You can find useful resources for HELP Flag here.
You can find useful resources for HELP Flag here.
The clinical utility of the platelet count as a marker of lung cancer was first established in 2005 (Hamilton et al 2005). In that study of 247 lung cancer cases and 1235 matched controls from general practices in Exeter, the positive predictive value for lung cancer associated with thrombocytosis (platelet count > 400 x 109/l) was 1.6% (95% confidence interval 0.8 to 3.1).
In a cohort study of 40,000 patients with thrombocytosis (Bailey et al 2017), 11.6% (95% CI 11.0 to 12.3) of males aged 40 years and over were diagnosed with cancer in the following year (any site excluding non-melanoma skin cancer). The equivalent figure in females was 6.2% (95% CI 5.9 to 6.5). The risk of cancer increased to 18.1% (95% CI = 15.9 to 20.5) for males and 10.1% (95% CI = 9.0 to 11.3) for females when a second raised platelet count was
recorded within 6 months. Lung and colorectal cancer were more commonly diagnosed with thrombocytosis.
Thrombocytosis is listed as a clinical feature of lung and endometrial cancer in the latest version of NICE guideline NG12 (Suspected cancer: recognition and referral), published in 2015.
A study of patients with platelet counts at the upper end of the normal range (Mounce et al 2020) found that men aged 60 years and over with a platelet count of 326 – 400 × 109 /l had a 1-year cancer incidence of over 3%.
Studies of patients with thrombocytosis in Ontario have also reported an elevated cancer risk associated with the test result (Giannakeas and Narod 2021 and Giannakeas et al 2022).
The age and sex personalised platelet count thresholds for the England, Canada and Australia were first report in Mounce et al (2024).