How collection works
Dec 23, 2025
How Does the Collection Work?
The Rythm at-home collection kit is designed so that a simple process performed at home produces blood samples that can be tested using the same clinical laboratory methods as traditional blood draws. Every component of the kit supports the pre-analytical phase of testing, which is the stage where most laboratory variability is introduced if not carefully controlled.
If you are only looking for step-by-step instructions, you can watch our collection video here. This article explains why each step exists and how the system preserves laboratory-quality data.
Overview of the Collection Process
Before diving into the details, here is the full process at a glance:
You warm the upper arm to increase capillary blood flow.
You clean and dry the skin to reduce contamination and improve device adhesion.
You apply and activate the Tasso+ device for controlled capillary blood collection.
You cap and protect the sample for transport.
You apply gauze and a bandage to support healing.
Each step is designed to reduce pre-analytical variability before your sample ever reaches a laboratory analyzer.
Warming the Collection Site
The Sodium Acetate Phase-Change Heat Pack
Before collection, you warm the upper arm using a reusable click-to-heat pack. Warming increases superficial blood flow through local vasodilation, which improves capillary filling and user comfort. It also reduces the likelihood of incomplete collection.
These heat packs rely on a reversible physical phase change. Inside the sealed pouch is a supersaturated solution of sodium acetate trihydrate. When the internal metal disc is flexed, microscopic disruptions trigger crystallization. As the crystal lattice forms, latent heat is released and the temperature stabilizes within a narrow range.
The temperature plateau is self-limiting and designed for safe skin contact. Because this is a physical phase change rather than a consumptive chemical reaction, the pack can be reused repeatedly by boiling until the crystals dissolve and allowing the solution to cool undisturbed.
For collection purposes, warming improves microcirculation, increases the total capillary volume available to the device, improves filling efficiency, and enhances comfort.
Expert depth
Local warming has long been used in capillary sampling to increase blood flow and reduce failed collections. Improved perfusion reduces reliance on prolonged collection times and helps maintain consistent plasma composition.
Preparing the Skin
The Alcohol Wipe
The isopropyl alcohol wipe reduces microbial load on the skin, removes oils and topical residues, and improves adhesion of the collection device. Adhesion quality directly affects the integrity of the vacuum seal required for efficient capillary filling.
It is important to allow the alcohol to dry completely. This reduces stinging, avoids dilution of the first microvolume of blood, and improves adhesive performance. Letting the alcohol dry fully is one of the most important steps for a successful collection.
Collecting the Blood
The Tasso+ Device
The Tasso+ device is the primary collection instrument used in the Rythm kit. It is an FDA-cleared Class II medical device under the 510(k) pathway for single-use blood lancets with integrated sharps-injury-prevention features¹.
The device functions through a controlled sequence:
The warmed and cleaned upper arm is prepared, and the device is adhered using a medical-grade adhesive.
The adhesive ring creates a closed environment required for consistent vacuum action.
When activated, a sterile lancet performs a rapid dermal puncture and retracts immediately into a protected chamber.
Negative pressure draws capillary blood into the attached microtube.
Collection continues until the intended volume or recommended time is reached.
The filled tube is detached, capped, and prepared for transport.
This design is associated with higher sample volumes than traditional fingerstick methods and is designed to minimize manual pressure, which can introduce interstitial fluid and hemolysis. In multiple published studies, most users report lower perceived pain compared to fingerstick or venipuncture, with high acceptability across age groups² ³ ⁴ ⁵.
Expert depth
Vacuum-assisted capillary collection reduces operator-dependent variability. Immediate lancet retraction and enclosed collection reduce hemolysis risk relative to repeated squeezing or milking techniques used in fingerstick sampling.
The Collection Tube
Lithium Heparin Microtubes
Rythm uses lithium heparin microtubes for biochemical testing. Lithium heparin prevents coagulation by inhibiting thrombin and related enzymes without strongly chelating calcium or magnesium, preserving biochemical fidelity across many analytes.
Lithium heparin plasma is suitable for metabolic panels, liver function testing, inflammation markers, and many hormone assays. It is also well suited for short-term ambient transport when properly validated.
Studies of Tasso-collected capillary plasma show strong agreement with venous lithium heparin plasma or serum specimens across multiple assay categories⁴ ⁶.
Expert depth
Compared with EDTA or citrate, lithium heparin allows broader compatibility with routine chemistry assays and avoids dilutional effects. Its stability profile supports overnight shipping for selected analytes when validated.
Gauze and Bandage
Supporting Normal Healing
After device removal, gauze is applied briefly to support hemostasis through platelet plug formation. A bandage protects the site from friction, sweat, and environmental exposure, supporting rapid and uncomplicated healing.
