Negative chest X-rays in primary care patients with lung cancer

Background: The main investigation for suspected lung cancer in primary care is a chest X-ray. Reports from secondary care show that some patients with normal chest X-rays transpire to have lung cancer. The assumption is that this occurs rarely in primary care. Aim: The aim of this study was to examine the frequency of misleading chest X-rays in primary care, and whether there were any particular symptoms associated with them. Design of study: Retrospective cohort study of the primary care records of 247 lung cancer patients diagnosed between 1998-2002. Setting: All general practices in Exeter Primary Care Trust, Devon, UK. Method: All chest X-rays and all common symptoms of lung cancer reported to primary care were identified from the medical records. X-ray results were categorised into three groups by the radiologist's report: normal; abnormal but no malignancy suspected (together classified as negative X-rays); or abnormal with possible malignancy. Results: Of the 247 patients, 164 (66%) had a chest X-ray taken in primary care during the year before diagnosis: 126 of these (77%) were abnormal with possible malignancy; 21 (13%) were abnormal but with no malignancy suspected; in 17 (10%) the X-ray was reported as normal. Thus, 38 of 164 patients (23%; 95% confidence interval = 16 to 32%) had a negative X-ray. Negative X-rays were less common in the 90 days before diagnosis. No particular symptoms were significantly associated with negative X-rays. Conclusion: Nearly a quarter of chest X-rays requested from primary care in lung cancer patients are negative. Further investigation is warranted with continuing or changing symptoms, even if the X-ray is not suggestive of malignancy.