iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Freeze a blood sample only when the specific test permits it, and follow that test’s instructions for the specimen fraction, tube, temperature, storage period, freeze-thaw limit and thaw procedure. Whole blood, serum and plasma are not interchangeable; there is no universal freeze-thaw protocol.
Start with the test and specimen type
Before freezing anything, identify the assay and confirm which specimen it accepts: whole blood, serum or plasma. Then check the current test instructions and the laboratory’s validated standard operating procedure (SOP) for the collection tube, processing steps, storage temperature and duration, permitted number of freeze-thaw cycles, and post-thaw handling. These details vary by test. CLSI PRE04 offers general handling principles for routine whole-blood, serum and plasma specimens, but points to test- and measurand-specific requirements for detailed instructions. CLSI PRE04
Do not assume that a tube of whole blood should be frozen. In the cited CDC serology workflows, blood is processed to separate serum before the serum is stored frozen. Other assays may specify a different specimen or preparation, so those examples are not universal directions. CDC-10244 specimen instructions and CDC’s 2024 syphilis testing recommendations
- Whole blood: Keep or process it as the assay specifies; do not substitute a frozen whole-blood specimen for serum or plasma.
- Serum: Separate it from the clot when the method requires serum, then use the specified storage container and conditions.
- Plasma: Use the collection and processing instructions for the particular plasma assay. Coagulation testing, for example, has focused specimen guidance in CLSI H21. CLSI H21, sixth edition
The specimen fraction matters because an assay’s instructions are written for a particular material and handling path. A serum storage example does not establish a plasma procedure, and a plasma example does not show that whole blood can be frozen for the same test. Even within a broad category such as serology, the required specimen, storage time and permitted handling can differ. Confirm that the test name and specimen type on the instructions match the sample you actually have.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
If the instructions are unclear, incomplete or appear to conflict, do not guess from another test’s protocol. Ask the performing laboratory or consult the laboratory’s designated SOP before freezing. Freezing is not a substitute for required processing, and an apparently convenient general-purpose freezer setting does not establish that the specimen will remain suitable for a particular assay.
A practical workflow for freezing a sample
The sequence below is a decision workflow, not a universal laboratory protocol. The test’s current instructions take precedence at each step.
- Confirm that freezing is allowed. Check the assay instructions and SOP for the accepted specimen fraction, tube, and storage conditions. If these are unclear, ask the performing laboratory before collecting or freezing the sample.
- Process the specimen as specified. Follow the method’s requirements for clot formation, centrifugation and separation. Do not transfer a centrifugation setting or processing time from a different assay.
- Choose the specified storage container. Use the material and closure required by the method. The cited CDC instructions include clean polypropylene tubes for serum or plasma and, for CDC-10244, a sterile threaded tube with an O-ring. Confirm suitability and sterile status where required, as well as temperature and material compatibility, with the laboratory’s validated procedure. CDC-10244 specimen instructions and CDC’s 2024 syphilis testing recommendations
- Decide whether to aliquot. If the test permits aliquots, divide the specimen into suitable portions before freezing so later testing does not require repeatedly thawing the same container. Do not create aliquots if the assay instructions or validated SOP do not permit them.
- Apply the test-specific storage conditions. Use the required temperature and maximum storage period, and follow the laboratory’s procedures for freezer monitoring and specimen identification. A value specified for one test is not a safe default for another.
- Record handling information required by the SOP. Keep the specimen’s identity and relevant processing and storage details traceable according to laboratory policy. The sources do not establish one universal set of record fields.
- Thaw and handle the specimen only as directed for that assay. Check the method for thaw conditions, mixing, any post-thaw holding limit and acceptance criteria. Do not infer these from the storage temperature.
In practice, the first check should happen before collection whenever possible. Confirm the exact test, the required specimen fraction, and whether the lab accepts a frozen specimen. If the specimen is being sent to a reference laboratory, use that laboratory’s current submission instructions as well as local procedures; a local workflow may not automatically meet the receiving laboratory’s requirements.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Processing details are also linked to the specimen type. In the CDC-10244 workflow, serum is separated from the clot, refrigerated within 8 hours, and transferred to the specified tube; that workflow gives a particular centrifugation setting. Those steps illustrate why timing, separation and container instructions should be treated as a connected method, not copied piecemeal. Do not apply the CDC-10244 centrifugation setting or processing times to a different assay unless its instructions say to do so.
