Reactive Thrombocytosis Patients Research Articles

Clinical course and short-term outcome of postsplenectomy reactive thrombocytosis in children without myeloproliferative disorders: A single institutional experience from a developing country.

To evaluate the clinical outcome and complications in the pediatric population who had splenectomy at our institution, emphasizing the incidence of postplenectomy reactive thrombocytosis (RT) and its clinical significance in children without underlying hematological malignancies. The medical records of pediatric patients undergoing splenectomy were retrospectively reviewed for the period 1999-2018. The following variables were analyzed: Demographic parameters (age, sex), indications for surgery, operative procedures, preoperative and postoperative platelet count (postplenectomy RT), the use of anticoagulant therapy, and postoperative complications. The patients were divided into two groups according to indications for splenectomy: The non-neoplastic hematology group and the non-hematology group (splenectomy for trauma or other spleen non-hematological pathology). Fifty-two pediatric (37 male and 15 female) patients who underwent splenectomy at our institution were reviewed. Thirty-four patients (65%) were in the non-hematological group (splenic rupture, cysts, and abscess) and 18 patients (35%) in the non-neoplastic hematological group (hereditary spherocytosis and immune thrombocytopenia). The two groups did not differ significantly in regards to the patients' age, sex, and preoperative platelet count (P>0.05 for all variables). Forty-nine patients (94.2%) developed postplenectomy RT. The percentages of mild, moderate and extreme thrombocytosis were 48.9%, 30.7%, and 20.4%, respectively. The comparisons of RT patients between the non-neoplastic hematology and the non-hematology group revealed no significant differences in regards to the patients' age, sex, preoperative and postoperative platelet counts, preoperative and postoperative leukocyte counts, and the average length of hospital stay (P>0.05 for all variables). None of the patients from the cohort was affected by any thrombotic or hemorrhagic complications. We confirm that RT is a very common event following splenectomy, but in this study it was not associated with clinically evident thrombotic or hemorrhagic complications in children undergoing splenectomy for trauma, structural lesions or non-neoplastic hematological disorders.

Quantification of IGF‐1 receptor is useful in the differential diagnosis of essential thrombocytosis from reactive thrombocytosis

To make a definite diagnosis of essential thrombocytosis (ET) from reactive thrombocytosis (RT), the most reliable criteria are the presence of driver mutations, namely JAK2, CALR, or MPL gene mutations. In the absence of these driver mutations, so-called triple-negative ET, the differential diagnosis could be difficult. Although bone marrow biopsy could be helpful, it may be difficult in some cases, to do gene sequence analysis to identify other clonal marker gene mutations than the driver mutations, as only very few were found. IGF-1R quantification by flow cytometry in mononuclear cells (MNC) from peripheral blood was performed in 33 patients with ET (untreated or off treatment with hydroxyurea), 28 patients with RT, and 16 normal volunteer controls. We found IGF-1R levels were significantly elevated in ET patients compared to RT patients or controls. A cutoff value of 253 was chosen from the logistic regression to predict each patient's group, a value ≥253 meant that a patient belonged to the ET group (sensitivity 96.4% and specificity 68.6%). We suggest that adding quantification of IGF-1R in blood MNC by flow cytometry is useful in differentiating ET from RT.

Quantification of IGF-1 Receptor Is Useful in the Differential Diagnosis of Essential Thrombocytosis from Reactive Thrombocytosis

