Which tests are most useful in distinguishing between reactive thrombocytosis and the thrombocytosis of myeloproliferative disease?

Association of human platelet antigen polymorphisms with platelet count and mean platelet volume

OBJECTIVES

Although recent genome-wide association studies have identified a number of single nucleotide polymorphisms associated with platelet count and mean platelet volume (MPV), it is unclear whether polymorphisms in the human platelet antigens (HPA) genes are associated with platelet count and MPV. The aim of this study was to determine the association of the HPA-2, -3, -5 and -15 polymorphisms with platelet count and MPV.

METHODS

The HPA were genotyped by 5'-nuclease assay in 139 healthy Chinese Han individuals, while platelet count and MPV from the same samples were measured using an hematology cell analyzer.

RESULTS

The platelet count was significantly lower in the individuals with the HPA-2aa genotype compared to those with HPA-2ab (P = 0.020), and significantly higher in individuals with HPA-5aa and HPA-15aa genotypes compared to those with HPA-5ab (P = 0.045) and HPA-15ab/bb (P = 0.032), respectively. On the other hand, platelet count of individuals with the HPA-3aa and HPA-3ab/bb genotypes did not differ significantly (P = 0.084). The MPV was significantly lower in individuals with HPA-5aa genotype compared to those with HPA-5ab (P = 0.001) but did not differ among the HPA-2, -3 and -15 genotypes. Furthermore, HPA-2, -5 and -15 polymorphisms were identified as independent factors for the platelet count and HPA-5 polymorphism was shown as an independent factor for MPV.

CONCLUSIONS

This study demonstrates that HPA-2, -5 and -15 polymorphisms are associated with the platelet count while HPA-5 polymorphism is associated with MPV. This finding will further our understanding of the association of HPA polymorphisms with platelet-related diseases.

Incidence and etiology of thrombocytosis in an adult Turkish population

The aim of the study was to determine the incidence and etiology of thrombocytosis in an adult Turkish population. The medical records of 2000 patients were reviewed retrospectively to determine (i) the etiology of elevated platelet counts, (ii) additional laboratory parameters (i.e., complete blood counts), and (iii) the presence of thromboembolic complications. Within 5 years, 174 678 platelet counts had been performed for 124,340 patients. Of the 124,340 patients, 2000 (1.6%; mean age, 55.2 +/- 17.4 years; range 16-94 years; male-to-female ratio, 3.6:1 [1570:430]) had one or more platelet counts of 500 x 10(3)/mm3 or higher during the study period. Secondary thrombocytosis was the most frequent cause of an elevated platelet count and occurred in 1934 cases (96.7%). Infection was the most common cause of secondary thrombocytosis, occurring in 1001 patients (50.1%). Compared with secondary thrombocytosis, primary thrombocytosis was significantly associated with a higher rate of thromboembolic complications. It is concluded that a high platelet count may have both diagnostic and therapeutic implications. Secondary thrombocytosis is a common finding and mostly secondary to infection. Primary thrombocytosis has a higher risk for thromboembolic events than does secondary thrombocytosis.

Platelet-rich plasma serotonin levels in chronic myeloproliferative disorders: evaluation of diagnostic use and comparison with the neutrophil PRV-1 assay

In a prospective study of 109 subjects, an enzyme-linked immunosorbent assay (ELISA) was used to measure platelet-rich plasma (PRP) serotonin levels in patients with polycythaemia vera (PV; n = 27), essential thrombocythaemia (ET; n = 14), myelofibrosis with myeloid metaplasia (MMM; n = 30), secondary or spurious polycythaemia (SP; n = 22) and controls (n = 16). Nine study subjects who were taking a selective serotonin reuptake inhibitor (SSRI) all displayed a markedly decreased PRP serotonin level (median, 24.2 ng/10(9) platelets; range, 0-49.3) and were therefore excluded from further analysis. Among the remaining 100 subjects, the median and range of PRP serotonin levels, in ng/10(9) platelets, was significantly lower in MMM (89.5; 0-278.3), PV (204.8; 0-496.0) and ET (385.3; 136.8-1025.7) compared with both SP (608.8; 369.0-1780.1) and controls (567.2; 359.9-1071.1). Neutrophil polycythaemia rubra vera-1 (PRV-1) expression was concurrently assayed by real-time polymerase chain reaction in 69 patients (23 PV, 17 SP, 12 ET, seven MMM, 10 controls). PRP serotonin measurement performed as well as the PRV-1 assay in distinguishing PV from SP (93% vs. 86% test accuracy). The current study suggests that PRP serotonin concentration might be considered as one of the several biological markers that complement each other for the diagnosis of PV.

Aetiology and clinical significance of thrombocytosis: analysis of 732 patients with an elevated platelet count

OBJECTIVE

To determine the aetiology and clinical significance of an elevated platelet count (thrombocytosis) in a large cohort of patients.

DESIGN

A retrospective review of the medical records was performed on all patients, who had at least one platelet count > or = 500 x 10(9) L-1.

SETTING

Departments of Medicine and Surgery, University of Ulm, Germany.

SUBJECTS

A total of 732 patients with thrombocytosis.

MAIN OUTCOME MEASURES

Classification of thrombocytosis and thromboembolic complications, and evaluation of laboratory parameters distinguishing between primary and secondary thrombocytosis.

