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HelpTest Code MBLF Mannan Binding Lectin Complement Pathway, Functional, Serum
Ordering Guidance
The most appropriate primary assays to use as screening methods for complement deficiencies are COM / Complement, Total, Serum and AH50 / Alternative Complement Pathway, Functional, Serum. Abnormal results in one or the other, none, or both assays will help direct further testing. If total complement and AH50 are both normal but the suspicion of a complement deficiency remains, this test for the lectin pathway function is recommended. After the initial 3 pathways of complement functional status are evaluated, the analysis of individual components and regulators may uncover functional or quantitative defects in certain components.
This test is rarely useful when ordered in isolation.
As the heat-labile fraction of the immune system, complement activation in vitro has been a challenge for researchers and scientists. Because of the thermal instability of complement proteins, it is often necessary to repeat testing to rule out a possible pre-analytical issue with a sample type, real complement consumption, or dysregulation.
Specimen Required
Patient Preparation:
1. Specimen should not be collected earlier than 48 hours following plasma exchange.
2. Fasting is preferred.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Immediately after specimen collection, place the tube on wet ice.
2. After sample has clotted on wet ice, centrifuge at 4° C and aliquot serum into plastic vial.
3. Freeze specimen within 30 minutes of centrifugation. Sample must be placed on dry ice if not frozen immediately.
Additional Information:
If a refrigerated centrifuge is not available, it is acceptable to use a room temperature centrifuge, provided the specimen is kept on ice before centrifugation, and immediately afterward, the serum aliquoted and frozen.
Useful For
Investigating recurrent meningococcal disease in young children
Investigating recurrent or severe infections in adults
Investigating glomerular kidney diseases
Additionally, deficiencies or dysregulation within the complement system may be identified in patients when this test is used in combination with related tests.
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name
MBL Complement Path, Func, SSpecimen Type
Serum RedSpecimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Frozen | 14 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Clinical Information
Complement proteins are components of the innate immune system. There are 3 pathways to complement activation: the classical pathway, the alternative (or properdin) pathway, and the lectin (or mannan binding lectin: MBL) pathway.
The total complement assay (COM / Complement, Total, Serum) is the best screening assay for complement abnormalities of the classical complement pathway (C1qrs, C4, C2, C3, C5, C6, C7, C8, C9). The COM assay will be abnormal if there are specific hereditary or acquired C1-C9 complement component deficiencies or if there is consumption of complement due to immune (or autoimmune) complexes.
Abnormalities in the alternative pathway may be evaluated with the AH50 functional assay (AH50 / Alternative Complement Pathway, Functional, Serum). The alternative pathway shares C3 and C5 through C9 components but has unique early complement components designated factors D, B, and P, as well as regulatory factors H and I. This pathway can be activated by hydrolysis of C3 or by microbial polysaccharides and does not require immune complex formation as a trigger. Patients with deficiencies in the alternative pathway factors (D, B, P, H, and I) or late complement components (C3, C5-C9) are unusually susceptible to recurrent Neisserial meningitis. Dysregulation of the alternative pathway is also observed in cases of atypical hemolytic uremic syndrome and rare kidney diseases such as C3 glomerulopathies.(1)
MBL is an acute phase protein, one of several lectins and collectins that initiate lectin pathway complement activity. These proteins play a role in host defense, recognizing pathogen- and damage-associated molecular patterns. MBL associates with MBL-associated serine proteases (MASP-1, -2, and -3) to activate complement components C2 through C9. MBL deficiency is a common finding worldwide due to the broad genetic distribution of deficient MBL2 alleles (5%-30% or higher in isolated populations).(1-3) Seven haplotypes are commonly observed, with a potential for 28 possible combinations.(4)
MBL activity of less than 10% may be found in a normal population at frequencies of 20% to 30%, a finding confirmed by Mayo Clinic during validation studies.
MBL function assessment is recommended as second-tier testing when total complement and alternative complement analyses are both within reference intervals, and the clinical presentation of recurrent infections, along with suspicion of complement dysregulation, remains in the differential.
Reference Values
≥10%
Day(s) Performed
Wednesday
Report Available
2 to 8 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
86161