Efficacy of the Latham blood processor to perform plateletpheresis

Complications of donor apheresis

A decreasing blood donor pool in the presence of increasing blood transfusion demands has resulted in the need to maximally utilize each blood donor. This has led to a trend in the increasing use of automated blood collections. While apheresis donation shares many reactions and injuries with whole blood donation, because of the differences, unique complications also exist. Overall, evidence in the literature suggests that the frequency of reactions to apheresis donation is less than that seen in whole blood donation, though the risk of reactions requiring hospitalization is substantially greater. The most common apheresis-specific reaction is hypocalcemia due to citrate anticoagulation, which, while usually mild, has the potential for severely injuring the donor. Other reactions to apheresis donation are uncommon (e.g., hypotension) or rare (e.g., air embolism). More worrisome, and in need of additional study, are the long-term effects of apheresis donation. Recent evidence suggests that repeated apheresis platelet donations may adversely effect thrombopoiesis as well as bone mineralization. Granulocyte donation has also been implicated in unexpected long-term consequences.

Quo vadis haemapheresis. Current developments in haemapheresis

The techniques of haemapheresis originated in the development of centrifugal devices separating cells from plasma and later on plasma from cells. Subsequently membrane filtration was developed allowing for plasma-cell separation. The unspecificity of therapeutic plasma exchange led to the development of secondary plasma separation technologies being specific, semi-selective or selective such as adsorption, filtration or precipitation. In contrast on-line differential separation of cells is still under development. Whereas erythrocytapheresis, granulocytapheresis, lymphocytapheresis and stem cell apheresis are technically advanced, monocytapheresis may need further improvement. Also, indications such as erythrocytapheresis for the treatment of polycythaemia vera or photopheresis though being clinically effective and of considerable importance for an appropriate disease control are to some extent under debate as being either too costly or without sufficient understanding of the mechanism. Other forms of cell therapy are under development. Rheohaemapheresis as the most advanced technology of extracorporeal haemorheotherapy is a rapidly developing approach contributing to the treatment of microcirculatory diseases and tissue repair. Whereas the control of a considerable number of (auto-) antibody mediated diseases is beyond discussion, the indication of apheresis therapy for immune complex mediated diseases is quite often still under debate. Detoxification for artificial liver support advanced considerably during the last years, whereas conclusions on the efficacy of septicaemia treatment are debatable indeed. LDL-apheresis initiated in 1981 as immune apheresis is well established since 24 years, other semi-selective or unspecific procedures, allowing for the elimination of LDL-cholesterol among other plasma components are also being used. Correspondingly Lp(a) apheresis is available as a specific, highly efficient elimination procedure superior to techniques which also eliminate Lp(a). Quality control systems, more economical technologies as for instance by increasing automation, influencing the over-interpretation of evidence based medicine especially in patients with rare diseases without treatment alternative, more insight into the need of controlled clinical trials or alternatively improved diagnostic procedures are among others tools ways to expand the application of haemapheresis so far applied in cardiology, dermatology, haematology, immunology, nephrology, neurology, ophthalmology, otology, paediatrics, rheumatology, surgery and transfusion medicine.

Frequently used plateletpheresis techniques result in variable target yields and platelet recruitment of donors

BACKGROUND

Standard plateletpheresis techniques and effects on platelet (PLT) donors were investigated to provide an informative basis for advancement of apheresis software.

STUDY DESIGN AND METHODS

Three paired groups with 33 male and 22 female blood donors were prospectively investigated by analyzing blood counts of donors and products. Four apheresis platforms, the COBE Spectra LRS and the Trima v4 (Gambro BCT) and the AS.TEC204 and the COM.TEC (Fresenius Hemocare), were compared. Deviations of the collected from programmed PLT targets and donor PLT recruitment were calculated for single-unit PLT concentrates (SU-PCs; 3 x 10(11) PLTs) and double-unit PLT concentrates (DU-PCs; 6 x 10(11) PLTs).

