FDA LDT Ruling and Spectroscopy Diagnostics: What Changed

If you are building a spectroscopy-based diagnostic test - FTIR pathogen identification, Raman tissue classification, NIR blood analysis - the regulatory ground shifted under your feet in 2025. The FDA tried to bring Laboratory Developed Tests under device regulation. A federal court said no. The FDA rescinded the rule. And now you have a strategic decision to make that will determine your time to market, your addressable market, and your competitive position for the next five years.

This article breaks down what happened, what it means for spectroscopy diagnostics specifically, and how to think about your regulatory strategy in the current environment.

This article is educational and does not constitute legal or regulatory advice - consult qualified regulatory professionals for your specific situation.

What the FDA tried to do

In May 2024, the FDA published a final rule amending 21 CFR § 809.3 to explicitly state that in vitro diagnostic products are devices under the Federal Food, Drug, and Cosmetic Act "including when the manufacturer of these products is a laboratory." That single phrase - nine words - would have pulled approximately 80,000 existing Laboratory Developed Tests across 1,200 laboratories into the FDA's device regulatory framework.

The rule was not a sudden power grab. The FDA had signaled its intent for years, arguing that LDTs had evolved far beyond the simple tests Congress had in mind when it carved out enforcement discretion in the 1970s. Modern LDTs include complex genomic panels, AI-driven classifiers, and multi-analyte algorithms - functionally identical to commercial IVD kits but subject to none of the same oversight.

The phase-in was gradual. Five stages over four years:

Carve-outs existed for rare disease tests, tests approved under New York's Clinical Laboratory Evaluation Program (CLEP), and tests without an FDA-approved equivalent. But the broad trajectory was clear: the era of unregulated LDTs was supposed to end.

What actually happened

The rule never took effect. Here is the timeline:

• May 29, 2024: The American Clinical Laboratory Association (ACLA) and the Association for Molecular Pathology (AMP) filed separate lawsuits in the U.S. District Court for the Eastern District of Texas, challenging the rule as beyond the FDA's statutory authority. The cases were consolidated before Judge Sean D. Jordan.
• June 2024: The Supreme Court decided Loper Bright Enterprises v. Raimondo, ending Chevron deference - the doctrine that had required courts to defer to federal agencies' interpretations of ambiguous statutes. This was devastating for the FDA's position. The LDT rule depended on the FDA's interpretation that "device" in the FD&C Act encompasses laboratory testing services. Without Chevron deference, that interpretation had to survive independent judicial review.
• March 31, 2025: Judge Jordan vacated the rule in its entirety. The ruling held that LDTs are professional medical services, not physical devices in interstate commerce. The methodology laboratory personnel use to evaluate samples - even using reagents and instruments - constitutes a professional service, not a product. Congress vested LDT oversight with CMS under CLIA, not with the FDA.
• May 30, 2025: The FDA and DOJ declined to appeal. The deadline passed without action.
• September 19, 2025: The FDA issued a formal rescission rule, reverting 21 CFR § 809.3 to its pre-2024 language. This was an administrative clean-up confirming the court's judgment, not a voluntary policy change.

The LDT rule is dead. Not dormant, not paused - vacated by a federal court with no appeal.

The current regulatory landscape

With the LDT rule gone, the regulatory framework for laboratory-developed tests has reverted to the status quo that existed before May 2024. Here is what that means in practice.

LDTs: CMS/CLIA oversight only

Laboratory Developed Tests - tests designed, manufactured, and used within a single CLIA-certified laboratory - are regulated by the Centers for Medicare & Medicaid Services under the Clinical Laboratory Improvement Amendments (CLIA). No FDA premarket review is required.

CLIA requires:

• CLIA certification for high-complexity testing (spectroscopy-based diagnostics are high-complexity)
• Qualified personnel - laboratory director (board-certified pathologist or PhD with relevant experience), testing personnel with appropriate education and training
• Quality control - calibration, function checks, maintenance, proficiency testing
• Quality assurance - written policies, procedure manuals, annual review

What CLIA does not require:

• Premarket submission to any federal agency
• Formal clinical validation dossiers
• Adverse event reporting to a federal registry
• Software lifecycle documentation (IEC 62304)

The laboratory validates the test internally and documents that validation per CLIA requirements.

