Circulation levels of acute phase proteins in patients with Takayasu arteritis

Takayasu arteritis (TA) is an immune-mediated disease with an unknown etiology. Assessment of disease activity in patients with TA is challenging owing to the absence of reliable serologic markers. Because circulation levels of acute-phase proteins fluctuate with the severity and extent of the inflammatory reaction, they may be potential biomarkers for the identification of TA activity. To test this hypothesis, certain acute-phase proteins were examined in TA patients and controls.

The study included 43 prospectively selected TA patients, with 18 in active phase and 25 in inactive phase. The Sharma modified criteria were used for disease diagnosis, and the National Institutes of Health criteria were used for TA activity assessment. Circulation levels of acute-phase proteins, including serum amyloid A (SAA), fibrinogen, complement C4-binding protein (C4BP), C-reactive protein, serum amyloid P, haptoglobin, alpha-acid glycoprotein, transthyretin, alpha1-microglobin, and complement fraction C3c and C4a were investigated by enzyme-linked immunosorbent assay in each participant.

Circulating levels of SAA and C4BP were significantly increased in active TA patients compared with inactive TA patients and in controls, with (SAA: 95.9 [interquartile range, 51.9] vs 49.2 [82.0], P = .009; and 23.9 [50.1] mg/L, P = .001, respectively; C4BP: 88.5 [72.6] vs 61.7 [57.7], P = .023; and 32.6 [32.1] mg/L, P < .001, respectively). The levels of both proteins in inactive TA patients were still higher than those in controls (SAA: 49.2 [82.0] vs 23.9 [50.1] mg/L, P = .021; C4BP: 61.7 [57.7] vs 32.6 [32.1] mg/L, P = .025). No difference was found in the levels of the other acute-phase proteins studied.

SAA and C4BP may be useful biomarkers in determining the disease activity of TA. More work should be done to test these results in a large cohort of patients in a longitudinal manner.