Which non-cancerous diseases are associated with thrombocytosis and do these associations change with gender, age, and platelet count, a secondary analysis study using English electronic medical records and cancer registry data.

Problem

Thrombocytosis is an excess of platelets, which are acute-phase reactants, therefore, they increase in response to various stimuli, including systemic infections, inflammatory conditions, bleeding, and tumours. The recently discovery of the association between thrombocytosis and cancer detection is well known, yet 89% of patients with thrombocytosis don't have or develop cancer. In this study, our primary aims are 1) identify which clinical outcomes other than cancer are associated with thrombocytosis and how common these associations are, and 2) identify if these associations change by patient age, gender or platelet count. Understanding other conditions associated with thrombocytosis will help clinical practitioners to rule out cancer when an alternative explanation is present.

Approach

This study is a secondary analysis of a dataset of 40,000 patients aged 40 years and over with a platelet count of >400x109/l in the Clinical Practice Research Datalink (CPRD) from 2000 - 2013. A literature search was carried out to identify candidate diagnoses that have been linked to a raised platelet count. The electronic medical records of included patients will be searched for any new record of these conditions in the year following the patients’ first raised platelet counts, and the incidence of each of these conditions estimated. Analyses will be stratified by age group and sex. We will investigate whether the extent to which platelet count is elevated is associated with different diagnoses.

Findings

The literature search identified 14 candidate conditions. These disease have been allocated into first division and second division. At the time of abstract submission, we were generating code libraries for each disease. By July, we will have estimates of incidence for each condition in the cohort as a whole, and stratified by age and sex.

Consequences

Identifying commonly diagnosed conditions after a raised platelet count is of vital importance to enable primary care clinicians to carry out appropriate investigations and history taking in patients with unexpected thrombocytosis. The link between cancer diagnosis and thrombocytosis is now well established in clinical practice; knowledge of other associated conditions will also be valuable in helping clinicians to rule out cancer when another recognised cause of a raised platelet count is present. It may be that age, gender and platelet count change the strength of association of the identified clinical diseases with thrombocytosis. Therefore clinicians can make a more confident diagnoses for a patient with thrombocytosis with a demographic that has been strongly associated with a disease.