Commercial IVDs: Full FDA oversight

The court's ruling did not change the FDA's authority over commercially marketed IVDs. If you package your spectroscopy diagnostic test as a kit and distribute it to other laboratories or clinical sites, it is a device. Full stop. You need 510(k) clearance, De Novo authorization, or PMA approval before marketing.

The critical boundary is distribution. Same test, same science, same performance - but the moment you sell it to another lab, you cross from CMS/CLIA to FDA jurisdiction.

New York CLEP: The de facto national standard

New York State's Clinical Laboratory Evaluation Program has reviewed LDTs since 1991. Any laboratory that wants to offer its LDT to New York patients - including labs physically located in other states - must obtain CLEP approval. Because New York's patient population is large enough that most commercial labs want access, CLEP has functioned as a de facto national analytical validation standard.

CLEP requires analytical validation data, performance characteristics documentation, proficiency testing verification, and quality systems documentation. It is substantially more rigorous than base CLIA requirements, though less burdensome than an FDA submission.

With the federal LDT rule gone, CLEP remains the most rigorous US LDT validation requirement. If you are planning a spectroscopy LDT with national commercial ambitions, New York CLEP approval is effectively mandatory.

What this means for spectroscopy diagnostics

The rescission creates a strategic opportunity for spectroscopy diagnostic companies that most have not fully processed. Here is the picture.

The LDT path is wide open

A spectroscopy-based diagnostic test - FTIR bacterial identification, Raman tissue classification, NIR analyte quantification - developed and performed within a single CLIA-certified laboratory is an LDT. No FDA submission. No 18-month regulatory timeline. No $250K-500K regulatory program.

You need:

• A CLIA-certified laboratory (your own or a partner's)
• Validated analytical and clinical performance data
• Qualified personnel
• Documented quality systems per CLIA requirements

That is a 3-6 month program, not a 12-24 month program.

This is particularly significant for spectroscopy because the first generation of spectroscopy-based clinical diagnostics is just reaching commercial deployment. FTIR bacterial identification systems (Bruker IR Biotyper) are CE-marked in Europe but have no FDA clearance. Raman-based diagnostics are in SBIR-funded development. The LDT path lets spectroscopy diagnostic companies get to market years before an FDA submission would allow.

The ML model question

If your spectroscopy diagnostic uses a custom ML model - a convolutional neural network for spectral classification, an SVM for pathogen identification, a random forest for tissue typing - the SaMD classification question intersects directly with the LDT decision.

Under the LDT framework: your ML model, running inside your CLIA-certified laboratory, analyzing spectra from your instruments, is part of your LDT. CMS/CLIA does not distinguish between library-search classification and deep learning classification. Both are validated under the same CLIA framework.

Under the FDA framework (if you go commercial): that same ML model makes your software SaMD, triggering IEC 62304 lifecycle requirements, design controls, and a De Novo submission. The regulatory burden increases by an order of magnitude.

This asymmetry is the core strategic insight. The same test, with the same ML model, faces radically different regulatory requirements depending on whether you deploy it as an LDT or a commercial IVD. For spectroscopy startups building AI classification pipelines, this decision should be made before you write your first line of production code.

The instrument is still regulated

The LDT exemption covers the test methodology - your spectral acquisition protocol, your preprocessing pipeline, your classification algorithm. It does not cover the spectrometer itself. Bruker's Alpha II, Horiba's LabRAM, Renishaw's inVia, and Thermo's Nicolet are all commercially marketed devices subject to FDA oversight regardless of how you use them.

This is a feature, not a bug. The instrument manufacturer has already handled the device regulation for the hardware. Your LDT builds on that regulated foundation. When you validate your LDT, you validate the complete system - instrument plus your methodology - but you do not need to re-submit the instrument through the FDA.

Decision framework: LDT vs. 510(k) vs. De Novo

The regulatory path you choose is not just a compliance question. It determines your business model, your addressable market, your timeline, and your competitive positioning. Here is how to think about it.