RESULTS

Regarding SU-PCs, the productivity of the COM.TEC machine was superior to the AS.TEC204 machine, because of shorter processing time (54 min vs. 67 min) and higher yields (2.90 x 10(11) PLTs vs. 2.75 x 10(11) PLTs). Compared to the Spectra machine, the Trima v4 machine showed higher collection efficiencies (CEs) and shorter processing time and complied better with the programmed target (SU-PCs, 3.24 x 10(11) PLTs vs. 3.70 x 10(11) PLTs; DU-PCs, 6.87 x 10(11) PLTs vs. 7.56 x 10(11) PLTs). Harvests of the Spectra machine (DU-PCs) exceeded the target by 40 percent, which resulted in high PLT loss for donors. A longer processing time resulted in some higher CEs (SU-PCs, 53%; DU-PCs, 58%), which could contribute to this result. PLT recruitment compensated PLT loss to some extent.

CONCLUSION

The major finding was that the newer devices (COM.TEC and Trima) gave more predictable yields than the older devices (AS.TEC204 and Spectra) and resulted in lower PLT deficit. PLT software should be improved to minimize relevant variations of collected yields regarding the programmed target.

Peripheral blood stem cell collection with reduced platelet loss to the patient/donor

Apheresis procedures that optimize peripheral blood stem cell (PBSC) harvesting also result in a significant loss of platelets to the patient/donor because of their similar densities. We compared the percent drop in platelet count and hemoglobin concentration in the patients before and after PBSC collection using two different collection chambers with the CS-3000. A modified plateletpheresis procedure was utilized. Seven patients underwent 38 PBSC collections during steady state hematopoiesis using the standard A-35 collection chamber. At the end of the procedure, a second low-speed centrifugation of the PBSC concentrate was performed in the manual mode, with siphoning out and return of the PRP to the patient through a transfer pack. For 14 patients who underwent 113 PBSC collections, a small volume collection chamber (SVCC) was substituted for the A-35 chamber and the second centrifugation step was omitted. These patients were also primed with 4 g/m2 of cyclophosphamide. The percent drop in platelet count in the patients after the collection procedures was significantly less in the SVCC group (20.4 +/- 9.1 vs. 36.0 +/- 12.3, P = 0.000), even after correction for the difference in the volume of blood processed between the two groups (3.2 +/- 1.4 vs. 3.9 +/- 1.3, P = 0.006). The percent drop in hemoglobin concentration was also less with the SVCC both before (5.4 +/- 3.8 vs. 11.7 +/- 3.0, P = 0.000) and after (0.8 +/- 0.6 vs. 1.3 +/- 0.3, P = 0.000) correction for the difference in the volume of blood processed.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of platelets collected by a new portable apheresis device

We studied the efficiency of platelet collection by the Mobile Collection System (MCS) using two types of experimental protocols and evaluated the effect of storage at 22 degrees C on the platelet concentrates (PC). MCS is a new blood cell separator that combines discontinuous flow features with a new computerized operating system and can be used to harvest either full units of apheresis PC (SDP protocol) or half units of PC together with one to two units of plasma (PLP protocol). On the average, 1.98 x 10(11) +/- 0.46 x 10(11) (mean +/- SD) platelets were obtained by the PLP protocol and 3.01 x 10(11) +/- 0.70 x 10(11) and 4.2 x 10(11) +/- 1.12 x 10(11) by the early and later versions of the SDP protocols, respectively. The mean number of WBC per PC ranged from 3.3 to 4.7 x 10(8). During the storage period pH stayed above 7.0. On the average, the production of one molecule of lactate corresponded to the consumption of 0.538 molecules of glucose, indicating that less than 8% of glucose was consumed by the oxidative pathway. There were only small increases in LDH and B thromboglobulin concentrations. Furthermore, the ability of platelets to recover from osmotic shock and to aggregate following exposure to dual agonists declined only slightly during storage, indicating that both viability and function of platelets collected by the MCS were preserved during storage.

