[Variations of serum amyloid A protein and interleukin-6 in patients with low concentration of serum C-reactive protein].

Both C-reactive protein (CRP) and Serum amyloid A protein(SAA) are determined as an indicator of inflammation and tissue damage. But serum CRP in the range less than 10 micrograms/dl was not correlated with SAA. We determined CRP, SAA and interleukin-6(IL-6) in sera of patients who had received corticosteroid therapy. CRP decreased extremely after administration of more than 50 mg/day corticosteroid. However, SAA and IL-6 levels changed independently from CRP levels. In the patients under long-term corticosteroid therapy, CRP decreased rapidly to the level below the reference range and remained low, while SAA decreased but to the level in the reference range, and IL-6 levels was unchanged. When they were complicated with infectious disease during the corticosteroid therapy, CRP increased to or above the reference level but not so markedly, however, SAA increased markedly and exceeded the upper reference range three or four days earlier than the day of CRP increase. It is suggested that serial SAA monitoring will be reliable for the early diagnosis of infection if the patients is taking corticosteroid therapy.