DIAGNOSING DIABETES

What is Diabetes Mellitus?

Diabetes Mellitus is a disorder characterized by a higher than normal blood glucose (hyperglycemia).

 

Why does blood sugar remain high in certain persons?

Insulin is a hormone that is produced by the beta cells in the pancreas (a gland which lies just behind the stomach). Since Insulin normally controls the levels of glucose in the blood, persons who have a deficiency either in the production of or in the usage of Insulin, have elevated levels of blood glucose.

The sugars and starches that we eat are converted into Glucose, which is transported in the blood. For glucose to leave the blood stream and enter cells where it is burned to provide energy, Insulin is required. So without insulin, cells are deprived of glucose and energy, and the level of glucose in the blood rises.

 

How is Diabetes Mellitus detected?

Diabetes Mellitus is detected by estimating glucose in the blood. The test is best conducted on the plasma of an individual, by photometric methods (automated or otherwise). The diagnosis is confirmed by performing the Modified OGTT.

 

How is Diabetes Mellitus diagnosed?

The earlier practice of diagnosing DM by estimating a fasting sample followed by five samples collected at half hourly intervals known as OGTT (Oral Glucose Tolerance Test) has now been replaced by a simpler version which entails only two needle pricks to the patient as one fasting and one sample 2 hours after 75 gram Glucose load are taken. This is sometimes known as Modified Oral Glucose Tolerance Test. The results obtained can be compared with the WHO recommended values for the diagnosis of Diabetes Mellitus (DM), Impaired Fasting Glycemia (IFG) or Impaired Glucose Tolerance (IGT). (See chart under GLUCOSE LEVELS)

 

Are there any special conditions for taking this test?

Yes. Before taking OGTT for the confirmation of Diabetes Mellitus, you should be consuming a normal diet containing more than 150 Gms of carbohydrates for at least 3 days prior to the test. The first blood sample is taken after 8 – 14 hours fast.

 

  

What are the different types of blood samples on which glucose can be estimated?

Blood consists of cells and a watery part called “plasma”. Most advanced laboratories use plasma for the estimation of glucose hence the result is known as “plasma glucose”. In the laboratory sample tube a chemical is added to stop the utilization of sugar by the cells, after the blood sample is added into it (so that the glucose level does not fall when stored for a few hours).

 

The term blood glucose is used to indicate the estimation of glucose on “whole blood” whether obtained from a vein (Venous blood) or by a finger prick (Capillary blood).

 

When blood is kept in a tube that does not contain a chemical (a plain tube), the blood clots after some minutes. The separated watery part is called ‘serum’. This is normally not used for estimation as the red cells in contact with the serum keep using the available glucose for their survival; resulting in lower levels of glucose at the time of estimation. The longer they stay in each other’s contact, the lower the level. The serum, thus, does not provide a dependable glucose level result.

 

What type of sample is used in home monitoring machines?

Capillary whole blood is used for estimating glucose in these machines since the blood obtained by a finger prick is the capillary blood.

 

Do the glucose values obtained by the home monitoring machines correlate with those obtained from the laboratories?

No.  The values are different for capillary whole blood, venous whole blood and plasma. (Please see Glucose Values for detailed values)

 

What is the normal reference range for blood glucose?

Please see the charts given under GLUCOSE LEVELS.

 

What do the terms IFG & IGT stand for and what is their significance?

The plasma glucose levels falling in the IFG (Impaired Fasting Glycemia) and IGT categories are not diabetic, but they are not normal either. These values are pre-diabetic or in other words, the person having these values is more prone to become diabetic. Such persons should take utmost care by regulating their diet and by regular exercise so that their conversion into overt Diabetics is prolonged as much as possible.

 

What are the ideal levels of glucose in the blood in a person with Diabetes?

Please see the charts given under GLUCOSE LEVELS.

 

What is HbA1c and how does it help persons with diabetes?

The measurement of HbA1c actually is the measuring of the amount of glucose sticking to the hemoglobin in the red blood cell. The result indicates the average of the level of HbA1c in the blood during the past 4 – 6 weeks, hence a good indicator of glycemic control.

For details, please read Hemoglobin A1c.

 

                                   HEMOGLOBIN A1c (HbA1c)                          TOP

(Pronounced as H-b-A-one-c)

 

 

What is HbA1c?

Hemoglobin is the compound in the red blood cells that transports oxygen. There are several variants of which Hemoglobin A constitutes about 90%. The ‘1’ is the subtype of ‘A’ and ‘c’ is the subscript to the ‘1’. Therefore, measurement of HbA1c actually is the measuring of the amount of glucose sticking to the hemoglobin in the red blood cell.

 

How is this test done?

The blood sample for this test can be given at any time of the day without any relation to meals, as the result indicates the level of HbA1c in the blood during the past 4 – 6 weeks.

 

How is the determination of a hemoglobin variant useful in the control of diabetes?

