More than 300 patients undergoing dialysis at Dublin's Beaumont Hospital are to be tested for hepatitis B after one patient receiving the treatment was found this week to have been infected with the virus at some stage in the past.
The discovery has promoted the hospital to test all dialysis patients for the virus to ensure there has been no cross-infection. But Beaumont said yesterday the likelihood of any cross-infection having occurred was "relatively small".
In a statement it said that before commencing dialysis, the patient who has now tested positive was tested for the virus, and the result was negative. All new dialysis patients are tested for both hepatitis B and C, it stressed.
"The result received from the National Virus Reference Laboratory in this case late last year was negative. Subsequently, and most unusually, a routine test this week showed positive. The laboratory performed additional tests on the original sample, and this confirmed that the patient had been previously exposed to the virus," it said.
"The more recent positive result indicates that the patient had been exposed and infected with hepatitis B many years ago, and the test subsequently became negative as the infection resolved. Between the first and second tests, due to a change in the patient's underlying condition, the hepatitis B blood test became positive again," it added.
It stressed there was no problem with the test and the same test was used on both occasions.
Although the risk of cross-infection was low it was wise to trace back all potential exposures of patients and staff to this patient and, where appropriate, to test, it added.
Hepatitis B is spread through blood or bodily fluids and can cause serious liver disease such as cirrhosis and liver cancer.
Last year an inquiry into the infection with hepatitis C of a patient while undergoing dialysis at Beaumont in 2001 was unable to determine how the patient became infected. It established that on one particular date another patient with a similar strain of hepatitis C had used the same dialysis machine and it said it was possible infection occurred on that day.
However, the procedures in place and the records maintained strongly suggested that this was unlikely, it claimed.
Beaumont said yesterday it regretted the anxiety additional testing may cause for its dialysis patients but emphasised "there is no cause for any undue concern".
Medical staff will contact all patients to explain the need for the new tests, which should be completed within three months. Patients seeking additional information or reassurance may contact the hospital at 1800 202935.