Variability Makes Urine Glucose Testing Unreliable

I posted this back in 2008, but it gets a lot of hits so I thought Id repost it.
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Youve just been to the doctor. He found sugar in your urine. But your blood sugars are usually in the 90s fasting, and around 140 mg/dl after meals, at least when you check. And isnt the renal threshold, or the level of blood glucose above which kidneys fail to reabsorb, and thus spill glucose into urine, often stated as 180 mg/dl?

Might your sugars be going higher without you knowing it?

In addition to home testing, a simple A1C test might indicate that fact. ¹

However, theres the possibility you could be spilling glucose at levels below 180 mg/dl. A fair amount of normal variability exists in the renal threshold - both among individuals and within an individual - which makes urine testing not a very dependable tool for detecting a high blood glucose.

Here are a few erences I found to that effect:

Tests Of Glycemia In Diabetes, Diabetes Care, 2004

"Reasons why the use of urine glucose testing to estimate blood glucose concentrations in diabetes management is undesirable include the following:

1. Although the renal threshold for glucose in healthy adults corresponds to a plasma glucose concentration of ~180 mg/dl (10 mmol/l), there is wide individual variation. Of particular importance are findings that adults, especially those with long-standing diabetes, may have substantial increases in this threshold, resulting in underestimation of the blood glucose level. Conversely, children and, particularly, pregnant women may have very low or variable renal thresholds, resulting in overestimation of the blood glucose level.
2. Fluid intake and urine concentration affect urine test results.
3. The urine glucose value lects an average level of blood glucose during the interval since the last voiding and not the level at the time of the test.
4. A negative urine glucose test does not distinguish between hypoglycemia, euglycemia, and mild or moderate hyperglycemia. Thus, urine glucose testing is of limited value in preventing hypoglycemia and hyperglycemia.
5. Urine glucose testing, which uses a color chart with which the test strip color is compared, is less accurate than capillary blood glucose monitoring, which typically uses a digital readout from a lectance meter.
6. Some drugs interfere with urine glucose determinations.
7. Evaluation of urine dipsticks reveals high imprecision at low glucose concentrations. Manufacturers claim that the test strips are positive if urinary glucose concentrations are 100 mg/dl or greater, but the data indicate this does not always occur."

Heres an older study that found pretty wide margins, +/- 150 mg/dl, in estimates of blood glucose from urine glucose...

Validity Of Urine Glucose Measurements For Estimating Plasma Glucose Concentration, Diabetes Care, 1983

"Although our observations show a significant correlation (P less than 0.0001) between plasma glucose concentration and urine glucose concentration or urine glucose excretion rate, the wide confidence limits [95% confidence limits (minimum) +/- 150 mg/dl] on plasma glucose concentration estimated from urine glucose measurements limit the clinical applicability of such estimates."

And one that found a mean of 130 mg/dl, much lower than 180 mg/dl, although it was a special population...

The Influence Of Renal Threshold On The Interpretation Of Urine Tests For Glucose In Diabetic Patients, Diabetes Care, 1980

"In a group of 65 insulin-dependent diabetic patients there was a wide variation in renal threshold, with a mean of 130 mg/dl (range 54-180 mg/dl). Threshold tended to rise with age, and it is suggested that the higher the renal threshold, the higher is the mean blood glucose achieved by the patient."

And a even older study, but telling ...

Renal Threshold For Glucose: Normal And In Diabetics, British Medical Journal, 1940

"The study of the renal threshold in diabetics and normals with healthy renal function shows frequent upward and downward deviations from the accepted "normal" figure of some 170 mg. per 100 c.cm.

The conception of a "normal" threshold is false. There is an average renal threshold, just as there is an average blood pressure, and the many deviations from it should be looked upon as physiological -- a matter of individual idiosyncrasy, and of no pathological significance."

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¹ HbA1C or just A1C is an abbreviation for glycosylated hemoglobin, blood levels of which can identify average glucose levels for an individual over approximately 120 days, the life span of a red blood cell.