Aliquoting can reduce the need to thaw an entire stored sample repeatedly, but the portions must be appropriate for the assay and the laboratory’s procedure. The guidance cited here does not set a universal aliquot volume, container size, label format or number of portions. Those choices belong in the applicable method or validated SOP. If aliquots are permitted, plan them around the intended testing workflow rather than making assumptions about how much material a future test will require.
Examples of storage conditions—and why they are not interchangeable
The following figures belong to named CDC or WHO workflows. They illustrate how much storage instructions can differ; they should not be combined into a general rule for blood samples.
| Source and scope | Supported handling details | Important limit |
|---|---|---|
| CDC test submission instructions, CDC-10244 | For this workflow, separate serum from the clot, refrigerate it within 8 hours, and keep it at 2–8°C; freeze if storage will exceed 48 hours. Frozen serum may be stored at −20°C or lower for up to 8 weeks before shipping. The described workflow specifies centrifuging collection tubes for 10 minutes at 1,000–1,300 g. | These are instructions for CDC-10244, not a general serum storage window or centrifugation setting. |
| CDC, Laboratory Recommendations for Syphilis Testing, United States, 2024 | For the described serum collection workflow, allow approximately 15–30 minutes for clot formation at room temperature. The recommendations describe keeping plasma at 2–8°C and testing within 5 days, or freezing it at ≤−20°C for longer storage. | The report notes that plasma storage times vary by test. The serum clotting guidance and plasma storage example are not a single protocol for every syphilis assay or blood test. |
| WHO laboratory guidance, cited protocol | For that workflow, plasma may be stored at −65° to −80°C for up to 6 months, with no more than two plasma freeze-thaws. | The temperature, duration and cycle limit apply to the cited workflow only. |
The differences are consequential: one CDC submission workflow uses a specific 48-hour threshold and an 8-week frozen storage limit, while the 2024 syphilis recommendations distinguish refrigerated testing within 5 days from longer-term frozen storage, and the cited WHO protocol specifies a much colder range and a maximum of two plasma freeze-thaws. Do not select the most convenient figure or the longest duration without confirming that it applies to the assay in hand.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
These examples answer common questions such as “How long can serum be frozen?” only when the test and workflow match. For the named CDC-10244 submission, the stated frozen-serum limit is up to 8 weeks at −20°C or lower before shipping. That is not a universal stability claim for all serum tests. Similarly, the WHO value of up to 6 months at −65° to −80°C applies to its cited plasma workflow; it should not be used to extend another assay’s storage period.
The 2024 CDC syphilis recommendations also separate refrigerated handling from frozen storage in the described plasma context: plasma is kept at 2–8°C and tested within 5 days, or frozen at ≤−20°C for longer storage. The report explicitly notes that plasma storage times vary by test. The numbers therefore do not resolve how long every plasma sample can be stored, nor do they indicate that colder storage is always required or better for every analyte.
For CDC-10244, the specified centrifugation step is 10 minutes at 1,000–1,300 g, while the CDC syphilis workflow describes approximately 15–30 minutes at room temperature for clot formation. These are processing examples attached to their particular workflows, not general values to combine. Tube type, clot formation, separation and storage instructions should be followed as a coherent test-specific process.
Why repeated freeze-thaw cycles matter
Repeated freezing and thawing can reduce the activity of some analytes and affect results. CDC warns that repeated cycles may reduce antibody activity and produce erroneous serology results. CDC-10244 specimen instructions CDC’s 2024 syphilis recommendations also describe aliquoting plasma to avoid repeated freeze-thaw. CDC’s 2024 syphilis testing recommendations
Free tools Windows power users keep installed
One-click scans. No signup required.
Aliquoting is a way to reduce unnecessary cycles, not permission to freeze a specimen or split it into portions when the test does not allow that handling. Record and respect the cycle limit in the relevant method or SOP. If a specimen has already undergone more cycles than permitted—or its freeze-thaw history is unknown—contact the performing laboratory for an assay-specific decision rather than assuming it remains acceptable.
There is no defensible universal answer to “How many times can you freeze and thaw a blood sample?” The number depends on the specimen and assay. The WHO protocol cited above specifies no more than two plasma freeze-thaws for that workflow; CDC warns against multiple cycles for its serology instructions. Neither statement establishes a safe limit for every test. If repeated use is anticipated, check in advance whether the method permits aliquots and what cycle limit applies.
