But one of two medical technologists working at the laboratory mistakenly swapped the labels for the two samples, leading to the male patient being diagnosed with anaemia.

Luk Che-chung, chief executive of United Christian Hospital, said blood was given to the man, who was being treated for general geriatric conditions.

'The male patient had no anaemia but received two bags of blood based on the lab report,' Dr Luk said.

Meanwhile, a transfusion for the 24-year-old female patient, who had just given birth, was delayed for 10 hours.

The blunder posed no danger to the patients, both of whom were in stable condition and under close monitoring, Dr Luk said.

An independent panel will be set up to probe the incident, with a report to the Hospital Authority head office due in six weeks.

The medical technologists suspected of the mislabelling were working as usual, although the hospital had 'stepped up supervision' of their work, Dr Luk said.

It was confirmed that the blunder did not lead to an incorrect blood-type transfusion.

'The two blood results were swapped, but it was definitely not a wrong transfusion,' Dr Luk said.

The incident was noticed on Monday, when the two patients underwent examinations and discrepancies were identified in the blood tests of the patients when they were compared with their previous results.

The blunder occurred in a small window of time when the pathology department's computer system was under routine maintenance, which is performed in the small hours of every month's second Sunday.

During such maintenance, blood specimens are labelled manually.

Patients' rights activist Tim Pang Hung-cheong urged the hospital to step up its examination system at the laboratory, pointing out that mix-ups like this could jeopardise patients' lives.

'It was lucky in this incident that the doctor realised that the laboratory result did not match up with the clinical symptoms of the anaemia patient. Otherwise, the patient and her baby could have been in danger,' he said.

The legislator representing the medical sector, Kwok Ka-ki, said if a patient with severe anaemia did not have a timely transfusion, he or she could pass out and even die.

'Such mix-ups are unacceptable. What would happen if the hospital mixed up the laboratory reports of cancer patients? The impact on the patients could be more immediate and dangerous', he said.

But he said he was glad that such incidents had been promptly announced since the Hospital Authority stepped up its reporting of medical incidents in August.

Recent blunders

October 2 Unsterilised equipment is used to perform neurosurgery on a patient at Queen Elizabeth Hospital

June A chemotherapy drug is injected into the spine instead of the vein of a cancer patient in Prince of Wales Hospital. The patient dies

February Prince of Wales Hospital radiologists make a mistake when treating a lung cancer patient, irradiating wrong part of the lung

November 2006 A Pamela Youde Nethersole Eastern Hospital patient is given wrong drug for an angiogram