[Thrombocytosis in the oncology-haematology clinic: description, aetiological diagnosis and progression thrombocytosis]. / Trombocitosis en la consulta de oncohematología. Descripción, diagnóstico etiológico y evolución.

INTRODUCTION: Thrombocytosis is a common cause of patient referral to a paediatric haematologist specialist which requires a significant number of laboratory tests and visits to confirm the diagnosis. The aim of our study has been to analyse the characteristics of patients referred to our centre for specialised thrombocytosis assessment. Based on this assessment we established the criteria patients must fulfil to be recommend for further hospital study. PATIENTS AND METHODS: We categorised the 33 patients referred for thrombocytosis assessment according to sex, age, origin, personal and family history, platelet count at diagnosis and the reason why the red and white blood count at diagnosis (Haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin, leukocyte, neutrophils, lymphocyte and monocyte count), maximum platelet count during follow-up and other complementary examinations were done. The final diagnosis itself and number of previous visits before were also considered. The classification used to grade thrombocytosis was: low (500-700 X 10(3)/microl), mild (700-900 x 10(3)/microl), severe (900-1.000 x 10(3)/microl) and extreme (> 1.000 x 10(3)/microl). RESULTS: There was no predominance of males or females. 45 % of patients were under 2 years old and 55 % of them came from their primary care centre. The mean platelet count at the first medical visit was 669,000 (mild thrombocytosis). During follow-up, 24 % of the patients reached extreme platelets levels. In 28 % the initial blood count was performed because of an infection. The most frequently requested laboratory test was iron metabolism (82 % of the cases). All cases correspond to secondary thrombocytosis (48 % were reactive to infections, 24 % secondary to iron deficiency, and 15 % were associated to both causes). The mean number of visits before hospital discharge was 5.12. CONCLUSIONS: The finding of thrombocytosis in the majority of the cases studied was casual or in the context of an infectious process. Most of the thrombocytosis were mild. Due to the extremely low incidence of primary thrombocytosis in childhood and the fact that diagnosis is made by exclusion of other possibilities, the initial study of these patients should be done in primary care centres. The first conditions to be ruled out are infectious, inflammatory or bleeding processes. Once these causes are excluded, the most useful complementary test is to measure iron level given the relation between iron deficiency and thrombocytosis. Once these causes are ruled out and thrombocytosis persists, it would then be indicated to refer the patient to a paediatric oncology-haematology department for a more exhaustive follow-up.