Blood Test Patterns Improve Cancer Risk Assessment in Primary Care

Unexplained weight loss is a common but nonspecific presentation in primary care that can precede several types of cancer, making referral decisions difficult. Routine blood tests may produce borderline results that are hard to interpret in isolation, while changes over time can reveal patterns that a single measurement may miss. A new study now shows that tracking trends in common blood tests alongside unexplained weight loss can help identify patients at increased risk of cancer and support earlier investigation.

Researchers at the University of Oxford evaluated patterns over time in 26 commonly used primary care blood tests among patients with unexplained weight loss. The approach examined changes across repeat measurements, rather than relying solely on whether a single result was abnormal. The study, published September 17 in PLOS Medicine, tested whether temporal trends improved risk stratification for overall and site‑specific cancers compared with abnormalities on single tests.

The analysis included more than 275,000 patients, among whom nearly 14,000 were diagnosed with cancer within six months. Investigators related both individual abnormal results and longitudinal trends to subsequent cancer diagnoses. Abnormal values such as low hemoglobin or increased platelet counts were recognized as potential indicators, and the study specifically examined whether monitoring trends could uncover cancer‑related changes that remained within conventional reference ranges.

Overall, 23 blood test trends were associated with elevated risk of any cancer. After accounting for age and sex, several trends were more discriminative for cancer diagnosis than single abnormal results. Examples included trends in white blood cell (WBC) count and neutrophils linked to lung cancer, and trends in red blood cell (RBC) count, hematocrit, and the platelet‑to‑lymphocyte ratio associated with prostate cancer. The authors state that incorporating patterns of blood test abnormalities with unexplained weight loss could help identify primary care patients who should undergo additional cancer testing.

“We show how blood test results are made more accurate for cancer by adding patient age and sex. This relatively simple calculation could easily be performed at the laboratory,” said Brian Nicholson, study author.

“In some instances, monitoring how a patient's blood test results change over time could offer further value. We plan to assess how well blood test abnormalities and trends inform cancer risk in patients with other types of non-specific symptoms, such as fatigue and vomiting,” stated Pradeep Virdee, study author.