C3, C4 is what we usually order.
The classical complement pathway activates C4 as well as C3. This can lead to low C3 and C4 levels which lead to decreased CH 50. This would typically be seen with complement activation driven by immune complexes (lupus, hepatitis C, cryoglobulinemia).
Alternative complement pathway activation is typically driven by bacterial or microbial antigens: C3 is directly activity producing low C3 and decreased CH 50 C4 is normal. C3 may also be directly activated by C3 nephritic factor which is an antibody which activates C3 convertase directly (associated with dense deposit disease).
Diseases which do not have bacterial/microbial antigens or circulating immune complex will typically have normal levels of serum complement and normal CH 50. IgA nephritis does not cause low serum complements as IgA is a poor complement activator. ANCA diseases do not produce circulating immune complexes, for us, complement levels are normal. For unclear reasons, anti-GBM disease typically presents with normal complement levels
Six classical diseases come to mind when one sees low C3 and low C4.
Subacute bacterial endocarditis
MPGN 1 and 2
Cryoglobulinemic glomerulonephritis ( usually c4 more than c3)
- ► 2017 (52)
- ► 2016 (45)
- ► 2015 (63)
- ► 2014 (95)
- ► 2013 (133)
- ► 2012 (201)
- ► 2011 (370)
- IN THE NEWS: Three trials SHOCK the NEPHROLOGY WOR...
- IN THE NEWS:- Angiotensin-receptor blockade and r...
- CONSULT ROUNDS: Hypocomplementemia!
- IN THE NEWS ---> Stem Cells and Kidney Damage
- Answer to Immunology Quiz 2
- Rituximab for induction?
- TOPIC DISCUSSION: Phosphorous containing foods
- Panel Reactive Antibody? how do you calculate?
- Topic Discussion: MYH9 Nephropathies
- Pediatrics Grand rounds continue
- CLINICAL CASE 18, ANSWER and SUMMARY
- New blogs of interest
- Topic Discussion: Primary vs Secondary Membranous
- CLINICAL CASE 17, ANSWER AND SUMMARY
- TOPIC DISCUSSION: Amylase in the urine?? Hmm!!
- Gurudakshina in Nephrology
- Are you aware of MICA antibodies?
- ISBP Conference Sept 2010
- Innovative Nephrology teaching tools!
- Kamal Shah's Blog: An Indian CKD registry now exis...
- CLINICAL CASE 16 , ANSWER and SUMMARY
- IN THE NEWS- Proteinuria and Avastin
- CONSULT ROUNDS: Dialysis Membrane Reactions- Type ...
- IN THE NEWS ---> New treatments for cystic diseas...
- Immunology Quiz 1 Answers
- Rituximab induced lung injury
- TOPIC DISCUSSION: DIABETIC NEPHROPATHY!!
- B cell signature and Tolerance
- Nephrology World on Intragraft gene expression
- Kidney Transplant as an Outpatient Procedure
- IN THE NEWS ---> Detective Nephron strikes again!...
- IN THE NEWS --->NephrologyonDemand
- CONSULT ROUNDS: ANURIC RENAL FAILURE
- CONSULT ROUNDS: Hydronephrosis without evidence on...
- Journal Club: B regulatory cells
- CLINICAL CASE 15 , ANSWER and SUMMARY
- ▼ June (36)