Quantifying the risk of non-Hodgkin lymphoma in symptomatic primary care patients aged ≥40 years: a large case-control study using electronic records.

BACKGROUND Non-Hodgkin lymphoma (NHL) is the sixth most common cancer in the UK; approximately 35 people are diagnosed and 13 die from the disease daily. AIM To identify the primary care clinical features of NHL and quantify their risk in symptomatic patients. DESIGN AND SETTING Matched case-control study using Clinical Practice Research Datalink patient records. METHOD Putative clinical features of NHL were identified in the year before diagnosis. Results were analysed using conditional logistic regression and positive predictive values (PPVs). RESULTS A total of 4362 patients aged ≥40 years, diagnosed with NHL between 2000 and 2009, and 19 468 age, sex, and general practice-matched controls were studied. Twenty features were independently associated with NHL. The five highest risk symptoms were lymphadenopathy, odds ratio (OR) 263 (95% CI = 133 to 519), head and neck mass not described as lymphadenopathy OR 49 (95% CI = 32 to 74), other mass OR 12 (95% CI = 10 to 16), weight loss OR 3.2 (95% CI = 2.3 to 4.4), and abdominal pain OR 2.5 (95% CI = 2.1 to 2.9). Lymphadenopathy has a PPV of 13% for NHL in patients ≥60 years. Weight loss in conjunction with repeated back pain or raised gamma globulin had PPVs >2%. CONCLUSION Unexplained lymphadenopathy in patients aged ≥60 years produces a very high risk of NHL in primary care. These patients warrant urgent investigation, potentially sooner than 6 weeks from initial presentation where the GP is particularly concerned.