A woman's X-ray results, showing a mass on her lung, wasn't acted on for 20 months, a report has found.
The discovery was made when the woman returned to hospital after feeling unwell. She died two months later of cancer.
Health and Disability Commissioner Anthony Hill says Southern District Health Board failed to have an appropriate system for managing and acknowledging test results.
This led to the failure to follow up the women's report.
The woman, Mrs A, who was 66 at the time, went to a hospital emergency department in 2013 with a cough and chest tightness.
The examining doctor ordered a chest X-ray and did not note anything of concern.
She diagnosed chronic obstructive pulmonary disease with acute asthma and Mrs A was discharged.
Five days later, the formal radiologist's report identified a mass and recommended a follow-up X-ray or CT scan.
The doctor reviewed the report in the memo tab of her inbox, but did not electronically acknowledge the results.
She went on 10 days' leave the next day, stating that the X-ray results were not immediately urgent and they could be actioned on her return.
However, on her return, the X-ray report was no longer visible in her memo tab and she did not recall the report.
Mrs A did not receive the recommended follow-up X-ray or CT scan.
Mr Hill found the DHB's IT system allowed results to disappear from the view of the clinician's memo tab.
Unattended and unacknowledged reports remained in the clinician's "unacknowledged work list", but ED staff were using only the memo tab.
Mr Hill made a number of recommendations, including that the DHB should consider a warning system to alert clinicians to the existence of unacknowledged results.
He also recommended the DHB provide a written apology to the woman's family.