The effect of plateletpheresis on the Fenwal CS-3000 on donor platelet counts

To evaluate the risk of significant plateletpheresis-induced thrombocytopenia in normal volunteer donors undergoing plateletpheresis less frequently than every 56 days and to help understand factors influencing platelet yield in these donors, pre- and postapheresis platelet counts (X 10(3)/microliter) and platelet yields were analyzed from 916 plateletpheresis procedures (Fenwal CS-3000) on 607 donors (405 men, 202 women). The mean preapheresis platelet count was 265 +/- 59 (SD) (range 155-650) (men 256 +/- 55 [170-444]; women 284 +/- 65 [155-650]; P less than .001, t-test). After an average platelet yield of 4.08 X 10(11), the mean postplatelet count was 185 +/- 46 (range 72-420) (men 184 +/- 42 [80-345]; women 194 +/- 52 [72-500]; P less than 0.1). The percent decrease in platelet count (mean 29.4 +/- 13, range -28.1-65.5) had positive correlations with platelet yield (P less than .01, r = 0.10), predonation platelet count (P less than .001, r = 0.29), and age (P less than .01, r = .10) and a negative correlation with weight (P less than .001, r = 0.18) Both the percent decrease and platelet yield were significantly higher in women than in men (P less than .001, t-test), and platelet yield was best predicted by preapheresis platelet count in both sexes (r = 0.65). The effects of plateletpheresis on donor platelet count thus vary widely among donors. Although a decrease of greater than 50% was not a rare event (5.9% of all procedures), in only three instances (0.3%) was the actual postapheresis platelet count below 100 (72, 94, 95). Thus, plateletpheresis in normal donors appears unlikely to produce clinically significant thrombocytopenia immediately after apheresis.

Continuous-flow techniques for platelet concentrate collection: a step toward standardization and yield predictability

This study chronicles leukocyte- and erythrocyte-depleted platelet concentrate collection by a dual stage channel in which three variables: 1) donor peripheral blood platelet concentration, 2) total blood processed, and 3) collection volume were statistically correlated with platelet yield as determined by a multiple regression analysis of single variables. Platelet concentration in the final yield was related to donor precount and collection rate, and could be varied as indicated for individual applications. Total blood processed was established by procedure time, which in turn was defined by citrate-induced calcium changes in the donor. Reduction in peripheral blood platelet concentration averaged 24% for a mean platelet yield of 3.8 X 10(11). An average of 40% of transfused platelet concentrates were recovered in recipient peripheral blood 1 hr posttransfusion and were hemostatically effective, as determined by correction of bleeding time. Platelet yields and patient response were sustained during current collection procedures, verifying the principles described during the investigative period.

Preliminary Study on Plateletpheresis with the CS-3000 Blood Cell Separator Using a Single Phlebotomy Technique

A coaxial dual flow catheter has been tested for thrombapheresis with a continuous flow blood cell separator in order to render the procedure as comfortable as possible for our donors.

Therefore, two groups of five donors underwent a standard plateletpheresis: 3500 ml of blood were withdrawn at a speed of 35-45 ml per minute and were anticoagulated with ACD-A in a 1/9 ratio to whole blood.

In the first group one vein puncture was effectuated with the coaxial catheter after local anesthesia. Two 14G catheters were used in the second group. In both groups the platelet yield was studied as well as the half life of 111-Indium-oxinate labeled platelets after autologous transfusion.

Although the comfort of the donors was greatly improved, the one needle procedure resulted in a mean platelet yield of 1,28.1011 while the two needle procedure yielded 3,46.1011 platelets.

In contrast, the survival of the platelets after autologous transfusion did not differ significantly in the two groups: t 1/2 in group I was 3,94 d, in group II 3,66 d.

It is advocated that the poor efficacy of the single needle procedure might be due to recirculation.