When to pursue the LDT path

Choose the LDT path when:

• You have access to a CLIA-certified laboratory (your own or a partner's) where the test will be performed
• You want speed to market - CLIA validation can be completed in 3-6 months vs. 12-24 months for FDA
• Your initial market is a single site or small number of sites where you control the laboratory operations
• You are pre-revenue and need to generate clinical data and revenue before investing in FDA regulatory programs
• Your test has no FDA-cleared predicate - meaning the De Novo path (the likely FDA route for novel spectroscopy diagnostics) is the only FDA option, and it is the longest and most expensive submission type

The LDT path is the pragmatic first step for most spectroscopy diagnostic startups. Get the test running clinically, generate revenue, collect real-world performance data, and use that data to fund and inform a subsequent FDA submission if commercial distribution is the long-term goal.

When to pursue FDA clearance (510(k) or De Novo)

Choose the FDA path when:

• You want to distribute the test commercially - sell kits, license software, or deploy across sites you do not operate
• You want broad market access - thousands of laboratories, not the handful you can operate yourself
• You want reimbursement advantages - some commercial payers treat FDA-cleared tests preferentially in coverage decisions
• A predicate device exists - if an FDA-cleared spectroscopy diagnostic exists for your intended use, a 510(k) submission is faster and cheaper than De Novo (currently, few predicates exist for spectroscopy diagnostics)
• Your competitive strategy depends on the regulatory moat - FDA clearance is an expensive barrier that protects market position once achieved

The hybrid approach

For most spectroscopy diagnostic companies, the optimal strategy is sequential:

Phase 1: LDT deployment. Validate and deploy your test in a CLIA-certified laboratory. Start generating clinical data and revenue. Timeline: 3-6 months.

Phase 2: Data collection. Use clinical deployment to collect the performance data, edge cases, and real-world evidence that will strengthen your FDA submission. Timeline: 6-12 months of clinical operation.

Phase 3: FDA submission. Submit for De Novo authorization (or 510(k) if a predicate now exists). You are submitting with real-world clinical data, not just bench studies. Your cash flow from LDT operations funds the regulatory program. Timeline: 12-18 months for submission and review.

Phase 4: Commercial distribution. With FDA authorization, expand beyond your own laboratory to commercial distribution. The clinical workflow software, HL7 integration, and operational processes you built for the LDT deployment transfer directly to the commercial product.

This phased approach is not about avoiding regulation. It is about sequencing your regulatory investment so you have a deployed, revenue-generating product - and real clinical evidence - before you take on the cost and timeline of an FDA submission.

LDT vs. FDA-cleared IVD: Comparison

The legislative horizon

The LDT situation is not permanently settled. Two competing legislative approaches are active in Congress, and spectroscopy diagnostic companies should be tracking both.

The VALID Act (H.R. 3694 / S. 1932)

The Verifying Accurate Leading-edge IVCT Development Act has been reintroduced in the 119th Congress with bipartisan sponsorship. It would create a new statutory category - "in vitro clinical tests" (IVCTs) - giving the FDA explicit authority over both commercial IVDs and LDTs under a unified, risk-based framework.

If the VALID Act passes, the LDT exemption effectively ends. All diagnostic tests, including spectroscopy-based LDTs, would require some form of FDA oversight proportional to their risk classification. The Act includes streamlined pathways for lower-risk tests, but even streamlined FDA pathways are substantially more burdensome than current CLIA-only requirements.

As of mid-2026, the VALID Act has been introduced but has not advanced to committee markup or floor vote. Industry support is divided - device manufacturers favor it, clinical laboratory associations oppose it. Passage is uncertain.

The Enhancing CLIA Act (H.R. 8890)

A competing approach introduced by Rep. Neal Dunn would strengthen CMS/CLIA oversight without involving the FDA. It would establish a national LDT performance database, create a voluntary third-party review pathway for analytical and clinical validation, and build a centralized error reporting system.

This approach is endorsed by ACLA and would keep LDTs firmly in the CMS domain while addressing the legitimate concern that current CLIA requirements do not capture enough performance data for complex modern tests.

