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FAQ re Cord Blood Storage
Summary of Topics below
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1. Is it better to collect cord blood before or after delivery of the placenta?
Answer: This is a close call.
References:
Example: One bank which collects ex utero has a slide show of the collection process.
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References:
- Solves P, et al. 2003; Bone Marrow Transplant. 2003 Feb;31(4):269-73. In a sample of 569 vaginal deliveries, a larger volume and a higher number of stem cells were harvested from the in utero collection group.
- Lasky, LC, et al. 2002; Transfusion Oct;42(10):1261-7 They say that, in terms of sample volume and cell count, there is "no advantage of either method".
- Surbek, DV, etal. 2000; Am J Obstet Gynecol Jul;183(1):218-21 They prefer in utero collection for cesarean delivery
Example: One bank which collects ex utero has a slide show of the collection process.
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2. What is the optimum cord blood collection method, gravity drip versus syringe?
Answer: Studies have shown that pulling the blood out with a syringe tends to draw a bigger sample than simply letting the blood drip by gravity into a bag.
References:
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References:
- Bertolini F, et al. (1995) J Hematother Feb;4(1):29-36. "Comparative study of different procedures for the collection and banking of umbilical cord blood."
- Elchalal U, et al. (2000) Am J Obstet Gynecol. Dec;183(6):1587-8. These authors advocate flushing all the blood out with saline, which is a more aggressive method than simply pulling out blood, and is not in routine use.
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3. What is the optimum cord blood storage container, bags or vials?
Scientific answer:
Existing scientific studies do not show a significant difference between the cell dose and cell viability of cord blood stored in bags versus vials. There have been successful transplants with cord blood that had been stored for years using either method.
History:
Historically, the use of bags and vials have existed in parallel for over a decade. On the one hand, public cord blood banks have always stored cord blood in traditional blood bags, presumably because they were founded by traditional blood banks and this was a consistent practice for them. But on the other hand, research institutions usually stored cord blood in vials, which allow multiple portions per collection and are less expensive to maintain.
Thus, when private companies began offering family storage in the mid-1990's, some adopted the bag method and others adopted the vial method. A given bank would use one method or the other, not both, because their freezer would be equipped with racks for holding either one or the other. Also, the loading of the racks had to be balanced for mechanical and temperature stability.
There have always been pros and cons to vials versus bags as a storage method. Vials have the advantage that the cord blood is stored in multiple portions, which gives the family the option to use part of the collection and save the rest. Vials have the disadvantage that because they are very small, they are very prone to temperature fluctuations, and should not be transfered in the lab without insulation. Bags have the advantage that they are a "closed system" where the blood can be processed and stored in the same container, thus minimizing the risk of contamination during a transfer. Bags have the disadvantage that they shatter if not handled carefully.
Regulatory answer:
In a recent revision of AABB standards, the accrediting agency AABB has made it a requirement for cord blood collections to be accompanied by small portions for future testing, and these small portions must be "integrally attached" to the main collection. The requirement for the testing portions to be "integrally attached" is new. It is intended as a safety precuation, to insure that all cord blood belonging to a particular person is adequately labeled, and there can never be any confusion as to which testing portion belongs to which collection.
The new AABB requirement tends to favor bag storage over vial storage. It is easy to create attached testing portions with a blood bag, by crimping small segments of tubing attached to the bag. It is harder to attach multiple vials to each other in a cryogenic tank. Some banks which stored in vials have switched to bags in order to comply with this regulation. Other banks are operating under a variance from the AABB, while they investigate options or prepare for the transition. The AABB has provided a FAQ page which addresses this topic.
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Existing scientific studies do not show a significant difference between the cell dose and cell viability of cord blood stored in bags versus vials. There have been successful transplants with cord blood that had been stored for years using either method.
History:
Historically, the use of bags and vials have existed in parallel for over a decade. On the one hand, public cord blood banks have always stored cord blood in traditional blood bags, presumably because they were founded by traditional blood banks and this was a consistent practice for them. But on the other hand, research institutions usually stored cord blood in vials, which allow multiple portions per collection and are less expensive to maintain.
Thus, when private companies began offering family storage in the mid-1990's, some adopted the bag method and others adopted the vial method. A given bank would use one method or the other, not both, because their freezer would be equipped with racks for holding either one or the other. Also, the loading of the racks had to be balanced for mechanical and temperature stability.
There have always been pros and cons to vials versus bags as a storage method. Vials have the advantage that the cord blood is stored in multiple portions, which gives the family the option to use part of the collection and save the rest. Vials have the disadvantage that because they are very small, they are very prone to temperature fluctuations, and should not be transfered in the lab without insulation. Bags have the advantage that they are a "closed system" where the blood can be processed and stored in the same container, thus minimizing the risk of contamination during a transfer. Bags have the disadvantage that they shatter if not handled carefully.
Regulatory answer:
In a recent revision of AABB standards, the accrediting agency AABB has made it a requirement for cord blood collections to be accompanied by small portions for future testing, and these small portions must be "integrally attached" to the main collection. The requirement for the testing portions to be "integrally attached" is new. It is intended as a safety precuation, to insure that all cord blood belonging to a particular person is adequately labeled, and there can never be any confusion as to which testing portion belongs to which collection.
The new AABB requirement tends to favor bag storage over vial storage. It is easy to create attached testing portions with a blood bag, by crimping small segments of tubing attached to the bag. It is harder to attach multiple vials to each other in a cryogenic tank. Some banks which stored in vials have switched to bags in order to comply with this regulation. Other banks are operating under a variance from the AABB, while they investigate options or prepare for the transition. The AABB has provided a FAQ page which addresses this topic.
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4. What is the long-term viability of frozen cord blood?
(Actually, all the studies of cord blood viability have been done on samples of separated Mono-Nuclear Cells, not whole blood.) Answer: So far, recovery of viable stem cells from cord blood is over 90% at 15 years.
References:
Background information: In theory, it should be possible to store cells for millenia at -196 C, the temperature of liquid nitrogen. Below -130 C, no liquid water exists in cells, which prevents biochemical reactions between molecules dissolved in water. At -196 C there is not enough thermal energy in the cell to drive any biochemical reaction. The only degradation that can occur at this temperature is reactions caused by cosmic background radiation. It can be calculated that, at normal terrestrial conditions, it would take about 2000 years before such reactions caused a significant amount of damage.
References:
References:
- Kobylka, P., et al. 1998, Transplantation, 65(9):1275-1278.
- Mugishima, H., et al. 1999, Bone Marrow Transplant, 23(4):395-396.
- Broxmeyer, H. E., et al. 2003 pnas.0237086100
Background information: In theory, it should be possible to store cells for millenia at -196 C, the temperature of liquid nitrogen. Below -130 C, no liquid water exists in cells, which prevents biochemical reactions between molecules dissolved in water. At -196 C there is not enough thermal energy in the cell to drive any biochemical reaction. The only degradation that can occur at this temperature is reactions caused by cosmic background radiation. It can be calculated that, at normal terrestrial conditions, it would take about 2000 years before such reactions caused a significant amount of damage.
References:
- Mazur P. 1988, Ann NY Acad Sci. 541:514-31. "Stopping biological time. The freezing of living cells"
- Mazur P. 1984, Am J Physiol. 1984 Sep;247(3 Pt 1):C125-42. "Freezing of living cells: mechanisms and implications."
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Last modified: 21.January 2010
Copyright 2000 - 2010 Frances Verter
Copyright 2000 - 2010 Frances Verter