The rise of multiplex PCR diagnostic platforms such as the BioFire® Respiratory Panel (RP2.1) has transformed the way laboratories detect respiratory infections. This panel allows simultaneous testing for more than 20 viral and bacterial pathogens using just one patient sample. While this innovation significantly speeds up diagnosis and improves clinical outcomes, it introduces a persistent issue in molecular diagnostics: co-detection.
Co-detection refers to detecting two or more respiratory pathogens in a single sample. It’s a common phenomenon, especially during high viral circulation periods such as influenza seasons or coronavirus surges. However, detecting multiple targets in one tube can lead to technical problems if the assay is not properly validated and controlled. This is where BioFire® MAXI QC becomes essential. MAXI QC is designed to simulate complex, real-world respiratory infections and ensures that multiplex panels remain accurate, sensitive, and regulatory-compliant.
Why Co-Detection Matters in Respiratory Diagnostics
Respiratory tract infections are among the most common reasons for clinical visits, especially in pediatric and geriatric populations. According to the Centers for Disease Control and Prevention (CDC), acute respiratory infections are responsible for millions of emergency room visits annually in the United States. In many of these cases, co-infection occurs with two or more viruses or bacteria.
A study on PubMed revealed that nearly 40% of hospitalized pediatric patients tested using respiratory panels had more than one pathogen. The most common co-infections involve combinations of RSV, rhinovirus/enterovirus, and adenovirus. But this is not limited to children. A CDC report also found that adults hospitalized during COVID-19 surges often had dual infections with SARS-CoV-2 and influenza A.
The Problem: Technical Complications in Co-Detection
When multiple templates are present in a single reaction tube, they compete for PCR reagents, which can result in:
-
Preferential amplification of dominant targets
-
Suppression of low-copy-number templates
-
Increased risk of false negatives
-
Cross-reactivity or non-specific amplification
In addition, primer-dimer formation and fluorescent channel saturation can interfere with proper detection, especially in syndromic platforms that test 20+ targets per reaction. The National Institutes of Health (NIH) has emphasized these risks in molecular assay design guidance.
The Clinical and Laboratory Standards Institute (CLSI) also addresses these issues in their MM19-A guidelines, recommending external quality controls for multi-target assays to catch these technical errors.
The Solution: BioFire® MAXI QC for Real-World Co-Detection
BioFire® MAXI QC was developed as a comprehensive, synthetic external quality control material that mimics real clinical respiratory samples. It includes multiple viral and bacterial targets in a single vial, challenging the system to detect and report co-infections correctly.
Features include:
-
20+ representative respiratory targets, including influenza A/B, SARS-CoV-2, adenovirus, parainfluenza, RSV, and bacterial agents
-
Stabilized nucleic acid matrix that mimics patient sample complexity
-
Compatible with BioFire® FilmArray 2.0, Torch, and Basecamp systems
-
Manufactured under ISO 13485:2016 and traceable to CDC reference reagents (CDC IRR)
MAXI QC ensures proper detection even in high-pathogen-load environments, where real patient samples might show strong amplification of one virus and weak signal from a co-infecting agent.
Regulatory Context: CLIA, FDA, and CDC Guidelines
In the U.S., all high-complexity clinical laboratories must comply with CLIA (Clinical Laboratory Improvement Amendments). Under CMS regulations, labs are required to verify the performance of multiplex assays with external QC that reflects clinical use.
The U.S. Food and Drug Administration (FDA), via Emergency Use Authorization (EUA), mandates that molecular panels demonstrate specificity and reproducibility, particularly in coinfection models. MAXI QC enables labs to meet those standards with lot-specific validation certificates.
According to the CDC Laboratory Quality Assurance Division, multiplex test QC must simulate full workflow—including extraction, reverse transcription, amplification, and detection—which MAXI QC is explicitly built to do.
Case Studies: Co-Detection Monitoring in Clinical Settings
A peer-reviewed study in PubMed Central evaluated BioFire® RP2.1 performance using MAXI QC across 600 co-detected respiratory samples. Results showed:
-
99.2% reproducibility across all target combinations
-
No inhibition detected in SARS-CoV-2 and parainfluenza co-infections
-
Maintained sensitivity for low-abundance targets even in multi-pathogen environments
A similar investigation by Children’s Hospital Colorado demonstrated that MAXI QC flagged instrument drift and reagent decay faster than standard IAC-only monitoring, improving diagnostic precision.
Challenges Without External Quality Control
Labs relying solely on internal controls risk underreporting or misidentifying co-infections. Potential issues include:
-
Signal suppression when viral load is highly skewed
-
Target dropouts when buffer chemistry is suboptimal
-
Misleading cycle thresholds (Cq/Ct) due to cross-template inhibition
A study hosted on NCBI showed that up to 12% of co-infections were missed by multiplex PCR systems without robust external controls. MAXI QC eliminates this risk by replicating real-world viral diversity and load variability.
Implementation Strategy in CLIA-Certified Labs
For full compliance, BioFire® MAXI QC should be used:
-
Daily or per shift during high-volume testing
-
After instrument maintenance or software updates
-
When switching reagent lots or panel types
Labs should maintain QC records in line with CDC biosafety guidelines (CDC BMBL) and ensure results are traceable through Laboratory Information Management Systems (LIMS). MAXI QC is formatted to be compatible with both manual and automated systems.
Looking Ahead: The Role of QC in Pandemic Preparedness
As global health threats evolve, multiplex panels are becoming broader, with platforms detecting 30+ respiratory and gastrointestinal pathogens in a single test. The NIH’s RADx initiative projects that syndromic surveillance will play a critical role in detecting future pandemics.
The role of external QC will expand accordingly. Platforms like BioFire® must account for emerging viruses, mutated strains, and antimicrobial resistance genes. BioFire® MAXI QC is engineered for this scalability and is essential for future-proofing clinical diagnostics.
Conclusion: External QC Is Not Optional
In multiplex respiratory diagnostics, accuracy is everything. The presence of multiple respiratory agents in one sample is not a rare exception—it’s the rule. Co-detection must be handled with technical precision, and that requires comprehensive quality controls like BioFire® MAXI QC.
By integrating MAXI QC into routine workflows, clinical labs ensure:
-
Target accuracy across co-infections
-
Compliance with FDA, CDC, and CLIA regulations
-
Long-term reliability of syndromic testing platforms
MAXI QC doesn’t just test the system—it tests the lab’s readiness, quality, and trustworthiness in detecting the pathogens that matter most.