A UK population-based case-control study of blood tests before cancer diagnosis in patients with non-specific abdominal symptoms.

Background: Abnormal results in commonly used primary care blood tests could be early markers of cancer in patients presenting with non-specific abdominal symptoms.

Methods: Using linked data from the UK Clinical Practice Research Datalink (CPRD) and national cancer registry we compared blood test use and abnormal results from the 24-months pre-diagnosis in 10,575 cancer patients (any site), and 52,875 matched-controls aged ≥30 presenting, with abdominal pain or bloating to primary care.

Results: Cancer patients had two-fold increased odds of having a blood test (odds ratio(OR):1.51-2.29) and 2-3-fold increased odds of having an abnormal blood test result (OR:2.42-3.30) in the year pre-diagnosis compared to controls. Raised inflammatory markers were the most common abnormality (74-79% of tested cases). Rates of blood test use and abnormal results progressively increased from 7 months pre-diagnosis in cancer patients, with relatively small corresponding increases in symptomatic controls. In cancer patients, the largest increases from baseline were raised platelets in males with abdominal pain (increased 33-fold), raised white blood cell count in males with abdominal bloating (increased 37-fold) and low albumin in females with either symptom (increased 22-41 fold).

Conclusions: Common blood test abnormalities are early signals of cancer in some individuals with non-specific abdominal symptoms and could support expedited cancer diagnosis.