A FEW WORDS... Explainer on Nu.Q Test (from Ep 5)

* What it is: A plasma-based nucleosome assay used for cancer screening and monitoring in healthy, asymptomatic dogs only.

* What it isn't: A cancer-specific diagnostic test or a substitute for pathology.

* The Goal: It acts as a non-specific biomarker of pathological cell turnover.

* The Origin: Developed with the highly regarded Texas A&M Gastrointestinal Laboratory, the same team that did so much to establish B12, TLI and PLI testing within general practice.

🔬 The Biology: Why Nucleosomes?

* Normal Cells: Usually die via apoptosis; nucleosomes are degraded internally with minimal release into the blood.

* Aggressive Tumors: Often have high necrotic cell death and rapid proliferation.

* The Result: These "leaky" necrotic cells dump DNA-histone complexes (nucleosomes) into the circulation.

📊 Sensitivity Breakdown: Who to Test?

The test is most effective for high-turnover, systemic malignancies.

Circulating nucleosome test sensitivity varies by tumour type and reflects biological behaviour rather than diagnostic accuracy alone.  Tumours with a high degree of necrosis, rapid cell turnover, or early systemic involvement are

more likely to produce detectable circulating nucleosomes.

• Hemangiosarcoma shows the highest sensitivity (≥82%), consistent with its aggressive nature, high necrotic burden, and early systemic disease.

• Lymphoma has a similarly high sensitivity (≥77%), reflecting marked metabolic activity and early systemic effects.

• Histiocytic sarcoma demonstrates moderate sensitivity (≥54%), in keeping with intermediate proliferative and necrotic activity.

• Malignant melanoma (not iridal melanoma) shows variable sensitivity (approximately 45%), which is strongly influenced by tumour site and stage at presentation.

• Soft tissue sarcomas have low sensitivity (≈27%), as they are often localized and exhibit slower cellular turnover.

• Mast cell tumours show the lowest sensitivity (≥20%), likely due to poor systemic release of nucleosomes despite malignant behaviour. 

Clinically, a negative nucleosome result does not exclude neoplasia, particularly for tumour types that are biologically less likely to shed nucleosomes into the circulation.

> ️ Nu.Q® Vet has a 97% specificity, meaning false positives in healthy dogs are rare.

🐕 Case Selection

Don't test indiscriminately! Use a risk-based approach:

* Senior Dogs: Incorporate into annual screening for dogs ≥7-10 years old depending on breed and appropriate communication with owners.

* High-Risk Breeds: Potentially start earlier for Golden Retrievers, Labs, Boxers, GSDs, Rottweilers, and Flat-Coated Retrievers.

* Note: Low-grade/localized tumors like soft tissue sarcomas do not increase nucleosomes, so are not typically detected in this test.

🛑 What if the result is "Moderate"?

A moderate elevation requires vigilance, not an immediate diagnosis.

* Wait: Repeat the test in 2–4 weeks with a strict 24-hour fast.

* Transient Inflammation: Transient Inflammation could resolve and the subsequent test will therefore be negative.

* Investigate: If elevation persists, move to imaging: Thoracic X-rays, Abdominal Ultrasound.

* Budget: ensure the client is well aware of the costs of imaging and sedation, and the potential need for CT if nothing is detected on routine screening in practice.

🐱 Looking Ahead: Feline Nu.Q®

* Historically, feline lymphoma was difficult to detect with this method.

* New for 2026: A feline-specific assay has been reported with improved performance for lymphoma; clinical validation is ongoing.