Specimen:

Whole Blood

Collection Medium:

Minimum:

Preferred Minimum:  8 mL whole blood
Absolute Minimum:  4 mL whole blood

Analytic Time:

3 months

Reference Range:

None detected

Interpretive Data:

Complement Factor B

Atypical Hemolytic-Uremic Syndrome
The clinical manifestations of hemolytic-uremic syndrome (HUS) include 
hemolytic anemia, thrombocytopenia and acute renal failure. Most cases 
are associated with epidemics of diarrhea caused by 
verocytotoxin-producing bacteria.

 Atypical hemolytic uremic syndrome (aHUS) is a rarer disease.  It is 
not associated with Stx-HUS infection and neither does it present with 
watery, bloody diarrhea (Warwicker et al., 1998).  It can be either 
sporadic or familial, and has an extremely unfavorable prognosis, with 
about 50% of persons progressing to ESRD and 25% dying during the acute 
illness; transplantation in many survivors is unsuccessful (Schieppati 
et al., 1992; Taylor et al., 2004).  Genetic studies have shown that 
approximately 50% of cases of aHUS are caused by mutations in MCP, CFH 
and IF (Caprioli et al., 2006). Gain of function mutations in 
Complement Factor B have been identified in persons with aHUS 
(Goicoechea de Jorge et a., 2007).  Identifying the genetic cause of 
aHUS is extremely important as it can help to direct clinical treatment 
decisions.

Complement Factor B (FB)
Factor B is a zymogen that carries the catalytic site of the complement 
alternative pathway convertase C3bBb.  The FB gene contains 18 exons 
and encodes the 764 amino acid protein, Complement Factor B.  There 
have been at least two reported cases of Factor B-deficient patients.

Sensitivity is greater than 99%.

Comments:

Please print, complete and submit the Kidney Testing Requisition 
from the Molecular Otolaryngology & Renal Research Laboratory, to 
Specimen Control/Mailouts with the specimen and the Epic Requisition.

Methodology:

Oligonucleotide primers have been designed to amplify each exon of CFB.  
Because CFB contains many non-disease causing polymorphisms, it is 
sequenced directly using overlapping primer sets.

CPT Code:

83891, 83894, 83898 (x17), 83904 (x17), 83912