Cold-chain handling: when temperature matters, and when it doesn't
Many hereditary-cancer samples ship at ambient temperature on purpose. Knowing which specimens are stabiliser-protected versus genuinely cold-dependent — and how to package, monitor, and read a temperature excursion — is the difference between a usable sample and a recollection.
Why this matters before you reach for an ice pack
Cold chain is a means, not a goal. The goal is delivering nucleic acid to the laboratory at a quality sufficient for the assay — a multi-gene panel, a single-gene BRCA1/BRCA2 test, or whole-exome sequencing. Some collection systems achieve that with a chemical preservative and need no refrigeration at all; others rely on temperature to hold degradation in check. Reaching for dry ice when the kit was designed for ambient transport can be wasteful, and occasionally harmful: freezing a tube formulated for room temperature can crack it or compromise the matrix.
This page explains the two regimes — stabiliser-protected ambient and cold-dependent — and the monitoring and packaging that distinguish a controlled shipment from a hopeful one. It is an educational explainer, not medical or regulatory advice; confirm requirements with your laboratory's specimen-requirements sheet and a qualified courier for any clinical sample.
The handling decision, swab to sequencer
A short workflow for deciding whether a given specimen needs cold chain.
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1 — Identify the matrix and preservative
Saliva in a chemical-lysis kit (e.g.
OG-500/OGR-500), a dry buccal swab, or whole blood in anEDTAtube each behave differently. The preservative, not the courier, sets the rules. - 02
2 — Read the kit's validated range
The manufacturer's stability data defines the allowed window — ambient for years, refrigerated for days, or frozen for long-term archive. Treat that document as the source of truth.
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3 — Match packaging to that range
Ambient-stable kits ship in an insulated mailer with no coolant. Refrigerated needs gel packs; deep-frozen needs dry ice (
UN1845) with venting. - 04
4 — Add monitoring proportional to risk
A robust ambient kit may need none; a refrigerated or frozen shipment crossing time zones warrants a single-use logger to evidence the chain.
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5 — Reconcile on receipt
The lab checks the logger and visual indicators against the validated range, records any excursion, and decides accept / qualify / recollect before extraction.
Temperature tiers by specimen and use
Representative handling regimes for common hereditary-cancer specimens. Always defer to the specific kit's technical datasheet — values below are typical published ranges, not a substitute for it.
| Specimen / kit | Working tier | Typical transport stability | Coolant | Notes |
|---|---|---|---|---|
Saliva, chemical-lysis (OG-500 / OGR-500) | Ambient (15–30 °C) | Years at room temperature | None | Preservative lyses cells and inhibits nucleases; long-term 4 °C storage is not recommended by the maker — ambient or frozen only. |
Buccal swab, dry (FTA-type card) | Ambient | Months, desiccated | None (desiccant) | Keep dry; humidity, not heat, is the main enemy. |
Whole blood, EDTA (K2EDTA) | Refrigerated (2–8 °C) | ~5–7 days at 2–8 °C; ≤3 days at room temp | Gel packs | Do not freeze the whole tube; ship as stored for ~2-day delivery. |
| Extracted DNA / RNA, working aliquot | Refrigerated to frozen | Days at 4 °C; long-term at −20 °C / −80 °C | Gel packs or dry ice | RNA is far more labile than DNA; minimise freeze–thaw cycles. |
| Frozen tissue / cell pellet | Deep-frozen | Hold below −20 °C; archive at −80 °C | Dry ice (UN1845) | Sublimes at ~−78.5 °C; outer pack must vent CO₂. |
Table 1. Temperature tiers mapped to specimen type, transport window, and coolant. Ranges reflect manufacturer technical specifications and laboratory specimen-requirements guidance.
How long the matrix holds, by storage condition
Approximate published transport/holding windows for whole blood in EDTA versus stabiliser-protected saliva. Saliva is bar-capped at the chart ceiling because validated stability runs to years — the point is the order-of-magnitude gap.
Stability degrades beyond ~3 days at ambient.
~5–7 days; do not freeze the tube.
Capped for scale — validated to multiple years at room temperature.
