The announcement led to an 11.9% fall in the share price of the Alva company, which closed down 2p at 14.75p.
It is another blow for Omega, coming after it recorded a 22% fall in profit for its last financial year as wet weather hit demand for its allergy products and it felt the impact of health spending cuts.
Omega is seeking to commercialise a testing kit, based on technology developed by the Burnet Institute in Australia, that determines if an HIV patient's white blood cell count has fallen to a level where retroviral drug treatment is needed.
It produced three batches to test its manufacturing process.
"We have reviewed the results from patient samples tested using the first reference batch and there has been more variability in the results than expected," Omega told investors. "This has generated some additional work as we refine production processes.
"We continue to work closely with the Burnet Institute with the aim of achieving a successful transfer of the technology and we estimate that the additional work to complete the three-batch evaluation could now take until the end of December 2013. We will reaffirm this timeline by the end of October 2013."
Omega had originally hoped to have the kits in production by autumn this year.
The test uses a finger-prick blood sample and produces a result in 40 minutes. Part of its attraction, according to Omega, is that minimal staff training is required and there is no need for sophisticated equipment.
Tests currently have to be carried out at hospitals because of the processes involved, leaving millions of people in poorer countries unable to get access to them.
In May Omega raised £4 million from investors largely to back the roll-out of the kits.
Last year it was awarded a £150,000 Scottish Enterprise grant through Regional Selective Assistance which will be paid out in three tranches.
It has also received a £1m increase in funding from its bankers at Bank of Scotland.
Keith Redpath, analyst at broker Finncap, said: "Whilst this results in a delay to the technology transfer process, we believe that Visitect CD4 remains sufficiently ahead of competing developments that it will still be the first to market."
Omega employs around a quarter of its 120 workers at Alva. It plans to issue a trading update on October 17.