To make a definite diagnosis of essential thrombocytosis (ET) from reactive thrombocytosis (RT), the most reliable criteria are the presence of driver mutations, namely JAK2, CALR, or MPL gene mutations. In the absence of these driver mutations, so-called triple-negative ET, the differential diagnosis could be difficult; bone marrow biopsy could be helpful, but in some cases it may be difficult, to do gene sequence analysis to find other clonal marker gene mutations than the driver mutations, only very few were found. We studied IGF-1R quantification by flow cytometry in mononuclear cells (MNC) from peripheral blood, a substitute for performing endogenous erythroid colony formation (EEC), in 33 patients with ET (untreated or off treatment with hydroxyurea), 28 patients with RT, and 16 normal volunteer controls. We found IGF-1R levels significantly elevated in ET patients compared to RT patients or controls. A cutoff value of 253 was chosen from the logistic regression to predict each patient's group, a value ≥253 meant that a patient belonged to the ET group (sensitivity of 68.6% and specificity 96.4.%). Therefore, we suggest adding quantification of IGF-1R in blood MNC by flow cytometry is useful in differentiating ET from RT , we suggest this maybe added to the minor criteria for diagnosing ET. Funding Statement: JCW received grants from Celgen Corp. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Declaration of Interests: The author declares no conflicting interests with the commercial funder relating to using products, consultancy, patents, product development, or market products. The other authors declare no competing financial interests. Ethics Approval Statement: Peripheral blood was obtained from patients with written informed consent, the protocol for which was approved by the IRB of Brookdale University Hospital.

Quantification of IGF-1 Receptor May be Useful in the Differential Diagnosis of Essential Thrombocytosis from Reactive Thrombocytosis- Suggested to Add IGF-1Receptor Quantification As the Minor Criteria for the Diagnosis of ET

Introduction. The 2016 revision to the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia lists the criteria for the diagnosis of essential thrombocythemia (ET ) as 1) Platelet count more than 450 x 109/L 2) BM biopsy 3) Not meeting WHO criteria for BCR-ABL CML, PV, PMF, myelodysplastic syndromes, or other myeloid neoplasms, 4) Presence of JAK2, CALR, or MPL mutation The minor criteria included Presence of a clonal marker or absence of evidence for reactive thrombocytosis .Among these criteria , the most reliable criteria for diagnosis of ET is the presence of JAK2, CALR, or MPL mutation, these mutually exclusive mutations with respective incidences of 55%, 25%, and 3% , so approximately 17% are so called ET . These 17 % cases will depend on other criterias to make a definite diagnosis as ET. Bone marrow criteria is helpful in some cases but in many cases, the differential from re-active thrombocytosis (RT) could be misleading , So a substantial portion of triple-negative patients with ET have evidence of polyclonal: the use of cytoreductive drugs in these patients is questionable We have recently published using IGF-1R quantification by flow cytometry could be helpful in differentiating polycythemia from secondary polycythemia Now we also found quantification of IGF-1R by flow cytometry to be helpful in the diagnosis of ET from reactive thrombocytosis. Materials and Methods: Nineteen patients with ET (treatment naive), 20 with reactive thrombocytosis (RT) (5 sickle cell disease, 5 arthritis, 5 iron deficiency, 3 metastatic Cancer, 2 with infection, one with bleeding) and 23 normal volunteer controls were studied. Flow cytometry: MNC were isolated from peripheral blood then incubated with fluorophore-conjugated primary antibody or isotype controls for 30 min at room temperature and analyzed by FACS Calibur System (BD Biosciences, San Jose, CA). PE-conjugated antibody against human IGF-1R was purchased from R&D Systems. Results: Untreated ET patients had significantly higher IGF-1R (290.8, 86.83-475.2) than RT patients (127.0, 47.75-177.2),(P =220 means that a patient belongs to ET group, with sensitivity of 47.4% and specificity equal to 94.7%. Conclusion: Quantification of IGF-1 receptor may be useful in the differential diagnosis of Essential thrombocythemia from reactive thrombocytosis, especially in those cases where no driver mutations were detected (triple negative). Disclosures Wang: Celgen: Research Funding.

Qualitative and quantitative modifications of von Willebrand factor in patients with essential thrombocythemia and controlled platelet count

