure optimal performance, streamlined validation and quicker development time. We have competitive turnaround times on all products with an early emphasis on manufacturability and scale-up.
- Wide array of products: Being able to easily switch between products with a single supplier makes it simpler to iteratively design your assays for optimal performance. LGC has the most complete qPCR probe chemistries portfolio across the market with BHQ, BHQplus, BHQnova (dual-quenched), MGB, LNA probes, Molecular Beacon and Scorpions Primers. We also supply hundreds of PCR reagents, so you can find the right choice for your setup.
High-quality products: We are the original inventors of the best-in-class BHQ quencher, offering superior pre- and post-sale product support and unparalleled manufacturing expertise. We screen all longmers for template contamination to ensure we never synthesise oligos that could act as false positives. We can also manufacture under ISO 9001 and ISO 13485 requirements.
- Reliable supply: During the COVID-19 pandemic, shortages of reagents limited testing capacity for many labs. LGC Biosearch Technologies has a proven track record of rapidly scaling up production in response to COVID-19, as well as the swine flu pandemic and avian flu. We manufacture our own CPG and phosphoramidites, and this vertical integration means that we can maintain a reliable supply of oligos.
Delivering for patients
LDTs cover a wide range of tests, from basic lab-modified tests to highly sophisticated genome analyses. Many of these tests serve needs that standard IVD products cannot meet, either because the patient population is too small, the science is too new or the customisation required is too great.
LDTs empower clinical labs to innovate and rapidly meet diagnostic needs when off-the-shelf kits fall short. As regulations evolve, laboratories will need to carefully consider compliance on several fronts. Collaborating with experienced industry partners like LGC Biosearch Technologies can help you develop high-quality assays that deliver reliable results.
References
- Food and Drug Administration. Laboratory Developed Tests Regulatory Impact Analysis (Final Rule) https://www.fda.gov/about-fda/economic-impact-analyses-fda-regulations/laboratory-developed-tests-regulatory-impact-analysis-final-rule Accessed 26 August 2025.
- Rychert J, Schmidt RL, Genzen JR (2023) Laboratory-Developed Tests Account for a Small Minority of Tests Ordered in an Academic Hospital System. Am J Clin Pathol 160(3):297-302. doi: 10.1093/ajcp/aqad051
- Kaul KL et al. (2017) The Case for Laboratory Developed Procedures. Academic Pathology 4:2374289517708309 doi: 10.1177/2374289517708309
- Lin Y and Thomas SN (2023) Impact of VALID Act implementation on mass spectrometry-based clinical proteomic laboratory developed tests. J Mass Spectrom Adv Clin Lab 28:30-34 doi: 10.1016/j.jmsacl.2023.02.001
- Shelton DN et al. (2020) Abstract 6483: Performance characteristics of the first FDA-cleared droplet digital PCR (ddPCR) IVD assay for monitoring chronic myelogenous leukemia Cancer Res 80 (16_Supplement): 6483 doi: 10.1158/1538-7445.AM2020-6483
- Budelier MM and Hubbard JA (2023) The regulatory landscape of laboratory developed tests: Past, present, and a perspective on the future. J Mass Spectrom Adv Clin Lab 28:67–69. doi: 10.1016/j.jmsacl.2023.02.008
- Milbury CA et al. (2022) Clinical and analytical validation of FoundationOne®CDx, a comprehensive genomic profiling assay for solid tumors. PLoS One 17(3):e0264138. doi: 10.1371/journal.pone.0264138