Coolant choice by target tier
Indicative cold-retention character of common transport coolants. Dry ice sublimes at roughly −78.5 °C and is required for genuinely frozen payloads; refrigerated gel packs hold a 2–8 °C-style window; ambient kits need no coolant at all. Bars are illustrative of the target tier, not duration.
Common cold-chain questions
What exactly counts as a temperature excursion?
An excursion is any exposure outside the specimen's validated storage or transport range — too warm or too cold — for any length of time. For a 2–8 °C blood shipment that includes both a warm spike and an unintended freeze. The laboratory reconciles the logger trace against the kit's range and decides accept, qualify, or recollect; a brief, documented excursion is not automatically a rejection.
Dry ice or gel packs — how do I choose?
Match the coolant to the target tier, not to a sense of 'colder is safer'. Refrigerated payloads (2–8 °C, e.g. EDTA blood) use gel packs; frozen payloads (tissue, frozen aliquots) use dry ice (UN1845), which sublimes near −78.5 °C. Never put a room-temperature-formulated kit such as OG-500 on dry ice — freezing can fracture the tube and is contrary to its design.
Do ambient-stable saliva kits need any monitoring?
Usually little or none for routine transit, because the chemical preservative holds the sample stable for years at room temperature. Loggers are most valuable on refrigerated and frozen shipments, where a few hours out of range can matter. Match monitoring to the actual risk of the tier.
Is a temperature logger a regulatory requirement?
It depends on the specimen and route. Diagnostic specimens commonly ship as UN3373 Biological Substance, Category B under Packing Instruction 650 (a triple-pack rated −40 °C to 55 °C); dry ice adds UN1845 obligations and venting. Loggers evidence the chain and are best practice for temperature-sensitive payloads — confirm specifics with your courier and lab.
What does an excursion mean for my result?
For a hereditary-cancer test, a degraded sample most often means a recollection request, not a wrong answer — laboratories have quality gates that fail an unusable specimen rather than report from it. This page can't tell you whether your sample was affected; your laboratory and ordering clinician or genetic counsellor can.
Glossary
Terms used on this page.
- Cold chain
- An unbroken series of temperature-controlled storage and transport steps that keeps a specimen within its validated range from collection to assay.
- Temperature excursion
- Any exposure outside a specimen's validated storage or transport range — warm or cold — that must be assessed before use.
- Ambient-stable
- A kit whose chemistry preserves nucleic acid at room temperature, so no refrigeration or coolant is required (e.g. stabiliser-lysis saliva systems).
- UN3373
- Biological Substance, Category B — the dangerous-goods classification for most diagnostic specimens, shipped under Packing Instruction 650's triple-pack.
- UN1845
- Carbon dioxide, solid (dry ice) — a Class 9 hazard; packaging must vent subliming CO₂ to avoid pressure build-up.
- Logger
- A single-use or reusable device that records time–temperature data across a shipment so the receiving lab can verify the chain.
“The most reliable cold chain is often the one you don't build: when the chemistry holds a sample at ambient temperature, a logger and a padded mailer beat a melting ice pack and a guess.”
- [1]DNA Genotek — Oragene technical specifications. DNA Genotek. Oragene OG-500 / OGR-500 saliva collection — sample stable for years at room temperature; long-term 4 °C storage not recommended.↗
- [2]Ambry Genetics — Specimen requirements. Specimen requirements for genetic testing: whole-blood EDTA handling, refrigerated 2–8 °C transport windows, and freezing cautions.↗
- [3]IATA / Mercury — Biological packaging guide. IATA Packing Instructions PI 650 (UN3373) and PI 954 (UN1845 dry ice); triple-pack rated −40 °C to 55 °C; venting requirements for dry ice.↗
- [4]DHL — Shipping UN3373 Category B. Requirements guide for UN3373 Biological Substance, Category B, including temperature logging and dry-ice venting.↗
- [5]Contract Pharma — Temperature excursions. Definition and management of temperature excursions in temperature-sensitive shipments; validated ranges and reconciliation.↗
Pick the right tier before you pick the courier
Cold-chain handling starts with knowing your specimen's validated range. Continue with sample stability and storage, or review the shipping containers that meet UN3373 and UN1845 requirements.