The complement fixation antibody titer is the reciprocal of the highest dilution of serum that prevents lysis of target red blood cells to the extent defined by USDA protocols (endpoint dilution of 1 32 = antibody CF titer of 32).
Collum [ 22] showed recovery of herpes simplex virus type I in 19 (33%) of 54 conjunctival swabs while complement fixation antibody to HSV type I was present in 48 (96%) samples of sera.
On March 10, a serum specimen demonstrated a complement fixation antibody titer of 16, a 4-fold rise compared to a titer <4 in a February 25 specimen drawn in Sierra Leone.
The percentages of patients with detectable complement fixation antibody at enrollment and at 4, 12, and 24 weeks were 38% (12/32), 61% (17/28), 59% (16/27), and 23% (5/22), respectively.
Serology is especially useful in documenting asymptomatic infections, but is not useful for patient management because a ≥ 4-fold rise in complement fixation antibody titre in serum samples collected 2 weeks apart is necessary to make the diagnosis of influenza A infection.
The diagnostic enigma is that C. burnetii is difficult to culture, and detection in Cyprus was first done by complement fixation of antibodies [ 22, 23].
Serum from patient 5 was positive for Mycoplasma pneumoniae immunoglobulin (Ig) M (enzyme-linked immunosorbent assay [ELISA]) antibody with a fourfold increase in complement fixation (CF) antibody titer in acute- (<1 40) and convalescent-phase sera (1 160).
An acute complement fixation test antibody screen for "atypical" bacteria and respiratory viruses was also performed, which included Mycoplasma IgM antibody, M. pneumoniae, Chlamydia pneumoniae and C. psittaci, as well as Coxiella burnetii and Legionella pneumophila serogroup 1 6 in the post-vaccine study.
IgG or IgM binds to the new antigen on the blood cells, lysing blood cells via either complement fixation or antibody-dependent cell cytotoxicity.