Essential thrombocythemia (ET) is characterized by increased platelets and prevalent thrombosis. An acquired von Willebrand factor (VWF) disease has been hypothesized and inconsistently associated with extreme thrombocytosis or rare bleeding in ET.Whether VWF is modified in ET patients with controlled platelet count remains unclear. We studied different VWF- and platelet-associated parameters in ET patients treated according to current recommendations. Sixty-nine ET patients (M=29; median age, 62 [48-70]years; platelets, 432 [337-620]×10(3) μL(-1) ), 69 matched controls and 10 subjects with reactive thrombocytosis (RT) were studied. VWF:antigen (Ag), activity (act), electrophoretic patterns, VWF:propeptide, plasma glycocalycin (GC), glycoproteinV (GpV), ADAMTS-13, elastase, C-reactive protein and serum thromboxane (TX)B2 were measured. In ET patients, VWF:Ag was increased by 31±13% vs. controls (P<0.01), without dependence of blood groups, while VWF:act was reduced by 21±12% vs. controls and by 50±24% vs. RT (P<0.01). The VWF:act/VWF:Ag ratios in ET were reduced by 35±17% vs. controls and RT patients (P<0.001) and significantly associated with: immature or total platelet counts, GC, GpV and TXB2 . In multivariable analysis, only GC inversely predicted ET patients' VWF:act/VWF:Ag ratios (β=-0.42, P=0.01). By electrophoresis analyses, high-molecular-weight VWF multimers were variably reduced with atypical cleavage bands in ET only. VWF:propeptide, ADAMTS-13 and elastase levels were normal in ET patients. Platelet-associated ADAM-10 and ADAM-17 hydrolyzed VWFm invitro, showing patterns similar to those in ET samples. In ET patients with controlled platelet counts, the VWF:act/VWF:Ag ratio is decreased and predicted by GC, a product of platelet activation. ADAM-10 and/or ADAM-17 might be involved. In vivo platelet activation, which characterizes ET, might contribute to disease-specific VWF alterations.

Gene Expression Profiling Distinguishes Essential Thrombocythemia from Polycythemia Vera Patients and Identifies a Common Expressed Set of Genes in Relation to JAK2V617F Status

Introduction. The existence of the JAK2V617F mutation in a high proportion of Myeloproliferative Disorders (MPD) BCR-ABL-negative has provided important insight into the pathogenesis of these diseases. However, much of the molecular abnormalities associated to BCR-ABL-negative MPD remain unknown, specially in those which do not display JAK2V617F. In a previous study, we performed gene expression analysis by using the microarray technique in 20 essential thrombocythemia (ET) patients (44K whole human genome oligo microarrays, Agilent Technologies) and the results were confirmed in 40 ET patients by using TaqMan® Low Density Arrays Arrays (LDA, Applied Biosystems). In our previous experience the results showed different gene expression patterns in ET and a supervised clustering of the data identified genes differentially expressed between JAK2V617F-negative and JAK2V617F-positive ET patients, and a characteristic gene expression profile for JAK2V617F-negative patients (Puigdecanet et al.,2008).Aim. Our aim was to confirm the ET gene expression profile in an extended group of patients and to explore the differences and similarities in polycythemia vera (PV) and reactive thrombocytosis (RT) patients by real-time quantitative RT-PCR (RQ-PCR) technique using the LDA platform. In addition, we wanted to analyze the relationship between gene expression data and JAK2V617F status.Patients and Methods. The following patients were included in the study: 58 ET (23 JAK2V617F-negative, 34 JAK2V617F in heterozygosity and one JAK2V617F in homozygosity) and 41 PV (7 JAK2V617F-negative, 25 JAK2V617F in heterozygosity and 9 JAK2V617F in homozygosity) patients, diagnosed according to the WHO criteria (2001) and who had never received cytoreductive treatment, and six patients with RT. Based on the previous results, we designed a new LDA platform containing 96 assays in duplicate, which included the most expressed genes in ET in relation to healthy controls and the most differentially expressed genes between JAK2V617F-negative and JAK2V617F-positive ET patients. The RQ-PCR analysis was performed in RNA from peripheral blood granulocytes and the relative gene expression quantification was achieved using GAPDH as the endogenous control and a pool of 10 healthy individuals as the calibrator.Results. ETvsPV: The majority of the genes studied presented significant higher expression in ET than in PV patients. Interestingly, FOSB was one of the most differentially expressed gene (FC= 8.3), and CISH and C13orf18 did not distinguish between the two groups.ET: We confirmed the differentially expression of the majority of the genes previously detected between JAK2V617F-negative and JAK2V617F-positive ET patients and we extended the set of genes. Among them, we highlight the differential expression of CISH, FOSB and C13orf18 genes (p<0.01).PV: Supervised analysis showed that CD44, BATF and CISH clearly distinguish JAK2V617F-negative PV patients from the JAK2V617F-positive.ET and PVvsRT: Some differentially expressed genes between ET and RT patients were detected, but the most significant gene was TNF (p<0.001), which presented a higher expression in RT (FC=5.9). The same difference was observed between PV and RT.Conclusions. We have detected a different gene expression pattern in ET and in PV patients. However, we also identified a set of genes which expression was related to JAK2V617F status, both in ET and PV patients. These findings would be interesting to identify other signal transduction pathways besides JAK-STAT involved in the pathogenesis of ET and PV.

