Clinical relevance of thrombocytosis in primary care: a prospective cohort study of cancer incidence using English electronic medical records and cancer registry data

Abstract

BackgroundThrombocytosis (raised platelet count) is an emerging risk marker of cancer, but the association has not been fully explored in a primary care context.AimTo examine the incidence of cancer in a cohort of patients with thrombocytosis, to determine how clinically useful this risk marker could be in predicting an underlying malignancy.Design and settingA prospective cohort study using Clinical Practice Research Datalink data from 2000 to 2013.MethodThe 1-year incidence of cancer was compared between two cohorts: 40 000 patients aged ≥40 years with a platelet count of >400 × 109/L (thrombocytosis) and 10 000 matched patients with a normal platelet count. Sub-analyses examined the risk with change in platelet count, sex, age, and different cancer sites.ResultsA total of 1098 out of 9435 males with thrombocytosis were diagnosed with cancer (11.6%; 95% confidence interval [CI] = 11.0 to 12.3), compared with 106 of 2599 males without thrombocytosis (4.1%; 95% CI = 3.4 to 4.9). A total of 1355 out of 21 826 females with thrombocytosis developed cancer (6.2%; 95% CI = 5.9 to 6.5), compared with 119 of 5370 females without (2.2%; 95% CI = 1.8 to 2.6). 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. One-third of patients with thrombocytosis and lung or colorectal cancer had no other symptoms indicative of malignancy.ConclusionThrombocytosis is a risk marker of cancer in adults; 11.6% and 6.2% cancer incidence in males and females, respectively, is worthy of further investigation for underlying malignancy. These figures well exceed the National Institute for Health and Care Excellence-mandated risk threshold of 3% risk to warrant referral for suspected cancer.

Non‐invasive liver fibrosis scores are strongly associated with liver cancer mortality in general population without liver disease

“…However, there is no previous evidence to suggest that there is an association between raised FIB‐4 or APRI score and hepatic metastases. After adjusting for age it remains unclear what biological plausibility there would be for an association between hepatic metastases and raised FIB‐4 (or APRI), given that in a chronic inflammatory state such as metastatic malignancy, platelets would tend to be higher and it has been demonstrated previously that high platelets are a risk factor for undiagnosed cancer . High platelets would result in a lower FIB‐4 and APRI score.…”

Assessing patients at risk of symptomatic-but-as-yet-undiagnosed cancer in primary care using information from patient records

“…Such analyses, of the 'cancer signature' of different pre-diagnostic features, can help to devise cost-efficient investigation strategies, individualising the cascade of specialist diagnostic tests, depending on the presenting symptoms and initial test findings. 13,20 Echoing other recent evidence, 21 a substantial proportion of cancer patients who presented with unintended weight loss were diagnosed in stages other than stage IV. 6 An issue beyond the optimisation of risk prediction algorithms for symptomatic-but-as-yet-undiagnosed cancer is their appropriate and dependable incorporation into everyday clinical practice, a complex problem in need of implementation research.…”

“…6,7 Unlike information about the presence/absence of symptoms, information about the results of diagnostic tests could additionally allow for appreciation of 'dose-response' associations (e.g. using exact inflammatory marker, 7 or platelet count, 13 values), which could enable further individualising of risk estimates. Incorporating quantification of unintended weight loss in prediction models might be possible in the future, if the recording of patients' weight as part of primary care encounters was to become uniform and systematic.…”

Clinical implications of increased testing in primary care

“…This can have counter intuitive implications; we have shown, for example, that people with normal test results have an increased risk of cancer 23. This is because merely conducting a test predicts cancer, and this additional risk is only partly eliminated by a negative test result.…”