Comparative Study of Erythrocyte Sedimentation Rate (ESR) three Sampling Techniques: Whole Blood in Tri-Sodium Citrate, Whole Blood in Ethylene Di Amine Tetra Acetic Acid (EDTA) , EDTA Blood Diluted with Tri–Sodium Citrate

Background: ESR is a simple, inexpensive test commonly used for screening of infective, inflammatory and neoplastic processes. The recommended standard method for ESR by the International Committee for Standardization in Hematology(ICSH) is the Westergren method where blood is allowed to sediment under optimum conditions in a westergren tube for a given period of time Recommended samples to be used for the test by ICSH are citrate,EDTA diluted in citrate and direct EDTA. When direct EDTA is used ICSH gives a formula to calculate a value that corresponds to citrate values.

Aim: In our study we compared ESR values done on three different samples. Whole blood collected into 3.8% Trisodium-citrate(4:1)(Method1) , EDTA(Method 2), EDTA anticoagulated blood later diluted with 3.8% Tri sodium citrate(4:1)(Method 3)

Methodology: 194 patients’ samples were analyzed irrespective of clinical conditions and gender. Samples were taken into citrate (in a ratio of 1:4, Citrate to blood) and EDTA anticoagulants. Citrate and EDTA samples were mounted directly into the westergren tubes and a third tube was mounted with EDTA blood from the EDTA tube diluted 1:4 with citrate in the laboratory.

Results: 194 results were grouped on HCT as 67 samples with HCT 0.35 and 127 with HCT > 0.35. Mean, SD and range of ESR for methods 1,2 and 3 were (33.81, 22.48,2-118) ,(46.53, 25.02 ,3-122) (32.31, 22.02,2-121)There was no significant difference between(P=0.23) method 1 and method 3. EDTA values were higher than citrated samples and difference was statistically significant (P=0.00). However when the values given by ICSH were substituted for EDTA values (method 2) they were comparable to methods 1 and 3(P=0.59; P=0.98) in patients with HCT<0.35. When HCT was >0.35 the difference was significant with the citrate samples (P=0.00) but not with the samples later diluted with citrate (P=0.103).All tests were conducted at 5% significance level.

Conclusion: ESR gives comparable values when samples are collected into citrate and when collected into EDTA and later diluted with citrate. When EDTA samples are directly mounted the corresponding value given by ICSH is valid when HCT is <0.35