Long-term follow-up of donors cytapheresed more than 50 times

11 volunteers who had donated white blood cells or platelets more than 50 times over a 5- to 9-year period were studied to determine whether any adverse consequences of many cytaphereses could be detected. Among the donors no significant differences were found in 18 hematological and biochemical parameters when compared to a group of age- and sex-matched nondonor controls. Despite extensive cumulative lymphocyte losses sustained by these donors, the ratio of T, B, helper and suppressor cells has been maintained within the normal range. No detrimental effects of multiple cytapheresis on the donors' health has been demonstrated to date.

A new method to collect granulocytes using a low dose of hydroxyethyl starch

A new granulocyte collection method employing discontinuous flow centrifugation and low donor dose of hydroxyethyl starch (HES) is presented. Following the procedure, the increase in serum polysaccharide concentration was 100 mg/dl, about 20% of that seen after standard discontinuous flow leukapheresis. The average efficiency of granulocyte collection by this method is about 64%. The average yield of WBC from 2,600 ml of donors' whole blood is 1.64 +/- 0.54 x 10(10) (mean +/- 1 SD) and the average granulocyte yield is 1.33 +/- 0.51 x 10(10) (mean +/- 1 SD). The granulocytes were shown to migrate to the sites of infection in vivo. This approach is an improvement over standard discontinuous flow leukapheresis because of the high efficiency of granulocyte collection and because multiple procedures are possible without exposing donors to more HES than is currently given during a single procedure.

Plateletpheresis experience with the Haemonetics Blood Processor 30, the IBM Blood Processor 2997, and the Fenwal CS-3000 Blood Processor

Comparisons were made of the apheresis instruments Haemonetics Blood Processor 30, IBM Blood Processor 2997 and Fenwal CS-3000, for collection of platelets from normal donors. With each instrument the mean recovery was at least 4 x 10(11) platelets per procedure, and each instrument afforded a safe and reliable collection. The Haemonetics Blood Processor gave the lowest recovery of platelets per minute per procedure. The IBM Blood Processor 2997 required the longest time for set-up and priming and processed 1.5 liters more donor blood per collection than the other instruments. The Fenwal CS-3000, which is a computer-controlled instrument, was the least time consuming. The donor suffered a significantly greater drop in platelet count after collection with the IBM Blood Processor 2997 (31%) than after collection with the other instruments (19%), and we were unable to account for this observation.

Recovery, life span, and function of stored plateletpheresis units

Plateletpheresis units collected using the Haemonetics Model 30 or the IBM 2997 cell separator were stored for 24 h at 22 degrees C. Autologous recovery and life span measurements averaged 64 +/- 13% (1 SD) and 8.9 +/- 1.3 (1 SD) days. The hemostatic effectiveness of these preparations were satisfactory; the corrected increment 4-6 h and 18-24 posttransfusion was 20,400 and 13,400/microliter/m2, respectively, and the bleeding time showed improvement in each patient. There was no significant difference in these parameters between collection devices.

Oncology Grand Rounds. Platelet transfusion--clinical applications in the oncology setting

The increased availability of platelets for transfusion has been a major factor in the improved prognosis noted in patients with acute nonlymphocytic leukemia. This review summarizes our current understanding of the proper use of platelet transfusion for patients with leukemia and cancer, with a particular emphasis on the management of alloimmunized patients. The need for careful and close collaboration between the blood bank and the referring clinicians is emphasized. Cryopreservation of autologous platelets, which can be of considerable assistance in the management of alloimmunized patients, and a summary of the large number of questions that still require further investigation are presented.

Redistribution of platelets during discontinous flow platelet pheresis

Greater numbers of platelets are recovered during discontinuous flow centrifugation than can be simply accounted for by the decrease in total circulating platelets in the donor. There is a linear relationship between the logarithm of the circulating platelet count and the number of plateletpheresis bowls filled. The disappearance of platelets from the peripheral circulation occurs at a greater rate in splenectomized donors than in normal donors, and the rate of platelet disappearance in normal donors is less than what would be expected if there were no in vivo platelet storage pools. The data suggest the redistribution of platelets from the spleen in normal donors during the time course of the procedure.

