Post-collection processing

What Happens to Your Sample After You Mail It: Stability, Shipping Logistics, and The Science Behind Fast, Reliable Results

When you collect a sample using Rythm’s kit, an enormous amount of biochemical and logistical engineering is activated behind the scenes to make sure your results are accurate, stable, and delivered in less than 7 days. What most people never see is that the pre-analytical phase, meaning everything that happens before your blood reaches the instrument, is the most important determinant of test reliability.

This article explains how we protect your sample’s stability, how shipping and temperature exposure are managed across clinical diagnostics, why chain-of-custody matters, and what conditions can cause a laboratory specimen to be rejected. The work that happens between collection and analysis is invisible to most people, but it is the foundation of laboratory accuracy.

Sample Stability, The Science of Keeping Blood Analytes Intact

Once blood leaves the body, it begins to undergo predictable biochemical changes. Enzymatic reactions continue, cells consume glucose, gases diffuse, metabolites shift, proteins degrade, and in the wrong conditions, hemolysis or clot formation can occur. None of this is unique to at-home testing, it is true for every blood sample collected in healthcare settings.

Rythm Health uses lithium heparin microtubes, which inhibit coagulation rapidly without strong chelation of divalent cations. This anticoagulant choice is critical because it reduces clot formation during transport, stabilizes many chemistry analytes that are sensitive to delayed processing, and minimizes additive-related interference.

Most importantly, we intentionally selected a panel of biomarkers with stability windows that cover up to 4 days for this panel, even without refrigeration or centrifugation. This design choice supports the realities of overnight shipping and protects against minor transit delays. Many traditional laboratories and clinics also ship their samples, often over long distances, and this method is standard practice throughout clinical diagnostics. With Rythm, your sample is protected, stable, and ready for precise analysis.

How Traditional Clinical Laboratories Transport Samples

Consumers often imagine that walk-in collection centers process blood on site. In reality, very few clinical laboratories analyze specimens in the same building where they are collected. After a venipuncture, specimens are placed into temperature-buffered containers, leave the draw site in scheduled courier pickups, move through regional hubs, and often travel overnight. Final analysis may occur 12 to 24 hours after collection.

This pipeline is similar to at-home testing workflows. The only difference is where the sample begins its journey. In one case it originates from a collection center, and in the other it originates from your home.

All clinical diagnostics depend on safe, rapid transport. Shipping blood is normal and expected in this industry. The key is managing temperature, anticoagulation, and time. These variables are integrated into the Rythm system.

Full Chain-of-Custody, Tracking Your Sample at Every Stage

One of the unique advantages of the Rythm Health system is its complete internal chain-of-custody. Because we own the entire operational pathway, from warehouse to clinical laboratory, your sample never leaves our oversight.

This structure allows us to scan and track each specimen at every transition point. Kits are scanned when they leave our warehouse, we know when they are delivered, we receive automated updates when your sample is checked into the FedEx system, and we verify when it arrives at our laboratory. All steps are timestamped and continuously monitored.

Just as important, we communicate with you throughout this process. Clients receive text message updates that report every major event, including when the kit ships, when it arrives, when the collected sample re-enters the shipping network, when it reaches our laboratory, and when results are ready. This level of transparency allows you to know exactly where your specimen is and what is happening to it at each stage.

This closed-loop visibility is uncommon in traditional laboratory systems, which often involve third-party collection centers, separate courier services, and independent laboratory facilities. Our internal chain-of-custody ensures that we know where your sample is at all times, whether it has encountered delays, and whether it has arrived safely within validated stability windows.

Temperature Sensitivity, Why All Blood Samples Require Careful Handling

Blood is biologically active, and many analytes are sensitive to environmental conditions. High temperatures can accelerate cellular metabolism, enzymatic degradation, or red-cell fragility. Freezing temperatures can cause structural damage and immediate hemolysis.

These vulnerabilities apply to all clinical testing. Every major laboratory occasionally receives samples that are overheated or frozen during transport, especially during seasonal temperature extremes. Rejecting temperature-compromised samples is a standard and necessary part of clinical laboratory practice.

