A mix-up of tissue samples in a Dunedin
medical laboratory led to a woman undergoing treatment and
surgery for cancer that she did not have, the Health and
Disability Commissioner has found.
A 62-year-old woman, named only as Mrs A in the
commissioner's decision, saw an oral surgeon in March 2011
about pain and swelling around the area of a previous tooth
In April 2011, a biopsy of the area was taken.
The biopsy was sent to MedLab Dental, part of the University
of Otago's Dental School, where it was mixed up with another
The tissue sample labelled as Mrs A's showed squamous cell
carcinoma, a form of cancer, and she was then referred to a
district health board for treatment.
She underwent extensive surgery.
After the surgery, a hospital pathologist took a sample from
the tissue that was removed and found no cancer.
It then became clear the original biopsy was labelled
A DNA test confirmed Mrs A's sample and another patient's
sample had been transposed and wrongly labelled at MedLab
The other patient had a second biopsy sent to MedLab Dental
two weeks after the mix-up occurred which showed squamous
The Health and Disability Commissioner found MedLab Dental
breached the Code of Health and Disability Services
Consumers' Rights when the tissue samples were wrongly
The commissioner concluded the mix-up was caused by human
error, and ordered MedLab to review its tissue samples and
identify any other labelling mix-ups and change its system
for receiving biopsies and labelling them.
Medlab Dental Oral Pathology Diagnostic Service head Prof
Alison Rich, responding to the Otago Daily Times in an email,
said the lab had since introduced computer-generated
barcoding of slides, and a verbal double-check of the patient
name and specimen number against details on the request form
and specimen pot.
At the time of the mistake, the lab was complying with
standard laboratory procedures, and had been accredited by
International Accreditation New Zealand, she said.
She said neither of the staff members concerned remembered
anything out of the ordinary.
''Our own thorough investigations have not been able to
establish how the error occurred.''
It was extremely unlikely a similar error could recur, she
''The policies and procedures in place are robust and staff
are vigilant to reduce the risk of this or related errors.
''The staff deeply regret this error, but it is important to
recognise the excellent service the laboratory has provided
over many years,'' Prof Rich said.
- Sophie Ryan, APNZ
Additional reporting Eileen Good