Quantitative Analysis of Wild Type and V617F JAK-2 Expression in Neutrophils of Polycythemia Vera and Essential Thrombocythemia Patients at Diagnosis.

The reported frequency of the V617F mutation of JAK-2 appears to vary depending on diagnosis, techniques and cohorts of patients, often already treated. Our aim was to determine the frequency of V617F JAK-2 in polycythemia vera (PV) and essential thrombocythemia (ET) at diagnosis and to quantify its expression at the mRNA level. Neutrophil cDNA was available for 113 MPD patients at diagnosis (56 PV, 57 ET) and 47 controls (26 secondary erythrocytosis (SE), 21 reactive thrombocytosis (RT)) from 5 centers; diagnosis was made following WHO criteria. All patients had a test of endogenous colony formation and a PRV-1 mRNA assay; all ET patients had a bone marrow biopsy in favour of ET. Reverse transcription followed by quantitative real-time PCRs (qPCRs) specific for wild type (WT) JAK-2, V617F JAK-2 and ABL were performed in duplicate; results were expressed as number of copies of WT or V617F JAK-2/100 copies of ABL. V617F JAK-2, never found in SE and RT, was expressed in 96.6% of PV and 70.2% of ET at diagnosis; in this series, the frequency of endogenous colony formation was 84.3% in PV and 78.6% in ET. All but 2 PV patients had elevated PRV-1 levels; one of the 2 PV with normal PRV-1 expression did not express V617F JAK-2. In the ET series, only 15/57 patients (26.3%) had elevated expression of PRV-1; all but one expressed V617F JAK-2. In both PV and V617F JAK-2-positive ET, PRV-1 and mutant JAK-2 expression levels were correlated (PV: r = 0.450, p = 0.0006; ET: r = 0.540, p = 0.0005). Levels of expression of both WT and V617F JAK-2 were significantly different in PV and in ET. ET neutrophils expressed an average of 144 V617F JAK-2 and 462 WT JAK-2 /100 ABL vs. 496 WT JAK-2/100 ABL for RT patients; the V617F/WT ratio for ET was always < 0.7. In PV, two groups of patients were distinguished. The first group (the majority, 60.8%) expressed an average of 975 WT JAK-2 and 733 V617F JAK-2/100 ABL, hereby doubling the total expression of JAK-2 compared to SE (average: 821 WT JAK-2/100 ABL); the V617F/WT ratio of these patients was always < 3. The second group (the minority, 39.2%) expressed low levels of WT JAK-2 (average: 247 copies/100 ABL) and high levels of V617F JAK-2 (average: 1515 copies/100 ABL), hence also doubling the amount of JAK-2 mRNA but with a V617F/WT ratio ≥ 3. Analysis of the cDNA of patients with a V617F/WT ratio < 3 by sequencing showed both WT and mutated (G/T) sequences, whereas patients with a V617F/WT ratio ≥ 3 showed only the mutated (T/T) sequence. In conclusion, 96.6% of PV and 70.2% of ET at diagnosis expressed V617F JAK-2 as measured by allele-specific RT-qPCR. PV was characterized by moderate or high levels of V617F JAK-2 and global over-expression of JAK-2; in contrast, both WT and V617F-JAK-2 were expressed at low levels in ET. Such differences in V617F JAK-2 expression would be expected if clonal neutrophils harbouring the mutation represented a higher percentage of total neutrophils in PV than in ET; in addition, transcription of WT JAK-2 in neutrophils appears to be regulated differently in PV and in ET.

