Development and validation of a model for stratifying haematological malignancy risk in primary care using basic blood tests.

Haematological malignancies are rare in primary care and are hard to predict. Existing prediction models often require a specific working diagnosis and are based on extensive clinical information, access to which may be limited at initial work-up in primary care. We aimed to develop a tool for estimating overall risk of haematological malignancy in primary care patients using simple data inputs. Including all full blood cell counts (FBCs) measured from 2000 to 2016 in 856 403 adult primary care patients in Eastern Denmark, we used machine learning to develop CBC-HEMA, a risk assessment tool using FBCs, age, sex and C-reactive protein measures to stratify 'any haematological malignancy' risk within 6 months, 1 year and 3 years with area under the curve (AUC) of 0.81, 0.78 and 0.71 respectively. Predictions of chronic lymphoid leukaemia and myeloproliferative disease were excellent, while CBC-HEMA was unable to accurately predict non-Hodgkin lymphoma and plasma cell dyscrasia. External validation was conducted in 123 015 primary care patients from Western Denmark with similar results and in 418 410 individuals from the background population cohort UK Biobank with inferior performance showing unfitness in screening healthy populations. The CBC-HEMA https://shiny.sund.ku.dk/CopLab/blood-cancer-risk-prediction/ may support risk assessment in primary care but cannot replace a clinical evaluation.