Importance of Diabetes Diet and Blood Sugar Testing Strips in a Diabetic’s Life

Diet plays an important role in a diabetic’s life. Since all that we eat can affect the level of glucose in our body, it is important to take care of all that is included in daily diet. Here is a sample Diabetes Diet plan for a diabetic patient:

Diabetes Diet Plan

Morning

6 a.m. – Take ½ teaspoon fenugreek powder + water.

7 a.m. – A cup of sugar free tea and a mary biscuit.

8.30 a.m. A plate upma or oatmeal and half bowl sprouted grains. Have a cup of low fat milk without sugar

10.30 a.m. A fruit or low fat buttermilk, or lemon water

Afternoon

1 p.m. - 2 roti of mixed flour, a bowl of lentil, a bowl of yogurt, a bowl of vegetable, and a plate of salad.

Evening

4 pm - A cup of tea without sugar and a toast or a biscuit.

6 pm – A cup of soup

Night

8.30 pm - 2 roti of mixed flour, a bowl pulse, half bowl green vegetable, and a plate of salad.

10.30 pm – A cup of milk without sugar.

It is important to strictly avoid sugar, molasses, honey, sweets, and dry fruits. It is important to include a light exercise regime daily. For instance, you can go for 35-40 minute brisk walk daily. Also avoid oily food and increase the intake of fiber foods in meals.

Apart from following a strict diet, it is important that a diabetic patient checks his glucose levels daily at regular intervals. This is easy via using Diabetes Blood Sugar Test Strips.

Diabetes Blood Sugar Test Strips

Glucose testing is an imperative component of a diabetic’s daily health care. Without testing, a diabetic can easily become ill as his glucose levels may not be healthy. The test is conducted via using a glucose testing meter that uses diabetes blood sugar test strips.

The Blood Sugar Testing Strips are one of the major components of any diabetes monitoring system. A wide range of diabetes test strips are accessible these days on the market. These test strips are used in combination with a blood glucose monitor. The patient needs to prick himself to draw blood and apply to the test strip. The blood glucose monitor will detect the accurate amount of blood glucose present in the body.

Read more info about Diabetes Diet and Blood Sugar Testing Strips .

Choosing Wisely Unnecessary Testing and the Simplistic Use of Web 1 0 to Attempt Physician and Patient Behavior Change

The Model T

There are certain Disease Management Care Blog behaviors that the spouse finds.... objectionable.  She has verbally educated the DMCB about them and has left written notes about them.  Since these communications havent worked all that well, are there any other "channels" she could use? 

The DMCB spouse may be tempted to use the approach of the Choosing Wisely web-site. It provides lists of widely used medical tests and treatments that are typically unnecessary.  The lists (located here) were compiled as part of a joint physician and education project by organizations such as the American College of Cardiology (dont do stress tests in patients without cardiac symptoms) and the American College of Physicians (dont get back x-rays if the ache is non-specific). According to the press reports heralding the availability of this just opened web-site (for example), its purpose is to prompt patients and physicians "to work together" to not only make clinically wise choices, but save the U.S. health care system a lot of money.

The DMCB knows that the academic experts and organizations that developed these lists have been talking and writing about these wasteful tests and treatments for decades.  Waste has been the subject of infinite numbers of continuing education programs, grand rounds, published review articles, national meetings and guidelines.

Those approaches havent worked. 

So is the fix is to repackage the information and post it as simple text on a web page?

The DMCB cant say its impressed.  While the evidence underlying the clinical recommendations themselves is superb, there isnt any evidence that internet-based physician instruction is any better than traditional methods.  And if the purpose of the Choosing Widely web site is to prompt patient behavior change, the evidence that web-based education is better than print is pretty skinny there too. 

Its ironic that the intellectual rigor of the lists themselves wasnt matched by the same evidence-based approach to using the internet for this exercise in the first place.

Whats more, if these groups insisted on using the internet, the least they could have done was deploy a Web 2.0 approach.  The current Choosing Wisely site is so.... has been. 

That being said, there is some information that could be of use to the population health management service providers.  In contrast to the physician organizations, the DMCB is confident that theyll know how to package and present the information so that it can have a real impact.

The DMCB wishes Choosing Wisely good luck.  And in the meantime, it looks like the DMCB spouse will have to continue to rely on verbal and written feedback.... for now.