Answers to your questions (Sasi's)

Answer to Chaur Lee’s query:

The factors that influence ESR results can be listed under two headings. First, those physical changes in blood plasma and cells, which to some degree the test is measuring and secondly those technical variables that must be avoided when performing the test.

Physical Changes in Blood
The ESR comes about via the interaction between red cells and plasma, therefore any physical variation in either component of blood will affect the result.

The rate of fall is dependent on: - Shape and size (density and surface area) of the red blood cell.Large cells fall faster than small cells. The presence of fewer cells allows for a faster fall rate that increased cell numbers. Cell shape variations , for e.g. abnormal cell morphologies such as sickling (HbS), may slow the rate of sedimentation. Increased albumin slows the fall of cells. An increase in other plasma proteins may increase the rate of fall. Changes in the red cells due to anaemia also usually increases the rate.

- Viscosity of the plasma. This is affected by a number of factors such as concentration of albumin or gamma globulins. Plasma proteins that affect the ESR include the immunoglobulins (IgM) and a number of the acute phase proteins including fibrinogen, C-reactive protein, alpha-1-anti-trypsin, haptoglobin, etc. These acute phase proteins increase with tissue damage (e.g. lupus or rheumatoid arthritis), pregnancy, chronic inflammation and chronic infection and hence increase the ESR rate.

Technical Variables
A number of external factors will affect the result.
Correct mixing of the blood sample before setting up the test is one of the most important factors influencing the ESR result.
Also, the rate of fall is affected by the tube diameter, angle of the tube sides to vertical, temperature, amount of vibrations present, and length of the tube. If a 3o tilt from vertical is present, it is possible that an error factor of 30% may be introduced in the test. A narrow lumen in the ESR tube will slow down the sedimentation rate giving lower results.

Other factors
Females tend to have higher ESR, and menstruation and pregnancy can cause temporary elevations.
Drugs such as dextran, methyldopa (Aldomet), oral contraceptives, penicillamine procainamide, theophylline, and vitamin A can increase ESR, while aspirin, cortisone, and quinine may decrease it.
Age also affects ESR. ESR increases with age in general.


Answer to Charmaint’s query:
Generally, ESR is a marker for inflammation.
It has been also a marker for temporal arteritis and rheumatoid disease as mentioned in my blog. Its also a marker for Lupus.
Apart from that, ESR can also be used as a prognosis marker of ischemic stroke and heart failure.
Many other diseases also increase the ESR: Infection, kidney disease, anemia, diseases involving white blood cells, cancer, and autoimmune and inflammatory diseases.


Answer to Kent’s query:
My lab’s using the Westergren method.
The Westergren method employs a 200 mm, 2.5 mm diameter tube vertically aligned column. The column is filled with blood anticoagulated with EDTA. The distance that the column of blood falls in one hour is recorded and reported in mm/ at the end of 1st hour.
The Wintrobe method employs a shorter tube (100mm) and a different anticoagulant (ammonium oxide and potassium oxalate) is used to mix with the blood.
It has one advantage over the Westergren method as it is able to correct for anaemia while testing patients with marked anemia provides no useful ESR data when using the Westergren method.
Though the Wintrobe method is sensitive for mild elevations, it has a higher false positive rate.
The Westergren method is also more sensitive for changes at elevated levels and may be more useful where the ESR is being used to evaluate the response to therapy for instance, in diseases such as temporal arteritis. Hence, the Wintrobe procedure is not used in most laboratories, the Westergren method being preferred.

Answer to Alex’s query:
Yes Alex, ESR is not diagnostic for any particular disease. It only aids in the diagnosis of the two diseases mentioned in my blod.
The two diseases that Ive mentioned, Temporal arteritis and Polymyalia Rheumatica are basically inflammatory diseases. For instance, ‘Temporal arteritis’ means means "inflammation of the temporal arteries." Since ESR measures inflammation, it is used to aid in the diagnostic aspect of these diseases, to confirm if there is inflammation in the first place. (The ESR rate in these diseases will be always be higher than normal.). When an inflammatory process is present, the high proportion of fibronogen in the blood causes red blood cells to stick to each other. The red cells form stacks called 'rouleaux' which settle faster.
Hence, ESR acts as a marker for these inflammatory diseases.
As for your query on the reference ranges:
The size of the red blood cell affects the ESR reading. The size changes according to the age. For instance, red blood cells are larger in neonates, though smaller in other children. Hence, the reference range is calculated accordingly.

Answer to Elaine’s query:
In our lab, we run control once in the morning daily using the high, normal and low controls which are commercially prepared. We also run another Internal Qc using internally pooled blood (from real patients) three times a day to make sure the precision of the FBC readings amongst the three machines stay constant throughout the day.
And Elaine, guess there was a misinterpretation of what I’ve mentioned about ABO grouping and ESR. Sorry! for not being clear. What I meant was, in our lab, once the EDTA tubes arrive at the haematology department, FBC is run first. Then, ESR is done. Only after these two tests are complete, the respective EDTA tubes are directed to ABO bloodgrouping. ESR is given the next priority after FBC as only then, there is a gurantee that the volume of the sample would be sufficient for ESR. If the respective EDTA tubes happen to go through all the other tests before ESR is run, by the time the tubes reach the ESR section, the volume of blood may not be sufficient for an effective ESR to be run. Hence, I did not mean that ABO bloodgrouping has to be done together with ESR hehe. Hope I’ve cleared your doubts on that.