The patient's early-stage cervical cancer went undetected during routine cervical screenings in 2017 and 2020.
But after a diagnosis was made in 2021, a review conducted at the patient's request found those smear tests had been misread and were abnormal, delaying her diagnosis.
The patient, who went on to develop more advanced cancer, complained to the Health and Disability Commissioner because she did not want others to experience what happened to her.
Health and Disability Commissioner Morag McDowell said Heath New Zealand failed to provide a reasonable standard of care and the right to information by not communicating their findings within a reasonable time.
"Regrettably, it took nearly seven-and-a-half months for clinicians to disclose this information to the woman and her whānau. It was accepted by Health New Zealand that this delay impacted the woman emotionally, physically and financially."
McDowell said there were a lack of clear processes which caused confusion over who was responsible for disclosing the smear review findings.
She said the review, which only occurred following the patient's request, and its delayed disclosure to the woman, also created uncertainty around Health New Zealand's procedures during serious events and after a cancer diagnosis.
"Patients are entitled to an open, truthful and timely discussion about what went wrong and why. It ensures that people are at the centre of their care, helps people to understand what the consequences are for them and their ongoing care, and is the first stage in fostering a culture of learning to improve clinical care for the future."
McDowell said Health New Zealand was not responsible for the misinterpretation of the smear tests, as false negative results with the cervical screening testing used at the time were somewhat unavoidable.
She said recent changes to cervical cancer screening had made it more effective and it was expected the false negative rate would reduce significantly.
McDowell said she encouraged women, especially wāhine Māori, to get tested under the new HPV screening method and for all healthcare providers to tautoko (support) and manaaki (take care of) their participation in the screening programme.
Health New Zealand is developing new guidance for staff in open communication to help complex circumstances of open disclosure.
