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PubMed2000

Prognostic study of continuous variables (white blood cell count, peripheral blast cell count, haemoglobin level, platelet count and age) in childhood acute lymphoblastic leukaemia. Analysis Of a population of 1545 children treated by the French Acute Lymphoblastic Leukaemia Group (FRALLE).

Many cutpoints have been proposed to categorize continuous variables in childhood acute lymphoblastic leukaemia (white blood cell count, peripheral blast cell count, haemoglobin level, platelet count and age), and have been used to define therapeutic subgroups. This variation in the choice of cutpoints leads to a bias called the 'Will Rogers phenomenon'. The aim of this study was to analyse variations in the relative risk of relapse or death as a function of continuous prognostic variables in childhood ALL and to discuss the choice of cutpoints. We studied a population of 1545 children with ALL enrolled in three consecutive protocols named FRALLE 83, FRALLE 87 and FRALLE 89. We estimated the risk of relapse or death associated with different values of each continuous prognostic variable by dividing the sample into quintiles of the distribution of the variables. As regards age, a category of children under 1 year of age was distinguished and the rest of the population was divided into quintiles. The floated variance method was used to calculate the confidence interval of each relative risk, including the reference category. The relation between the quantitative prognostic factors and the risk was monotonic for each variable, except for age. For the white blood cell count (WBC), the relation is log linear. The risk associated with WBC values in the upper quintile was 1.9 times higher than that in the lower quintile. The peripheral blast cell count correlated strongly with WBC (correlation coefficient: 0.99). The risk increased with the haemoglobin level, and the risk in the upper quintile was 1.3 times higher than that in the lower quintile. The risk decreased as the platelet count increased: the risk in the lower quintile was 1.2 times higher than that in the upper quintile. The risk increased gradually with increasing age above one year. The small subgroup of patients (2.5% of the population) under 1 year of age at diagnosis had a risk 2.6 times higher than the reference category of patients between 3 and 4.3 years of age. When the risk associated with a quantitative prognostic factor varies monotonously, the selection of a cutpoint is arbitrary and represents a loss of information. Despite this loss of information, such arbitrary categorization may be necessary to define therapeutic stratification. In that case, consensus cutpoints must be defined if one wants to avoid the Will Rogers phenomenon. The cutpoints proposed by the Rome workshop and the NCI are arbitrary, but may represent an acceptable convention.

Adolescent↗
PubMed1995

Decreased platelet counts and decreased platelet serotonin in poststreptococcal nephritis.

Mean platelet survival time in patients with acute poststreptococcal glomerulonephritis (APSGN) is reduced to 50-60% of the control values, and glomerular deposits of platelet factor 4 are found in these patients. In order to investigate further systemic platelet changes of pathogenic, clinical or prognostic significance, we measured the platelet serotonin (5-HT) content and the blood platelet counts during the 1st week of the disease in 27 patients with APSGN. Platelet 5-HT was significantly reduced in patients with APSGN as compared with patients with impetigo without glomerular involvement (785 +/- 54 vs. 1,329 +/- 94 ng 5-HT/10(9) platelets; p < 0.001). Similarly, the mean blood platelet count was reduced to 247 +/- 16 x 10(3) as compared with 303 +/- 14 x 10(3) in the controls (p < 0.05). Thirteen (48%) of these patients had individual values of platelet 5-HT lower than the 95% confidence interval calculated in the control group. No significant correlation was observed between the concentration of 5-HT and either the severity of the disease judged by the amount of urinary protein excretion and the serum creatinine value or the presence of circulating immune complexes. Significant correction of the platelet 5-HT content (to 1,180 +/- 111 ng/10(9) platelets; p < 0.01) and of the platelet counts (to 309 +/- 21 x 10(3); p < 0.01) were observed in the longitudinal study at least 2 weeks later. Platelet activation, with secretion of granular content and increased consumption, may explain these findings. Additionally, the reduced mean age of the circulating platelets could contribute to their decreased 5-HT levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed2001

Problems with platelet counting in thrombocytopenia. A rapid manual method to measure low platelet counts.