Plateletpheresis by discontinuous centrifugation: effect of collecting methods on the in vitro function of platelets

The in vitro function of platelets collected by two different methods during centrifugal plateletpheresis was compared. The RBC method involves collecting platelets with red cells followed by a supplementary spin to remove them, whereas the no-RBC method requires collecting platelets only from the buffy coat without red cells. Platelet response to adenosine diphosphate (ADP), epinephrine and collagen was slightly reduced in platelet-rich plasma (PRP) prepared by no-RBC technique and was markedly decreased in samples obtained by the RBC technique when compared to prepheresis controls. The decrease in platelet response to ADP, epinephrine and collagen was apparent in three testing systems: aggregation, release of serotonin and reptilase clot retraction. Both plasma and platelets appeared to be affected by the pheresis procedure. Platelet preparations obtained by both RBC and no-RBC techniques showed an increase of platelet factor 3 activity and an enhancement of aggregation, release of serotonin and clot retraction induced by thrombin as compared to prepheresis controls. Postpheresis platelet-poor plasma contains platelet membrane fragments which exhibit a high platelet factor 3 activity. The results showed that the RBC method, although providing a higher platelet yield, caused more qualitative alterations in platelets than in those obtained by no-RBC method, and that both methods of collecting platelets activated the procoagulant activity of platelets.

Efficacy of platelets collected by semi-continuous flow centrifugation (Haemonetics Model 30)

The viability of both autologous and donor platelets collected by means of a semi-continuous flow centrifuge (Haemonetics Model 30) was measured. Radiochromium labelled pooled platelets harvested from six passes and reinfused into their normal donors showed recoveries and survivals of 58% +/- 8 and 9.6 d +/- 0.8 compared with normal values of 65% and 9.5 d +/- 0.6, respectively. When the viability in aplastic thrombocytopenic recipients of platelets collected from normal donors by the Haemonetics Model 30 was compared with that of platelets collected from the same donors by multiple bag plateletpheresis the results were very similar: recoveries of 82% +/- 18 and 80% +/- 25 and survivals of 3.9 d +/- 2.0 and 3.8 d +/- 1.3, respectively. The in vitro function of the collected platelets in response to aggregating agents was normal when measured within 60 min of collection at pH 7.4. The relationship between bleeding time and post-transfusion platelet count in aplastic, thrombocytopenic patients showed that in vivo function was maintained.

Platelet transfusion therapy

Platelet transfusions are of unquestionably proven benefit for the correction of thrombocytopenia or functional platelet disorders, and they have allowed for more intensive antineoplastic therapy. With the advent of blood component therapy most modern blood banks now have the capabilities for supplying at least limited quantities of platelets. Refinements in procurement methods will inevitably lead to a greater supply of platelets and the establishment of larger transfusion programs. These programs will need to incorporate facilities for platelet storage, recruitment of suitable donors, selection of special donors for refractory patients, and methods for quality control. As antineoplastic therapy becomes more aggressive, such transfusion programs will become an integral part of the operation of cancer treatment centers.

Laboratory and clinical effects of the infusion of ACD solution during plateletpheresis

Transfusion of massive amounts of citrate anticoagulated blood during plateletpheresis with the intermittent flow centrifuge can produce symptoms and electrocardiographic changes suggestive of hypocalcemia. Following 15 procedures the ionized calcium decreased by an average of 32.4%, the average postpheresis serum citrate was 26.7 mg/dl and the QT interval was prolonged by 0.08 sec. Twelve plateletphereses performed with half-strength ACD solution caused an average decrease in ionized calcium of 16%, serum citrate levels of 12.5 mg/dl and QT prolongation of 0.04 sec. No donors experienced significant clinical symptoms with citrate infusion rates of less than 65 mg/kg/h. Solutions with citrate concentrations lower than ACD-A should be developed for use in plateletpheresis procedures involving citrate infusion rates greater than this.

