Cancer incidence in patients with a high normal platelet count: a cohort study using primary care data.
Oxford University Press (OUP)
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Reason for embargo
Under embargo until 12 April 2019 in compliance with publisher policy.
Background A platelet count >400×109/l (i.e. thrombocytosis) is a recently discovered risk marker of cancer. The risk of undiagnosed cancer in patients with thrombocytosis is 11.6% for men and 6.2% for women; well above the 3% risk threshold set by NICE for cancer investigation. Patients with a platelet count at the upper end of the normal range (325-400x109/l) could be at increased risk of undiagnosed malignancy. Objective To quantify the risk of an undiagnosed cancer in patients with a platelet count at the upper end of the normal range. Methods A primary care-based cohort study using Clinical Practice Research Datalink (CPRD) data from 2000 - 2013. The study sample comprised 2704 individuals stratified by platelet count: 325-349 x 109/l; 350-374 x 109/l; 375-399 x 109/l. Incident cancer diagnoses in the year following that platelet count were obtained from patient records. Results Cancer incidence rose with increasing platelet count: 2.6% (95% CI 1.9 to 3.6) in subjects with a count of 325-349x109/l; 3.7% (95% CI 2.5 to 5.3) in subjects with a count of 350-374x109/l; and 5.1% (95% CI 3.4 to 7.5) in those with a count of 375-399x109/l. Colorectal cancer was the most commonly diagnosed type in all three groups. Cancer incidence was consistently higher in males than in females. Conclusion These results suggest that clinicians should consider cancer in patients with a platelet count >375x109/l, and review the reasons for blood testing and any additional reported symptoms. Until these results are replicated on a larger scale, recommendations for clinical action cannot be made.
The Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis receives funding for a research programme from the Department of Health Policy Research Programme. It is a collaboration between researchers from seven institutions (Queen Mary University of London, UCL, King’s College London, London School of Hygiene and Tropical Medicine, Hull York Medical School, Durham University, and the University of Exeter). Obioha Ukoumunne is supported by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care South West Peninsula. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, or the Department of Health.
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.
Published online 12 April 2018.