Because most automated platelet counters cannot be relied on in thrombocytopenia, clinicians face a problem when decision making is based on platelet counts. Therefore we evaluated a visual platelet counting method from a blood smear with white blood cells (WBCs) as reference (PCW = platelet count based on WBC). Platelet counting for 74 thrombocytopenic (<120 x 10(9)/L) children was performed with PCW and with an automated counter (impedance principle); both methods were compared with evaluation by phase-contrast microscopy as the standard method. The PCW correlated well with the phase-contrast microscopy evaluation (y = -0.38 + 1.01x, r2 = 0.99). For platelet counts <20 x 10(9)/L the maximal deviation was 2 x 10(9)/L. The correlation between automated counts and the standard method was poor. The regression was y = 9.63 + 0.94x, r2 = 0.86. For platelet counts <20 x 10(9)/L the maximal deviation was 37 x 10(9)/L; on average, 7 x 10(9)/L platelets were counted in excess when compared with the standard method. PCW, in contrast to the automated impedance method, discriminated platelets from nonplatelet particles such as debris, fragments of red blood cells (hemolytic-uremic syndrome [HUS]) and of blast cells, and identified platelets of abnormal size. In addition, the appearance ofplatelets, WBCs, and RBCs gave clues to the etiology of thrombocytopenia, such as leukemia, infection, HUS, familial macrothrombocytopenia, and immune thrombocytopenia. PCW is a fast, reliable platelet counting method requiring less experience than the phase-contrast method. Visual evaluation from a stained smear clearly differentiates platelets and nonplatelet particles in contrast to most automated counters. In addition, the original smear can be preserved and reevaluated.

Blood Platelets↗
PubMed1992

Platelet counting using plasma platelet concentrate samples.

Platelet counting using samples of plasma from platelet concentrates prepared for transfusion was assessed. The methods employed included a manual phase-contrast method, and counting with Coulter S Plus and Sysmex E-2500 counters. All methods were reproducible (mean CV of 4.9, 2.2 and 1.4%, respectively). However, neat samples of platelet concentrates analysed by Coulter counter were inaccurate (mean count of 863.8 x 10(9)/l compared to 1018.9 x 10(9)/l counted manually). Moreover, the Coulter platelet counts were non-linear above 900 x 10(9)/l, whereas the E-2500 platelet counts were linear to 2700 x 10(9)/l. A one-in-three pre-dilution was required to obtain accurate, linear counts with the Coulter counter, whereas the E-2500 was accurate without pre-dilution (mean count of 1030.2 x 10(9)/l compared to 1018.9 x 10(9)/l counted manually). In conclusion, the method of platelet counting may affect true platelet yields.

Automation↗
PubMed1963

Platelet counting using the Coulter electronic counter.

A method for counting platelets in dilutions of platelet-rich plasm using the Coulter electronic counter is described.(1) The results obtained show that such platelet counts are at least as accurate as the best methods of visual counting. The various technical difficulties encountered are discussed.

Journal Article↗
PubMed1967

Automatic platelet counting with the Couler particle counter.

A method for accurately counting platelets is described using the Coulter counter model B fitted with a standard 100mu aperture tube. This enables the counter to be used for red and white cell as well as platelet counts using the same aperture tube. The method uses standard equipment except for a small inexpensive electronic speed controller.

Automation↗
PubMed1990

Differences between the effects of EDTA and citrate anticoagulants on platelet count and mean platelet volume.

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.

Adenine↗
PubMed1991

Effect of EDTA on platelet count and other platelet parameters in blood and blood components collected with CPDA-1.

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.

Adenine↗
PubMed2001

Standardisation of platelet counting accuracy in blood banks by reference to an automated immunoplatelet procedure: comparative evaluation of Cell-Dyn CD4000 impedance and optical platelet counts.

