How do you interpret elevations in antiphospholipid antibodies that are lower than Sapporo criteria?

I would refer to the following article that provides the most up-to-date definitions (including the definitions for low-level antibodies) and risk stratification tools including APL-S and GAPSS that are developed for people with autoimmune conditions. The article also discusses the levels of evidence and limitations of some of these tools and definitions.

1. The actual numeric value (21 is probably less concerning than 39)
2. Whether both IgG and IgM and whether both ACL and anti-B2GPI are positive vs. a single positive value (assuming LAC is negative for this question)
3. Whether there is a history of an underlying autoimmune dis...

I would seriously consider positive aPL test results in the context of other factors, such as clinical evidence for thrombosis or positive ANA.