Weight loss is a non-specific cancer symptom for which there are no clinical guidelines about the investigation in primary care. Therefore it poses a diagnostic challenge to clinicians in non-specialist settings such as primary care.Brian D Nicholson atand colleagues conducted a diagnostic test accuracy review and meta-analysis to summarise the available evidence on weight loss as a clinical feature of cancer in patients presenting to primary care.The researchers concluded that weight loss is highly predictive of cancer in primary care settings.
The researchers sorted out studies reporting 2 × 2 diagnostic accuracy data for weight loss (index test) in adults presenting to primary care and a subsequent diagnosis of cancer (reference standard) and included them in analysis. QUADAS-2 was used to assess study quality. Sensitivity, specificity, positive likelihood ratios, and positive predictive values were calculated, and a bivariate meta-analysis performed.
The investigators included a total of 25 studies with 23 (92%) using primary care records. Of these, 20 (80%) defined weight loss as a physician’s coding of the symptom; the remainder collected data directly. One defined unexplained weight loss using objective measurements. Positive associations between weight loss and cancer were found for 10 cancer sites: prostate, colorectal, lung, gastro-oesophageal, pancreatic, non-Hodgkin’s lymphoma, ovarian, myeloma, renal tract, and biliary tree. Sensitivity ranged from 2% to 47%, and specificity from 92% to 99%, across cancer sites. The positive predictive value for cancer in male and female patients with weight loss for all age groups ≥60 years exceeded the 3% risk threshold that current UK guidance proposes for further investigation.
It was concluded that a primary care clinician’s decision to code for weight loss is highly predictive of cancer. For such patients, urgent referral pathways are justified to investigate for cancer across multiple sites.
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