Summary 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 < 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 < 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 < 0.01) in the counts between the sixth and the seventh hour. Our observations show that platelet counts in citrated blood samples arc lower than those in EDTA and highlight the necessity to present citrated samples mixed with dried EDTA when characterizationor quality control of blood and blood components is required. Analysis of the mean platelet volume (MPV) showed significantly lower values (6–13%, P < 0.05) in the citrated samples as compared to the same samples in EDTA, and a significant increase (4–6%, P < 0.01) on the addition of EDTA to the citrated samples after the sixth hour analysis.

In view of the currently available data, prevention of alloimmunization requires filters with higher efficiency to achieve a reduction in the number of leukocytes below 10 million per transfusion. Two versions (Pall PL-100 and PL-50) of the new generation leukocyte-depletion filters were studied. Single donor (SDPC)- and pooled multiple donor (MDPC) platelets were run in parallel. At a flow rate of 10 ml/min, the PL-100 filter was shown to effectively reduce the number of residual leukocytes to far below the critical immunogenic threshold of 10 million in all SDPC units and in 77% of MDPC units. Apheresis platelets appear not only to be better depleted than pooled multiple donor platelets, but also to have a better post-filtration platelet recovery (96% versus 84%). The efficiency of the smaller version of the filter (Pall-50) was higher than that of the Pall-100 filter for both single and pooled multiple donor platelet concentrates (PC). Leukocytes were absent in more than 92% of units in both types of concentrates. The maximal number of detected leukocytes was 2.2 million in a pool of 6 units. The outcome of filtration of 5-day-old pooled platelets was less favorable than filtration of 1- or 2-day-old pooled platelets, indicating that filtration soon after preparation is preferred to filtration after storage. Post-filtration platelet integrity, activation state, function, and morphology were all well preserved in both single and multiple PCs.

For safe blood transfusion, developing countries face considerable problems including serological screening and confirmation of blood-borne virus infections (HCV, HTLV-I, HIV and HBsAg). Confirmation tests are not only costly but also require sophisticated techniques and expertise. In order to provide this support we have attempted to perform a virus antibody confirmation test on samples dried on blotting paper (BP). Forty-nine sera derived from selected patients and donors from Bombay, and nine donors' sera from Bellarussia were transported on BP. In control experiments, dilutions of antibody-positive sera (HIV, HTLV-I & HCV) and 'blinded' HTLV-I antibody-positive and antibody-negative donors were applied on BP. Eluates from snipped BP were tested initially by screening tests, and the reactives were subjected to confirmatory tests for three types of virus antibody tests (HCV, HTLV-I & HIV) by blotting methods and neutralisation tests for HBsAg. There was considerable reduction of titres in dry sera but all BP-derived dry specimens gave excellent qualitative concordance with their liquid-equivalent sera, and the HTLV-I-positive donor was identified and reconfirmed correctly. Presence of only HCV antibody was confirmed in all the nine selected Bellarussian donors. Blood donors in Bombay had 3% HIV antibody, 6% HBsAg and none had HCV antibody, while selected patients showed substantially higher levels of these markers: HIV-antibody 64%, HBsAg 57% and HCV-antibody 17% confirmed positive. The cause of this high level remains to be established. Dry samples received by post seem to be an economical approach to a first step in providing some levels of independent confirmation of reactives in developing countries.

We have shown in this study that addition of dried K2EDTA (1.5 mg/ml) to blood samples anticoagulated with CPDA-1 increases significantly the platelet count and mean platelet volume (MPV) of whole blood, red cell concentrate (RCC) and platelet concentrate (PC), but not of platelet-rich plasma (PRP) or of platelet-poor plasma (PPP). Transmission and scanning electron microscopy illustrated that platelet aggregates which are present in some components are dispersed on mixing of the sample with EDTA and that this is accompanied by a change in platelet morphology. Determination of the platelet distribution width (PDW) indicated that the platelet populations in whole blood and RCC seem to be more uniform in size than the populations in PRP, PPP and PC. The determination of MPV and PDW changes after addition of EDTA may provide a new approach to quality control of PC.

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