We have all heard the terms such as: HIGH,LOW, A1C and now we are hearing the term TIR (Time-in-Range). Today I want to discuss the meaning of these terms and acquaint you with this new term TIR.
LOW-in diabetes management usually means the blood glucose (sugar) reading is less than 4 mmol/L (72 mg/dl). When readings are this low the symptoms of hypoglycemia are evident and treatment needs to happen.
HIGH- in diabetes management usually means your blood glucose reading is equal to or greater than 11mmol/L (198 mg/dl). Symptoms of high blood sugar such as increase in thirst, more frequent urination are no doubt evident and treatment to lower the blood glucose down should happen. We all know that prolonged hyperglycaemia can lead to unwanted diabetes complications.
A1C (also known as hemoglobin A1C, glycosylated hemoglobin)-The A1C is a blood test that provides information about your average levels of blood glucose over a 2-3 month period. This helps determine how well your diabetes has been managed over the time period. This term has been used for years to help guide us and the health providers with an idea of whether or not we need to improve our management of diabetes. An A1C could be good but if this value reflects a wide variations of highs and lows then the value is probably not ideal.
The red blood cells contain protein and when sugar enters in the blood it binds to these proteins. This binding creates glycated hemoglobin and the more sugar the higher the value of glycated hemoglobin (A1C). The Canadian Diabetes Guidelines suggest a goal for an A1C value of less than 7%. If your level is between 5.7 and less than 6.5%, you are considered to be in the pre-diabetes range. If the A1C is 6.5% or higher, then you are in the diabetes range. The A1C can now be used to diagnose diabetes as compared to years ago, this was not considered. The A1C value for children could differ and also for people who do not recognize the symptoms of hypoglycemia or the elderly. There is no one value that is appropriate for all patients with diabetes.
An estimated average glucose reading can be determined by knowing the A1C value. For example: an A1C value of 10 % is converted to an average blood sugar level of approximately 13 mmol/L (240 mg/dl). In the perfect world, the A1C value should be done about every 3 months but there are cases where diabetes has been in good control and twice yearly may be recommended and be appropriate for that individual.
There are certain situations that could cause your A1C value to be inaccurate. Some examples of this include:
If you were bleeding a lot, the protein in the red blood cell might be low and give you a lower A1C value
If you had a blood transfusion, your A1C might be lower
If your iron is low in your blood then your value might be higher
Your results might have been sent to a different lab so variations in reading at another facility could account for reading variations
If you have liver or kidney disease
Diabetes Canada has an excellent YouTube video on A1C.
Time-in-Range (TIR)- recently this term has surfaced in the diabetes world. TIR is a new parameter to evaluate blood glucose control.
Time-in-Range is the percentage of time that a person spends within their blood glucose target range which has been determined by you and your health-care provider. There will be variations between people but even for the same individual depending on their management requirements at any particular time. General guidelines suggest between 3.8 -10 mmol/L ( 70-180 mg/dl). This range should equate to an TIR greater than 70%.
We are being told that this single number captures a better picture of how our blood glucose is being managed throughout a day. Please refer to this reference to see visual examples. A Time-in-Range of 30% means that you are in your target range for 8 hours a day.
There is some reference to Time-below-range also referred to as TBR. Time-below- range is just as important so as to avoid hypoglycaemic reactions. A high percentage for the TBR tells us we need to make some adjustments to our management program. If I check my TIR on my pump now it tells me that over the last 7 days I am in range 79% of the time (almost 19 hours per day) but my time above range is approximately 3.5 hours (15%) which I don't like to see. However, fighting an infection can raise blood sugars so I have to try harder. If I check for a 14 day average I have almost the same results. Even though I am within an acceptable range I would still like it to be better but I am so pleased that my low percentage is minimal which has always been my problem.
Literature suggests that the TIR tells us more what life with diabetes is really like because it captures the variations in blood glucose throughout the day. This is in contrast to the A1C which is an average over a 2-3 month period.
Energy levels, moods, and quality of life vary from day to day for everyone but especially so for people with diabetes. The TIR can help capture these differences and help us make treatment decisions sooner.
A time-in-range value of 70% correlates with an A1C of approximately 7%, however, a time-in-range of 50% correlates to an A1C of approximately 8%
It is suggested that we use 14 days' worth of blood glucose data to determine our TIR.
At your next appointment talk to your team about this new parameter. You need to discuss TIR, TBR as well as time-above-range.
TIR is not a replacement for measurement of A1C. Rather, we should think of it as another tool to help us achieve and maintain overall glucose control. It appears to reflect our daily life experiences better which could help us make our management changes sooner.
I hope this topic was of interest to you. I know when I first heard about it I questioned its relevance to my management. For those of us who have had diabetes for so many years, we can look back and see how things have changed and how they have influenced our management. Time will tell how TIR will fit into our daily diabetes management.
References:
2)Diatribe
4)Diabetologia(2020)- by Andrew Advani . .
The information provided here does not replace any medical advice from your diabetes case managers.
Stay safe and Happy Halloween.
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