Lab value confusion

Daytonite, BSN, RN · Oct 24, 2009

but what in the world do they mean by 1.3-1.5x the normal?

1.3 to 1.5 times the normal lab value. the normal lab value will be listed on the lab form and will vary between the different laboratories. it is a figure the lab uses based on what they have determined is a normal standardized sample of blood that is giving normal values which they use to compare to the samples of patient's blood they receive. all you need to do is compare the patient's results with what the lab has reported as "normal".

or 2-3 the control value?

2 to 3 times the control value. the control value will be reported on the lab form and will vary between the different laboratories. it is a figure the lab has pre-determined from standardized tests and compares against actual patient blood samples. all you need to do is compare the patient's results with what the lab has reported as "control value".

see

pt (when on coumadin):
- http://www.labtestsonline.org/understanding/analytes/pt/glance.html
- http://www.webmd.com/a-to-z-guides/prothrombin-time (3 pages)
[*]ptt (when on heparin):
- http://www.labtestsonline.org/understanding/analytes/aptt/glance.html
- http://www.webmd.com/a-to-z-guides/partial-thromboplastin-time (3 pages)

vme1 · Oct 24, 2009

Thank you so very much!

tlc2u · Oct 24, 2009

i am having a difficult time understanding the lab values for heparin and coumadin.
ok so we check the aptt for heparin and pt/inr for coumadin. but what in the world do they mean by 1.3-1.5x the normal? i am used to seeing it as 1.5 to 2 x the norm but it is possible that your literature says 1.3 - 1.5x the norm. the short answer: heparin is a blood thinner used in the prevention of blood clots. it makes a patients blood take 1.5-2 times longer in seconds for the blood to clot than if the patient was not taking a blood thinner. the normal value or blood clotting time is either from a lab drawn to determine how long it takes for your patient's blood to clot or a mean normal value from a laboratory for how long it takes for an averaged number of people's blood to clot. see the example below. if the norm used is 30 seconds then (1.3 - 1.5 x 30seconds= a rate of blood clotting of 39-45 seconds when the patient is taking heparin because heparin thins the blood and it takes a longer time for the blood to clot in a patient on heparin or warfarin (coumadin).
"the ptt test allows the provider to check that there is enough heparin in the blood to prevent clotting, but not so much as to cause bleeding."
the nurse's role is to check the lab values and see to it that it falls between 1.5 to 2 times the normal. the greater the pt/ptt values, the longer it takes the blood to clot.
high pt/ptt = risk for bleeding.
low pt/ptt = risk for blood clots/ stroke.
or 2-3 the control value? the inr is a method of standardizing the pt for coumadin anticoagulation. before the inr, different labs using different reagents had different controls and widely differing pt value ranges.
an inr of 1 means the blood clots "normally" for that pt. the greater the inr, the longer it takes the blood to clot.
an inr of 3 means the blood takes about three times as long to clot compared with the normal value for that pt.
the warfarin (coumadin) dosage for people being treated to prevent the formation of blood clots is usually adjusted so that the prothrombin time is about 1.5 to 2.5 times the normal value (or inr values 2 to 3). a patient may take warfarin to anticoagulate for atrial fibrillation (target inr around 2.5) or for a mechanical heart valve (target inr 3).
what am i looking for? the nurse's role is to check the lab values and see to it that it falls between 1.5 to 2 times the normal for pt and ptt. you are looking for if the value is higher than this there is a risk for bleeding. if the value is lower there is a risk for blood clots/stroke.
what's good what's bad? aaahhh! i'm a visual/go by examples learner and frankly these power points just aren't cutting it!

some of this you may already know but i thought it was worth posting.

how to remember heparin is ptt and coumadin (warfarin) is pt

either remember that the two t's for ptt are 2 upwards marks like a capital h for heparin has two upwards marks.

or remember:

you can find the right answer by counting to 10:

- - - - - - - - - - = 10

h e p a r i n (7 letters) + 3 (ptt) = 10

c o u m a d i n (8 letters) + 2 (pt) = 10

here's another one:

what is the antidote for heparin overdose?

protamine sulfate (just remember p m s) or remember there is a p in heparin

what is the antidote for too much coumadin?

vitamin k (just remember the hard "c" sound at the beginning of coumadin!)

pt and ptt or aptt are lab tests which measure how long it takes a patient's blood to clot. since this time varies from person to person a lab might be drawn to determine the normal clotting time for a patient. or the mean normal value may be used as explained below.

also you may notice that in your studies of lab values in general that one textbook versus another may quote slightly different numbers for the lab values. that is because each individual laboratory determines a mean normal reference by taking the normal values from a group of patients from that lab and dividing that by that number of patients to get an average or mean value.

aptt prolongation of 1.5 - 2.5 times the mean normal reference interval.

example: aptt mean normal = 30 seconds (10/16/06 to present)

therapeutic range = 45 - 75 seconds (1.5 - 2.5 x mean normal)

another method of heparin therapeutic ranges of patients actually receiving units of heparin is as follows:

therapeutic range =

0.1 units = 44 seconds (aptt)

0.3 = 63 seconds

0.7 = 101 seconds

take note that other factors may affect your lab values, green leafy vegetables, liver, multivitamins and other food rich in vitamin k may counter the effect of warfarin, on the other hand some drugs like aspirin may also increase its effect.

cut and copy the words below into a google search and you should find "2" links to allnurses posts with some of this info and other good information too.

"the ptt test allows the provider to check that there is enough heparin in the blood to prevent clotting, but not so much as to cause bleeding."

vme1 · Oct 25, 2009

Click...the light bulb just turned on! It all makes sense. The examples were perfect. You're values are right because I've got all my books in front of me and they all say 1.5 - 2. I think it was just an error on the power point. My exam is on Monday and I'm glad I don't have to memorize and THEN learn. Thanks for all your help!

tlc2u · Oct 25, 2009

Your welcome !!!

The other posts I mentioned from allnurses have other pertinent information like why a patient would be on Heparin and Coumadin at the same time and a mention of meds etc. that might cause changes from the norm. They may be worth skimming over.