mHam test results and next-generation sequencing in TMAs. The mHam test is a cell-based in vitro viability assay that tests the ability of a PIGA mutant (CD55 and CD59–deficient) cell line to regulate complement. Each participant is represented by a symbol. A black circle indicates that no rare variants in APC-regulatory genes were detected; a green circle indicates that a rare variant was detected in an APC-regulatory gene, and an open triangle indicates that next-generation sequencing was not performed. A positive mHam test is defined as cell killing > 20.5% (dotted horizontal line) after exposure to patient serum. The median value of cell kill is depicted for each group. Patients with partial HELLP fit some, but not all, of the clinical criteria for HELLP.