Change Healthcare, the IT company that installed the Health Service Executive computer system containing a serious glitch, has begun an internal investigation.

The software error in the National Integrated Medical Imaging System (Nimis) meant potentially thousands of patient records from MRIs, X-rays, CT scans and ultrasounds were recorded incorrectly and may have led to patients’ undergoing unnecessary treatment. Change Healthcare, which is based in Canada, said it is “working hard to understand exactly what happened in this case”.

Yesterday the HSE’s director general, Tony O’Brien, claimed the company knew about the bug but failed to notify the Irish health service. The HSE has said 15,000 patients may have to be recalled to have scans and tests redone.

Unnecessary procedures

The software error meant the less-than character (<) did not appear when patient records were archived. A patient whose risk of developing a condition was found to be “less than 50 per cent”, for example, would have that risk mistakenly recorded as “50 per cent”. This could lead to a doctor overestimating the seriousness of a patient’s condition and ordering unnecessary procedures.

Change Healthcare issued a software patch, to fix the glitch, in August 2016, but as the company did not flag the problem with the less-than character the HSE did not install the update. Mr O’Brien said the company had not told the HSE about the error or said a patch for it was available last August.

In the past six years 23,302,968 records have been created on Nimis, for 6,109,043 people. Of those records, 21,131 were affected by the “<” error. The HSE is working to establish what effect the error had on patient outcomes in 2,500 of the affected scans. It says it will widen its own investigation to cover more affected scans if it turns out that large numbers of patients were affected.

Change Healthcare said on Saturday that it would provide further information as soon as it could once its internal investigation was complete.