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At least 109 records · Page 6Linked to original sources
PubMed1984

Platelet count and mean platelet volume in an Algerian population indicating a low prevalence of Mediterranean macrothrombocytopenia.

Platelet count was 225 X 10(9)/l in 225 healthy male Algerians and 263 X 10(9)/l in 208 females. The mean platelet volume was 9.15 fl in the males and 9.30 in the females. The figures agree with those obtained in a British and an American population, but differed from those of an Australian population of immigrants from Mediterranean countries, essentially Italy and Greece. The prevalence of Mediterranean thrombocytopenia must therefore be low in Algeria.

Algeria↗
PubMed1989

Effects of 3-azidothymidine on platelet counts, indium-111-labelled platelet kinetics, and antiplatelet antibodies.

Treatment of the acquired immunodeficiency syndrome with 3-azidothymidine (zidovudine; AZT) can induce severe neutropenia and anemia, while platelet counts increase. In order to understand the mechanism by which this favorable effect on platelets is induced, we prospectively studied platelet kinetics and platelet serology in 8 hemophiliacs receiving the drug. All patients underwent a second investigation after 3 months of treatment. Four patients were thrombocytopenic before treatment. Platelet counts increased significantly already after 1 week of treatment (p = 0.03), when only 3 patients remained thrombocytopenic. In these latter patients a further increase of platelet counts was noticed during the following 3 months. Platelet life-span was shortened in all patients at the initial investigation and a significant prolongation was measurable at the second evaluation (p = 0.015). Platelet-associated immunoglobulin G was increased in 3 patients at the first investigation and in 4 patients at the follow-up. Platelet-associated complement (PAC3d) was elevated in all subjects at the first determination. It decreased in 6, but increased in 2 patients thereafter; thus these changes did not become significant (p = 0.078). Immunofluorescence studies revealed antiplatelet antibodies in 7 patients' sera before treatment, and in 5 sera during drug therapy. At both investigations, the antibodies bound to the platelet glycoprotein IIIa as was demonstrated by immunoprecipitation of radiolabeled platelet proteins. We conclude, that AZT treatment improves platelet counts in HIV-infected hemophiliacs primarily by a prolongation of platelet survival without having a significant influence on antiplatelet antibody binding.

Autoantibodies↗
PubMed2001

Change in platelet count predicts eventual maternal outcome with syndrome of hemolysis, elevated liver enzymes and low platelet count.

OBJECTIVE: To profile the rates of change for platelets and lactate dehydrogenase (LDH) in patients with the syndrome of hemolysis, elevated liver enzymes and low platelet count (HELLP) to reflect and possibly predict disease severity. METHODS: Serial determinations of the platelet count and serum LDH were analyzed retrospectively for 545 patients with HELLP syndrome and 94 severely pre-eclamptic patients. A repeated measures (mixed model) analysis of variance (ANOVA) was utilized to estimate the rates of change for LDH and platelets in each group. RESULTS: Patients who developed class 1 or 2 HELLP syndrome exhibited a rapid deterioration in platelet count of 45-50,000/microl per day compared to 30,000/microl per day for class 3 and non-HELLP severe pre-eclampsia. For LDH, values increased at a rate of approximately 1400 IU/l per day, 600 IU/l per day, 300 IU/l per day and 200 IU/l per day for patients with classes 1, 2 and 3 and for non-HELLP severe pre-eclampsia, respectively. CONCLUSION: The rate of change of platelets and LDH appeared to correlate well with eventual syndrome severity and this can be used to enhance patient assessment beyond the value of a single test for either laboratory parameter.

Adult↗
PubMed2002

Growth factor levels in platelet-rich plasma and correlations with donor age, sex, and platelet count.

