Kathryn Sutton¹, Andrew Broadfoot^1, Megan Yu¹, Diana Loncar^1, Jocelyn Jiang¹, John Quin¹, Karl Baumgart¹

¹Douglass Hanly Moir Pathology, Sydney, Australia

Background: Ro antibody results are typically reported as detected or not. Recent studies suggest only high levels of these antibodies in pregnant women confer a risk  of complications, particularly congenital heart block (1).

 

Aim: To assess the feasibility and potential clinical utility of providing quantitative Ro90/52 results to clinicians we examined the range and distribution of quantitative Ro60/52 levels in our patient population.

 

Method: De-identified samples positive for either Ro52 or Ro60 on the Bio-Plex 2200TM during routine testing were analysed on the Bioflash chemiluminescence analyser to obtain quantitative levels. Additional data collected included age, gender, and ANA results.

 

Results: 178 patient samples were analysed; 57 were co-positive for Ro60 and 52, with 78 and 43 positive for only anti-Ro60 and anti-Ro52 respectively. Quantitative values exhibited a wide range for Ro60 (5.3 CU – 128,721 CU) and Ro52 (29.4 CU – 80,542 CU). 25.9% of samples fell in the high-risk range (Ro60>10,000CU) with 8.1% in the very high risk range (Ro60>50,000CU) defined by previous literature (1).

 

Discussion: This study describes quantitative Ro60 and Ro52 levels in Australian patients. Identification of Ro52/60 levels that place mothers at risk for foetal heart complications in pregnancy could facilitate better triage of intense pregnancy monitoring and selection for intervention. We propose a laboratory workflow for identifying and reporting quantitative Ro52/60 results in women of childbearing age.

Reference
(1) Jaeggi E, Kulasingam V, Chen J, Fan CS, Laskin C, Hamilton RM, Hiraki LT, Silverman ED, Sepiashvili L. Maternal Anti-Ro Antibody Titers Obtained With Commercially Available Immunoassays Are Strongly Associated With Immune-Mediated Fetal Heart Disease. Arthritis Rheumatol. 2023 Sep;75(9):1556-1565. doi: 10.1002/art.42513. Epub 2023 Jun 11. PMID: 36996277.