Bowel cancer screening: Rising number of samples need retesting because of transit delays

Some bowel cancer screening samples don't get tested because of delays in transit. Health New Zealand and NZ Post say they are not to blame. Illustration / Paul Slater

Thousands of bowel cancer screening kits need retesting every year because they arrive at a laboratory too late. Health New Zealand and NZ Post suggest the fault lies with the patients. One family, however, points the finger at the postal service. Isaac Davison investigates.

A rising number of bowel cancer screening samples need retesting each year because of delays in getting them to a laboratory.

New Zealanders are sent a bowel cancer screening kit after they turn 60 years old and are encouraged to send it back as soon as possible after collecting a stool sample.

About 230,000 people submit samples each year and the scheme is credited with picking up about 2000 cancer cases since it was introduced in 2017.

Data released under the Official Information Act show around 21,000 samples a year, or about 8 per cent, are not tested for various reasons. In these instances, participants are asked to re-send a sample but around 4000 people a year do not do so.

This “spoil rate” of around 1-2 per cent has remained steady since the bowel cancer screening programme began and Health New Zealand Te Whatu Ora notes that it is in line with international standards.

However, the rate of samples which were delayed in transit had risen over that time and accounted for a third of all the cases in which patients were asked to resubmit samples in 2023.

Health New Zealand said samples that arrive within nine days to 14 days (4888 samples in 2023) were still tested and if a person gets a negative result, they are asked if they want to resubmit a sample. This is to make sure the transit times did not impact the result.

Another 2027 samples arrived after 14 days in 2023 and patients were asked to resubmit. In the first 11 months of 2023, nearly 3500 people asked to resubmit a sample for various reasons (not just transit delays) did not do so.

Health NZ did not track whether people who did not resubmit a sample had gone on to test positive.

Health New Zealand said the transit delays were not at its end. Its laboratories reported every quarter on their turnaround times and delays between receiving a kit and testing a sample were rare.

National Public Health Service director of prevention Alana Ewe-Snow said delays could reflect the time it took a participant to post the sample or postal delays.

New Zealand Post also said it was not at fault.

“NZ Post processing and delivery operations are all working exactly as they should and investigations have shown no NZ Post cause for delays,” a spokeswoman said. She said NZ Post advises people to post samples on the day they do their test.

One family is certain that the problem lies with the postal service.

A Napier man, who wanted to remain anonymous, told the Herald he immediately sent off a sample after receiving the kit in the mail. He was highly motivated because his father had died of bowel cancer.

But he was concerned the sample would not make it to a laboratory in time because he lived in a rural area. His family usually put their outbound mail at the end of their driveway to be picked up by NZ Post.

To ensure there was no delay, the man drove 5km to the city to hand-deliver it to a post office.

He was surprised to be told by Health New Zealand that the sample was delayed in transit and he would have to resubmit one.

The key factor could be when the sample was posted. Health officials recommend that participants in bowel cancer screening not post their samples on Friday, Saturday or Sunday to avoid delays. The Napier man’s family cannot recall which day they posted his sample.

Around 3.5 per cent of the people who screened for bowel cancer in New Zealand last year received a positive result and were referred for a colonoscopy to check for cancer or advanced tumours. Of those that had a colonoscopy, around 7 per cent tested positive for cancer.

Health Minister Dr Shane Reti has said he expects the bowel cancer screening age to be lowered this Parliamentary term. Photo / Michael Cunningham

It comes as officials develop plans to lower the bowel cancer screening age from 60 to 55 years old in New Zealand.

Health Minister Shane Reti has previously told the Herald he expects the expanded screening programme to be in place this parliamentary term.

*This story was updated to clarify that samples which are received within 14 days are still tested.

Isaac Davison is an Auckland-based reporter who covers health issues. He joined the Herald in 2008 and has previously covered the environment, politics, and social issues.