Response to FDA Alert

The first paragraph of this letter states “The US Food and Drug Administration (FDA) is alerting clinical laboratory staff and healthcare providers that false reactivity, or “false positive”, Rapid Plasma Reagin (RPR; non-treponemal) test results, when using the Bio-Rad Laboratories BioPlex 2200 Syphilis Total & RPR Kit, can occur in some people who received a COVID-19 vaccine. Based on information provided by the manufacturer, Bio-Rad Laboratories, RPR false reactivity was observed in some individuals for at least five months following a COVID-19 vaccination.”

The FDA also states “It is not known if other RPR tests may be affected similarly. …Treponema pallidum particle agglutination (TP-PA) and treponemal immunoassays do not appear to be impacted by this issue.”

On December 9, 2021, in response to a request for information from the FDA, ASI replied to the FDA that over the last 3 years, ASI had not been made aware of any false reactive results from the use of our RPR test kits, (2019 – 2021).

In the three years reported to the FDA by ASI, ASI manufactured and sold tens of millions of RPR tests and has had zero complaints or notifications that false reactive test results occurred with the carbon antigen.

Arlington Scientific, Inc. as one of the leading manufacturers of RPR nontreponemal Syphilis tests in the United States and worldwide, we have not had any indications of false positive results with our nontreponemal RPR syphilis tests on either our automated or manual platforms. Both methods use the same RPR carbon antigen for testing.

Bio-Rad does not use ASI RPR reagents nor controls in its aforementioned test kits. Bio-Rad’s test kit is not a “traditional” RPR test. Quoting from “A Manual of Tests For Syphilis”, 9th edition, ©1998, page 194: “The rapid plasma reagin (RPR) 18-mm circle card test is a macroscopic, nontreponemal flocculation card test used to screen for syphilis. The antigen is prepared from a modified Venereal Disease Research Laboratory (VDRL) antigen suspension containing choline chloride to eliminate the need to heat inactivate serum, ethylenediaminetetraacetic acid (EDTA) to enhance the stability of the suspension, and finely divided charcoal particles as a visualizing agent.” The Bio-Rad test is extremely different. It utilizes magnetic beads and measures fluorescence to interpret the reaction.

In April of 2020, Bio-Rad voluntarily recalled the BioPlex 2200 Syphilis Total and RPR Test Kits (recall number Z-2982-2020) due to false positive results.

In the December 17 letter, the FDA stated “… treponemal immunoassays do not appear to be impacted by this issue.” However, ASI is aware of recent reports that state the opposite. One major US institution stated: “There has been a two to threefold increase in TP-PA initial and repeat positive rates for syphilis test results without a corresponding increase in confirmatory rates.” Another major institution reports a false positive TP-PA rate of 9% without a corresponding increase in confirmation rates.

ASI can report that in the production and use of tens of millions of RPR tests over the past three years ASI has received zero (0) reports of false positives using the ASI RPR test kits with or without COVID-19 vaccinations.