Blood test trend versus single threshold abnormality to discriminate cancer from non-cancer in patients with unexpected weight loss: A retrospective cohort study

Unexpected weight loss is a non-specific symptom that can indicate cancer, but interpreting historical blood test results may improve the ability to identify undiagnosed cancer in patients presenting to primary care. A retrospective cohort study conducted in England analyzed patients with unexpected weight loss and measured the discrimination provided by blood test abnormalities and trends.

The study observed that adjusting for age and sex increased the discriminatory power of blood test trends in cancer discrimination in some cases, with the highest AUC being 0.82 (95% CI [0.81, 0.83]). This included trends for cancer overall, mean cell volume in bowel cancer and lymphoma, white blood count and neutrophil trends in lung cancer, and aspartate aminotransferase, red blood cell count, haematocrit, and platelet-to-lymphocyte ratio trends in prostate cancer.

The study's limitation was that it did not account for potential bias in who was tested and was restricted to patients with at least two tests in each trend window. Therefore, interpreting blood test abnormalities after adjusting for age and sex can improve the triage process for cancer investigation in primary care patients with unexpected weight loss.