Abstract
BackgroundThrombocytosis is an excess of platelets, which is diagnosed as a platelet count >400 × 109/l. An association of thrombocytosis with undiagnosed cancer has recently been established, but the association with non-malignant disease has not been studied in primary care.AimTo examine, in English primary care, the 1-year incidence of non-malignant diseases in patients with new thrombocytosis and the incidence of pre-existing non-malignant diseases in patients who develop new thrombocytosis.Design and settingProspective cohort study using English Clinical Practice Research Datalink data from 2000 to 2013.MethodNewly incident and pre-existing rates of non-malignant diseases associated with thrombocytosis were compared between patients with thrombocytosis and age- and sex-matched patients with a normal platelet count. Fifteen candidate non-malignant diseases were identified from literature searches.ResultsIn the thrombocytosis cohort of 39 850 patients, 4579 (11.5%) were newly diagnosed with any one of the candidate diseases, compared with 443 out of 9684 patients (4.6%) in the normal platelet count cohort (relative risk [RR] 2.5, 95% confidence intervals [CI] = 2.3 to 2.8); iron-deficiency anaemia was the most common new diagnosis (4.5% of patients with thrombocytosis, RR 4.9, 95% CI = 4.0 to 6.1). A total of 22 612 (57.0%) patients with thrombocytosis had a pre-existing non-malignant diagnosis compared with 4846 patients (50%) in the normal platelet count cohort (odds ratio 1.3, 95% CI = 1.2 to 1.4). There was no statistically significant difference in cancer diagnoses between patients with and without pre-existing disease in the thrombocytosis cohort.ConclusionThrombocytosis is associated with several non-malignant diseases. Clinicians can use these findings as part of their holistic diagnostic approach to help guide further investigations and management of patients with thrombocytosis.
Highlights
Thrombocytosis is a higher than normal value of platelets in human plasma.[1]
In the thrombocytosis cohort of 39 850 patients, 4579 (11.5%) were newly diagnosed with any one of the candidate diseases, compared with 443 out of 9684 patients (4.6%) in the normal platelet count cohort; irondeficiency anaemia was the most common new diagnosis (4.5% of patients with thrombocytosis, risk ratios (RR) 4.9, 95% CI = 4.0 to 6.1)
A total of 22 612 (57.0%) patients with thrombocytosis had a preexisting non-malignant diagnosis compared with 4846 patients (50%) in the normal platelet count cohort
Summary
Thrombocytosis is a higher than normal value of platelets in human plasma.[1]. The currently accepted normal range in the UK is 150–400 × 109/l.1 Platelets are acute-phase reactants; they may increase in response to infection, inflammation, bleeding, and tumours.[2,3,4,5] Their main roles are haemostasis and clot formation, and they have a possible additional role in immune response.[4,6] The association of thrombocytosis with cancer has been recognised, with 11% of patients with thrombocytosis identified in primary care being diagnosed with cancer in the following year.[7]. Platelets are acute-phase reactants; they may increase in response to infection, inflammation, bleeding, and tumours.[2,3,4,5] Their main roles are haemostasis and clot formation, and they have a possible additional role in immune response.[4,6] The association of thrombocytosis with cancer has been recognised, with 11% of patients with thrombocytosis identified in primary care being diagnosed with cancer in the following year.[7] It is less well understood which other diagnoses are present in the 89% of patients with thrombocytosis who do not have cancer. It would be clinically helpful to know the alternative diagnoses associated with thrombocytosis to guide clinical decision making in primary care, to avoid investigation for possible cancer when the patient has an existing condition potentially explaining the thrombocytosis. No previous studies in primary care have explored the association of thrombocytosis with non-malignant diseases. An association of thrombocytosis with undiagnosed cancer has recently been established, but the association with non-malignant disease has not been studied in primary care
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