Labs don't always control the volume of blood samples they receive. Pediatric collections, ICU patients, or archived biobank specimens often come with strict volume limitations. Balancing these constraints while maintaining the sensitivity and reproducibility of downstream workflows is a key operational challenge.

The problem is particularly acute in RNA-based assays, where input requirements vary widely depending on the assay type and the abundance of the RNA target. For instance, monitoring fusion transcripts such as BCR-ABL or PML-RARA, or running MRD panels for blood cancers, typically relies on blood or bone marrow aspirates. In many of these cases, even securing 500 µL of sample can be difficult. In these workflows, RNA yield and integrity are critical; an underperforming extraction can obscure rare transcripts, distort expression levels, and compromise the reliability of results.

On the other end of the spectrum, transcriptomics workflows such as oncology-focused gene expression profiling typically require at least 1 mL of blood to ensure comprehensive RNA yield and representation. Rare transcript detection, HLA typing, and biomarker discovery protocols may demand up to 2 mL, especially when aiming for robust performance in next-generation sequencing or digital PCR assays.

These input requirements are not arbitrary; they are shaped by both the biology of circulating RNA species and the technical constraints of isolation and detection platforms.

That’s why the RNA extraction step becomes a critical bottleneck. Extraction kits and protocols must therefore be flexible enough to handle a range of input volumes, while still delivering consistent performance in terms of RNA yield, purity, and integrity. 

Cambrian’s RNA extraction platform is engineered for precisely this flexibility, performing reliably across inputs from 200 µL to 2 mL of whole blood.

Integrity across variable input volumes

At the core of the protocol is a dual-chemistry system designed to preserve RNA integrity across all sample volumes. Lysis begins with Reagent R, which inactivates RNases by breaking their disulfide bonds, preventing degradation at the earliest stage. This action is reinforced by guanidinium isothiocyanate (GITC), a chaotrope that denatures proteins and stabilizes RNA throughout the extraction process.

The workflow delivers efficient cell lysis, robust RNase inactivation, and high-purity RNA recovery. A built-in DNase step eliminates genomic DNA, followed by a chaotropic wash that removes protein contaminants and prevents nuclease reactivation. The final elution in an RNA-stabilizing buffer protects transcripts for downstream applications such as qPCR, RNA-seq, or digital PCR.

This scalability has been validated in a comparative analysis of 21 samples. RNA yield increased proportionally with input volume: 0.5 mL of blood produced an average of 2.17 µg, 1 mL yielded 5.64 µg, and 2 mL delivered 9.61 µg. Such predictable performance allows researchers to fine-tune RNA output based on experimental needs, without compromising data quality.

View the full protocol here to see how Cambrian safeguards RNA integrity across any sample size.

What blood input volumes do your workflows demand? Discover how the Cambrian kit fits seamlessly into them here.