Plateletpheresis using the haemonetics model 30 cell separator

Plateletpheresis using the Haemonetics Model 30 cell separator results in a mean collection of 5.5 X 10(11) platelets. This product contains substantial numbers of erythrocytes and mononuclear cells which can be effectively removed by centrifugation but with a 23% loss of platelets as well. The mean decrement in donor's platelet count during the procedure, which is 78,000/mm3, is not commensurate with the number of platelets collected suggesting donor platelet mobilization. Platelets collected by this technic, when transfused into unselected recipients, give platelet increments comparable to platelets produced in the standard batch manner.

Utilization of a new strength citrate anticoagulant during centrifugal plateletpheresis. I. Assessment of donor effects

A reduction of donor effects during centrifugal plateletpheresis with the Haemonetics Blood Processor was achieved by reducing the concentration of the citrate anticoagulant. Serum citrate and ionized calcium levels, immediately and 1 h post-pheresis, were affected to a lesser extent by using 5.0 g total ionized citrate (TIC) THAN WITH EITHER 8.0 G OR 11.0 G. Total calcium, bicarbonate, prothrombin time, partial thromboplastin time, ECG, and platelet counts were affected to a similar degree by all three TIC formulations. The total number of platelets collected per litre of blood processed was not significantly different among the three TIC formulations. In vitro studies employing the screen filtration pressure (SFP) technique showed no evidence of platelet aggregates in whole blood collected into either 0.01 M or 0.005 M citrate and agitated or left stationary at room temperature for 5 h. The use of different citrate concentrations in plateletpheresis is discussed.

Clinical experience with transfusion of cryopreserved platelets

Multiple units of platelet concentrate obtained by plateletpheresis of normal, 'random' or HL-A matched donors were pooled and frozen in polyolefin bags using 5% dimethysulphoxide (DMSO) as a cryoprotective agent and a controlled freezing rate of I degrees C/min. The platelets were stored at approximately-I20 degrees C for as long as 20I days, thawed rapidly at 37 degrees C, washed once and resuspended in ACD plasma prior to transfusion. Two different final concentrations of platelets (approximately 2.7 and 9.0 X 10(12)/1.) were studied. Twenty-three thrombocytopenic patients have received a total of 40 frozen platelet transfusions. The mean freeze-thaw loss was 2I% and was similar for both platelet concentrations. All transfusions were well tolerated and there were no side effects attributable to the small amounts of DMSO infused. Increments in platelet counts I h after transfusion ranged from 0 to 102 X 10(9)/1. with an overall mean corrected increase in evaluable patients of 12 800 (increase x surface area (m2)/number of platelets transfused x 10(11)). Corrected increases tended to be greater with the low concentration of platelets. Overall, the increase in count for the frozen platelet transfusions was 65% of the increments obtained with fresh platelet transfusions administered within 1 week of the frozen platelets. Bleeding times were partially corrected after four out of six transfusions with post-transfusion counts greater than 50 X 10(9)/1., and active haemorrhage was controlled in some patients by frozen platelet transfusions. These results indicate that pooled platelets can be frozen, thawed and transfused with reasonable efficiency. The frozen platelets can circulate and function haemostatically and may eventually play an important role in supportive care.

A standardized technique for efficient platelet and leukocyte collection using the Model 30 Blood Processor

