SHBC1613

J.Q.THAM¹, Y.G.LEE¹, G.L.WEE¹, P.Y.HENG¹, M.S.WONG¹

Khoo Teck Puat Hospital¹

Antinuclear antibodies (ANA) ELISA-based test panels are useful screening tests for common autoimmune diseases. The Department of Laboratory Medicine of Khoo Teck Puat Hospital offers ANA-ELISA screen as an individual test request. ANA-ELISA positive specimens were only reported as ‘positive’, requiring clinicians to request for Anti-Extractable Nuclear Antigen panel (ENA) to identify the autoimmune antibodies that are present. In May 2019, a new autoimmune antibody identification panel (AAP) using immunoblot strips was added as an in-house reflex test to ANA-ELISA positive samples.

The immunoblot test strips are coated with highly purified antigen to detect antibodies against specific intracellular antigens. The antibodies detected by the in-house immunoblot assay is the same as the ENA panel that is sent to a referral laboratory. We assessed the difference in waiting time between ANA-ELISA request to an ENA/AAP result in the pre-implementation period and the post-implementation period.

Pre-implementation of the new test assay, patients from outpatient clinics waited a range of 10 days to a maximum of 191 days between the initial ANA-ELISA request and the follow-up ENA panel test results. In contrast, the implementation of a reflex in-house AAP test after a positive ANA-ELISA test ensures the TAT to complete autoimmune antibody screen results is 7 days.

In addition to a shorter TAT, in-house reflex testing reduces the need for the patients to return to the hospital for multiple consultations and specimen collections. A well-designed ANA reflex test algorithm can also improve appropriateness of autoimmune diagnostics.