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At least 73 records · Page 4Linked to original sources
PubMed2005

The influence of various hematology analyzers on component platelet counts.

Hematology analyzers designed to count platelets in samples of whole blood are used to enumerate the total number of platelets in components prepared for transfusion. This report addresses the issue of variability in platelet counts obtained with different models of hematology analyzers. The influence of a common calibration procedure, involving one level of porcine platelets, on the extent of variability was also evaluated. Identical sets of samples of simulated and apheresis-derived human platelets were counted by multiple laboratories in 3 separate studies. In the first 2 exercises, 7 samples of both porcine platelets and modified goat erythrocytes with targeted platelets counts from 0.2 to 4.0 x 10(12)/L were counted without prior dilution. In both exercises, the samples were counted multiple times after routine calibration using instructions provided by the manufacturers of the various hematology analyzers used. In the second exercise, the samples were recounted after the hematology analyzers were recalibrated with a common calibrant consisting of porcine platelets at a targeted concentration of 0.5 x 10(12)/L. In the first and second exercises, 20 and 18 hematology analyzers were used, respectively. In the third exercise, 6 samples prepared from a single unit of apheresis platelets with targeted counts from 0.2 to 1.64 x 10(12)/L were shipped by an overnight courier and counted in triplicate on the day of arrival. Eleven hematology analyzers were used. The influence of recalibration was evaluated statistically by using the 95% prediction interval for the mean of a future set of observations. The platelet counts measured with a specific type of hematology analyzer provided the data to calculate the 95% prediction interval. With routine calibration, a wide variability in platelet counts was observed with all levels of both simulated and apheresis-derived human platelets. For example, with porcine platelets at a targeted level of 0.4 x 10 (12)/L, the platelet counts ranged from 0.31 to 0.47 x 10(12)/L. Recalibration reduced the extent of variability observed with all levels of simulated and apheresis-derived human platelets by increasing the observed platelet counts determined with a subset of hematology analyzers that produced platelet counts in the lower portion of the range. With recalibration, the mean platelet counts obtained with most hematology analyzers, especially with samples having targeted platelet levels no greater than 1.0 x 10(12)/L, were within or near the 95% prediction interval determined with the instruments that provided the highest platelet counts with routine calibration. With recalibration, the reproducibility of the platelet counts was considered to be good for all hematology analyzers with all levels of simulated and apheresis-derived human platelets for most of the instruments. The coefficient of variance did not exceed 6%, with most of the values ranging from 1% to 3%. This study therefore found that the platelet counts of platelet concentrates can be markedly influenced by the type of hematology analyzer used. A common calibration procedure designed specifically for the range of platelet counts in platelet products may be beneficial considering that many different hematology analyzers are being used to count platelets.

Animals↗
PubMed2006

Methods for counting platelets in severe thrombocytopenia.

Accurate platelet counts in severe thrombocytopenia are critical in clinical practice to facilitate decisions at prophylactic platelet-transfusion thresholds. Until recent years, the accuracy of platelet counts has been limited by the reliance of hematology analyzers on calibration material values derived from the manual platelet counting method. The calibration of hematology analyzers in thrombocytopenia and the reduction of variation between instruments have been hindered by a lack of adequate quality control materials, making the accuracy of automated methodologies in routine practice difficult to assess. This situation could now be vastly improved by the use of the International Reference Method (IRM) to assign calibration materials and by further knowledge of the accuracy and limitations of the particular types of automated platelet count available to the clinician. These changes will improve clinical confidence in the accuracy of a platelet count and thus inform clinical decisions at the current level of prophylactic platelet transfusions.

Automation↗
PubMedDate not supplied

Platelet count assessment from peripheral blood smear (PBS).

OBJECTIVE: To visually count platelets in a peripheral blood smear and compare with an automated machine platelet count. METHODS: Thirty-five peripheral blood smears were made from blood specimens counted on an automated blood cell machine: twenty-three thrombocytopenic specimens, 1 with high platelet count and 11 with normal counts. Ten and 25 high-power fields were microscopically averaged and then multiplied by 15,000 and 20,000 to arrive at a platelet count in 1,000 per microliter. Comparisons between visual and machine counts were drawn. RESULTS: There was fair concordance in 27 specimens. In three specimens underestimation was found, overestimation in five. A 15,000 multiplier gave slightly better results than 20,000. Average in 10 high-power fields was as good as 25. Abnormal counts could be assessed as well as normal. CONCLUSION: Average in 10 high-power field on a blood film microscopically and multiplying by 15,000 gives a platelet count reasonably close to automated machine counts in thousands per microliter.

