SINGAPORE - The Health Sciences Authority (HSA) has recalled nine lots of a brand of HIV screening test kits after it was found that some people in the early stages of an HIV infection can receive false negative HIV results with the kits.

Local importer Unison Collaborative issued an urgent Field Safety Notice on May 11 to 26 clinics and one hospital in Singapore which were supplied with the affected lots. The notice advised users to stop using the kits and recommended retests for individuals who had tested negative using the affected lots.

The recalled kit, SD Bioline HIV Ag/Ab Combo, is a rapid HIV Antigen and Antibody combo test. There is a window period of up to three months during the early stages of HIV infection when blood tests may be unable to detect the infection, but the rapid test kit allows for earlier screening. The nine lots were recalled as they had reduced sensitivity which could result in false negative HIV results for those tested during the early stages of an HIV infection.

According to the manufacturer, when a patient is in the very early window period, the lower sensitivity of the affected lots may reduce detection, with the possibility of a false negative result for this subset of patients.

The product owner, Korea-based rapid diagnostics test developer Standard Diagnostics, Inc, recalled the affected lots and the local importer, Unison Collaborative, notified HSA.

Other than the 26 clinics and one hospital that were supplied with the affected lots, another nine healthcare facilities were supplied with kits not from the affected lots. As a precaution, HSA has directed all 36 healthcare facilities to stop using the kits and to use alternative test kits until further notice.

It also advised clinics and hospitals to review the HIV test results of all individuals tested using the affected lots and to perform re-tests if necessary.

Additionally, it advised those with a high risk of HIV exposure who took rapid HIV tests between February last year and May this year to check with their clinics if they need to take the test again.

HSA said in its release on Monday (June 5) that all rapid HIV tests are intended to be used only as an initial screening test, and are not meant to confirm HIV infection.

Positive rapid test results must be confirmed by sending a blood specimen to a clinical laboratory for Enzyme Immunoassay (EIA) testing and further confirmation testing by Western Blot if necessary.

Additionally, those who use test kits are routinely advised to return for another, more than three months after their last exposure, to confirm that they are HIV negative. This is to rule out early infections that may not have been picked up at the first screening.