Traditional proteomics is a little like Count Dracula, dependent on blood to fuel its efforts. But researchers aren’t vampires; they can venture into broad daylight in search of other forms of sustenance.

It’s no surprise that plasma and serum are the most common matrices used in proteomic biomarker analysis. Widely collected in clinical trials and biobanks, they reflect systemic biology as the body’s “dumping ground,” gathering proteins from all tissues. Yet, many other sample types beyond blood are teeming with insightful proteins and can be collected more routinely and closer to the site of disease.

Consider urine. Collecting a urine sample requires no needle stick and can be sampled frequently. Since urine comes from the kidneys, it reflects nephropathy or toxicity directly. But there’s a catch: proteins in urine (and other biofluids) are very dilute and require a sensitive assay to detect biologically meaningful targets reliably.

Given the sensitivity limitations of many multiplex protein assays, several of our customers and collaborators have asked whether the attomolar detectability of the NULISA platform can provide deep coverage in what we refer to as alternative sample types. Alamar has systematically evaluated the NULISA platform’s performance in several alternative sample types where superior sensitivity is critical.

Table 1 lists the expected detectability ranges (defined as above the limit of detection in at least 50% of samples) for sample matrices studied so far. Check out the Beyond Blood Tech Note on alternative sample types to delve into the research and pilot studies that inform some of these results.

Table 1. Summary of NULISAseq protein detectability across a broad range of sample types. Note that overall detectability may vary based on the collection method, disease biology, and other variables. For more information about a particular sample type, please email us at support@alamarbio.com.

Beyond blood: collection frequency

While serum and plasma are considered minimally invasive and routinely collected, there are challenges with venipuncture, as well as the transport and storage of vials. Specialized staff and equipment are often necessary, and many individuals are averse to needle sticks. These drawbacks limit the potential of blood-based sampling for conducting trials that include participants from remote locations and for longitudinal studies that involve multiple time points. Unlike cross-sectional studies, longitudinal studies can effectively identify biomarkers associated with early disease that change in response to disease progression or therapy (Hartl et al., 2021). 

Since many alternative sample types can circumvent the challenges of blood draws in a non-invasive manner, they can facilitate aspects of trial design critical to translational biomarker discovery, including:    

• Frequent sampling to monitor disease progression and treatment response in real time.
• Large cohort studies, free from geographic limits or invasive procedures, enable more inclusive and compliant participation, including at-home collections.
• Applications of precision medicine that need repeated, context-specific biomarker measurements.

Trial inclusion and repeat sampling have driven the development of various microsampling devices that capture whole blood and plasma in lieu of traditional blood draws. Since these systems typically gather less than 10 μl of fluid, sensitive proteomics platforms like NULISA are ideal for maximizing the potential of microsampling. Alamar has evaluated several leading microsampling devices, including the Mitra Microsampling device, TelImmune Duo, Capitainer systems, and TASSO+ devices. Both NULISAseq panels showed at least 85% target detectability in these small volumes, with the NULISAseq CNS Disease Panel 120 run in the TASSO+ device topping the list at over 97% detection.

Learn more about NULISA performance in dried blood spots and plasma in this tech note. 

With increased participation and sampling comes increased requirements for sample processing and consistency. Automated proteomic analysis systems facilitate biomarker translation by eliminating human error and reducing hands-on time. NULISA experiments are performed on the automated ARGO HT platform, enabling high-throughput operations where researchers can focus on the data rather than sample prep. The workflow only requires scientific staff to apply specimens to the 96-well panels and load the instrument. Within eight hours, the system automatically generates results (singleplex) or a pooled NGS library ready for sequencing (multiplex).

Beyond blood: proximity to diseased tissue

Samples that are more localized to tissues of interest often contain increased discriminating signals, especially in early stages of disease. Minimally invasive specimens like saliva, urine, nasal swabs, stool, and tear fluid can provide tissue-specific information about immune activity, disease pathology, or severity stratification, either alone or alongside serum or plasma.

Urine provides a more direct insight into kidney function than blood derivatives, as demonstrated in a recent study from Dr. Jamie Lin’s lab at the MD Anderson Cancer Center. Dr. Lin’s team analyzed plasma and urine using the NULISAseq Inflammation Panel 250 to identify biomarkers of acute interstitial nephritis (AIN), a rare but serious kidney injury associated with immune checkpoint therapy. Urine yielded a richer source of differentially expressed proteins than plasma, even though target detectability was 73% in urine compared to 95% in plasma (Long et al., 2025). Read more about how their research discovered a two-protein uremic signature that can distinguish AIN from non-AIN with 94% accuracy in our blog on cancer immunotherapy.

Here’s a summary of additional sample types discussed in the white paper:

• Tear Fluid: Collection methods pioneered at Maastricht University open a window into ocular and neurodegenerative diseases, yielding >70% detectability of NULISAseq CNS Disease Panel 120 biomarkers, including tau and amyloid-beta species linked to Alzheimer’s disease.
• Extracellular Vesicles (EVs): NULISA enables the detection of ultra-low-abundance proteins carried in plasma, CSF-derived, or tissue-specific EVs. CSF EVs from the Ace Alzheimer Center in Barcelona reported greater than 90% coverage of the NULISAseq CNS Disease Panel 120 targets, including hallmark Alzheimer’s markers.
• Saliva & Nasal Swabs: Non-invasive samples in a pilot with Virginia Commonwealth University demonstrated 70%+ detectability of NULISAseq Inflammation Panel 250 biomarkers associated with respiratory and oral diseases, including key low-abundance cytokines.
• Stool: While a challenging matrix for proteomics, host-related proteins offer insight into the gut-brain axis and gastrointestinal health. In a small pilot study with the University of Wisconsin, Madison, several proteins in the NULISAseq Inflammation Panel 250 showed significantly different abundances in patients with Alzheimer’s compared to controls.
• Brain Homogenates: Brain lysates prepared postmortem by the US Department of Veterans Affairs yielded different protein extraction efficiencies depending on the choice of buffer. Consult the tech note to determine the proper buffer-target pairing.

The interstitial and synovial fluids surrounding cells and joints, respectively, offer extensive tissue-specific biomarker information. Indeed, both biofluids achieved over 95% detectability with the NULISAseq Inflammation Panel 250. Promising microsampling technologies aim to make collecting interstitial fluid routine and non-invasive in clinical settings (Jiang et al., 2024).  

Making the most of alternative sample types

Sample types beyond blood can provide additional context for biomarker discovery and utility, and in some cases, simplify collection in a non-invasive manner. Protein signatures of disease progression or therapy response may be amplified in samples that spend their time closer to tissues of interest. Highly sensitive and automated proteomic technologies like NULISA are needed to detect the exceedingly low abundance of biologically relevant targets in these protein-scarce sample types and establish consistent, high-throughput workflows.

We’ve documented much of our experience with alternative sample types in the white paper, which includes a “Tips and Best Practices” section to facilitate your endeavors. To find out how the versatility of NULISA continues to evolve, please write to us at support@alamarbio.com.