RESULTS

Of the total of 732 patients, 89 (12.3%) had primary and 643 (87.7%) had secondary thrombocytosis. Essential thrombocythaemia was observed in 40 of 89 patients (45%) with primary thrombocytosis. The most frequent causes of secondary thrombocytosis were tissue damage (42%), infection (24%), malignancy (13%) and chronic inflammation (10%). Primary thrombocytosis was significantly associated with a higher platelet count and an increased incidence of both arterial and venous thromboembolic complications. In secondary thrombocytosis, thromboembolic events were restricted to the venous system and occurred only in the presence of other risk factors. Mean values of leucocyte count, haematocrit, erythrocyte sedimentation rate, fibrinogen, serum potassium and lactate dehydrogenase were significantly different in primary and secondary thrombocytosis.

CONCLUSIONS

The finding of an elevated platelet count on routine blood examination has diagnostic, prognostic and therapeutic implications. It is of clinical importance to distinguish between primary and secondary thrombocytosis, as thrombotic complications occur more frequently in primary thrombocytosis. Unless additional risk factors are present, secondary thrombocytosis is not associated with a significant risk for thromboembolic events.

Diagnostic and differential criteria of essential thrombocythemia and reactive thrombocytosis

Among the chronic myeloproliferative disorders essential thrombocythemia (ET) is known to be a distinct clinical entity in which an excessive number of morphologically and functionally abnormal platelets are produced. The clonal nature of the disease is well established. Based on a review of the literature the present authors propose the following novel criteria for the diagnosis of ET: A1. Platelet count in excess of 600 x 10(9)/L. A2. No increase in red-cell mass (RCM) in the presence of stainable iron in the bone marrow or failure of iron trial (RCM < 36 mL/kg in males and < 32 mL/kg in females; or RCM < 25% above mean normal predicted value*). A3. No Philadelphia chromosome. A4. Megakaryocytic hyperplasia (= increased megakaryocyte number and size) in histological sections of bone marrow and/or increased megakaryocytic ploidy (two-color flow cytometry); no collagen fibrosis. B1. Splenomegaly on isotopic scan or echogram. B2. Unstimulated growth of BFU-E and/or CFU-Meg present. B3. Normal ESR/fibrinogen. The diagnosis of ET is considered to be established if A1 + A2 + A3 + A4 or A1 + A2 + A3 + two B-criteria are fulfilled. (* Br J Haematol 1995; 89:748-756.)

Issues in the diagnosis and management of essential thrombocythemia

OBJECTIVE

To summarize the current trends in the diagnosis and management of essential thrombocythemia (ET) and to discuss the treatment of young and pregnant patients with ET.

DESIGN

We review our experiences in the diagnosis and management of ET.

MATERIAL AND METHODS

A definitive diagnosis of ET at initial examination is seldom possible because of the low incidences of associated clonal cytogenetic abnormalities and palpable splenomegaly. The criteria of the Polycythemia Vera Study Group for the diagnosis of ET are provided, as are the clinical and laboratory features that help to distinguish ET from reactive thrombocytosis.

RESULTS

Patients with ET have an almost normal life expectancy if thrombohemorrhagic complications are controlled. Although a previous history of thrombosis is an established risk factor for further episodes, the adverse effects of extreme thrombocytosis and age are less well defined. Determining which patients require therapy is controversial. The management of young or pregnant patients necessitates special considerations.

CONCLUSION

Until additional data become available, no strong recommendations can be given in support of or against specific therapy for asymptomatic young patients. We favor treatment in asymptomatic patients with cardiovascular risk factors but not in asymptomatic women who are pregnant or are of childbearing age.

Primary thrombocythaemia: a composite approach to diagnosis

Traditional diagnostic criteria for primary thrombocythaemia (PT) remain essentially negative, aiming to exclude other myeloproliferative disorders and causes of reactive thrombocytosis (RT). It would be useful to have positive markers. We have examined several parameters to see how well they discriminate between PT and RT. Three groups of patients were studied: new, untreated PT (17), treated PT (12) and RT (17). Data consisted of: ESR, plasma fibrinogen, factor VIIIC, von Willebrand factor antigen (vWF:Ag), PDW, platelet nucleotide ratio (ATP:ADP) serum erythropoietin (Epo), ristocetin cofactor (vWF:RiCoF), multimeric structure of vWF, interleukin-6, evidence of clinical ischaemia and erythroid colony formation. Erythroid colonies were assayed in a serum-free system with the addition of Epo, IL3 or alpha-IFN to produce a discriminant function (DF) successfully used in the diagnosis of primary polycythaemia in an earlier study. Acute phase reactants (ESR, fibrinogen, VIIIC, vWF:Ag) and IL6 were the best discriminants, while PDW and serum Epo were less so. ATP:ADP and clinical ischaemia were nondiscriminatory in this study. Reduction in vWF:RiCof and in high molecular weight multimers were clearly associated with PT. Endogenous erythroid colonies were nondiscriminatory, but half the PT group and only one patient in the RT group obtained a DF suggestive of myeloproliferative disorder. Judicious use of a battery of tests may provide support for diagnosis of PT in difficult cases.