The Model 30 Blood Processor is a safe and simple means of harvesting blood cell components. Presently cell collection depends on a visual assessment by the operator of the indistinct boundaries of cell fractions. To determine when each cell component could best be harvested, serial samples were taken from the output port at fixed intervals anf the results of counts and differentials were graphed and tabulated. Studies in normal donors were done using acid-citrate-dextrose (ACD), 2 per cent sodium citrate in 6 per cent hydroxyethyl starch (HES), or heparin as anticoagulants. There was considerable overlap between the latter part of the platelet band, the leukocyte band and the rising hematocrit with all three anticoagulants. Normally functional lymphocytes could be harvested efficiently (approximately 80%) using ACD or heparin. Platelets could be harvested from ACD very efficiently (approximately 90%). Granulocytes could not be harvested from ACD (less than 10%) since they were dispersed in the red blood cell (RBC) layer. Using HES, granulocytes could be harvested efficiently (approximately 70%) by extending collection into the RBC layer. Based on these data, a standard technique for cell collection has been devised. The flow rate is slowed to 20 ml/min and collection is carried 30 ml (90 seconds at a rate of 20 ml/min) for platelets. The RBC loss is approximately 6 to 8 and 2 to 3 ml/pass respectively. These studies indicate that the Model 30 is a highly efficient apparatus for blood cell separation, but the volume of blood processed is limited by the intermittent blood flow.

Statewide support of thrombocytopenic patients with ABO matched single donor platelets

Use of ABO matched, HLA nonmatched platelet units obtained from single donors by pheresis, using the Haemonetics 30 Cell Separator, has a lowered hepatitis risk, and possibly delays the onset of the refractory state. Pheresis also offers a method of obtaining HLA matched platelets for the already refractory patient. A mean of 4.2 X 10(11) platelets are collected in about 1 1/2 hours. ABO matched, HLA nonmatched platelets produced corrected increments of more than 2500/mm3 per 7 X 10(10) platelets infused in 67 per cent of transfusions to nonselected recipients. The procedure is simple, safe, and requires little time. It is a worthwhile large-scale program for a regional blood center to undertake in order to provide optimal therapy for thrombocytopenic patients.

Frozen autologous platelets in the supportive care of patients with leukemia

Multiple units of platelet concentrate obtained by intensive plateletpheresis of patients with leukemia in remission were pooled and frozen using 4 to 5 per cent dimethylsulfoxide and retransfused during periods of thrombocytopenia. Plateletpheresis was well tolerated by all donors and an average platelet yield per unit of 0.99 X 10(11) (n = 155) was obtained. The results of 107 transfusions to 36 patients are presented. An average of 32.4 per cent of the platelets were lost during the freeze-thaw process. Freezing loss was lowest at a freezing rate of one degree C per minute, at a lower final concentration of platelets, and when polyolefin bags were used. The mean corrected posttransfusion count increment was 6,400/mul (range 600-19,000 xm2/10(11) platelets transfused). In vivo results did not correlate with freezing rate but were statistically significantly better at lower platelet (approximately 0.16 X 10(11) platelets/10 ml) concentrations. Eleven patients, including some who were refractory to random donor platelets were supported entirely with autologous platelets during reinduction therapy for leukemia. When administered prophylactically the autologous platelets seemed to prevent hemorrhage during periods of thromobocytopenia although in most patients bleeding times were not corrected posttransfusion. This study demonstrates that frozen autologous platelets can be used in the supportive care of thrombocytopenic patients. Further technical improvements are necessary before platelet freezing becomes practical for widespread use.

Terminal deoxynucleotidyl transferase activity in human leukemic cells and in normal human thymocytes

Peripheral leukocytes from patients with and without leukemia were assayed for presence of terminal deoxynucleotidyl transferase. Activity of this enzyme was detected in circulating leukemic cells from 11 to 13 patients with acute lymphoblastic leukemia, and in one of four with chronic myelogenous leukemia in blast crisis, but not in leukocytes from patients with other kinds of leukemia or in normal leukocytes. Its presence in a patient with chronic myelogenous leukemia in blast crisis lends biochemical support to the suggestion that some patients with chronic myelogenous leukemia undergo a lymphoblastic rather than a myeloblastic crisis. The thymocyte and leukemic-cell enzyme have the same substrate and primer preference. Normal thymocytes and leukemic cells contain two forms of terminal deoxynucleotidyl transferase that can be separated by phosphocellulose chromatography. The enzyme may provide a means for classifying leukemic cells on a biochemical basis independently of classic morphologic and clinical criteria.