INTRODUCTION: Platelet-rich plasma contains autologous thrombocyte growth factors and might be promising for acceleration of dentoalveolar bone regeneration. In this study, it was analysed for platelet counts and growth factor concentrations. MATERIAL AND METHOD: Platelet-rich plasma was isolated by discontinuous cell separation from 158 healthy men and 55 women aged 17-62 years. One hundred and fifteen specimens (stratified for age and gender of the donor) were analysed for growth factor concentrations and platelet count. RESULTS: The platelet count in platelet-rich plasma (1,407,640+/-320,100/microl) was 5 times higher than in donor blood (266,040+/-60,530/microl). Platelet-derived growth factor AB (117+/-63 ng/ml), transforming growth factor (TGF) beta -1 (169+/-84 ng/ml), and insulin-like growth factor (IGF) I (84+/-23 ng/ml) were found in large amounts, while platelet-derived growth factor (PDGF) BB (10+/-8 ng/ml) and transforming growth factor beta -2 (0.4+/-0.3 ng/ml) were found in small amounts only. The growth factor content was not well correlated with the platelet count in whole blood nor with the platelet-rich plasma (r(p)=0.35). No influence of gender or age on platelet count or growth factor concentrations was discovered (except IGF-I). CONCLUSIONS: While there was substantial variation in the growth factor content of platelet-rich plasma, the factors influencing this are still worthy of further investigation. Furthermore, a technique whereby the growth factor content could be rapidly assessed in platelet-rich plasma may be of therapeutic benefit.

Adolescent↗
PubMed2004

Quantitative trait loci for steady-state platelet count in mice.

Platelet count in humans is a strongly genetically regulated trait, with approximately 85% of the interindividual variance in platelet numbers attributable to genetic factors. Inbred mouse strains also have strain-specific platelet count ranges. As part of a project to identify novel factors that regulate platelet count, we identified two inbred mouse strains, CBA/CaH and QSi5, with substantial differences in platelet count (mean values of 581 vs. 1062 x 10(9)/L). An F(2) intercross resource of 1126 animals was bred from these two parental strains for a genomewide scan for quantitative trait loci (QTL) for platelet count. QTL were identified on MMU1 (LOD 6.8, p < 0.0005) and MMU11 (LOD 11.2, p < 0.0005) by selectively genotyping animals from the extremes of the F(2) platelet count distribution. Three other QTL of suggestive statistical significance were also detected on MMU7, 13, and 17. It is noteworthy that no QTL were detected in the vicinity of the genes encoding thrombopoietin ( Thpo), and its receptor ( c-Mpl), both known to influence platelet production. Comparison of gene expression levels between the parental mouse strains by microarrays also showed little difference in the mRNA levels of these known candidate genes. These results represent the first published use of a genetic linkage-based approach in a mouse model toward the identification of genetic factors that regulate platelet count.

Animals↗
PubMedDate not supplied

[Evaluation of interferences in electronic platelet count].

A platelets count was performed on 100 subjects using both the electronic counter and a manual method; the results obtained concerning healthy subjects are overlapping. In subjects with structural alterations regarding platelets and red blood cells, the electronic counter method has overestimated the number, yet making note of it.

Evaluation Studies as Topic↗
PubMed1985

Influence of splenectomy and the functional hyposplenism of coeliac disease on platelet count and volume.

Platelet count and volume were measured in 84 splenectomised subjects, 142 patients with coeliac disease and 77 healthy subjects. An inverse, non-linear correlation between platelet count and volume was found in healthy subjects and coeliac patients, but was not present in splenectomised subjects who had higher platelet counts (P = 0.0001) and mean platelet volumes (P = 0.0001) than healthy subjects. Platelet counts correlated with splenic function in patients with coeliac disease and were higher in patients with severe hyposplenism than in normosplenic coeliacs (P = 0.0001). Splenic function did not influence the mean platelet volume (MPV) in coeliac disease but normosplenic coeliacs had higher MPV than normal subjects (P = 0.05). Serum iron and red cell folate were not correlated to MPV in coeliac disease. We conclude that splenic function effects platelet count and volume in non-coeliac subjects and platelet count in coeliac disease. However, other unidentified factor(s) influence the MPV in coeliac disease.

