Table 4.
Tests used in the differential diagnosis of atypical HUS
Primary step |
Screening for STEC in diarrhea (+) subjects→negative→low probability of STEC-HUS |
ADAMTS13 activity→normal→TTP is excluded |
PT, aPTT, fibrinogen→normal→DIC is excluded |
Pneumococcus antigen and Streptococcus pneumoniae in cultures→negative→Pneumococcus-related HUS is excluded |
H1N1 and influenza→normal→H1N1 and influenza-related HUS is excluded |
Blood homocysteine, urinary and blood MMA→normal→hereditary cobalamin defect is excluded |
Serum C3 and C4→C3↓ and C4 normal→alternative complement pathway defect is considered |
Secondary step |
Anti-CFH antibodies→positive→anti-CFH antibody HUS |
CFH, CFI, CFB levels |
CFH, CFI, MCP, C3 and CFB mutations |
Tertiary Step |
Wide mutation screening |
PTT partial thromboplastin time; C3: complement 3; C4: complement 4; CFB: complement factor B; CFH: complement factor H; CFI: complement factor I; DIC: disseminated intravascular coagulation; HUS: hemolytic uremic syndrome; MCP: membrane cofactor protein; MMA: metyl malonic acid; PT: prothrombin time; STEC: Shiga-toxin producing E. coli; TTP: thrombotic microangiopathy