A freeze-thaw count should not be treated as the only quality question. The test-specific instructions may also set a storage duration, temperature and post-thaw handling requirement. A sample that stayed within a cycle limit may still need review if its storage duration or temperature is uncertain. Conversely, do not reject or accept a specimen based on an invented general rule: consult the assay’s acceptance criteria and the laboratory responsible for testing.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Thawing: follow the assay, not a generic recipe
The available guidance does not establish one thaw temperature, thaw duration, mixing step, post-thaw hold time or visual rejection rule for all blood specimens. Those instructions depend on the test and specimen type. Use the current method insert and validated laboratory SOP to determine how to thaw the specimen, whether and how to mix it, how soon it must be tested, and what conditions require rejection or recollection. Do not substitute a water bath, a room-temperature hold, vigorous mixing or any other thawing technique unless the test instructions authorize it.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
When an instruction is missing or conflicts with another document, pause and resolve the discrepancy with the laboratory’s designated procedure or performing laboratory. In particular, do not extrapolate serum instructions to plasma, coagulation testing or whole blood. CLSI H21 is the focused CLSI reference for plasma-based coagulation assays and addresses specimen stability and rejection criteria; use the applicable current guidance rather than treating a general blood-handling standard as a substitute. CLSI H21, sixth edition
There is likewise no supported generic thaw duration to quote. A fixed number of minutes, a prescribed bath temperature, a mixing technique and an allowable delay before analysis would all imply a standard that the guidance does not establish. Find those instructions in the current method insert or validated SOP. If a method does not state a needed step, resolve the gap through the laboratory’s established process rather than filling it in from a different test’s instructions.
After thawing, acceptance is also test-specific. The sources here do not establish a universal rule based on appearance, nor a general post-thaw holding time. Follow the assay’s criteria and ask the performing laboratory if the storage history is incomplete, the specimen has exceeded its stated conditions, or handling has departed from the SOP. That decision should be made for the particular specimen and test rather than by applying an assumed visual or timing rule.
Freezer choice and storage controls
Use equipment capable of maintaining the temperature required by the assay, and follow the laboratory’s quality-system procedures for temperature monitoring and storage. A freezer’s nominal set point alone does not establish that a specimen has remained within its required conditions.
Recommended Free Tools
For serum, CDC’s 2024 syphilis recommendations caution against frost-free freezers because their automatic freeze-thaw cycles can harm frozen serum stability. CDC’s 2024 syphilis testing recommendations Apply that warning in the context of the cited guidance and the assay’s own storage requirements; it does not define storage equipment for every specimen or test.
For tubes or vials, confirm the required material, sterility, seal and temperature rating against the method and laboratory validation. CDC guidance cited here specifies polypropylene tubes in relevant workflows, but that does not establish that every polypropylene vial is suitable for diagnostic use. CDC-10244 specimen instructions and CDC’s 2024 syphilis testing recommendations
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Polypropylene cryogenic vials or aliquot tubes may be a relevant supply category for separated serum or plasma when the applicable method calls for them. A product description alone is not evidence that a vial is validated for clinical diagnostic use. Confirm sterile status when required, cap and seal compatibility, temperature rating, material compatibility and institutional validation. The cited guidance does not endorse a particular brand or consumer listing.
Freezer and temperature-monitoring equipment are part of laboratory quality-system considerations, but the appropriate equipment depends on the assay’s required storage conditions and institutional controls. Select and monitor equipment through the laboratory’s established procedures; do not assume a particular freezer type or set point satisfies every specimen requirement. For serum stored under the CDC syphilis recommendations, the frost-free-freezer caution is explicit because automatic cycles can be detrimental to frozen serum stability.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchCommon mistakes and how to avoid them
- Freezing before checking the specimen requirement: Confirm whether the assay needs whole blood, serum or plasma and whether frozen storage is allowed.
- Using another test’s temperature or time limit: Match the storage conditions to the exact method; CDC and WHO examples show that requirements can differ substantially.
- Thawing the same tube repeatedly: Use permitted aliquots to reduce repeat cycles, and observe the assay’s documented cycle limit.
- Assuming a thaw method or rejection rule: Get the thaw, mixing and acceptance instructions from the current test method or SOP; no general rule is established here.
- Storing serum in a frost-free freezer when the applicable guidance warns against it: Follow the CDC syphilis guidance and the assay’s validated equipment requirements.
