An ultra-sensitive clinical biomarker assay: quantitation of thymus and activation-regulated chemokine in human plasma

Considerations for Soluble Protein Biomarker Blood Sample Matrix Selection

Blood-based soluble protein biomarkers provide invaluable clinical information about patients and are used as diagnostic, prognostic, and pharmacodynamic markers. The most commonly used blood sample matrices are serum and different types of plasma. In drug development research, the impact of sample matrix selection on successful protein biomarker quantification is sometimes overlooked. The sample matrix for a specific analyte is often chosen based on prior experience or literature searches, without good understanding of the possible effects on analyte quantification. Using a data set of 32 different soluble protein markers measured in matched serum and plasma samples, we examined the differences between serum and plasma and discussed how platelet or immune cell activation can change the quantified concentration of the analyte. We have also reviewed the effect of anticoagulant on analyte quantification. Finally, we provide specific recommendations for biomarker sample matrix selection and propose a systematic and data-driven approach for sample matrix selection. This review is intended to raise awareness of the impact and considerations of sample matrix selection on biomarker quantification.

Stratum Corneum Tape Stripping: Monitoring of Inflammatory Mediators in Atopic Dermatitis Patients Using Topical Therapy

OBJECTIVE

The aim of this study was to explore the tape strip sampling technique in the assessment of stratum corneum levels of inflammatory mediators in a clinical trial setting.

METHODS

Thirty-eight inflammatory mediators were analyzed by a multiplex-assay in the stratum corneum, collected by adhesive tapes before and after 6 weeks of therapy, in mild and moderate atopic dermatitis (AD) patients (n = 90). Treatment was a ceramide- and magnesium-containing emollient.

RESULTS

Twenty-four mediators could quantitatively be determined. The Th2 mediators interleukin (IL)-4, IL-13, CCL2 (monocyte chemotactic protein-1), CCL22 (macrophage-derived chemokine), and CCL17 [thymus and activation-regulated chemokine (TARC)] were significantly decreased after therapy as well as IL-1β, IL-2, IL-8 (CXCL8), IL-10, acute-phase protein serum amyloid A, C-reactive protein, and vascular adhesion molecule-1. The decrease of CCL17 and IL-8 was correlated with the decrease in disease severity in a subgroup of moderate AD individuals.

CONCLUSION

Stratum corneum tape stripping offers a minimally invasive approach for studying local levels of immunomodulatory molecules in the skin. CCL17 (TARC) and IL-8 were found to be the most promising biomarkers of AD and might be useful for investigating the course of skin diseases and the effect of local therapy.

Influence of Pre-Analytical Factors on Thymus- and Activation-Regulated Chemokine Quantitation in Plasma

Thymus- and activation-regulated chemokine (TARC) in serum/plasma associates with the disease activity of atopic dermatitis (AD), and is a promising tool for assessing the response to the treatment of the disease. TARC also exists within platelets, with elevated levels detectable in AD patients. We examined the effects of pre-analytical factors on the quantitation of TARC in human EDTA plasma. TARC levels in platelet-free plasma were significantly lower than those in platelet-containing plasma. After freeze-thaw, TARC levels increased in platelet-containing plasma, but remained unchanged in platelet-free plasma, suggesting TARC was released from the platelets during the freeze-thaw process. In contrast, TARC levels were stable in serum independent of freeze-thaw. These findings underscore the importance of pre-analytical factors to TARC quantitation. Plasma TARC levels should be measured in platelet-free plasma for accurate quantitation. Pre-analytical factors influence the quantitation, interpretation, and implementation of circulating TARC as a biomarker for the development of AD therapeutics.