Well after some discussion I created my latest science experiment and I submit it for your review. At various points in time, as well as during some discussions here at FUD, I was wondering about the accuracy and reproducibility of all of these gadgets that measure and deliver insulin to our favorite diabetics. To help figure things out, I enlisted my son to ask his high school chemistry teacher if I could borrow an analytical balance to test things out. Mrs. B. was kind enough to allow me access to her Fisher 4 place balance that gets calibrated each summer.
As you can see in the first picture, the balance is currently accurate to the 3rd decimal place. i.e. that is a 2-gram calibration weight on the scale, and you can see the result.
I then used three insulin delivery devices, the Luxura pen my son was given at the hospital that was in continuous use for 6 months and absorbed the normal teenage abuse. The second was a 30 unit syringe that is marked in half units. The third was a Humalog Kwikpen. Unfortunately, my diabetic son was on a field trip and so I couldn’t take measurements with his insulin pump, but we are looking forward to doing that at a future date. I did three measurements at each dosing amount, and then averaged those.
Without further ado, here are the results, and they are kind of amazing considering how caveman like this technology (especially the syringe) is. As you can see both of the pens had very good consistency and were very close to the targeted amount of insulin. As expected, the syringe had the most variability, but I was impressed with how low the standard deviation was, considering I forgot to bring my reading glasses and so I could probably reduce that with a little better eyesight. With that said, still very impressive (at least to me).
Finally, one last picture of the aftermath. Remember kids, science is fun! My only regret is that I didn’t get to make my private test monkey go low so he could eat something fun in this experiment.
Very interesting data. Those numbers are reassuring, considering how the dose we give ourselves is always just a “best guess” anyway.
Thanks for sharing the experiment!
It would also be very interesting to see how different people compare with the syringes. Those who were dosing with syringes in the 50’s, 60’s, 70’s, and 80’s, versus those who were born into the era of pens instead of syringes.
I think syringe accuracy could be a great event at the FUD Olympics!
Please give Mrs. B a sincere thanks from all of us at FUD!
I personally was very impressed with the luxura pen that does 0.5 unit doses. Additionally, the disposable pens always look a little rinky-dinky to me, but man, it was right on target with the doses. So I tip my hats to the engineers in the room.
It has to be a pretty good feat to make a pen that can deliver 0.5 - 30 units and be accurate at each measurement.
I started in the aughties (11/5/03), and did MDI with 30u x 1u syringes for about 8 years. Never used a pen or had any desire to. I did administer doses to the nearest 1/4 u by eyeballing the space between the lines marked on the syringe; I never understood the need for specially-marked 1/2 u syringes. For me an error on the order of 1/4 u was small enough that it would be completely swamped by all the other uncertainties in dosing.