Adolescent↗
PubMed1995

Decreased platelet counts in infants of diabetic mothers.

Infants of diabetic mothers (IDMs) have hematologic indices consistent with increased fetal erythropoiesis, presumably in response to chronic intrauterine hypoxemia. We hypothesized that increased erythropoiesis, as is evident from increased nucleated erythrocyte counts, would be accompanied by interrelated changes in thrombopoiesis and would correlate with maternal glycemic control during pregnancy. We compared absolute nucleated erythrocyte counts and platelet counts obtained in the first 24 hours of life in 32 term, nonasphyxiated IDMs with 47 controls. The IDM group had higher absolute nucleated erythrocyte counts (1.0 +/- 1.3 x 10(9)/L versus 0.4 +/- 0.7 x 10(9)/L; p < 0.05), and lower platelet counts (235 +/- 77 x 10(9)/L versus 348 +/- 79 x 10(9)/L; p < 0.001) than controls. Absolute nucleated erythrocyte counts correlated inversely with platelet counts (r = -0.28; p < 0.02). These neonatal hematologic measurements did not correlate with various parameters of maternal glycemic control. We conclude that in IDMs, increased erythropoiesis is accompanied by decreased platelet counts. These data are consistent with the theory of an erythropoietin-induced shift of fetal multipotent stem cell differentiation toward erythropoiesis at the expense of thrombopoiesis.

Diabetes Mellitus, Type 1↗
PubMed2001

Increased circulating platelet-leukocyte aggregates in myeloproliferative disorders is correlated to previous thrombosis, platelet activation and platelet count.

Platelet-leukocyte adhesion may occur as a consequence of platelet activation and possibly plays a key role in the deposition of activated platelets and fibrin in the thrombotic plug. The aim of the present study was to assess by whole blood flow cytometry the presence of circulating platelet-leukocyte aggregates (PLA) and the platelet-leukocyte response to platelet agonist stimulation (ADP and TRAP) in 50 patients with chronic myeloproliferative disorders (MPD) and 30 controls. PLA were identified as platelet-granulocyte/monocyte aggregates (PGMA), platelet-monocyte aggregates (PMA) and defined as the percentage of leukocytes coexpressing the platelet-specific marker glycoprotein Ib. Compared to controls the mean percentage of PGMA and PMA was increased in unstimulated whole blood from patients with MPD (7.98 vs. 1.76%; p<0.001 and 12.34 vs. 3.2%; p<0.001, respectively). The percentage of PGMA was correlated to the platelet count (r=0.46; p<0.001), percentage of P-selectin (r=0.69; p<0.001) and thrombospondin (r=0.58; p<0.001) positive platelets and platelet expression of GPIV (r=0.33; p=0.02). The mean percentage of PGMA and PMA was significantly increased in ADP-stimulated whole blood of patients (57.14 vs. 47.92%; p=0.009 and 54.91 vs. 45.89%; p<0.001, respectively). Compared to patients without a history of thrombosis, patients having experienced microvascular disturbances or a thrombotic event had a higher mean percentage of PGMA and PMA in non-stimulated whole blood (10.07 vs. 6.34%; p=0.025 and 14.81 vs. 10.48%; p=0.021, respectively) and a higher percentage of PGMA in ADP stimulated whole blood (64.32 vs. 51.50%; p<0.01). These data document an increased frequency of PLA in non-stimulated whole blood in MPD associated with a previous history of thrombosis or microvascular disturbances.

Adenosine Diphosphate↗
PubMed2004

The platelet count accuracy of platelet concentrates obtained by using automated analysis is influenced by instrument bias and activated platelet components.

BACKGROUND AND OBJECTIVES: The blood platelet content (in numbers) of platelet concentrates is required for production quality control and to predict clinical responses. MATERIALS AND METHODS: This study compared the performance of automated counting from impedance and optical instruments to data from immunoplatelet reference analysis. RESULTS: All methods showed good linearity with evidence of significant instrument-specific deviations from the line of agreement. Relational formulae largely corrected bias, but did not resolve platelet count variability. A second confounding factor, related to the proportion of small (activated) platelets, was also shown to contribute to intermethod discrepancies. CONCLUSIONS: Blood processing centres should establish correction factors for each instrument compared to reference methods, such as the immunoplatelet count.

