TY - JOUR T1 - Interpreting negative test results when assessing cancer risk in general practice JF - British Journal of General Practice JO - Br J Gen Pract SP - 298 LP - 299 DO - 10.3399/bjgp21X716189 VL - 71 IS - 708 AU - Stephen H Bradley AU - Brian D Nicholson AU - Garth Funston Y1 - 2021/07/01 UR - http://bjgp.org/content/71/708/298.abstract N2 - Studies published over the last year have established the sensitivity of chest X-ray (CXR) for lung cancer (75%, 95% confidence interval [CI] = 68 to 83), cancer antigen 125 (CA125) for ovarian cancer (77%, 95% CI = 73 to 81), and the faecal immunochemical test (FIT) for colorectal cancer (91%, 95% CI = 85 to 96) in symptomatic people attending primary care.1–3 This research demonstrates how simple and accessible tests can be used by GPs to identify these cancers in most cases; however, it also raises questions about how GPs should respond to negative test results in situations in which there is some concern about the possibility for cancer, but criteria for an urgent suspected cancer referral are not met.With sensitivities of 75%–91%, specificities of 90%–94%, and negative predictive values exceeding 99%, individual patients can take a good deal of reassurance from a negative CXR, CA125, or FIT;1–3 however, it is important to recognise that the high negative predictive values of these tests are a function of the low prevalence of cancer in primary care (there are many more true-negative than false-negative results).Patients tested in primary care who have a negative CXR, CA125, or FIT are therefore very unlikely to have lung, ovarian, or colorectal cancer, respectively. But, the imperfect sensitivity of these tests means that around one in five to one in ten patients who do have cancer will have a negative test.A full-time equivalent GP would be expected to encounter roughly one case of lung cancer every year and, given the test’s sensitivity, one case on average would not be detected by CXR every 5 years.4–5 Onward referral of all patients who have possible symptoms of cancer but negative primary care tests is neither appropriate … ER -