Elevated Platelet Count before Ileal Pouch–Anal Anastomosis for Ulcerative Colitis is Associated with the Development of Chronic Pouchitis

Acute pouchitis (AP) after ileal pouch-anal anastomosis (IPAA) is common and easily treated. However, chronic pouchitis (CP) remains a difficult management problem and may represent a form of Crohn disease (CD) of the ileal pouch. Because CD patients have higher platelet counts than ulcerative colotis (UC) patients, we prospectively evaluated the association between preoperative platelet count and pouchitis development in 159 patients undergoing IPAA. Reactive thrombocytosis (RT) was defined as a platelet count > 450 x 10(9)/L. Median preoperative platelet count was 312 x 10(9)/L (range, 103 x 10(9)/L to 886 x 10(9)/L). One hundred twenty-five patients (79%) had a normal (150 x 10(9)/L to 450 x 10(9)/L) platelet count (-RT patient group). Twenty-eight patients (18%) had RT. Six patients (3%) had a platelet count below 150 x 10(9)/L. After a median follow-up of 13 months, 45 patients (28%) developed pouchitis. Pouchitis developed in 33 +RT patients (26%) versus 9 -RT patients (32%) (P = NS). UC patients who had +RT had a 25 per cent incidence of CP compared to only 7 per cent of those UC patients who had -RT (P = 0.03). The incidence of CP was significantly higher after IPAA in UC patients having thrombocytosis before surgery compared to UC patients having a normal platelet count before surgery.

Increase in platelet–large cell ratio in chronic myeloid leukemia

Thrombocytosis is defined as a platelet count of more than 400×10/l [1]. Differential diagnosis of thrombocytosis is not always obvious. Recently, automated hematological analysis has been common, and various parameters of blood cells can be used. However, there are many parameters whose significance are still unknown. Platelet–large cell ratio (P–LCR) is one of them, and is defined as the ratio of large platelets to total platelets, and is routinely performed by the automated hematological analyzer Sysmex NE-8000 (Sysmex, Kobe, Japan). In this parameter, a large platelet is defined as a platelet with a volume of 12 fl or more [2]. In this study, we examined the clinical usefulness of P–LCR in the differential diagnosis of thrombocytosis. The subjects studied were 50 patients with reactive thrombocytosis (RT), 30 patients with chronic myeloid leukemia (CML) (chronic phase), 15 patients with essential thrombocythemia (ET), and 5 patients with polycythemia vera (PV). P–LCR was higher in patients with CML (27.7 7.9 [mean S.D.]%; P 0.001), patients with ET (17.7 3.6%; P 0.002), and patients with PV (20.8 2.8%; P 0.005) than in patients with RT (13.4 4.1%) (Fig. 1). These findings are compatible with those of previous reports in which the number of large platelets increased in chronic myeloproliferative disorders, but not in RT [3,4]. Furthermore, the P– LCR was higher in patients with CML than in patients with RT (P 0.001), ET (P 0.001) or PV (P 0.001). When the mean+3 S.D. of the P–LCR in 50 patients with RT was determined as the ‘cut-off’ value for differential diagnosis of thrombocytosis between RT and CML, half of the P–LCRs (15/30) were above the ‘cut-off’ value in patients with CML. All of the P– LCRs were under the ‘cut-off’ in patients with RT, ET, or PV. Therefore, these data indicate the ‘cut-off’ value, which is the mean+3 S.D. of the P–LCR in RT patients is useful for the screening of CML in thrombocytosis.

Platelet c-mpl expression is dysregulated in patients with essential thrombocythaemia but this is not of diagnostic value.

