As a 2nd-year medical student I can make a quick comment, that for the most part, the mg/dL is so ingrained that most of the coursework is done in these units. On several occasions we were told, however, that there is a slow conversion process underway to molar values, but that will likely take decades. From the little clinical data that I've seen, and judging by the values in medical journals, very little reporting goes on in mmol/L. Most labs can't even use the liter symbol properly.
Remek On Sat, Nov 29, 2008 at 7:07 AM, Pat Naughtin < [EMAIL PROTECTED]> wrote: > On 2008/11/29, at 6:19 AM, Martin Vlietstra wrote: > > As a diabetic I watch my sugar level. In the UK it is measured in mol/L. > However, when I was working in Germany, it was measured in mg/dL. I can > see > two advantages of mg/dl: > > 1) There are never any decimal points - levels are typically 60 to 105. > 2) Knowing that an adult male typically has 5 litres of blood in his > system, > it is easy to calculate how much sugar I shoudl have in my bloodstream > without having to know the molecular formula for sugar. > > Dear Martin, > > Let me consider your first point. Some of what you say here appears to be > simply an artefact of the conversion process. This is probably best > explained with an example. > > Here is some data that I quote from the Mayo Clinic (at > http://www.mayoclinic.com/health/blood-sugar/SA00102 ) and I have > interspersed some remarks. > > Fasting blood sugar test > > What is a fasting blood sugar (glucose) test? Measures the amount of sugar > (glucose) in your blood after you fast for at least eight hours or > overnight. > > What's normal? A normal range is 70 to 100 milligrams of glucose per > deciliter of blood (mg/dL) or 3.9 to 5.6 millimoles per liter (mmol/L). > > Note the precision of the initial figures, 70 and 100, as these have an > implied accuracy to one significant figure. > > What level suggests prediabetes? A level of 100 to 125 mg/dL (5.6 to 6.9 > mmol/L) indicates impaired fasting glucose — commonly known as prediabetes. > To confirm the diagnosis, your doctor may repeat the fasting blood sugar > test several days to a week later. > > Now the figures have been rounded to the nearest 25. Presumably, we could > consider these figures as +/- 12.5 and this would make the second, higher, > figure of 6.9 somewhere between 6.25 and 7.64. > > Let's say 7 without a fractional component to match the significant figures > in the original data. The lower figure using rational and reasonable > rounding now becomes 6 without a decimal. > > What level suggests type 1 or type 2 diabetes? A level of 126 mg/dL (7 > mmol/L) or higher is consistent with either type 1 or type 2 diabetes. To > confirm the diagnosis, your doctor may repeat the fasting blood sugar test > on another day. If your test results are 126 mg/dL (7 mmol/L) or higher > twice in a row after at least eight hours of fasting, you may have diabetes. > Further testing may be needed to determine whether you have type 1 diabetes > or type 2 diabetes. > > Noter how the Mayo Clinic writer has now reversed the accuracy by assuming > that the value 7 mmol/L is accurate and precise and that the former value of > 125 mg/dL in the previous paragraph has now mysteriously become 126 mg/dL > without a word of explanation. > > This mystery is simply the result of a poor understanding of accuracy and > precision that lead to bad rounding practices. > > At another loaction ( > http://www.medicinenet.com/script/main/art.asp?articlekey=17384 ) you will > find this table where they didn't bother to specify any units at all: > > For most people, good blood sugar levels are: > > On waking up (before breakfast) 80 to 120 > > Before meals 80 to 120 > > 2 hours after meals 160 or less > > At bedtime 100 to 140 > > I will assume that they refer to mg/dL and that 18 is a reasonable > conversion factor to go from mg/dL to mmol/L based on the molar mass for > glucose as 180.15588 g/mol (12.0107 g/mol)(6) + (1.00794 g/mol)(12) + > (15.9994 g/mol)(6) = 180.15588 g/mol. If I use the implied accuracy of > these figures based on the number of significant figures, and I use > appropriate rounding then these figures become: > > For most people, good blood sugar levels are: > > On waking up (before breakfast) 4 to 7 mmol/L > > Before meals 4 to 7 mmol/L > > 2 hours after meals 10 mmol/L or less > > At bedtime 6 to 8 mmol/L > > These figures now look, to me, to be at least as easy as the German figures > that you quoted. > With respect to your second point, your figure of 5 kilograms of blood in a > normal male looks a little low to me. Working on a ratio that blood composes > about 1/11 (one eleventh) of a human body, then 5 kilograms of blood is only > enough for a man who has a body mass of 55 kilograms. > > Cheers, > > Pat Naughtin > > PO Box 305 Belmont 3216, > Geelong, Australia > Phone: 61 3 5241 2008 > > Metric system consultant, writer, and speaker, Pat Naughtin, has helped > thousands of people and hundreds of companies upgrade to the modern metric > system smoothly, quickly, and so economically that they now save thousands > each year when buying, processing, or selling for their businesses. Pat > provides services and resources for many different trades, crafts, and > professions for commercial, industrial and government metrication leaders in > Asia, Europe, and in the USA. Pat's clients include the Australian > Government, Google, NASA, NIST, and the metric associations of Canada, the > UK, and the USA. See http://www.metricationmatters.com > <http://www.metricationmatters.com/>for > more metrication information, contact Pat at > [EMAIL PROTECTED] or to get the free '*Metrication > matters*' newsletter go to: http://www.metricationmatters.com/newsletter to > subscribe. > >