Rythm mitigates these risks through packaging designed to buffer thermal variation, overnight express shipping, and internal monitoring of transit duration. All samples are inspected upon arrival for visible signs of heat or freeze exposure. The goal is to shorten the pre-analytical window as much as possible, which is the most important factor in preserving analyte integrity.

Hemolysis, A Common Pre-Analytical Challenge in All Blood Collection Methods

Hemolysis occurs when red blood cells break apart, releasing hemoglobin and intracellular components into the plasma. Hemolyzed samples can interfere with measurements of many different analytes, and for that reason, we will reject any hemolyzed sample.

Hemolysis may occur due to traumatic venipuncture, prolonged tourniquet application, vigorous tube mixing, excessive squeezing of fingersticks, or exposure to extreme temperatures. These factors can affect both venous and capillary collection methods.⁴ ⁵ ⁶

The Tasso+ device minimizes many of these risks because it uses vacuum-assisted upper-arm capillary flow rather than manual squeezing, which is a common source of hemolysis in traditional fingerstick methods. Even so, no collection method is entirely immune, which is why rapid transit and careful handling remain essential to pre-analytical quality.

Other Reasons Clinical Samples May Be Rejected

Every clinical laboratory, whether hospital-based, independent, or at-home, occasionally receives samples that cannot be analyzed. Rejection criteria protect assay validity and are part of maintaining clinical accuracy.

Lipemia
Lipemia results from high concentrations of lipids in the plasma. It causes turbidity that interferes with spectrophotometric and enzymatic assays. It can occur after high-fat meals or in individuals with significant hyperlipidemia.

Insufficient Volume
Automated analyzers require specific minimum volumes. Tasso+ typically yields adequate sample volume, but in rare cases the volume may be insufficient for all assays.

Clotting
Even small clots can obstruct analyzer probes. Lithium heparin reduces this risk but does not eliminate it fully.

Tube Damage or Leakage
Any breach in the primary container results in mandatory rejection for safety and analytical reasons. Rythm’s protective 3D-printed travel tube significantly lowers this risk.

Contamination
Contamination from environmental sources or improper sealing can compromise the sample. Rythm’s collection workflow is designed to minimize this possibility.

These rejection criteria are essential for ensuring that all results are scientifically sound.

Bringing It All Together; How Rythm Delivers Results in Less Than 7 Days

Your sample follows a carefully engineered sequence.

Day 1 to 3, Kit Shipment and Arrival
The kit is shipped via express delivery and arrives quickly.

Day 3 to 4, Collection and Overnight Return
After collection with the Tasso+ device and lithium heparin tube, the specimen is packaged and shipped overnight to our laboratory.

Day 4 to 5, Laboratory Intake and Processing
The sample is received, accessioned, and prepared for analysis.

Day 5 to 7, Analysis and Reporting
Results are generated, reviewed, released, and posted to your dashboard, usually well within seven days.

Because Rythm owns the entire pipeline, your specimen passes through fewer hands, faces fewer delays, and experiences less pre-analytical variability. The outcome is a tightly controlled process that supports accurate and timely results.

References on Pre-Analytical Laboratory Standards

1. Clinical and Laboratory Standards Institute. Procedures for the Handling and Processing of Blood Specimens for Common Laboratory Tests (GP44). Clinical and Laboratory Standards Institute; 2010.

2. Clinical and Laboratory Standards Institute. Collection of Diagnostic Venous Blood Specimens (GP41). Clinical and Laboratory Standards Institute; 2007.

3. Clinical and Laboratory Standards Institute. Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture (H3-A6). Clinical and Laboratory Standards Institute; 2007.

4. College of American Pathologists. Laboratory Accreditation Program Checklists. College of American Pathologists; accessed October 2025.

5. World Health Organization. WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. World Health Organization; 2010.

6. Rifai N, Horvath AR, Wittwer CT, editors. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018.

7. Centers for Disease Control and Prevention. Clinical Laboratory Best Practices for Specimen Handling and Processing. Centers for Disease Control and Prevention; accessed October 2025.

8. International Federation of Clinical Chemistry and Laboratory Medicine. Pre-analytical Phase Education Resources. International Federation of Clinical Chemistry and Laboratory Medicine; accessed October 2025.