Essential thrombocythaemia (ET) can be difficult to discriminate from an occult case of reactive thrombocytosis (RT). Since thrombopoietin (TPO) is the primary regulator of thrombopoiesis, we have investigated whether levels of TPO and/or its receptor, c-mpl, are of value in the differential diagnosis of ET. Plasma TPO levels in patients with ET, RT and other myeloproliferative disorders (MPDs) did not differ significantly from normal controls. However, surface c-mpl expression was significantly reduced in platelets from 18 ET patients, 0-65.5% of controls (P < 0.001). Immunoblots on five of these and five additional patients were consistent with absent or reduced c-mpl protein levels. The surface c-mpl expression results were significantly different from those in eight RT patients (21. 3-95.5%, P = 0.0015), but there was considerable overlap between the two groups and a reduced level was not restricted to ET. Furthermore, c-mpl expression in ET patients was not different from eight patients with other MPDs (0-87.6%, P = 0.06), nor could it differentiate between ET patients with monoclonal and polyclonal haemopoiesis. Although a low or absent c-mpl level is suggestive of a primary rather than a secondary thrombocytosis, it is insufficiently discriminatory to be used as a diagnostic marker for ET.

Impact of endogenous thrombopoietin levels on the differential diagnosis of essential thrombocythaemia and reactive thrombocytosis.

By using the newly commercialized Quantikine human TPO immunoassay, plasma thrombopoietin (TPO) concentrations were measured in 12 patients with essential thrombocythaemia (ET), 13 patients with reactive thrombocytosis (RT) and 11 healthy volunteers. For the healthy volunteers the mean plasma TPO concentration was 21.1+/-11.0 pg/ml. The mean plasma TPO concentration in the group of RT was slightly lower (16.4+/-8.6 pg/ml) but did not differ significantly from the control group. The mean plasma TPO concentration in ET patients (44.1+/-45.2 pg/ml) was significantly (p<0.05) higher than the mean for RT patients, but did not differ statistically from the mean of healthy volunteers. These data suggest a defective clearance of plasma TPO in patients with ET.

Excessive prolongation of the bleeding time by aspirin in essential thrombocythemia is related to a decrease of large von Willebrand factor multimers in plasma.

Patients with essential thrombocythemia (ET), who frequently have bleeding complications, may manifest an excessive prolongation of the bleeding time (BT) after ingestion of aspirin (ASA). The reason for this excessive prolongation of the BT is unknown, but it is attributed to qualitative platelet defects. Since patients with ET may also have acquired abnormalities of plasma and platelet von Willebrand factor (vWF), we questioned whether the excessive prolongation of the BT by ASA was related to changes in either plasma or platelet vWF. To that end, we studied BT and plasma and platelet vWF in ten ET patients, ten patients with reactive thrombocytosis (RT), and ten normal individuals, both before and after administration of 500 mg ASA for 7 days. In a second study, the effect of DDAVP infusion on plasma vWF in relation to the BT was studied in ten normal individuals and ten ET patients after treatment with 100 mg ASA for 3 days. In the first study, treatment with ASA resulted in a significant prolongation of the BT in normal subjects, RT patients, and ET patients. However, in five ET patients an excessive (> 2 SD) prolongation of the BT by ASA was observed. Although ASA induced no direct changes in either plasma or platelet vWF levels in either normal subjects, RT patients, or ET patients, all five ET patients who showed an excessive prolongation of the BT by ASA had significantly decreased levels of large vWF multimers in plasma. In the second study, infusion with DDAVP resulted in a significant increase in plasma large vWF multimers, paralleled by a normalization of (excessively) prolonged BT. Our data suggest that in ET inhibition of platelet function by ASA in the presence of concurrently decreased levels of large vWF multimers in plasma may have provoked the excessive BT prolongation.

