Thousands of patients suspected of having coronavirus suffered a setback yesterday after they were told today's appointments to provide a swab to find out if they have the infection had been cancelled.
Following the Department of Health's decision earlier this week to tighten the criteria for testing, it had been hoped that those who are self-isolating and have an appointment to provide a swab could continue to attend.
However, the HSE confirmed that patients were told by text yesterday that today's appointments would not go ahead, except for healthcare workers.
Most of the 40,000 people in the backlog for tests will not qualify and even those among them who fall into priority groups for testing must apply again and contact their GP.
GPs continued to be inundated with calls again yesterday following the confusion caused by the change in strategy.
The new criteria mean that a person has to have a fever and either a cough or breathing difficulties or sore throat to qualify for the test.
They must also fall into a priority group including people with underlying illnesses and healthcare workers.
A spokeswoman for the HSE said: "Testing will be targeted to those in an at-risk group or those with a high risk of exposure to Covid-19, who also have symptoms of fever and at least one other sign - cough, shortness of breath or sore throat.
"Given the large numbers seeking testing, it is appropriate to focus testing on those at greater likelihood of having Covid-19, in order to make best use of public health management and contact tracing.
"Healthcare workers with a confirmed appointment should attend their appointment regardless of the date."
People who were referred for testing on or before Tuesday received a text yesterday confirming that their referral had been cancelled, she said.
"Our laboratories will continue to analyse tests already taken. GPs provide clinical care for their patients throughout the Covid-19 pandemic," she added.
"People with symptoms - regardless of a test - need to self-isolate for 14 days and household members must restrict their movements."
Meanwhile, the Irish Nurses and Midwives Organisation (INMO) welcomed an announcement by Health Minister Simon Harris that student nurses would be paid during the Covid-19 crisis.
The INMO campaigned intensely for employment opportunities for student nurses for several weeks, as many were unable to work other jobs due to cross-infection risks.
The union said it understands that student nurses - including interns - will now be offered contracts as healthcare assistants, but INMO officials will be seeking further details and information.
In particular, the union will be clarifying the scope of the students' practice in these roles and how it can best be integrated with their academic progression and placements.
INMO general secretary Phil Ní Sheaghdha said: "This is a really welcome step from the Government.
"It's good news for the student nurses, who will now be paid for their work on the front lines.
"It's also good news for the wider health service.
"These are dedicated, talented, hard-working people who are keen to help in the global fight against Covid-19.
"Taking them on as paid staff not only values their work, but offers them clear protections as employees.
"We will now engage with the Government to determine the detail of this announcement, particularly on ensuring that students' academic progression isn't harmed by the crisis."
Mr Harris said around 4,000 student nurses and midwives will be offered a contract as a healthcare assistant (HCA) - which commands a salary of around €28,000-a-year - and be paid accordingly.
This will allow students to complete their placement in a HCA role and continue to complete their course.
Hundreds of student nurses have been working in hospitals and healthcare facilities as part of the battle against the spread of the disease - but many are not being paid for their work.