Protecting the Sample
The Rigid Travel Tube
After collection, the microtube is placed in a rigid travel container. While microcollection tubes are robust in clinical settings, they are not designed for the mechanical stresses of automated mail systems.
Mail transport exposes samples to compression, vibration, torsion, and impact forces. The rigid container acts as a protective exoskeleton, reducing the risk of microfractures, cap displacement, and anticoagulant ratio disruption. This step helps reduce pre-analytical variability before the sample reaches the laboratory.
Expert depth
Mechanical stress during transport is a known contributor to sample degradation. Physical protection reduces the risk of leaks, clotting artifacts, and hemolysis during shipment.
Scientific Validation
Capillary Versus Venous Equivalence
A growing body of peer-reviewed literature demonstrates that capillary blood collected using Tasso devices produces laboratory results comparable to venous sampling for many routine analytes⁴ ⁶.
A recent systematic review and meta-analysis comparing self-collected capillary blood with venous sampling found that laboratory results were largely concordant, and pain perception was generally lower with capillary self-collection⁷.
SARS-CoV-2 Serology
In paired sample studies using Tasso-SST devices, capillary and venous samples showed high quantitative and qualitative concordance for anti-SARS-CoV-2 IgG antibodies measured by ELISA⁴ ⁸. A large independent cohort study using unsupervised home collection reported success rates above 90 percent and excellent agreement between capillary and venous samples, even under simulated shipping stress conditions⁴.
High-Throughput Proteomics
In a pilot study using the Olink inflammation panel, capillary samples collected with Tasso+ showed acceptable correlation with matched venous samples when processed promptly. Longer processing delays increased variability, highlighting the importance of validated logistics for proteomic workflows⁹.
Chemistry and Liver Enzymes
Published studies show that capillary blood collected with Tasso devices performs comparably to venous samples for general chemistry, liver enzymes, and serologic testing¹⁰.
Expert depth
While evidence supports equivalence for many routine clinical assays, peer-reviewed pharmacokinetic validation for therapeutic drug monitoring remains limited. Rythm offers only assays with established analytical and pre-analytical validity under these collection conditions.
Bringing It All Together
You warm the arm to increase blood flow and comfort.
You clean and dry the skin to reduce contamination and improve adhesion.
You collect capillary blood using a controlled, vacuum-assisted device.
You protect the sample from mechanical stress during shipping.
You support normal healing at the collection site.
Each step is intentionally designed to preserve pre-analytical integrity so that the laboratory measures biology rather than collection artifacts. The result is an at-home collection system that produces laboratory-grade data suitable for validated clinical testing.
Related articles:
What Happens to Your Sample After You Mail It
How Rythm Runs a Full Clinical Panel With So Little Blood
References
FDA. 510(k) Premarket Notification for Single-Use Blood Lancet With an Integral Sharps Injury Prevention Feature (K221131). 2022.
Dasari H, Smyrnova A, Leng J, Ducharme FM. Feasibility, acceptability, and safety of a novel device for self-collecting capillary blood samples. PLoS ONE. 2024;19(5):e0304155.
Schröder D, Behrens E, et al. Pain and feasibility of capillary self-blood collection using the Tasso+ upper-arm device. Primary Health Care Research & Development. 2025.
Hendelman T, Chaudhary A, LeClair AC, et al. Self-collection of capillary blood using Tasso-SST devices for anti-SARS-CoV-2 IgG testing. PLoS ONE. 2021;16(9):e0255841.
Schmetzer C, Vogt E, Stellar L, et al. Self-collection of capillary blood and saliva for COVID-19 vaccine immunogenicity. Frontiers in Public Health. 2022;10:994770.
Applied Clinical Trials Online. At-home self-collection of blood specimens for safety lab testing via the Tasso+ device. 2023.
Comparison of laboratory results and pain perception in self-sampled capillary versus venous blood: a systematic review and meta-analysis. Clinical Biochemistry. 2025;138:110965.
Hendelman T, Chaudhary A, LeClair AC, et al. Comparison of capillary blood self-collection with venous phlebotomy for SARS-CoV-2 antibody measurement. Journal of Immunological Methods. 2023;520:113523.
El-Sabawi B, Huang S, Tanriverdi K, et al. Capillary blood self-collection for high-throughput proteomics. Proteomics. 2024;24(3–4):e2300607.
Maselli DJ, Hendelman T, et al. Standard venipuncture versus capillary blood collection for the prospective determination of abnormal liver chemistry. Journal of Applied Laboratory Medicine. 2023;8(3):535–550.