Analysis of Variance↗
PubMed1964

VARIATIONS OF THE PLATELET COUNT IN DISEASE.

Platelet counts were obtained in 675 patients with different hematological and other medical disorders. An indirect venous blood dry slide method which gave a normal range of 200 to 400 x 10(3) per cu mm was used. Platelet counts varied considerably in disease: In 20 patients, exclusive of myeloproliferative disorders, platelet counts in excess of 1,000 x 10(3) per cu mm were observed; in 20 patients, exclusive of leukemia and megaloblastic anemia, platelet counts were below 100 x 10(3) per cu mm. In general, platelet counts varied with the leukocyte count, but not with the degree of anemia.

Anemia↗
PubMed2003

Pseudoplatelets: a retrospective study of their incidence and interference with platelet counting.

AIMS: Spurious platelet counts can be found in acute leukaemias, as a result of the fragmentation of blood cells. Microscopic examination of a blood smear should be performed to detect the presence of these so called pseudoplatelets. When present, the platelet count should be corrected because of the important clinical consequences that a lower platelet count may have in these patients. METHODS: K(3)EDTA anticoagulated blood was measured on an automated blood cell counter, and a blood smear was made and stained according the May Grünwald-Giemsa method for microscopic observation. A 500 cell/particle differentiation was performed and the automated platelet count was corrected. RESULTS: The incidence of pseudoplatelets in 169 patients with acute leukaemia was studied. Pseudoplatelets were detected in 43 patients (25.4%), and seven patients (4.1%) were re-classified as having a major bleeding risk (platelet count, < 15 x 10(9)/litre). CONCLUSIONS: Platelets should be determined morphologically in patients with acute leukaemia and a routine screening method for the detection of pseudoplatelets should be developed.

Acute Disease↗
PubMed1984

The origin of platelet count and volume.

Platelet count and volume were measured in man (n = 51) and rat (n = 9). Bone marrow megakaryocyte nuclear and megakaryocyte planimetric areas were measured in man (n = 11) and rat (n = 9). Megakaryocyte cytoplasmic volumes were computed from the planimetric areas. Rat had a significantly higher (p less than 0.001) mean megakaryocyte cytoplasmic volume than man and a significantly wider range (p less than 0.01). Rat mean platelet volume was significantly lower (p less than 0.001) than man while the rat platelet count was significantly higher (p less than 0.001) than man. A computer simulation of the random binary sequential division of megakaryocyte cytoplasm was used to explain these observations. Transmission electron microscopy shows that the site of this binary sequential division is probably the pulmonary circulation. The number of circulating megakaryocytes ml-1 of blood which would maintain the observed platelet counts was computed. The ellipses of constant density associated with the bivariate Gaussian distribution of platelet count and mean volume were computed. Platelet volume distributions of 13 men within two standard deviations of the composite mean of platelet count and mean volume were used to construct the platelet volume distribution signature in normal man. A similar platelet volume distribution signature for rat was constructed. The two distributions were significantly different. Neither rat nor man had a log Gaussian platelet volume distribution, however the measured volume distributions tended towards a log Gaussian curve.

Adult↗
PubMed1985

Platelet count in radiation bowel disease: an aid to diagnosis.

This study reports the results of serial observations of simple haematological indices (haemoglobin concentration, white cell count and platelet count) in 25 patients who developed radiation bowel disease as a late complication of pelvic radiotherapy for malignancy. It is compared with a control group of 25 women patients who received pelvic radiotherapy but did not develop radiation bowel disease. There is a highly significant elevation in the platelet count (P less than 0.0001) at a time when the patients develop radiation bowel disease. The platelet count returns to normal after successful excision of the disease but the elevation recurs if further radiation disease develops in the urinary or gastrointestinal tracts. It is suggested that the platelet count may have a useful role in the diagnosis of radiation bowel disease.

