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.