Background:

Incidentally discovered thrombocytopenia in asymptomatic individuals often result in a referral to hematology. Clinical decisions for these individuals are mostly based on local practice, as little evidence exists on their risk of hematologic disease and death. We aim to lay ground for an evidence-based clinical approach to incidental thrombocytopenia with or without concurrent anemia by studying relative and absolute risk of being diagnosed with hematologic disease, death from hematologic disease and death from any cause.

Methods:

We studied 382,424 general population individuals from the United Kingdom (UK) Biobank aged 40-70 years, of whom 9,151 had thrombocytopenia with or without anemia. Individuals with leukocytosis, neutropenia or prior hematologic disease were excluded. As a validation cohort, we studied 104,358 Danish general population individuals. All individuals attended a health examination and had platelets, hemoglobin, leukocyte and differential count measured at study enrolment. Individuals were followed prospectively for up to 16 years for hematologic disease and cause-specific death using national registries, covering all deaths and almost all cancer cases in the UK and Denmark.

Results:

Among 382,424 individuals from the UK, 6,044 had hematologic disease during follow-up, 28,403 died from any cause and 1,213 died due to hematologic disease. For all analyses, the reference group was individuals with normal platelet count and normal hemoglobin.