Thrombopoietin levels in patients with primary and reactive thrombocytosis

Human c-mpl ligand or thrombopoietin (TPO) has been proved to be a critical cytokine in the physiological regulation of thrombopoiesis. Previous evidence suggested that TPO production is constitutive and TPO plasma levels are regulated by the platelet-megakaryocyte mass through c-mpl receptor-mediated uptake and metabolism. To evaluate whether this mechanism of TPO level regulation is also operative in subjects with an elevated platelet count, we evaluated serum TPO in 32 patients with thrombocytosis due to essential thrombocythaemia (ET) or polycythaemia vera (PV) and in 70 subjects with reactive thrombocytosis; 32 healthy subjects were also studied. TPO levels were significantly higher in the ET and PV groups (median 246.2 pg/ml, range 93.5-4596) and reactive thrombocytosis patients (median 287 pg/ml, range 82.7-1960.0) than in normal subjects (median 156.7 pg/ml, range 62.2-352.7). No significant difference was found between the two groups of patients, indicating that serum TPO levels cannot differentiate between primary and reactive thrombocytosis. No significant correlation was found between platelet count and TPO levels in either ET-PV or reactive thrombocytosis, whereas a trend toward a correlation between acute-phase reactants and TPO was observed in patients with reactive thrombocytosis. These results indicate that TPO clearance by platelets-megakaryocytes is not fully operative or is not the only mechanism of TPO level regulation in primitive and reactive thrombocytosis.

Two Methods for Intraplatelet Serotonin Evaluation: Their Use in Thrombocytosis

The content of platelet dense bodies is considered to be decreased in thrombocytosis associated myeloproliferative disorders and normal in reactive thrombocytosis. Intraplatelet serotonin i.e., 5-hydroxytryptamine (5HT), content is usually considered a particularly good marker. We report our experience of platelet 5HT levels evaluated by radioimmunoassay (RIA) and fluorimetric assays in patients with high platelet counts due to essential thrombocythemia (48 patients) or reactive thrombocytosis (34 patients). The diagnosis of essential thrombocythemia was made according to Polycythemia Vera Study Group criteria. A significant statistical difference was observed in serotonin platelet content between essential thrombocythemia and secondary thrombocytosis patients both with fluorimetric and RIA assays. On the contrary, no difference was evident between reactive thrombocytosis patients and normal control subjects. However, a significant difference was observed between 5HT in serum and platelet pellets when evaluated by RIA. Statistical analysis with the X2test showed that the sensitivity of the fluorimetric assay is slightly higher than that of the RIA assay; however, specificity is about the same with the two methods. It is possible that the two assays measure different molecules. At any rate, the fluorimetric assay seems to be better in evaluating the platelet content of 5HT at least in patients with high platelet counts. Key Words: Thrombocytosis—Serotonin.

The reduction of large von Willebrand factor multimers in plasma in essential thrombocythaemia is related to the platelet count

We have investigated the relationship between platelet count and large VWF (von Willebrand factor) multimers in the plasma of 36 patients with essential thrombocythaemia (ET) and 26 patients with reactive thrombocytosis (RT). In both ET and RT patients an inverse relationship could be established between platelet count and large VWF multimers in plasma as well in relatively decreased ristocetin cofactor/von Willebrand factor antigen and collagen binding activity/von Willebrand factor antigen ratios. A normalization of the platelet count was accompanied by restoration of a normal plasma VWF multimeric distribution. Our data suggest that increasing numbers of platelets circulating in blood result in increased removal of large VWF multimers from plasma.

Platelet Consumption in Thrombocythemia Complicated by Erythromelalgia: Reversal by Aspirin

The involvement of platelets in the pathogenesis of erythromelalgia, a frequent and characteristic microvascular thrombotic manifestation in patients with primary thrombocythemia and polycythemia rubra vera, was investigated by measuring the survival and turnover of 51Cr labeled autologous platelets in 10 patients with thrombocythemia complicated by erythromelalgia, in 10 asymptomatic thrombocythemia patients and in 6 subjects with reactive thrombocytosis. The mean platelet survival time of the erythromelalgia patients was 4.2 +/- 0.2 days, which is significantly decreased as compared with asymptomatic thrombocythemia patients (6.6 +/- 0.3 days, p < 0.001) and patients with reactive thrombocytosis (8.0 +/- 0.4 days, p < 0.001). The mean platelet survival time of asymptomatic thrombocythemia patients was significantly decreased (p < 0.01) as compared with reactive thrombocytosis patients. Treatment of erythromelalgia with aspirin increased the mean platelet survival time from 4.0 +/- 0.3 days to 6.9 +/- 0.4 days (p < 0.001) and was associated with an elevation of the platelet count of 216 +/- 30 x 10(9) platelets per liter (p < 0.001). Coumadin failed to improve platelet survival or symptoms caused by erythromelalgia. The increased platelet consumption in erythromelalgia is attributed to the formation of platelet thrombi in the arterial microvasculature. This conclusion is supported by the ability of aspirin to interrupt platelet consumption and clinical features of erythromelalgia.

