SINGAPORE - Khoo Teck Puat Hospital (KTPH) has taken disciplinary action against five of its staff members for their roles in an incident at its laboratory that resulted in some breast cancer patients receiving unnecessary treatment due to inaccurate test results.

The hospital on Monday (May 3) also apologised to the affected patients and said it will compensate them.

"We have reached out to all affected patients to offer our support, and we give the assurance that we will look into the appropriate compensation for each individual patient," said Associate Professor Pek Wee Yang, who is chairman of the KTPH Medical Board.

"We would also like to seek their understanding and patience as this process will take some time to complete. In addition, we will provide psychological counselling to these patients, where needed, during this period."

The staff members punished included those in management roles. The disciplinary action meted out ranged from stern warnings to financial penalties and cessation of employment.

Counselling, retraining and re-education are also being conducted for the staff.

In its statement, KTPH said the incident was caused by human error during the establishment of the staining procedure for human epidermal growth factor receptor 2 (HER2) tests.

The calibration error was not discovered due to a failure to conduct rigorous checks when the protocol was established, KTPH said.

This resulted in the over-staining of lab slides, which affected the interpretation of the results and led to a higher positive rate of HER2 than usual.

HER2-positive breast cancers are typically more aggressive than HER2-negative cancers. Some of the patients who were wrongly diagnosed with HER2-positive breast cancer received over-treatment as a result.

The investigation also revealed that the deviation in the HER2-positive rates compared with international benchmarks was noted early on during the laboratory's regular monitoring.

The section in charge of the tests conducted checks on the processes involved in interpreting the stained slides but attributed the deviation to differences in patient population. It did not recheck the accuracy of the staining protocol itself.

KTPH said staff from the section had failed to perform quality control checks properly, including monitoring and properly analysing the HER2-positive trend closely over time, which affected the interpretation of the over-stained slides and a delay in detection of the error.

The hospital added that these gaps contributed to the failure to detect the over-staining issue early, as well as in the subsequent years - from 2012 to 2020 - when the tests were conducted.

An internal review was conducted last year when the clinicians reviewing breast cancer cases noticed the higher-than-usual positive rate.

KTPH comes under the National Healthcare Group (NHG). An NHG review committee comprising experts in various disciplines from the healthcare industry conducted the investigation and made several recommendations to prevent similar incidents from occurring in future.

"We are determined to set things right to regain the trust and confidence of our patients. We will expeditiously rectify all gaps in our processes in the laboratory," said Prof Pek.

"Moving forward, we will ensure strict adherence to industry's best practices and international benchmarks."

About the incident

In November last year, Khoo Teck Puat Hospital (KTPH) was informed by its laboratory that its tests for human epidermal growth factor receptor 2 (HER2) were producing higher-than-expected rates of HER2-positive results for breast cancer patients.

At least 200 breast cancer patients received the wrong test results - they were told their cancer was HER2-positive, a less common and more aggressive form of the disease. Of this group, about half received unnecessary treatment as a result.

Once the testing flaw was discovered, the hospital stopped all such tests and identified the affected patients.

The samples - dating back to 2012, when KTPH started doing the tests - were then sent to various external laboratories to expedite retesting.

The test checks for HER2 proteins, which normally regulate the healthy growth of breast tissue.

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It works by introducing antibodies tagged with a coloured dye to a sample of breast tissue. These attach themselves to HER2 proteins, which show up as a stain when a doctor observes the sample under a microscope.

The intensity of the stain determines whether the result is HER2-positive or negative.

After discovering the error, KTPH informed the National Healthcare Group (NHG) and the Health Ministry in late November last year. It publicly announced the incident on Dec 11.

Those who were over-treated as a result of their mistaken HER2-positive diagnosis were prescribed the drug Herceptin, which can cause side effects like diarrhoea, chills and fever. In about three per cent to four per cent of cases, patients may also experience heart problems.

In January, Senior Minister of State for Health Koh Poh Koon addressed questions on the incident in Parliament. Ms Cheryl Chan (East Coast GRC) asked why it took so long for the error to be discovered.

Dr Koh noted that the test is complex and does not give a definitive answer. He said it takes a trained pathologist to make a judgment on the test result, but this could be affected by the multiple steps that require human intervention, such as the concentration of stains and how the tissue was handled.

It also requires a fairly large number of results to trigger an alert on the possibility of a disproportionate number of patients being diagnosed with the condition, Dr Koh had said.

This article was first published in The Straits Times. Permission required for reproduction.