Prophylactic and therapeutic platelet transfusions are increasingly used for patients with conditions associated with thrombocytopenia in order to prevent the development of potentially life threatening bleeding. These clinical strategies have led to a significant expansion in platelet unit manufacture, and this now represents a major resource and cost commitment for blood banks. As part of the manufacturing process, blood banks are required to implement control procedures, and the determination of platelet counts in particular is necessary to confirm that the quality of platelet unit production meets the standards defined by national or international guidelines. Apart from linearity analysis and comparisons of platelet counts given by different instruments, there has been no systematic standardisation of platelet counting methods in blood bank practice because to date there has been no suitable reference method for counting platelets in citrate anticoagulants. The recent introduction of an automated immunoplatelet procedure on the Cell-Dyn CD4000 provides a means of determining a true platelet count that is unaffected by changes induced either by storage or anticoagulant. The CD4000 in its routine configuration also provides simultaneous impedance and optical platelet counts and this study was therefore undertaken in order to compare all three different platelet counting methods in parallel with a representative series of platelet units. Platelet counts determined after sub-sampling of platelet units into EDTA vs plain non-anticoagulated tubes revealed no differences in impedance or immunoplatelet counts but generally lower optical counts when aliquoted into tubes that did not contain EDTA. This study therefore routinely used EDTA for platelet unit sub-samples. Comparative results of platelet counts for buffy coat platelet units (n = 36) aliquoted into EDTA indicated that the impedance count was higher than the reference immunoplatelet count by a mean factor of 1.25 while the optical count was lower by a mean factor of 0.87. The degree of impedance count overestimation was particularly consistent while the optical count underestimation was more variable. Linearity studies of 10 fresh platelet units showed no deviation in the range 0-2305 x 10(9) l(-1) for impedance and 0 to 1420 x 10(9) l(-1) for the optical counts, and the relative numerical relationships between impedance and optical counts were conserved throughout the range of dilutions tested. In the CD4000 optical analysis, blood samples anticoagulated with EDTA showed a distinctive elliptical population distribution that fell within the system thresholds. In contrast, the optical pattern observed for platelet units (in CPD) and ACD-anticoagulated venous blood showed a wider 90 degrees scatter with a population of platelet events above the upper parallel discriminator. As these were excluded from the optical count (but were still identified as platelets by the immunoplatelet method) it meant that the optical counts of samples in citrate-based anticoagulants were systematically lower than immunoplatelet counts. Platelet units (n = 15) analysed daily over a seven day period of storage revealed that the greatest decline in platelet counts was with the optical measurement while the most stable value was obtained by impedance analysis. The results of the immunoplatelet analysis further suggested a progressive increase in small platelets with increasing storage time. The use in this study of a standardised immunoplatelet reference method to examine the question of analyser suitability for determining platelet counts/yields of platelet units thus provided a number of important findings. An impedance platelet counting method is utilised by the great majority of haematology instruments in current use, and in common with the CD4000 analyser, a correction factor is employed to take account of RBC/platelet coincidence. This study found that when analysed samples such as platelet units were RBC-free, that an inappropriate correction factor was applied. Consequently, the CD4000 impedance platelet count will provide reliable platelet counts, irrespective of the day of platelet unit storage, when a factor of 1.25 is applied to the system-reported result. By comparison, optical methods are more likely to be affected by subtle morphological changes that may result from anticoagulants or progressive storage time. The method limitations documented by this study may well affect many other analysers and mean that the implementation of process control statistics related to platelet counts may be less reliable than previously assumed. It is suggested that standardisation could be much better achieved if there was some form of system cross-calibration that was referenced to an independent method such as an immunoplatelet assay. It is proposed that studies of this type should be extended to a wide assessment of platelet count accuracy of blood bank instruments in order to standardise data within national organisations. If consistent inter-instrument correction factors such as those documented here can be identified, it would considerably increase the relevance of determining platelet counts in production control processes.

Adult↗
PubMedDate not supplied

Hemoglobin and platelet count effect on platelet yields in plateletpheresis.

BACKGROUND: Platelet transfusion in thrombocytopenic patients, especially those with marrow failure, remains one of the most important support measures available. Treatment success depends on rational use of platelet transfusion. Platelet yield, reflected in transfused platelet dose, influences platelet recovery in the patient and allows prolonging intervals between transfusions. In this study, our main objective was to identify donor laboratory and clinical factors that showed some influence on platelet yield obtained by apheresis. METHODS: Healthy donor laboratory and clinical data were analyzed prior to performing plateletpheresis. Platelet yield was quantified after plateletpheresis procedure was concluded in two different ways: a) prefixed volume of 5,000 mL processed, and b) volume determined according to manufacturer recommendations. Age, gender, hemoglobin concentration, platelet and leukocyte count, height, and weight were included as yield-predicting donor variables. RESULTS: In group A, two variables were significant: donor platelet count and hemoglobin (Hb) concentrations with r = 0.554, and in group B, donor platelet count, Hb concentrations, and volume with r = 0.758. CONCLUSIONS: Donor platelet count and hemoglobin concentrations influence platelet yield: higher platelet count corresponds to higher yield, while hemoglobin shows an inverse relationship, i.e., the lower the hemoglobin concentrations, the higher the platelet yield.

Adolescent↗
PubMed1998

Functional compensation of the low platelet count by increased individual platelet size in a patient with May-Hegglin anomaly presenting with acute myocardial infarction.

Platelets are known to play a crucial role in normal hemostasis as well as in thrombus formation at sites exposed to blood flow, as in coronary thrombosis. Thus, low platelet count is a strong negative risk factor for the occurrence of arterial thrombosis, such as occurs in acute myocardial infarction. We encountered a patient with May-Hegglin anomaly, presenting with acute myocardial infarction in his sixth decade, even though his platelet counts had always been less than 50 x 10(3)/microl. We investigated the characteristics of his platelets under the effect of shearing and found that shear-induced platelet aggregation and binding of soluble von Willebrand factor (vWF) to platelets could be induced, even when the patient's platelet count was less than 10 x 10(3)/microl, but that virtually no aggregation or vWF binding by normal platelets could be induced by shearing when platelet counts were less than 50 x 10(3)/microl. We conclude that the low platelet counts in a patient with May-Hegglin anomaly can be functionally compensated for by larger individual platelets, in view of the vWF-dependent platelet thrombus formation occurring under the effect of blood flow and that that is why most patients with May-Hegglin anomaly do not have a bleeding tendency, even though their platelet counts are very low.

