HUNDREDS of referrals to Tallaght Hospital took up to nine years to be acted on because of heavy workloads at the hospital.
The unopened patient referrals dated as far back as 2001 were discovered late last year and have since been processed.
They related to referrals for electromyograms (EMG) - a procedure to test paralysis, muscle weakness or spasms and identify the cause of pain in the arms, hands, legs, feet and face.
The test of electrical activity in the muscles is used to detect muscle disorders or nerve problems.
The issue is to be raised by the Tallaght Hospital Action Group at a patient forum meeting next month to ensure that it does not happen again.
Altogether, 328 patient referrals made to the Tallaght hospital were not acted upon - some for up to nine years.
A hospital spokeswoman said the referrals came to light after an internal review of all services at the hospital last year in response to the Hayes Report into 59,000 unopened X-rays and 3,000 unprocessed GP referral letters.
The internal review "revealed a number of routine EMG referrals were not prioritised due to the quantum of urgent referrals being processed at Tallaght Hospital".
The spokeswoman added that all of these referrals had now been dealt with and "no adverse patient events resulted and no patient risk was identified".
She said that the HSE and HIQA were notified and stressed that all EMG referrals at the hospital now are tracked electronically.
Urgent EMG referrals are seen within a two to four-week period.
The unopened referrals were made by St James's Hospital, St Vincent's Hospital and from within Tallaght Hospital itself. The other two hospitals were told of the discovery late last year.
St James's Hospital carried out its own investigation and identified 66 referrals to Tallaght. A review by a consultant neurophysiologist found that nine patients had since died but the absence of any EMG study had not contributed to their deaths.
St James's now has its own EMG service and patients are no longer sent to other hospitals for the test.
Of the total referrals, four were from St Vincent's, 66 from St James's and 258 from within Tallaght Hospital.