- Assuming a container is suitable because it is labeled for freezing: Verify its material, sterile status, seal and temperature compatibility for the intended diagnostic workflow.
Other avoidable errors include treating refrigeration and freezing limits as interchangeable, assuming a sample is ready to freeze before the required separation step, or applying a test-specific centrifugation setting to another collection system. The CDC examples show that even closely related handling stages have their own instructions: one gives a clot-separation workflow and centrifugation parameters, while another specifies a clot-formation interval and separate plasma storage examples. Follow the full procedure for the intended test, not isolated numbers taken out of context.
Do not use the longest storage period found in a different protocol as a workaround when the correct limit is unknown. Nor should an unknown freeze-thaw history be treated as proof that a specimen is acceptable. Verify the history if possible and refer uncertain or out-of-specification specimens to the performing laboratory for a decision under its criteria.
Which laboratory references to use
For routine specimen handling across whole blood, serum and plasma, CLSI PRE04 provides general recommendations on handling, transport, processing and storage, while retaining the need for detailed requirements specific to the measurand and specimen type. It was published on August 3, 2023. CLSI PRE04 overview
For plasma-based coagulation assays, CLSI H21, sixth edition, was published on April 22, 2024 and addresses coagulation specimen handling, stability and rejection criteria. CLSI H21 For a specific clinical test, the current assay instructions and the laboratory’s validated SOP remain the operational references for specimen preparation, storage and thawing.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →These references serve different roles. PRE04 is a general guideline for routine handling of whole blood, serum and plasma; it does not replace detailed instructions for a particular measurand or specimen. H21 focuses on plasma-based coagulation testing, including fresh and frozen plasma stability discussion and specimen rejection criteria. For operational choices—such as the required collection tube, permitted storage interval or how to thaw—use the instructions applicable to the actual assay and laboratory workflow.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Frequently Asked Questions
Can you freeze blood samples?
Sometimes, but there is no universal answer for whole blood, serum or plasma. First check whether the specific assay accepts frozen material and which specimen fraction it requires. The cited CDC serology workflows separate serum before freezing; that is an example for those workflows, not a direction for every blood test.
Can you freeze serum or plasma?
Some methods permit frozen serum or plasma, but the required temperature, duration, container and freeze-thaw limit are test-specific. CDC-10244, the 2024 CDC syphilis recommendations and the cited WHO protocol give different examples. Use the current instructions for the exact test rather than choosing one of those values as a general rule.
How long can serum be frozen?
For the particular CDC-10244 submission workflow, serum may be stored at −20°C or lower for up to 8 weeks before shipping. That limit does not apply to all serum assays. Check the current test instructions for the applicable maximum storage period.
How many times can you freeze and thaw a blood sample?
There is no universal cycle limit. CDC warns that repeated cycles may reduce antibody activity and lead to erroneous serology results. The cited WHO workflow allows no more than two plasma freeze-thaws, but that limit belongs to that protocol only. Follow the assay’s stated limit and use aliquots only if permitted.
What is the correct way to thaw a frozen blood sample?
Use the thaw temperature, timing, mixing instructions and post-thaw limits specified by the assay and laboratory SOP. The cited guidance does not establish one method for all specimens, so do not assume a water bath, room-temperature thaw, mixing step or visual acceptance rule.
Can I store serum in a frost-free freezer?
CDC’s 2024 syphilis recommendations caution against frost-free freezers for stored serum because their automatic freeze-thaw cycles can be detrimental to frozen-serum stability. Apply that caution alongside the requirements for the particular assay and laboratory.
Should I freeze whole blood or separate serum first?
That depends on the assay. In the cited CDC serology workflows, blood is processed to separate serum before freezing. Do not assume this is correct for every test; confirm whether the method requires whole blood, serum or plasma and follow its processing instructions.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsWhat tube should I use for frozen serum or plasma?
Use the container required by the current method and laboratory validation. The cited CDC guidance specifies polypropylene tubes for relevant workflows, and CDC-10244 calls for a sterile threaded tube with an O-ring. Confirm material, required sterility, closure compatibility and temperature rating; a general freezer label does not establish diagnostic suitability.
The Bottom Line
Reliable freezing and thawing start with the exact test, specimen fraction and current validated instructions. Separate and store the specimen only as directed, use permitted aliquots to limit repeated thawing, and do not borrow another assay’s temperature, duration or thaw method. When any step or specimen history is uncertain, check with the performing laboratory.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
