A new analysis, published today, supports the benefits of improving access to blood tests in primary care for patients who may have cancer.

The issue has become a key problem for practices, faced with pressure to identify patients at risk whilst not overloading hospitals with referrals or risking patients facing delays after referral.

A study at University College London found two-fifths of patients who are subsequently diagnosed with cancer have primary care blood tests as part of their diagnostic process.

Writing in today’s British Journal of General Practice, the authors say given variable test use, research is needed on the clinical context in which blood tests are used in order to realise their full potential in supporting the diagnostic process.

Lead author Ben Cranfield said: “Diagnosis remains hard for many conditions. Despite much hope invested in novel diagnostic tests, our research highlights the help offered by common, ‘old’, blood tests and the potential from greater benefits derived from their use in the future.”

The team examined data from 39,752 patients on the English National Cancer Diagnosis Audit, who were diagnosed with cancer in 2018. They assessed common blood test use (FBC), urea and electrolytes (U&E), and liver function tests (LFTs), variation by patient and symptom group, and associations with the primary care interval and the diagnostic interval. They found in 41% of patients subsequently diagnosed with cancer (16,427) had had at least one common blood test. Out of this group, 95% (15,540) had an FBC; 89% (14,555) had a U&E; and 76% (12,414) had LFTs.

Blood testing was less common in females, and Black and minority ethnic patients but more common in patients over the age of 70. Fewer patients – 24% (3,341 out of 13,778) – presenting with alarm symptoms alone were tested than those with non-alarm symptoms alone, which was 50% (8,223 out of 16,487).

The authors say the variation in blood test use indicates potential for greater use in some patients, particularly those with vague symptoms and highlights clinical scenarios where GPs might underuse and overuse common blood tests within populations of patients subsequently diagnosed with cancer.

They write: “Future research should explore variation in blood test use within specific populations of patients with cancer and clinical scenarios and incorporate qualitative methods to help understand likely drivers of use (or lack of use) of common blood tests in patients presenting to a GP with new symptoms. In conclusion, common blood tests are frequently used in patients with cancer before referral, but their use is variable.”