Red blood cells have ‘insulin-independent’ transporters on their surface and so they do not require insulin for the uptake of glucose. When glucose molecules attach to HbA molecules HbA1c is formed by the process of ‘glycosylation’ or ‘glycation’ which occurs naturally in the body. Therefore, (a) the higher the level of glucose in the plasma, the glucose level inside the red cell will also be high (b) the longer the period of high level of glucose in the plasma, the higher the level of HbA1c.

Is everyday change in the level of glucose in blood reflected in the HbA1c level? 

Once the sugar is attached to hemoglobin, it stays there for the life of the red cell, which is about 120 days. Since HbA1c levels depend primarily on time-averaged blood glucose levels, it makes sense that HbA1c levels provide a reflection of glycemic control during the past 4 – 6 weeks.

 

What is the importance of this test?

As a key measure of glycemic control, HbA1c testing is becoming one of the most frequently-ordered laboratory tests for diabetic check-ups.

 

Why should more people know about this test?

 The publication of landmark clinical studies, the Diabetes Control and Complications Trial (DCCT) and the U.K. Prospective Diabetes Study (UKPDS) have shown that HbA1c estimation not only helps in maintaining a tight glycemic control but lowering the hemoglobin A1c number can delay or prevent the development of serious complications of the kidneys (nephropathy), eyes (retinopathy) and nerve diseases (neuropathy) in people with diabetes. This study also showed that lowering HbA1c levels by any number improves a person’s chances of staying healthy.

                   

How can hemoglobin A1c test result help people with diabetes?

If you are a diabetic and know the result of the HbA1c test, you can take an active role in the diabetes management. If your test result of HbA1c is close to normal, your treatment plan is probably working and it is likely that the blood sugar level is under control. If your HbA1c level is high, you must immediately consult your Diabetologist for his/her advice.

 

Is HbA1c the same as Glycated Hb?

Although this test is conducted by various techniques, almost all of them do not report true HbA1c. In such cases the reported HbA1c is calculated from estimation of total HbA1 fraction, which includes other sugar modified hemoglobins. Some methods measure all the other hemoglobin variants and then reported as Total Glycated Hemoglobin or Glycohemoglobin (GHb).

 

Is there a method available for estimating True HbA1c?

Currently the chromatographic method is the only method that estimates true HbA1c directly.

 

HbA1c test is being conducted at sindlab by a dedicated, fully automated instrument, which utilizes the chromatographic technique. This method was used as a reference method for the Diabetes Control and Complications Trial (DCCT). The National Glycohemoglobin Standardization Program (NGSP) also certifies this instrument and its reagents.

Routinely, the result of this test is available from sindlab on the same day but it can be given earlier if required on urgent basis.

 

Normal Range of HbA1c

Unfortunately all the different methods described above measure slightly different things therefore one reference range, which is given in percentage, can not be given that will fit all the methods. The laboratory conducting the test usually gives the range according to the method being employed.

In a non-diabetic person, the formation, decomposition and destruction of HbA1c reaches a steady state with about 3.0% – 6.5% of the hemoglobin being of the HbA1c subtype.

 

 

                                 SPERM FERTILITY EVALUATION                                    TOP

 

1.  What is the importance of semen evaluation by computerized instruments, as against manual methods?

The person conducting the test by manual technique can only see the sperms in two dimensions but tries to count the targets that move in three dimensions. Worse, when a microscopy sample is made very thin to reduce that third dimension, motility data is distorted. In almost all the laboratories of Pakistan, the manual technique is used. Semen analysis is one of the very few laboratory tests, which has required “estimates” by the person performing the test. It is easy to make estimates, but to be accurate and consistent is almost impossible. Using a computerized instrument eliminates all these elements.

2.  

   HHow does the automated QA instrument work?

The liquefied semen is sucked up a specially designed disposable capillary, which has a precise cross section, and inserted into the instruments optical chamber.

A precision light beam passes through the capillary. The resulting small changes in the light due to passing/moving sperm cells is picked up by the fiber optic sensor and measured by a phototransistor, or light sensor.

That signal is digitized and fed to a built-in computer, which uses a sophisticated algorithm to analyze the data and generate the displayed results.

 

3.           The various displayed results:

 

The conventional W.H.O. parameters of the total cell concentration, percent motile cells, percent motile cells and percent normal morphology are reported. In addition, the instrument generates the Sperm Motility Index (SMI) and Total Functional Sperm Concentration (TFSC).

For details, please see Definitions & Interpretation of the five Computerized Parameters.

 

4.  How accurate is this technology?

The QA instrument results are more accurate than a well-performed microscopy and are highly correlated with CASA system operated by a trained andrologist.

 

5.  How easy is it to make a procedural error?

It is very difficult. The internal computer will not permit the test to be carried out if the instrument fails its own self-test.

Similarly the internal computer will not permit a “wrong” button to be pushed. If the sample has not fully liquefied, it won’t climb into the capillary.

 

6.  How sensitive is the QA Instrument?

It is very sensitive. Even if the concentration of viable cells is extremely low (less than 500,000 motile cells /mL), the instrument can provide an accurate reading of the impregnation potential of the sample. The count below this number does not bear statistical correlation to the WHO parameters. They are, however, a confirmation of grave sub fertility to any physician.