What this means for your strategy

Neither bill is likely to pass quickly. Legislative timelines for diagnostic regulation are measured in years, not months. But the direction of travel matters for long-term planning.

If you are deploying an LDT today, you have a window of at least 2-3 years under current rules. Possibly longer. Use that window to get to market, generate clinical evidence, and build the operational infrastructure that will serve you regardless of which legislative framework eventually prevails.

If you are planning for 2028 and beyond, assume that some form of enhanced LDT oversight is likely - whether FDA-based (VALID Act) or CMS-based (Enhancing CLIA Act). Build your quality systems and documentation practices now so that compliance with a future framework is an incremental step, not a ground-up rebuild.

Reimbursement considerations

Regulatory pathway and reimbursement pathway are separate but linked. Here is the practical picture.

Both LDTs and FDA-cleared IVDs bill through the same mechanism: CPT codes reimbursed under CMS's Clinical Laboratory Fee Schedule (CLFS). FDA clearance is not required for Medicare reimbursement. The question is whether it helps.

Where FDA clearance helps with reimbursement:

• Some commercial payers use FDA authorization as a proxy for clinical evidence when making coverage decisions
• Hospital formulary committees may prefer FDA-cleared tests, particularly for newer technologies like spectroscopy-based diagnostics where the clinical evidence base is still developing
• In competitive situations - two tests for the same analyte - the FDA-cleared option has a credibility advantage with payers

Where the LDT path is adequate:

• Medicare/Medicaid coverage is determined by clinical utility, not FDA status
• Established CPT codes (which exist for many spectroscopic analyses) provide a reimbursement pathway regardless of LDT vs. IVD status
• Labs with strong clinical validation data and peer-reviewed publications can obtain coverage for LDTs

For spectroscopy diagnostics specifically, the reimbursement challenge is less about LDT vs. IVD and more about establishing spectroscopy-based tests as clinically valid and medically necessary - regardless of regulatory pathway. CPT codes for spectroscopic analysis exist but are not widely used in clinical settings. Building the evidence base for clinical utility is the higher priority.

What to do now

If you are building a spectroscopy-based diagnostic, here are the concrete next steps.

1. Decide your initial deployment model. Are you deploying in a laboratory you operate (LDT path) or distributing to other sites (FDA path)? This decision drives everything else. For most early-stage spectroscopy diagnostic companies, the answer is LDT first, commercial distribution later.

2. Secure CLIA-certified laboratory access. If you do not already have a CLIA-certified laboratory, identify a partner laboratory or begin the CLIA certification process for your own facility. High-complexity CLIA certification takes 3-6 months.

3. Design your validation protocol. CLIA validation requirements are less prescriptive than FDA requirements, but you still need documented analytical validation (accuracy, precision, sensitivity, specificity, linearity, reportable range) and clinical validation (comparison to reference method). Design the protocol before you start generating data.

4. Build your software with compliance in mind. Even on the LDT path, your clinical workflow software needs 21 CFR Part 11 compliant audit trails (you are in a regulated environment), HIPAA-compliant data handling, and documented operating procedures. If the FDA path is in your future, building IEC 62304 awareness into your development process now saves a painful retrofit later.

5. Track the legislative environment. Monitor the VALID Act and Enhancing CLIA Act progress. Subscribe to ACLA, AMP, and AdvaMed regulatory updates. The rules could change - build your quality systems to be adaptable.

6. Consider New York CLEP early. If your commercial ambitions extend beyond a single laboratory, New York CLEP approval is effectively required for national reach. The CLEP application process takes 3-6 months and requires the same analytical validation data you are generating for CLIA anyway. Start the process early.

The post-rescission environment is the most favorable regulatory climate for spectroscopy diagnostic startups in a decade. The question is not whether to take advantage of it - the question is how fast you can get your test validated, deployed, and generating the clinical evidence that will serve you regardless of what Congress does next. Platforms like SpectraDx can accelerate both the LDT and FDA pathways by providing compliant workflow infrastructure from day one.

For a deeper look at how SaMD classification affects your architectural decisions, and how to build AI classification pipelines that can operate under either regulatory framework, see our companion articles in the SpectraDx technical blog.