Automation↗
PubMed1998

Automated analysis of feline platelets in whole blood, including platelet count, mean platelet volume, and activation state.

A new whole-blood flow cytometric method has been developed for counting and sizing platelets in samples from cats, a species in which platelet and red blood cell sizes overlap significantly. The method is a modified version of the two-angle laser light scattering technology used by Bayer H*System hematology analyzers. The new method provided accurate platelet counts and mean platelet volumes (MPV, fl) for cats. The method also measured mean platelet component concentration (MPC, g/dl), a parameter which was shown to be sensitive to platelet activation state, and which decreased in value as activation progressed.

Journal Article↗
PubMed2005

[Reliability of low platelet counts--comparison of microscopic counts with automated hematology analyzer XE-2100].

Sysmex XE-2100 is an automated hematological analyzer with excellent features that can count platelets by both impedance and optical fluorescent method. Particularly, it is notable that platelet counts by optical fluorescent method (PLT-O) are automatically adopted when platelet counts by impedance method (PLT-I) are less than 50 x 10(3)/microl or platelets have abnormal distribution. We compared PLT-I with PLT-O, and also with microscopic counts, using the samples with thrombocytopenia. Regarding reproducibility, mean coefficient of variation values were 5.3% in both PLT-I and PLT-O, when no flags of "PLT Abn Distribution" appeared in the samples with thrombocytopenia. Coefficient of variation values was 10.4% in PLT-I and 5.9% in PLT-O, when flags of "PLT Abn Distribution" appeared in the sample with thrombocytopenia. Correlation among the data obtained by PLT-I, PLT-O and microscopic counts were excellent. When a large difference was observed between PLT-I and PLT-O, PLT-O was more closely consistent with microscopic counts. PLT-O was useful compared with PLT-I, and this system was considered to measure platelet counts more correctly in the samples with thrombocytopenia. Thus, it was suggested that reliable platelet counts could be reported even in the samples with thrombocytopenia by switching system in XE-2100.

Automation↗
PubMed1988

Platelet parameters. Part I. Platelet counts and mean platelet volume in normal and pregnant subjects.

Platelet counts and mean platelet volume (MPV) were studied in 564 normal subjects and 297 pregnant women using a Coulter Model S-Plus electronic counter. The reproducibility of these measurements both intra- and inter-sample was documented. The mean platelet count in the normal group was 283 x 10(9)/l while the mean MPV was 9.32 fl. An inverse correlation between platelet volume and platelet number was documented (r = -0.38; P less than 0.0001). By interval analysis, this inverse relationship was shown to be non-linear. In the pregnant subjects there appeared to be a progressive decrease in platelet count with advancing gestation; this reached a significant level when the first and third trimesters were compared with each other (P less than 0.05). The MPV was unchanged. The fact that the platelet count decreased in proportion to the red cell count suggested that a common factor, such as haemodilution, was in part responsible. There was again an inverse relationship between MPV and platelet number (r = -0.39; P less than 0.0001) shown to be non-linear by interval analysis.

Blood Platelets↗
PubMed2000

High platelet count in platelet-rich plasma reduces measured platelet inhibition by abciximab but not tirofiban nor eptifibatide glycoprotein IIb/IIIa receptor antagonists.

We evaluated the differential effect of platelet count in platelet-rich plasma (PRP) on the level of ex vivo inhibition of platelet aggregation provided by abciximab, eptifibatide, and tirofiban as part of a randomized, comparative trial of these agents on platelet function in patients with unstable angina pectoris undergoing percutaneous coronary intervention. Platelet count <350 K/microL in PRP reduced measured platelet inhibition by abciximab, but not eptifibatide nor tirofiban. This observation suggests the need for standardized, uniform platelet counts in PRP during future comparisons of the degree of platelet inhibition by these agents.

Abciximab↗
PubMed1998

[Platelet count and mean platelet volume in the Spanish population].

