Lactate Meter Self-Testing

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  • #30282

    About 6-8 weeks ago I completed a lactate profile test at CU Boulder, and they did a fantastic job. Unfortunately, the tech made it look too easy. He got seven blood samples from a single finger prick, only to have to do a second prick for the very last sample. I finally purchased a lactate meter a few days ago, and my attempt at performing a self-test went rather terribly. So a few questions are in order:

    1) Lancet Size: I practiced and experimented a bit before my test, but I can get 1 blood sample from a finger prick at best. My kit came with 33G lancets and I’m wondering if that is too small. The lancet device is at its deepest setting.

    2) Pausing: Since I’m self-testing, I wondered if I could briefly stop running to collect a blood sample, and then continue without screwing up the test. Perhaps make the test interval 5 minutes vs 3?

    Any tips would be appreciated 🙂

  • Keymaster
    Scott Johnston on #30285

    We’re about to publish a full article on Self Testing with a lactate meter. But here is an excerpt that includes much of the most germane info. This should answer some of your questions. It does take skill to get good samples and do not expect to do that on your first test. Instead practice and waste a few test strips before launching into a real test.

    Getting a Good Sample
    This sampling process may sound identical to the operation of a blood glucose meter for diabetics—and the meter and strips look identical to those devices and strips—but the testing procedure is much trickier. Getting a good sample takes some practice so don’t expect your first test be anything other than a learning experience where you waste some strips.

    Contamination of the blood sample seems to be the main reason for the error readings. The smaller the blood sample (and the Plus can use a tiny bubble of blood), the more likely it is to be contaminated by sweat or oil on the skin. Even with practice I still get about five times as many error readings with the Plus than I did with my old Pro. Here is what I do to minimize error readings:

    1) Use a fatter-gauge lancet than the fine (30-gauge) one that typically comes with the meter. You need to produce a droplet of blood sitting proud of the skin that is roughly 3mm (1/8 inch) in diameter. If you don’t get that nice big droplet after about 10 seconds, do another poke adjacent to the first rather than squeezing more and harder. It is likely that you missed a bigger capillary and that the tiny hole is already clotting shut
    2) Your blood sample should form a nice viscous droplet standing up on the skin. If the sample is thin and watery looking, do not waste a test strip. It is likely to be contaminated with sweat or the athlete is overly hydrated.
    3) Set the depth of the lancet penetration to maximum on the lancet holder. Usually there is a scale of 1 to 5. I always dial it up to 5. You need to hit a decent-sized capillary or you will not get enough blood.
    4) If you plan to self-test you will need to poke a finger as described below.
    5) During a finger poke, once the blood droplet has formed, I (the sample taker) use my little finger of the hand holding the meter to steady my hand against the athlete’s hand. For an ear poke, I brace my forearm against the athlete’s shoulder. You need something to stabilize against: The athlete is likely to be shaky, and even tiny tremors in your own hands can cause you to miss the droplet or go too deep and touch the skin.
    6) I prefer to poke earlobes rather than fingers. Fingers, especially of climbers and skiers, tend to be callused, making striking a motherlode capillary nearly impossible. Plus, hands tend to sweat a lot, making contamination more of a problem. I have yet to meet anyone with calluses on their earlobes. The skin is thin, and the lobe is highly vascularized. Earrings should be removed before the test as they can get in the way. I find that I get bigger droplets with smaller-gauge lancets when using earlobes. The disadvantage is that you can’t self-test on an earlobe.
    7) If it is cold out it can be very hard to get a good sample from a finger. In cold conditions blood flow to your extremities and especially fingers is reduced. Warm fingers are a must for this test so either pre-warm them in gloves or by windmilling the arms vigorously till the fingers turn red. Otherwise you’re are not going to get enough blood for a good sample. Some people suffer from a common condition called Reynaud’s Syndrome where the finger capillaries shut down with very little provocation. I’ve never heard of the earlobe being affected this way making this another reason to use that appendage.
    8) Have all your gear: lancet holder, meter, strips, paper tools laid out where they are easily reached during the test. I use a small towel to spread things out on. Rarely will you have a table when testing outdoors so get creative. A car hood, tree stump or log a big boulder can often be repurposed to a table.

    9) Squeeze out a nice 1/8-inch droplet and wipe it away with a paper towel. I do not use alcohol for this because I have gotten too many error codes when using alcohol. Perhaps it is my impatience, but the alcohol takes too long to fully evaporate. I find wiping away that first drop does the trick.
    10) Squeeze out another 1/8-inch drop and test this one by CAREFULLY approaching the droplet with the test strip (now installed in the meter) perpendicular to the skin. If you touch the skin with the test strip on a Plus, discard that strip and start over. You WILL get an error code. When the strip touches the top of the droplet, the blood wicks up the strip and the meter beeps. You only need to make contact between the test strip and the droplet. Going too deep runs the risk of touching the skin and blowing the reading.

    As for your second question about stopping. Not ideal but yes you will need to do this if you do not have a friend to help you.


    hamcurtis on #30427

    Thanks for the prompt response Scott! Looking forward to seeing the full article.

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