Ordering Recommendation

Initial screening for suspected deficiency in the alternative complement pathway.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Plain Red

Specimen Preparation

Allow specimen to clot for one hour at room temperature. Separate serum from cells ASAP and centrifuge at 2-8 degrees C and aliquot serum into ARUP standard transport tube. Freeze specimen immediately at -70 degrees C or lower freezer. (Min: 0.3 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Specimen types other than serum collected from RED TOP tubes. SST or serum gel tubes are not acceptable. Refrigerated or room temperature specimens. Specimens left to clot at refrigerated temperature. Specimens exposed to repeated freeze/thaw cycles. Grossly hemolyzed or grossly lipemic specimens or icteric specimens.


After separation from cells: Ambient: unacceptable; Refrigerated: Unacceptable; Frozen: 30 days if kept at -70 C


Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)


Sun, Wed


7-14 days

Reference Interval

Test Number
Reference Interval
  Alternative Complement Pathway Activity 31 percent normal or greater

Interpretive Data

See report.

Compliance Category

Laboratory Developed Test (LDT)


Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
2005374 Alternative Complement Pathway Activity 74520-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • AH50
  • Alternate Pathway
  • atypical hemolytic uremic syndrome
  • C3 glomerulonephrits
  • Dense-deposit disease
  • Functional Complement
  • Hemolytic Complement
Alternative Complement Pathway Activity (AH50)