Background: Thrombocytosis (raised platelet count) is an emerging risk marker of cancer, but the association has not been fully explored in a primary care context.Aim: To 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 setting: A prospective cohort study using Clinical Practice Research Datalink data from 2000 to 2013.Method: The 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.Results: A 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.Conclusion: Thrombocytosis 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.

Background: The faecal immunochemical test (FIT) was introduced to triage patients with low-risk symptoms of possible colorectal cancer in English primary care in 2017, underpinned by little primary care evidence. Methods: All healthcare providers in the South West of England (population 4 million) participated in this evaluation. 3890 patients aged ≥50 years presenting in primary care with low-risk symptoms of colorectal cancer had a FIT from 01/06/2018 to 31/12/2018. A threshold of 10 μg Hb/g faeces defined a positive test. Results: Six hundred and eighteen (15.9%) patients tested positive; 458 (74.1%) had an urgent referral to specialist lower gastrointestinal (GI) services within three months. Forty-three were diagnosed with colorectal cancer within 12 months. 3272 tested negative; 324 (9.9%) had an urgent referral within three months. Eight were diagnosed with colorectal cancer within 12 months. Positive predictive value was 7.0% (95% CI 5.1–9.3%). Negative predictive value was 99.8% (CI 99.5–99.9%). Sensitivity was 84.3% (CI 71.4–93.0%), specificity 85.0% (CI 83.8–86.1%). The area under the ROC curve was 0.92 (CI 0.86–0.96). A threshold of 37 μg Hb/g faeces would identify patients with an individual 3% risk of cancer. Conclusions: FIT performs exceptionally well to triage patients with low-risk symptoms of colorectal cancer in primary care; a higher threshold may be appropriate in the wake of the COVID-19 crisis.

Although the association between raised platelet count (thrombocytosis) and cancer has been reported in primary and secondary care studies, UK GPs are unaware of it, and it is insufficiently evidenced for laboratories to identify and warn of it. This systematic review aimed to identify and collate evidence from studies that have investigated thrombocytosis as an early marker of cancer in primary care. EMBASE (OvidSP), Medline (Ovid), Web of Science and The Cochrane Library were searched for relevant studies. Eligible studies had reported estimates of the association between thrombocytosis and cancer, in adults aged ≥40 in a primary care setting. Raw data from included studies were used to calculate positive predictive values and likelihood ratios (LRs) for cancer. Nine case–control studies were identified. Study quality was judged to be high. Included studies reported on the following cancer sites: colorectal, lung, ovary, bladder, kidney, pancreas, oesophago-gastric, uterus and breast. LRs indicated that thrombocytosis was a predictor of cancer in all sites except breast. In a consulting population, thrombocytosis is most highly predictive of lung and colorectal cancer. These results suggest that patients with thrombocytosis in primary care have an increased risk of cancer, and that some, but not all, cancers have raised platelets as an early marker. This finding is expected to be of use in primary care, for GPs receiving blood test results unexpectedly showing high platelet counts. Further research is needed to identify the cancers that are most strongly associated with thrombocytosis.

Background: A raised platelet count (thrombocytosis) measuring >400 × 10⁹/l is associated with high cancer incidence. It is uncertain whether platelet counts at the upper end of the normal range (high-normal: 326–400 × 10⁹/l) are also associated with cancer.Aim: To investigate cancer incidence following a normal platelet count in primary care.Design and setting: A prospective cohort study was undertaken using data from the Clinical Practice Research Datalink and National Cancer Registration and Analysis Service, dating from 1 May 2005 to 30 April 2014.Method: One-year cancer incidence was estimated for 295 312 patients with normal platelet counts (150–400 × 10⁹/l). Patients with platelet counts >325 × 10⁹/l were oversampled to maximise precision of estimates of cancer incidence. All patients were aged ≥40 years with no prior cancer diagnoses. The effects of age, sex, and smoking were explored. Non-melanoma skin cancers were omitted from exclusions and incidence.Results: One-year cancer incidence increased greatly with age, male sex, and higher platelet count. Males aged ≥60 years with a high-normal count had an incidence of 4.2% (95% confidence interval [CI] = 4.0 to 4.4). The highest incidence of 6.7% (95% CI = 5.3 to 8.4) was found in males aged ≥80 years, who had platelets in the range of 376–400 × 10⁹/l; this was 3.1 percentage points higher than the incidence for patients in the same age group with lower-normal counts of 150–325 × 10⁹/l. Risks for all female subgroups were <3%. Patients with high-normal platelet counts were most at risk of lung and colorectal cancers and, in general, had advanced-stage cancer at diagnosis.Conclusion: Platelet counts at the high-normal range in males aged ≥60 years may be indicative of an underlying malignancy, and referral for further investigation should be considered.

