2. Erythrocyte sedimentation rate (ESR) is a non-specific test for inflammation. It is easy to perform, widely available, Inexpensive making it a widely used screening test. It is also used a monitoring tool for response to treatment in conditions in which it is raised (tuberculosis, autoimmune diseases etc). Basics: The ESR test in performed in the laboratory by placing anticoagulated blood in an upright tube (Westegren's most often). At the end of one hour, the rate of the RBC sedimentation is measured.

3. Factors affecting the ESR A- Effect of plasma protein Increased in the concentration of fibrinogen and Immunoglobulin's due to tissue injury will increase rouleaux formation and hence the rate of sedimentation. plasma albumin retards sedimentation of RBCs. B- The RBC size and number The size and number of RBCs that show alterations in their bioconcavity, like spherocyte and sickle cells, usually do not exhibit increase rate, unless there is severe anemia. Increase red cell mass will retard the sedimentation rate e.g. polycythemia.

4. C- Technical factors Perpendicularity of sedimentation tube, slight deviations from the absolute. Vertical can increase the result. Temperature (RT 18-25 C) higher temperature cause false high results due to reduction in plasma viscosity Vibration can reduce the ESR.

5. Sedimentation Phases The initial lag phase (10m) The phase of rapid RBC falling (40m) The packing phase (10m). Normal value: ESR values tend to rise with age and are generally higher in women. ESR is also elevated in the black population and those with anemia.

9. Reference Range Adult females 0-20 mm/h Adult males 0-15 mm/hr Children (<10) 0-10 mm/hr

10. Mechanism ESR is determined by the interaction between factors that promote (fibrinogen) and resist (negative charge of RBCs - that repel each other) sedimentation. Normal RBCs settle slowly as they do not form rouleaux or aggragate together. Instead, they gently repel each other due to the negative charge on their surfaces. Increased rouleaux formation contributes to high ESR. Rouleaux are stacks of many RBCs that become heavier and sediment faster. Plasma proteins, especially fibrinogen, adhere to the red cell membranes and neutralize the surface negative charges, promoting cell adherence and rouleaux formation

11. Procedure Patient must fasting at least 4 hours before testing. The blood sample must be mixed with anticoagulant agent in this test. Put 0.4 ml sodium citrate + 1.6 ml blood. OR put 0.2 ml sodium citrate + 0.8 ml blood. Mix gently with out shaking then put in the graded tube and leave it stand vertically on the stand for 1 hour. Read the amount of plasma that appeared without moving it then leave it to the second hour and read another time.

12. The aggregated RBCs in the rouleaux formation have a higher ratio of 'mass to surface area' as compared to single RBCs and hence sink faster in plasma.

13. ESR of more than 100 mm/hr is strongly associated with serious underlying disorders like connective tissue disease, infections and malignancies. ESR is helpful in diagnosing two specific inflammatory diseases, temporal arteritis and polymyalgia rheumatica.

14. Some conditions with very high ESR >100 mm/hr Multiple myeloma. Connective tissue disorders - SLE, RA and other autoimmune diseases. Tuberculosis. Malignancies. Severe anemia. 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.

15. Some conditions with low ESR: Polycythemia Severe Leukocytosis Sickle cell disease (anemia( Hereditary spherocytosis Congestive cardiac failure Corticosteroid use Hypofibrinogenemia Note that sickle cell anemia and spherocytosis have low ESR unlike other anemia's. This is due to reduced rouleaux formation owing to the abnormally shaped RBCs in this condition.

16. Important Erythrocyte sedimentation rate is a non-specific test and is not diagnostic of any particular disease. It has a high sensitivity but low specificity. Never base a diagnosis solely on an ESR value, either normal or high. Interpretation of the result should always be along with the patient's clinical history, examination findings and results of other tests done. If high ESR is encountered without any obvious reasons, patient should be reassured and the test repeated after a reasonable amount of time (a couple of months).

17. ESR and C-reactive protein (CRP) are both markers of inflammation. Generally, ESR does not change as rapidly as does CRP, either at the start of inflammation or as it goes away. CRP is not affected by as many other factors as is ESR, making it a better marker of inflammation. However, because ESR is an easily performed test, many doctors still use ESR as an initial test when they think a patient has inflammation.