We’ve had two questions about Ristocetin since our 11.9.11 Problems with Ristocetin question from Kerri Klemm. Kerri’s question prompted me to contact Kathy Jacobs at Chrono-log Corp, a major distributor of ristocetin in the US and around the world. Here is a follow-up message from Kathy:
Hello George, Nice to hear from you and a very happy New Year to you and your family. As a followup to your email back in November about a lab experiencing difficulties with ristocetin testing, that lab is now purchasing ristocetin from us and is using our older Lot No. B-1186-8 which is working nicely for them. Here is the information on the new lot B-1186-9 compared to the old using both whole blood impedance and PRP/optical (light transmittance) testing:
First number is new lot second number is old:
1. WB @ 1.0 mg/mL = Average 20.5 vs 17 ohms
2. PRP @ 1.0 mg/mL = Average 76.3 vs 78.3%
3. PRP @ 1.25 mg/mL = Single Tests 78 vs 87%
4. PRP @ 1.5 mg/mL = Single Tests 86 vs 87%
5. PRP @ 0.9 mg/mL = Single Tests 2 vs 2%
6. PRP @ 0.75 mg/mL = Single Tests 0 vs 1%
So, it looks like the Chrono-log ristocetin is maintaining its viability.
Here is a side note: we had some issues with reagents stored frozen in aliquot tubes losing some or all of the reagent volume. We did a 3-month study with ristocetin using a wide variety of tubes. When I can get around to revising our procedures, we will be recommending the following tubes:
Free-standing polypropylene tubes [natural color or amber] with caps + O-ring seal. These are available from www.denvillescientific.com. Their part numbers are C19053 and C19046 [natural] or C19053-A and C-19048 [amber]. The tube volume size is 0.5 mL.
We do not recommend using any tubes with a volume less than 0.5 mL as we saw huge shifts in test results over a 3-month period of testing using tubes with a volume of 0.3 mL. We also weighed the tubes before storing and after thawing and saw more weight loss with this size tube.
Always good to hear from you, so please don’t hesitate to contact me whenever we can be of assistance. Have a great day! Kathy