TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: AHUSD    
Atypical Hemolytic Uremic Syndrome Complement Panel, Serum and Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Detecting deficiencies in the alternative pathway that can cause atypical-hemolytic uremic syndrome, dense deposit disease, and C3 glomerulonephritis

 

A second-tier test that aids in the differential diagnosis of thrombotic microangiopathies

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Individuals presenting with thrombotic microangiopathies (TMA) require clinical testing to identify the underlying cause. Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are both acute syndromes with many overlapping clinical features. Reduced levels of ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motives, member 13) activity is associated with TTP and is one laboratory feature that distinguishes TTP from HUS. HUS can also have a number of causes; one of the rarer forms of disease is caused by defects in the alternative pathway of the complement system, so called atypical-HUS (aHUS). Patients with defective alternative pathway regulation can benefit from biologics that suppress the complement system.

 

The purpose of this panel is to aid in the differential diagnosis of TMA. The suggested approach is to rule-out other causes of TMA first, since aHUS is one of the rarer causes of TMA. Additionally, the assays can be used in the setting of membranoproliferative glomerulonephritis (MPGN) and can help distinguish between immune-complex mediated or complement-mediated kidney disease. MPGN mediated by immune-complexes are ones resulting from infectious processes, autoimmune diseases, or monoclonal gammopathies; whereas complement-mediated MPGN can be subdivided in C3 glomerulonephritis and dense deposit disease, based on electron microscopy of the kidney biopsy histological findings. Despite phenotypic differences, these glomerular diseases share dysfunction of the alternative pathway as the defining pathophysiology.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

FACTOR B COMPLEMENT ANTIGEN

15.2-42.3 mg/dL

 

SC5b-9 COMPLEMENT

< or =250 ng/mL

 

FACTOR H COMPLEMENT ANTIGEN

18.5 to 40.8 mg/dL

 

C4d COMPLEMENT ACTIVATION FRAGMENT

< or =9.8 mcg/mL

 

CBb COMPLEMENT ACTIVATION FRAGMENT

< or =1.6 mcg/mL

 

COMPLEMENT C4

14-40 mg/dL

 

COMPLEMENT C3

75-175 mg/dL

 

ALTERNATIVE COMPLEMENT, PATHWAY (AH50) FUNCTIONAL

> or =46% normal

 

COMPLEMENT, TOTAL

30-75 U/mL

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be included.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

As with all complement assays, proper sample handling is of utmost importance to ensure that the complement system is not activated before clinical testing.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Daha MR: Role of complement in innate immunity and infections. Crit Rev Immunol. 2010;30(1):47-52. doi: 10.1615/critrevimmunol.v30.i1.30

2. Prohaszka Z, Varga L, Fust G: The use of "real-time" complement analysis to differentiate atypical haemolytic uraemic syndrome from other forms of thrombotic microangiopathies. Br J Haematol. 2012;158(3):424-425. doi: 10.1111/j.1365-2141.2012.09168.x

3. Cataland SR, Holers VM, Geyer S, Yang S, Wu HM: Biomarkers of terminal complement activation confirm the diagnosis of aHUS and differentiate aHUS from TTP. Blood. 2014;123(24):3733-3738. 10.1182/blood-2013-12-547067

4. Go RS, Winters JL, Leung N, et al: Thrombotic microangiopathy care pathway: A consensus statement for the Mayo Clinic Complement Alternative Pathway-Thrombotic Microangiopathy (CAP-TMA) Disease-Oriented Group. Mayo Clin Proc. 2016;91(9):1189-1211. doi: 10.1016/j.mayocp.2016.05.015

5. Willrich MAV, Andreguetto BD, Sridharan M, et al: The impact of eculizumab on routine complement assays. J Immunol Methods. 2018;460:63-71. doi: 10.1016/j.jim.2018.06.010