Background: Black men have higher prostate-specific antigen (PSA) levels and higher prostate cancer incidence and mortality than White men, while Asian men tend to have lower prostate cancer incidence and mortality than White men. Much of the evidence comes from the USA, and information from UK populations is limited. Methods: This retrospective cohort study used data on patients registered at general practices in England contributing to the Clinical Practice Research Datalink (CPRD) Aurum dataset. Those eligible were men aged 40 and over with a record of ethnicity and a PSA test result recorded between 2010 and 2017 with no prior cancer diagnosis. The aim was to assess the incidence of prostate cancer following a raised PSA test result in men from different ethnic groups. Additionally, incidence of advanced prostate cancer was investigated. Cancer incidence was estimated from multi-level logistic regression models adjusting for potential confounding factors. Results: 730,515 men with a PSA test were included (88.9% White). Black men and men with mixed ethnicity had higher PSA values, particularly for those aged above 60 years. In the year following a raised PSA result (using age-specific thresholds), Black men had the highest prostate cancer incidence at 24.7% (95% CI 23.3%, 26.2%); Asian men had the lowest at 13.4% (12.2%, 14.7%); incidence for White men was 19.8% (19.4%, 20.2%). The peak incidence of prostate cancer for all groups was in men aged 70–79. Incidence of prostate cancer diagnosed at an advanced stage was similar between Black and White men. Conclusions: More prostate cancer was diagnosed in Black men with a raised PSA result, but rates of advanced prostate cancer were not higher in this group. In this large primary care-based cohort, the incidence of prostate cancer in men with elevated PSA levels increases with increasing age, even when using age-adjusted thresholds, with Black men significantly more likely to be diagnosed compared to White or Asian men. The incidence of advanced stage prostate cancer at diagnosis was similar for Black and White men with a raised PSA result, but lower for Asian men.

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 National Institute for Health and Care Excellence (NICE) for cancer investigation. Patients with a platelet count at the upper end of the normal range (325–400 × 10⁹/l) could be at increased risk of undiagnosed malignancy. To quantify the risk of an undiagnosed cancer in patients with a platelet count at the upper end of the normal range. A primary care-based cohort study using Clinical Practice Research Datalink (CPRD) data from 2000 to 2013. The study sample comprised 2704 individuals stratified by platelet count: 325–349 × 10⁹/l; 350–374 × 10⁹/l; 375–399 × 10⁹/l. Incident cancer diagnoses in the year following that platelet count were obtained from patient records. Cancer incidence rose with increasing platelet count: 2.6% [95% confidence interval (CI) 1.9 to 3.6] in subjects with a count of 325–349 × 10⁹/l, 3.7% (95% CI 2.5 to 5.3) in subjects with a count of 350–374 × 10⁹/l and 5.1% (95% CI 3.4 to 7.5) in those with a count of 375–399 × 10⁹/l. Colorectal cancer was most commonly diagnosed in all three groups. Cancer incidence was consistently higher in males than in females. These results suggest that clinicians should consider cancer in patients with a platelet count >375 × 109/l, review reasons for testing and any additional reported symptoms. Until these results are replicated on a larger scale, recommendations for clinical action cannot be made.