Female↗
PubMed2005

Pretransfusion trigger platelet counts and dose for prophylactic platelet transfusions.

PURPOSE OF REVIEW: To assess critically both the blood platelet counts that prompt a platelet transfusion (i.e. trigger) in various clinical settings in patients with thrombocytopenia caused by marrow failure and the dose of platelets infused (i.e. number per each transfusion) for optimal hemostasis, feasibility, and safety. RECENT FINDINGS: Definitive studies (e.g. well-designed, prospective, randomized clinical trials) are not available either historically or at present to support evidence-based decisions. Instead, retrospective reviews and anecdotal reports provide observational data to assist in best guess clinical practices. SUMMARY: Reasonable clinical practice, until more definitive data become available, is to transfuse enough platelets per each transfusion to maintain the blood platelet count >10 x 10/L in stable nonbleeding patients, >20 x 10(9)/L in unstable nonbleeding patients, and >50 x 10(9)/L in bleeding patients or in those undergoing invasive procedures.

Humans↗
PubMed1975

An evaluation of the Coulter thrombocounter in counting platelets before and after contact with foreign surfaces and its use in tests of platelet retention.

The counting of platelets by electronic methods has become widely accepted by laboratories and the methods is considered to give better reproducibility than the conventional microscope count. Prompted by an impression that prior contact of whole blood with glass beads or cellulose-based dialysis membranes resulted in platelet counts showing a poor correlation between the electronic and microscopic methods of counting, an evaluation of the Coulter Thrombocounter was carried out with regard to its ability in counting platelets before and after contact with such foreign surfaces in two tests for the measurement of platelet retention. The effect of citrate and heparin anticoagulation with and without the addition of EDTA on the efficiency of the Thrombocounter was also studied. The results indicate that an excellent correlation is obtained between microscopic and electronically estimated platelet counts before foreign surface contact when EDTA is included in the anticoagulation, and that the Thrombocounter gives good reproducibility over a wide range of platelet counts. After contact with the foreign surfaces, the Thrombocounter significantly underestimated the platelet counts and thus overestimated the platelet retention values. Using the membrane test cell system with citrate plus EDTA anticoagulation, platelet retention results estimated by Thrombocounter platelet counts were significantly higher than those estimated by microscopic platelet counts but there was a good linear correlation between the two sets of results. Thus, the Thrombocounter may be used with this method. However, using the glass-bead column technique and the same anticoagulation, although the platelet retention results gave the same mean value with both methods of platelet counting, there was no correlation between the two sets of results indicating that microscopy alone should be used with this method. The other anticoagulant regimens rendered the Thrombocount inefficient for use in these tests of platelet retention.

Blood Cell Count↗
PubMed1997

Screening for EDTA-dependent deviations in platelet counts and abnormalities in platelet distribution histograms in pseudothrombocytopenia.

Screening for pseudothrombocytopenia caused by in vitro platelet clumping has been performed in 45,000 subjects attending a general hospital. In our region, the observed prevalence of EDTA-induced pseudothrombocytopenia in blood samples with an initial platelet count below 150 x 10(9)/l was estimated to amount to 0.1%. EDTA-induced pseudothrombocytopenia was confirmed by detection of platelet aggregates by means of microscopic evaluation from the blood smear. In routine investigations, pseudothrombocytopenia could be highly suspected when the Sysmex NE 8000 showed characteristic peculiarities in the white blood cell (WBC) scattergram and histogram. Platelet aggregation is avoided in such cases by the use of citrate as an anticoagulant instead of EDTA. Pseudothrombocytopenia was detected in 46 subjects. As a screening test for pseudothrombocytopenia, increased cut-off values derived from the WBC histogram demonstrated 90% sensitivity and 100% specificity. Automated flagging for platelet clumps, deviations reflecting MPV, or PDW abnormalities revealed lower scores with respect to sensitivity.

Anticoagulants↗