The field of sexually transmitted infection (STI) in vitro diagnostics (IVD) is undergoing rapid evolution.
Advances like multiplex real-time PCR assays and at-home collection kits are shifting testing from centralized labs to near-patient and over-the-counter settings. The FDA’s recent clearance of the first OTC STI diagnostic device underscores this shift, expanding access to screening for pathogens such as Chlamydia trachomatis and Neisseria gonorrhoeae—especially among high-risk and underserved populations.
These developments promise faster diagnosis, reduced stigma, and broader identification of infections. But for new entrants, navigating an FDA clinical trial is non-negotiable. Understanding what regulators expect—and structuring your study accordingly—is key to avoiding delays and bringing safe, effective diagnostics to the patients who need them.
Why Clinical Trial Design Matters More Than Ever
At MDC Associates, we specialize in FDA-regulated clinical trials for in vitro diagnostics. STI studies often involve complex logistics and large enrollment targets, but a well-crafted study can reduce overhead, speed recruitment, and improve regulatory outcomes.
Our team draws on decades of experience across STI programs to help clients build realistic timelines, anticipate regulatory scrutiny, and execute trials that deliver usable data the first time around.
Key Design Considerations for Clinical Trials
1. Specimen Type Selection
Which specimen types will you include in your intended use claim? Common options include urine, vaginal swabs, penile swabs, or a combination. This choice affects not just collection procedures but also study design, subject count, and operational feasibility.
Each type poses unique collection, handling, and recruitment considerations. Making strategic choices early helps streamline site setup, minimize protocol deviations, and ensure your device reflects real-world use cases.
2. Prevalence Realities
Despite strong demand, the prevalence of key STIs in the U.S. remains relatively low.
According to the CDC, recent data shows prevalence rates of:
- Chlamydia trachomatis: 495 cases per 100,000 persons
- Neisseria gonorrhoeae: 179.5 per 100,000
- Syphilis: 61.3 per 100,000
These rates mean you’ll need to be strategic about site selection and patient recruitment. Focus on clinics that serve higher-risk populations and conduct frequent STI testing. Also note: positive specimens from routine testing are often incompatible with FDA trials due to transport media or lab workflows. Build collection strategies that account for this from the start.
3. Drug Resistance Testing
If your IVD detects antimicrobial resistance—especially for Neisseria gonorrhoeae, where resistance is on the rise—you’ll need access to viable isolates. This adds complexity, as most labs now use molecular methods that render cultures nonviable.
You may need to secure resistant strains, adapt collection protocols, and work with reference labs equipped for culture-based testing. Planning for this early helps ensure your resistance claims are backed by valid, verifiable data.
4. Reference Testing Strategy
FDA expects a composite comparator: three FDA-cleared molecular assays, with two used on all specimens and a third as a tiebreaker.
Partner with reference labs experienced in this method well before launch. Early coordination helps avoid batch failures, documentation gaps, and site-level errors that can derail timelines and compromise study quality.
5. Timelines and Study Size
Expect these trials to outlast standard diagnostic studies. IRB and contracting can drag due to the sensitive nature of testing. Enrollment often ranges from 2,500 to 6,000 subjects—especially for low-prevalence targets like T. vaginalis or M. genitalium.
Build in extra time for patient identification, informed consent, and comparator testing. Don’t underestimate the impact of even minor enrollment delays on your submission timeline.
6. Clinical Site Strategy
To hit enrollment goals, you’ll likely need 10 or more active sites. This demands serious coordination across teams, consistent CRA oversight, and rigorous site training.
A strong site management strategy ensures uniform protocol adherence, high-quality data collection, and fewer audit findings—especially when working across multiple health systems or regions.
Partner With MDC Associates on Your STI Diagnostic Program
A strong plan from day one can define the success—or failure—of your IVD. MDC Associates brings over 35 years of hands-on experience in FDA regulatory consulting, trial design, and diagnostic submissions.
Whether you’re developing a professional-use PCR assay or pursuing an over-the-counter clearance, we help de-risk your program and move it forward with clarity and control.
Visit www.mdcassoc.com to learn more, or email bd@mdcassoc.com to schedule a call. Let’s move your STI diagnostic toward clearance—and into the hands of those who need it.
Frequently Asked Questions
A key step is holding a Q-Sub (pre-submission) meeting with FDA to align early on trial protocols, comparator strategies, and data expectations. This not only reduces risk of rework but helps build a regulatory foundation that supports your submission strategy. MDC Associates helps sponsors navigate each step, from Q-Sub planning through final protocol execution.
Products intended for OTC or at-home use must go further—requiring usability and human factors studies to show that untrained users can correctly follow instructions and interpret results. MDC supports clients through both traditional and consumer-facing pathways, helping mitigate risk through early study design and regulatory planning.
MDC Associates routinely supports clients through these early conversations, ensuring that every aspect of the protocol—from specimen handling to comparator assay choice—meets FDA expectations. When executed well, early engagement not only reduces downstream delays but builds reviewer confidence in your regulatory approach.
It’s also essential that your study accurately reflects the test’s intended-use environment, from point-of-care settings to centralized labs. Developers must plan and validate their statistical analysis methods in advance. MDC helps teams build performance strategies that hold up under FDA scrutiny and ensure every data point supports regulatory approval.
FDA will evaluate user-facing elements—such as labeling, packaging, and interpretation tools—with the same rigor as clinical performance metrics. MDC helps developers design these studies to meet human factors standards while supporting broader market adoption. Early collaboration with usability experts can prevent costly revisions and speed time to clearance.
For OTC or resistance-related assays, timelines can be even longer due to added study arms. MDC works closely with sponsors to optimize site selection, ensure startup efficiency, and build realistic schedules. Regular reviews and proactive risk mitigation help avoid last-minute bottlenecks that derail timelines.
Following clearance, you may need to submit post-market data, labeling updates, or surveillance reports depending on the regulatory pathway and FDA feedback. MDC offers ongoing support through this phase, helping clients stay compliant, plan for future updates, and maintain readiness for inspections or audits.
