The Federal Health Department and the Gut Foundation of Australia are in disagreement over the results of the latest tests for bowel cancer, which kills more than 70 people every year.

Last year the Health Department admitted that a technical change in the testing kits had seen a large number of people wrongly told they were free of cancer.

Now the results from the new kits are in and they show 4,444 people may now face a cancer diagnosis.

But while the health authorities say this number is to be expected, bowel specialists say it is abnormally high.

In 2008, five years after the home kits were introduced, the manufacturers changed the testing kit because some samples were over-heating in the mail, leading to inaccurate results.

Chief Medical Officer for the Federal Government, Professor Jim Bishop, says the number of patients returning positive results was starting to drift down.

"And so we did some investigations on the tests and we found that the buffer in the kit was not producing the same results as [the buffer] used before," Professor Bishop said.

The Health Department re-issued 108,000 testing kits and 7 per cent of those tested returned positive results.

This contrasts to about 2.7 per cent positive rates over the past three or four years.

Professor Bishop says people testing positive should not panic, but should have a colonoscopy immediately.

"We're testing for blood in the bowel motions, and the great majority of people with abnormal blood in the bowel motions won't have bowel cancer, but it is most important to follow up," he said.

"Those few who do have an adenoma [benign tumour] or a polyp [abnormal tissue growth] can be detected early."

Test questioned

The non-profit Gut Foundation, which raises awareness of digestive diseases, says a normal rate for positive test results would be 5 per cent.

Foundation head Professor Terry Bolin says that 7 per cent would be the top of a normal range.

"Which suggests to me, either there's a lot of cancer out there or the test is a little bit too sensitive," he said.

"There were too many false negatives 15 months ago and now there are a large number of positives.

"It does raise the concern that there might be too many positives and this test is perhaps a little bit too sensitive.

"But that's not a bad thing. It means that people are going to have a colonoscopy and we'll be able to find out whether they have a problem or not."

Professor Bolin says he supports the home screening program but it could be better.

"Offer the test to everyone, not just those aged 50, 55 and 65 - everybody in the community over the age of 40 is potentially at risk.

"And they need to discuss that risk and decide how they're going to manage it."

Both he and Professor Bishop agree the thousands of people who returned a positive test in their last screening should book in for a colonoscopy immediately.