The Health Science Authority (HSA) has recalled 584 faulty HIV screening kits, as it was reported that some people in the early stages of an HIV infection could have received false negative results.

The affected lots of SD Bioline HIV Ag/Ab Combo were supplied to 26 clinics as well as the National University Hospital (NUH). All were issued an urgent notice by the kits' local importer, Unison Collaborator on 11 May.

They were advised to stop using the kits and retest patients who were tested negative using the affected lots.

HSA said that of the recalled kits, potentially 547 have been used. Each kit can be used for 25 tests, therefore up to 13,675 tests could have been carried out. HSA also clarified that some patients would have returned for retests.

Faulty kits found to be less sensitive

The faulty rapid screening kits, from Standard Diagnostics, test for HIV with blood drawn from a pricked finger and produce results in approximately 20 minutes.

Usually, the rapid HIV Antigen and Antibody combo test allows users to screen for an HIV infection earlier – reducing the window period of up to three months during the early stages of infection, when conventional blood tests may not be able to detect the virus.

However, the faulty kits were reported to be less sensitive, therefore a patient in the very early stages of an infection might have obtained a false negative result.

"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," remarked HSA.

However, if an infected patient followed-up with a confirmation test at least three months after being exposed to the HIV virus, he or she would have correctly received a positive result despite the less sensitive faulty kits.

Unison Collaborative said that affected patients will not need to pay to retake the test.

Patients advised to follow standard procedure of retesting after 3 months

HSA also advised all high-risk patients who use any brand of rapid test kits to return for another test to confirm their negative status.

Action for Aids, one of the affected healthcare providers reported it received and used all 6,825 tests when it was notified.

However, its general manger, Ms Sumita Banerjee said if clients adhered to the standard procedure of retesting after three months, the faulty product would not have affected any of them.

"We would advise clients who feel that they have been affected by the recall and have not done a confirmation test to come to the clinic where they can be tested again and follow the standard protocol," she added.

As a precautionary measure, HSA said all 36 healthcare facilities in Singapore supplied with Standard Diagnostics' test kits have been told to stop using them and to turn to other brands of rapid HIV test kits until further notice.

It also emphasised that all rapid HIV tests are not meant to confirm an infection but used only as an initial screening test. Positive rapid test results must still be confirmed by sending a blood specimen to a clinical laboratory for Enzyme Immunoassay (EIA) testing and further confirmatory Western Blot testing if necessary.

The list of healthcare facilities supplies with the affected lots can be found here. MIMS

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