First drop of blood

[lance]

My warfarin manager told me the first drop of blood is required because it is a timed reaction test.

Not sure what to think. Are we splitting hairs? Some patients probably take longer for the first drop to appear than other patients who are willing bleeders.

So whether it is the first or second drop as long as it is applied within 15 seconds is what's important.

Does is really matter?

 

[Ross]

I think that is a myth. I've tested both ways and got the same results. I don't think it matters at all.

 

[Karlynn]

My instruction for my ProTime machine (I now have the INRatio) was to wipe off the first drop of blood so the test wouldn't be distorted by alcohol or soap residue and use the 2nd.

I still wipe off the first and use the 2nd.

 

[Gnusgal]

My instruction for my ProTime machine (I now have the INRatio) was to wipe off the first drop of blood so the test wouldn't be distorted by alcohol or soap residue and use the 2nd.

I still wipe off the first and use the 2nd.

Same here.

 

[dick0236]

I have had lab techs do it both ways, and I don't think it matters. As you put it, that's "splitting haires".

 

[Bina]

My Coaguchek XS specifies First drop.....I wash with regular soap, rinse and dry hands well before.

 

[Ross]

If you look at what the correct lab draw involves, first drops are thrown away. They are supposed to start the draw into a tube, pitch it in the trash and then take another vial and fill it for testing. Sort of like primming the line.

If you think it matters, easily debunkable. Test once with the first drop of blood then test again with a second drop. Bet you come out with the same results.

 

[lance]

Different manufacturers

Different manufacturers

It appears the different manufacturers don't all use the same reagents hence the first second drop requirement. Do users of monitors requiring drop two have instructions that blood must be applied within a certain time frame?

When vein draws for INR are done here the technicians use the first vial. I've never noticed a vial being discarded. Maybe an INR is being done in conjunction with other tests when one is.

 

[Ross]

When vein draws for INR are done here the technicians use the first vial. I've never noticed a vial being discarded.

Oh I have too lance, but that is not the proper procedure. Here again, I doubt that it makes any difference, but it's not the proper procedure for obtaining the sample. The Blue tipped vial is the INR reagent vial. I'll see if I can't find the procedure again and post it.

 

[Ross]

It appears my thoughts were correct, change is coming in the procedure.


Three recent studies discussed the possibility that the National Committee for Clinical Laboratory Standards (NCCLS) recommendations that the coagulation specimen should be the second or third tube collected are unnecessary. However, only one reagent/ instrument was used in each study. Our protocol differed from the previous studies because we performed the assays on three different reagent/instrument systems on the same samples. Our study used photo-optic, mechanical, and nephelometric systems of clot detection. After obtaining informed consent, we obtained two bluestoppered tubes of blood from 95 subjects: 15 normal patients and 80 patients currently on coumadin therapy. No discard tube was drawn for coagulation testing. A prothrombin time with an international normalized ratio and an activated partial thromboplastin time, were performed on each tube. Laboratory One used a MLA 1600C (Hemoliance) with Thromboplastin DS (PacificHemostasis, ISI of 1. 11) and APTT-LS (Pacific-Hemostasis). Laboratory Two used an STA (Diagnostica-Stago) with Neoplastine Cl+ (Diagnostica-Stago, ISI of 1. 14) and PTT-LT (Diagnostica-Stago). Laboratory Three used an ACL 300 with Plastinex (Biodata, ISI of 1.67) and Actin FSL (Dade Behring). No clinical or statistically significant differences were seen between the first or second tubes on any of the three reagent/instrument combinations in the PT in seconds, international normalized ratio reporting, or APTT results. Our results indicate that the NCCLS guidelines for obtaining a second tube when performing coagulation testing should be considered for elimination when new revisions are published.

http://findarticles.com/p/articles/mi_qa3890/is_199905/ai_n8829980

 

[Bina]

If a hospital or lab would ever throw away a tube of my precious blood, I would have yelled. LOL
I've never experienced a tech doing that. Our rule is first tube (lab) and first drop (at home).