Occurence, etiology, and clinical significance of extreme thrombocytosis: A study of 280 cases

purpose: To determine the etiology and to evaluate the clinical consequences of an extremely elevated platelet count. patients and methods: A review of the medical records was performed on all patients encountered during a 5 1/2-year period who had at least one platelet count of 1,000 × 10 9/L or greater. results: Of the total of 280 patients with extreme thrombocytosis (EXT), 231 (82%) had reactive thrombocytosis (RT), 38 (14%) had a myeloproliferative disorder (MPD), and 11 (4%) had cases of uncertain etiology. RT was more common than MPD in all age groups except those in the eighth decade and older. Symptoms of bleeding and/or vaso-occlusive phenomena were noted in association with EXT in 21 (56%) of the MPD patients but in only 10 (4%) of the RT patients. Treatment to lower the platelet count and/or inhibit platelet function was employed in 36 MPD patients and 23 RT patients. Eight patients with MPD and 34 with RT are known to have died, but no patient in either group is known to have died of a thrombotic or bleeding event when the platelet count was greater than or equal to 1,000 × 10 9/L. conclusions: Platelet counts greater than or equal to 1,000 × 10 9/L should not be considered rare events in the general, acute-care hospital population, and usually represent a reactive phenomenon.

Measurement of spleen size using gamma camera scintigraphy in essential thrombocythaemia.

By using gamma camera imaging the spleen size was determined in 33 consecutive patients with essential thrombocythaemia (ET) and in 33 consecutive patients with reactive thrombocytosis (RT). All ET patients were newly diagnosed and had not received myelosuppressive treatment prior to study; they all fulfilled the criteria for ET as established by the Polycythemia Vera Study Group. In both posterior and lateral projections, the spleen area in the group of ET patients was significantly larger than in the RT patients. The present study has shown that 39% of ET patients at diagnosis have splenic enlargement. Evaluation of spleen size is therefore a useful diagnostic test in patients presenting with unexplained thrombocytosis.

Heterogeneity of Human Platelets. VII. Platelet Monoamine Oxidase Activity in Normals and Patients With Autoimmune Thrombocytopenic Purpura and Reactive Thrombocytosis: Its Relationship to Platelet Protein Density

The level of platelet monoamine oxidase (MAO) activity has been used as a genetic marker for certain mental disorders. The purpose of this study was to investigate the influence of several nongenetic factors on platelet MAO activity. Platelet MAO, platelet count, mean platelet volume, per cent megathrombocytes, platelet protein, and platelet protein density were determined in 19 normal subjects and in patients with two clinical conditions associated with extremes in platelet count and mean platelet volume: 6 patients with autoimmune thrombocytopenic purpura (ATP), characterized by low platelet count and increased mean platelet volume; and 6 patients with reactive thrombocytosis (RT), characterized by high platelet count and decreased mean platelet volume. Platelet protein density was expressed as total platelet protein/total platelet volume. Patients with ATP, when compared to normal subjects, had 2.3-fold lower platelet protein density and 2.1-fold lower specific activity of MAO. Patients with RT, when compared to normal subjects, had 1.9-fold higher platelet protein density and 1.5-fold higher specific activity of MAO. Platelets from RT patients, when compared to ATP patients, had 4.3-fold greater protein density and 3.2-fold higher specific activity of MAO. Platelets from normal subjects were separated into five different platelet density fractions. Platelet MAO and protein content were found to be heterogeneously dispersed. The extreme heavy platelet fraction had 15-fold greater specific activity of MAO and 18-fold greater protein content, compared to the extreme light platelet fraction. We conclude that high specific activity of MAO is associated with platelets densely packed with protein. Accordingly, nongenetic factors such as changes in platelet number, volume, and protein content, which could be induced by stress, blood loss, iron deficiency, or other conditions, could contribute to changes in protein density, and consequently affect the specific activity of platelet MAO.