Question about blood drop collection for INRatio or Coagucheck machines

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TheGymGuy

TheGymGuy

Well-known member
Joined
Jan 3, 2011
Messages
999
Location
Rockville, MD
The person that comes to take my blood for INR weekly tests is using the INRatio machine with strips.

One question I have is that it takes my nurse about 30-35 seconds to get my blood collected from the moment she pricks my finger to the the moment we get blood on the test strip. Generally, first drop around 5-10 seconds after the prick, misses the strip or rather the hole in the strip (this happened last time too), then she take about 20 more seconds to clean the finger get another big drop (still same finger and same site) and then she makes the drop just right on the strip (so total time from prick to collection is 30-35 seconds).

Could this lead to a slightly lower INR measurement or since she gets brand new blood, even though it is the same site, it does not matter?

I have read in the coagucheck online manual to not take more than 15 seconds to collect blood, not sure what to make of this all.


Thanks for your response.
 
TheGymGuy said:
The person that comes to take my blood for INR weekly tests is using the INRatio machine with strips.

One question I have is that it takes my nurse about 30-35 seconds to get my blood collected from the moment she pricks my finger to the the moment we get blood on the test strip. Generally, first drop around 5-10 seconds after the prick, misses the strip or rather the hole in the strip (this happened last time too), then she take about 20 more seconds to clean the finger get another big drop (still same finger and same site) and then she makes the drop just right on the strip (so total time from prick to collection is 30-35 seconds).

Could this lead to a slightly lower INR measurement or since she gets brand new blood, even though it is the same site, it does not matter?

I have read in the coagucheck online manual to not take more than 15 seconds to collect blood, not sure what to make of this all.


Thanks for your response.
Click to expand...

Nurse needs better aim, according to test standards this may compromise the results. She should use a capillary tube at least to help improve her aim and because it looks better in a clinical setting. Right now she's trying paint a thin straight line with a huge and wide uneven brush.

Don't want the strips exposed to light too long and you don't want your blood exposed to the elements too long.
 
Julian, thanks for your response. I totally understand about the timing of things. My main question is whether long exposure increases or decreases measure INR?
 
You should follow the exact instruction manual for your particular machine.
The newest monitors are the INRatio2 and the Coagucheck XS.

Mine is the Coaguchek XS and it won't run a test if it doesn't like the blood drop etc. BUT exact prep instructions still need to be followed.
In my case: Washing hands with soap and water, drying well... NO alcohol wipes.
Sticking the finger only once, and using the FIRST large drop of blood.

Maybe your useless and inept clinic technician needs to back off and let you do it while she watches.
Verify the model of monitor and look up the instruction manual for it.
Good Luck.
 
I'm obviously not a doctor but I would say it decreases it from a logic point of view. Of course logic is just based upon my understanding so basically that discredits my point of view completely LOL!

My logic behind it is that because the blood is exposed to oxygen and light elements when out of the body it begins to change the makeup of the blood and of course effecting the coag properties of the blood. When you put the sample in the machine the chemical process is going to be based upon the info in the sample you gave and of course if nature has had too much or long of an opportunity to effect the blood; well your sample is not a good one.

I'm sure what you were really try to find out is how this Coag unit arrives at its results, the chemical process in which it determines the number. Without knowing this process I'm just talking out of my behind. My money is going to be on lower INR reading.

On a side note, the InRatio units have a built in "QC" system but don't know how it determines whether or not a quality sample is given. Another unknown to be solved.
 
To Bina

To Bina

While I've probably 10-12 tests done on my XS, I recently noticed a picture somewhere that looked like the person's finger had made contact with the strip (blood was smeared on the finger) as opposed to letting the drop fall on the strip. What do you do? Do you let it drop or do you actually make contact with the strip?
 
I don't have an XS, but from what I've seen here and on the Roche site, all you have to do is get a large enough drop and touch it to a notched side of the strip. At that point, capillary action will draw the blood into the strip. It's probably easier to get the blood to the strip this way than aiming for a small, illuminated dot.

You don't want to smear the drop, and you should get the first drop to the strip within fifteen seconds of making your incision.
 
I'm sorry that I didn't see this thread earlier.

The CoaguChek XS and InRatio models are designed to REQUIRE the FIRST drop of blood. This is because there are factors IN THAT FIRST DROP that influence the timing of the prothrombin clotting. Wiping off the first drop, for these meters, will give you a less accurate reading than if you use the first drop.

Using a later drop will influence results. Also, I wouldn't be surprised if this tech is also 'milking' the finger, in order to get more blood to the strip. This is expressly warned against by InRatio, and can also cause an incorrect INR because it mixes interstitial fluids with the components that the strips are testing.

This tech probably isn't preparing your finger for blood collection, either, warming it up and, perhaps, pinching the finger below the knuckle so that blood pools in the fingertip. She may not even be incising the finger in the right place.

Instructions for getting a good blood draw are available for download on the InRatio site. Perhaps you can download the manual and compare the technique (mal)practiced on your finger to the recommended technique in the manual. If it's different, it probably wouldn't hurt to print those pages and give a copy to the tech as a gift. If this tech isn't a total idiot, he or she may actually appreciate it -- but may still end up ignoring it.

(By contrast, the ProTime meter, which actually detects clotting, does not use the first drop. You have to wipe it off. You then have to get a pretty large drop onto a collection cup on the incision device, and then transfer it to the strip. It takes more time, isn't as easy to do, but may give more accurate results. If your tech has been doing INR testing for a long time, this is probably how blood for the ProTime meters was collected. The tech just didn't adopt the procedures required for the InRatio).
 
Thanks for your response Protimenow. Might you have a link to the said manual and collection pics handy. I could not find the link to pdf with google. Of course, my search terms might have been off.
 
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