There are concerns that women may be facing more delays in receiving smear test results under CervicalCheck.
Ireland-based MedLab Pathology has cleared 55,000 slides from the backlog, but is no longer carrying out work for the screening programme.
The lab here had been examining slides since the start of May, the Irish Times reported.
The overall backlog has now been brought down to 28,000, and it will now be up to Quest Diagnostics in the US to process a vast majority of the remaining slides.
It has led to fears over whether there will be enough capacity in the system to clear the remaining backlog.
Sinn Féin's health spokesperson Louise O'Reilly is worried women might be faced with more delays in getting their results.
She observed: "We know that there is an issue regarding capacity.
"This latest revelation I think is going to put additional pressure on a system that is already under pressure - and indeed additional pressure on women who want their results in a timely manner."
She called on the HSE to come forward and inform women whether there will be any implications from MedLab no longer being used for processing slides.
Deputy O'Reilly added: "I think that we need to have the HSE, out in front, letting women know exactly what the implications are going to be."
