Asymptomatic late thrombocytosis is a common finding in very preterm infants even in the absence of erythropoietin treatment

Abstract

Objectives Thrombocytosis is more prevalent in pediatric than in adult patients and is associated with complications or worsened outcomes after vascular events. This study aimed to determine the prevalence of thrombocytosis in very preterm infants who had not received human recombinant erythropoietin treatment (rHuEPO) and its relationship with other hematological parameters and clinical complications. Methods We performed a retrospective study of hematological and clinical data of very preterm infants who were admitted to our unit in their first 48 hours of life and stayed for longer than 1 week. Results Thrombocytosis was prevalent (32.6% of patients) in very preterm infants (≤32 weeks of gestational age, n = 193) who had not received rHuEPO. The platelet count was positively correlated with calendar age. Infants with thrombocytosis were significantly more premature (28.0 ± 2.1 versus 29.6 ± 2.2 weeks) and had a lower birth weight (1036 ± 304 versus 1303 ± 304) than those without thrombocytosis. Thrombocytosis was associated with retinopathy of prematurity after adjusting for gestational age and comorbidities, but not with other prematurity-associated complications. Conclusions Late asymptomatic thrombocytosis is common in very preterm infants at approximately 1 month of postnatal age and it may be associated with retinopathy of prematurity.

Pathophysiology, classification, and complications of common asymptomatic thrombocytosis in newborn infants

“…Erythropoietin (EPO), a regulator of erythrocyte production, is structurally similar to TPO with an amino terminal domain containing a sequence homologous to that of EPO [ 17 , 18 ]. Preterm infants with thrombocytosis show decreased red blood cell counts and elevated endogenous EPO levels due to anemia, which probably results in elevated platelet counts [ 4 ]. Increased production of thrombopoietic factors, cytokines, and other hematopoietic growth factors due to anemia might be related to elevated platelet counts as well [ 2 ].…”

“…In one study, thrombocytosis was found in 38% of low birth weight preterm infants [ 3 ]. Thrombocytosis was observed in 32.6% of preterm infants with a gestational age <32 weeks who had not received recombinant human EPO [ 4 ]. Higher TPO concentrations [ 3 , 32 ] and more sensitive megakaryocyte precursor cells [ 3 ] in preterm versus term infants are the speculated cause ( Fig.…”

“…Low expression of TPO receptor in preterm infants leads to the accumulation of free TPO, which has been suspected to induce thrombocytosis in preterm infants [ 12 ]. Anemia was frequently diagnosed in preterm infants with a gestational age < 32 weeks by Del Rey Hurtado de Mendoza et al [ 4 ], who reported an inverse correlation between decreased red blood cell counts and increased platelet counts in preterm infants.…”

“…Thrombocytosis frequently occurs in newborns and young infants younger than 2 years, with an estimated incidence of 3%–13% [ 3 ], although the exact prevalence is unknown. Thrombocytosis in newborn infants is considered a reactive process in most cases, and it is rarely associated with complications [ 4 ]. Whether similar risks such as hemorrhagic and thromboembolic complications in adults exist in newborn infants with thrombocytosis remains unclear.…”

Comparison of Mean Platelet Counts in Preterm Infants with and without Retinopathy of Prematurity

“…To date, the relationship between platelet counts and ROP remains poorly defined. Most studies observe an association between thrombocytopenia and ROP development or severity [ 12 , 13 , 14 ], while others find no association [ 15 , 16 ]; one recent study even documented that thrombocytosis is associated with ROP [ 17 ]. These differences may be attributed to differences in study methodology and statistical analysis, as the majority of these studies evaluated platelet levels as a qualitative variable.…”