CH50

An antinuclear antibody (ANA) test was strongly positive at 1:1,280, homogenous pattern, her rheumatoid factor was elevated, and complement factors C3, C4, CH50 were all low, suggesting an autoimmune process was present.

CH50 testing is the most common assay used to screen patients for the functional activity of the classical complement pathway, and in the work up of complement deficiency.

Complement profile initially revealed normal C4 and low C3 and CH50 (C3 84.1 mg/dL, normal 90-180 mg/dL and CH50 32%, normal 70%-130%).

Serological data of enrolled patients Anti-cardiolipin CH50 C4 C3 dsDNA ANA [beta]2- Glycoprotein Mean 4.5 80 0.14 0.55 4.2 7.64 3.7 Min 0.12 3 0.01 0 0.1 0.8 0.5 Max 43 135 100 180 600 1180 25.7 ANA: antinuclear antibod Table 3.

All seven patients that completed the study had a CH50 level below the limit of quantification after the ablating dose phase indicating total blockade of the terminal complement pathway.

Immunology workup revealed low complement C3 and C4 with high CH50, high titer of antidouble stranded DNA (dsDNA) antibody, positive LA, positive aCL, and negative aB2GPI.

The alternative and classical complement pathways were suppressed confirming drug action (CH50 and AP50 hemolytic assays < 10%).

A reduction in CH50 plasma levels and increased C3 in patients with EMAP could indicate a more severe complement pathway dysfunction compared to AMD and play a role in increased pseudodrusen formation and atrophy progression [1].

C3, C4, and CH50 were 46 mg/dL (90-180 mg/dL), 7mg/dL (10-40 mg/dL), and 116 CAE units (60-144 CAE units).

Laboratory studies reveal low C3 and CH50 early in the disease course with typically normal C4 [17,18].

Although C3 or C4 levels were also within normal range, CH50 was slightly higher (59.4 U/mL) than the normal range (32-48 U/mL).