RESUMO
Platelet counts on whole blood samples collected into tripotassium salt of EDTA, trisodium citrate (Na3 citr), citrate phosphate dextrose adenine formula 1 (CPDA-1) and acid citrate dextrose formula A (ACD-A), all showed a statistically significant drop (P less than 0.01) after 1 h standing at room temperature (RT) as compared with the immediate (within 30 min) counts. After 1 h the enumeration became stable in the EDTA samples but the drop continued up to 4-6 h in those samples taken into citrate. The decreases in citrate were significant (18-30%, P less than 0.001). The addition of EDTA (1.5 mg/ml) to the citrated samples after the sixth hour count created a significant rise (6-22%, P less than 0.01) in the counts between the sixth and the seventh hour. Our observations show that platelet counts in citrated blood samples are lower than those in EDTA and highlight the necessity to present citrated samples mixed wtih dried EDTA when characterization or quality control of blood and blood components is required. Analysis of the mean platelet volume (MPV) showed significantly lower values (6-13%, P less than 0.05) in the citrated samples as compared to the same samples in EDTA, and a significant increase (4-6%, P less than 0.01) on the addition of EDTA to the citrated samples after the sixth hour analysis.