Table 1. Steps for the diagnosis of atypical Hemolytic Uremic Syndrome (aHUS) in the study cohort.

Microangiopathic hemolytic anemia (decreased hemoglobin, presence of schistocytes, reticulocytosis, increased LDH, negative direct Coombs test), thrombocytopenia or 25% decrease in the number of platelets and worsening of the kidney function.
Activity of ADAMSTS 13 Enzyme	> 5% excludes severe deficiency
Suspension or reduction of the dose of calcineurin inhibitors and/or mTOR inhibitors	Persistence of the condition of microangiopathy suggests aHUS
Exclusion of viral infections (HIV; HTLV I/II; hepatitis B; hepatitis C; cytomegalovirus; Epstein-Barr)
Exclusion of Bacterial Infections (blood culture, urine culture, faeces culture)
Exclusion of autoimmune diseases (FAN, antiDNAn, ANCAc, ANCAp, rheumatoid factor)
Histology suggestive of microangiopathy
Exclusion of antibody-mediated rejection	C4d investigation negative in biopsy and absence of antidonor antibody
Diagnosis of aHUS
Supplementary study with investigation of mutation (aHUS panel)