Specimen Procedures
Blood Spot / Dried Blood Spot
DBS Panels for Select Markers — At-Home Collection, Neonatal Screening, and Beyond
Overview
Dried Blood Spot (DBS) testing is a biosampling method where a small volume of blood — typically obtained via a finger or heel prick — is blotted onto specialized filter paper and allowed to dry. This minimally invasive collection method offers significant advantages, particularly for remote or resource-limited settings, as the dried samples are stable and can be easily shipped to an analytical laboratory without the need for refrigeration. Once in the laboratory, a small disc of the saturated paper is punched out, and the blood components are eluted for analysis using methods such as DNA amplification, high-performance liquid chromatography (HPLC), or mass spectrometry.
DBS testing was pioneered by Robert Guthrie in the 1960s for widespread neonatal screening programs, enabling early detection of metabolic diseases like phenylketonuria (PKU) and congenital hypothyroidism. Today, DBS applications have expanded dramatically to include infectious disease diagnostics, therapeutic drug monitoring, nutritional assessments, and emerging biomarkers for chronic disease. The convenience of at-home collection kits, which allow individuals to collect their own samples and mail them to a lab, has made DBS a cornerstone of direct-access testing models.
Clinical Rationale
DBS testing plays a crucial role in identifying various conditions, deficiencies, and health patterns, primarily due to its ease of collection and sample stability. Beyond neonatal screening, DBS is increasingly utilized for infectious disease diagnostics — including HIV, hepatitis B, and hepatitis C — especially in regions with limited healthcare infrastructure. It aids in monitoring viral loads and antibody responses in resource-constrained settings where cold-chain logistics are impractical.
Furthermore, DBS is valuable in therapeutic drug monitoring (TDM), pharmacokinetic studies, and clinical trials, offering a convenient way to track drug levels and patient responses. Emerging applications include screening for Alzheimer's disease biomarkers (particularly phosphorylated tau), cardiovascular-kidney-metabolic health markers, and various nutritional deficiencies, expanding its utility in preventive and personalized medicine.
Key Biomarkers
| Biomarker | Clinical Application |
|---|---|
| PKU markers (phenylalanine) | Neonatal screening for phenylketonuria |
| Thyroid-stimulating hormone (TSH) | Congenital hypothyroidism screening in newborns |
| Hemoglobin variants | Sickle cell disorders and hemoglobinopathy screening |
| Vitamin D (25-OH) | Assessment of vitamin D status |
| Estrogen and Testosterone | Hormone level monitoring in direct-access testing contexts |
| Cortisol | Adrenal function and stress hormone assessment |
| Lipids (cholesterol, triglycerides) | Cardiovascular risk assessment |
| C-reactive protein (CRP) | Inflammatory marker assessment |
| Glycosylated hemoglobin (HbA1c) | Diabetes monitoring and glycemic control |
| HIV viral load and antibodies | HIV diagnosis and treatment monitoring |
| Hepatitis B and C markers | Hepatitis diagnosis and monitoring |
| Phosphorylated tau at amino acid 217 (p-tau217) | Early and accurate Alzheimer's disease biomarker |
| Therapeutic drug levels | Monitoring of medications including immunosuppressants and antiretrovirals |
Evidence Base
Smit et al. (2014) in PLoS Neglected Tropical Diseases highlighted the utility of filter paper, including DBS, in diagnosing infectious diseases, particularly in resource-limited settings, due to ease of collection, transport, and storage. Lehmann et al. (2013) in Clinical Chemistry and Laboratory Medicine discussed the historical and current applications of DBS in clinical chemistry, especially for neonatal screening, and its potential for future applications with advanced analytical methods.
Vojnov et al. (2022) in a systematic review and meta-analysis in PLoS Medicine evaluated the diagnostic accuracy of DBS for HIV-1 viral load testing, concluding that DBS is a reliable alternative to plasma for monitoring HIV patients, especially in resource-limited settings. Holroyd et al. (2022) demonstrated that DBS is a reliable method for diagnosing neonatal conditions, supporting its continued use in newborn screening programs. Palmqvist et al. (2024) in JAMA Neurology demonstrated that a blood-based test using DBS for phosphorylated tau at amino acid 217 (p-tau217) can accurately identify Alzheimer's disease, offering a less invasive and more accessible diagnostic tool.
Limitations and Caveats
DBS samples can be affected by hematocrit levels, as the spreading and drying of blood on filter paper is influenced by the proportion of red blood cells to plasma. High hematocrit can lead to underestimation of analyte concentrations, while low hematocrit can lead to overestimation. This variability can introduce systematic errors in quantitative analyses, particularly for analytes that are unevenly distributed between red blood cells and plasma.
The small sample volume inherent to DBS collection can be a limiting factor for certain analyses, particularly those requiring high sensitivity or multiple analyte measurements. Contamination during collection — such as from environmental factors or improper handling — can compromise sample integrity. Additionally, the stability of analytes in DBS samples can vary; while many analytes are stable for extended periods when stored correctly, some may degrade over time, especially under suboptimal storage conditions (high temperature or humidity). Standardization of DBS collection and processing protocols across different laboratories remains an ongoing challenge.
Clinical Note