Blood Platelets↗
PubMed1986

An epidemic of maternal thrombocytopenia associated with elevated antiplatelet antibody. Platelet count and antiplatelet antibody in 116 consecutive pregnancies: relationship to neonatal platelet count.

Twenty-eight (24%) of 116 pregnant women studied prospectively during an 8-month period in 1983 had platelet counts of less than 150,000/mm3 at least once during pregnancy. Thirteen of these were thrombocytopenic in both the prenatal and the peripartum period. Eighteen were restudied 3 to 12 months after delivery. One woman, who was pregnant again, had a platelet count of 140,000/mm3. In the others, platelet counts were in the normal range. Platelet-associated immunoglobulin G and serum antiplatelet antibody levels were elevated in 79% and 61%, respectively, of these 28 women on at least one occasion. However, 59% of 73 pregnant nonthrombocytopenic women had increased platelet-associated immunoglobulin G levels and 59% had positive serum antiplatelet antibody test results. Twenty women who had increased platelet-associated immunoglobulin G levels and positive serum antiplatelet antibody test results were normal 6 to 10 months after delivery. Of 105 infants studied, 10 were thrombocytopenic. Neonatal thrombocytopenia was not predicted by maternal platelet count, platelet-associated immunoglobulin G, or serum antiplatelet antibody. By the fall of 1984, the incidence of thrombocytopenia had dropped to two in 280 consecutive pregnancies. We conclude that (1) epidemics of thrombocytopenia can occur in pregnant women and (2) if a women is found to be thrombocytopenic for the first time during pregnancy, she should not be subjected to the measures advocated for the management of pregnancy in women with autoimmune thrombocytopenic purpura.

Adult↗
PubMed2001

Comparison of GP IIB/IIIA inhibitors and their activity as measured by aggregometry, flow cytometry, single platelet counting, and the rapid platelet function analyzer.

BACKGROUND: GP IIb/IIIa inhibitors have primarily been used short-term e.g., during PTCA. They failed to show clinical benefit during long-term therapy. One reason might be the absence of a method to monitor inhibitor activity. This study compared platelet aggregometry, the rapid platelet function analyzer (RPFA) test, single platelet counting, and flow cytometric determination of receptor occupancy to measure GP IIb/IIIa-receptor inhibitor activity. METHODS: Increasing doses of abciximab, tirofiban, and eptifibatide were added to whole blood in vitro. Whole blood was used for the RPFA, for single platelet counting and flow cytometry. Platelet rich plasma was prepared for aggregometry. RESULTS: The correlation between aggregometry and RPFA results was linear for abciximab and eptifibatide. Tirofiban was a stronger inhibitor with the RPFA (IC(50) 7.7nM) than with aggregometry (IC(50) 19.6nM). The single platelet counting technique showed that even supratherapeutic concentrations of all three inhibitors could not completely suppress microaggregation. Abciximab concentrations that were equipotent to tirofiban with aggregometry were less potent with regards to the inhibition of microaggregation. This difference was more pronounced with TRAP induced microaggregation than with ADP. The flow cytometric receptor occupancy test showed that occupancy was 95% with 5 microg/ml abciximab and almost 97% with 10 microg/ml. Tirofiban reached a maximum receptor occupancy of 56%, eptifibatide 64%. CONCLUSIONS: While aggregometry is time consuming the RPFA provides results fast and with little variability. There is still a discrepancy between aggregometry and RPFA results for tirofiban. The single platelet counting technique detects the inhibition of microaggregation the relevance of which for the clinical outcome is not known. The flow cytometric receptor occupancy assay is best suited for abciximab.

Dose-Response Relationship, Drug↗
PubMed2002

Comparison of reticulated platelet count and mean platelet volume determination in the evaluation of bone marrow recovery after aplastic chemotherapy.

Reticulated platelet count provides an estimate of thrombopoiesis in the same way as reticulocyte count is a measure of erythropoiesis. We applied thiazole orange (TO) staining, followed by fluorescence-activated flow-cytometric analysis, to platelets in whole-blood samples from normal subjects and 18 aplastic patients after chemotherapy for haematologic malignancies. The percentage of TO-positive platelets in 30 control subjects was 5.7 +/- 2.4% (mean +/- 1 SD), determining the threshold of reticulated platelet positivity as up to 10.5% (mean + 2 SD). In the 18 patients studied, the mean percentage of TO-positive platelets was 4.3 +/- 1.89% during aplasia and 23.3 +/- 9.43% during bone marrow recovery, respectively (P < 0.05). All patients had a percentage of TO-positive platelets of up to 10.5%. In comparison, mean platelet volume during bone marrow recovery increased in 12 cases of the 18 patients studied. We conclude that flow cytometric analysis of reticulated platelets is a sensitive and specific test for evaluating thrombopoiesis recovery during aplastic chemotherapy, and platelet transfusion should be reconsidered in these patients.

Adult↗