BACKGROUND: Platelet counts between 150 x 10(9)/l and 400 x 10(9)/l are considered as normal in the adult population. However in Spain it is not unusual to find lower counts in healthy people. SUBJECTS AND METHODS: We have studied platelet counts in 1,430 prospective healthy platelet donors. In 93 we measured mean platelet volume (MPV) in a blood sample collected in citrate (1:4 v/v) in order to avoid the platelet swelling induced by EDTA. Complete blood counts were performed on a Bayer-Technicon H*1. A reference range of 95% was calculated for platelet count and MPV, and the relationship between platelet count and sex, age, hemoglobin and MPV was studied. RESULTS: Mean (SD) platelet count (in x 10(9)/l) in men (195 [42]; n = 1,053) is lower (p < or = 0.0005) than in women (213 [47]; n = 377). The reference range in men is 123-295, in women 137-319 and in both 125 to 300. The mean (SD) for MPV (in fl) is 9.6 (0.7) (no significant differences between sexes) and the reference range is 7.8-11. There is an inverse linear relationship between the circulating platelets and their MPV measured in citrate at high concentration (r = -0.282, p = 0.006, n = 93) and in EDTA (r = -0.364, p < or = 0.0005, n = 1,430) and also between platelet count and Hb levels (r = -0.166, p < or = 0.0005). CONCLUSIONS: The mean of platelet count in women is higher than in males in a sample of Spanish population. There is an inverse linear relationship between platelet count and their MPV measures measured in citrate at high concentration and in EDTA. The reference range for platelet count seems to be lower than in other populations of North European origin.

Adult↗
PubMed1997

C3H mice have larger spleens, lower platelet counts, and shorter platelet lifespans than C57BL mice: an animal model for the study of hypersplenism.

Several studies have shown that C3H mice have a modal megakaryocyte ploidy class of 32N as opposed to the 16N found in all other mouse strains tested. In addition to higher megakaryocyte DNA content, C3H mice are characterized by greater 35S-sulfate incorporation into platelets but somewhat lower platelet counts than C57BL mice. The aim of this study was to determine the etiology of mild thrombocytopenia in C3H mice. Several studies have indicated that an increase in platelet 35S incorporation parallels increased megakaryocyte ploidy. Thus the higher 35S incorporation by C3H mouse platelets is likely related to their higher megakaryocyte ploidy, but these differences do not explain the lower platelet counts observed in C3H mice. To elucidate the paradox of relatively low platelet counts in C3H mice despite elevated platelet 35S incorporation, we performed a hematological evaluation (including assessment of platelet counts and lifespans) and measured (relative) spleen size in C3H and C57BL mice. Our data confirm earlier reports of significantly lower platelet counts in C3H mice (p < 0.0005) compared with C57BL mice. We also found that C3H mice have larger spleens (p < 0.0005) than C57BL mice. Other groups of C3H and C57BL mice were splenectomized to determine the role of the spleen in decreasing platelet counts in C3H mice compared with C57BL mice. C3H mice had an average platelet lifespan of 4.8 days, which was significantly shorter (p < 0.01) than the 5.7-day platelet lifespan observed in normal C57BL mice. Platelet lifespans for splenectomized C3H mice were significantly (p < 0.005) longer than those found in intact C3H control mice, but splenectomy of C57BL mice had no effect on their platelet lifespans (p < 0.40). The lengthened platelet lifespans of splenectomized C3H mice indicate that the spleens of C3H mice were sequestering or destroying platelets at a faster rate than the spleens of C57BL mice. These data lead to the hypothesis that the relatively large spleens of C3H mice produce mild thrombocytopenia with increased platelet production (shorter platelet lifespan) compared with spleens of C57BL mice.

Animals↗
PubMed1981

The platelet count and mean platelet volume.

The Coulter Model S-Plus Counter provides a measure of the platelet count and the mean platelet volume (MPV). An analysis of 5000 unselected blood specimens showed an inverse relationship between the number of circulating platelets and their MPV. In nearly 95% of normal adults the platelet count varied from 150 to 450 X 10(9)/l and the MPV from 7.0 to 10.5 fl. Thrombocytosis was found in iron deficiency anaemia, after trauma and acute blood loss and in rhematoid arthritis. Although there is a normal platelet distribution in pregnancy, patients with pre-eclampsia and uncomplicated hypertension in late pregnancy tended to have lower platelet counts and larger platelets than controls. A variable platelet pattern was found in infection, renal failure and treated malignant disease.

Anemia↗