[Serum amyloid A as a useful index of disease activity in polymyalgia rheumatica].

Purpose: To clarify the usefulness of measuring serum amyloid A (SAA) levels in patients with polymyalgia rheumatica (PMR), we compared this parameter to C-reactive protein (CRP).

Subjects and methods: The study included 10 patients with PMR, who could be prospectively followed up from the start of prednisolone (PSL) treatment until the CRP level decreased to 1 mg/dl or less. When the CRP level decreased, the subjects were divided into the group in which the symptom persisted (n = 6) and those in which the symptom disappeared (n = 4).

Results: In the group in which the symptom persisted, both CRP and SAA levels were significantly higher. When the CRP level decreased, there was no significant difference in the CRP level between the two groups. However, the mean SAA level in the group in which the symptom persisted (137.8 micrograms/ml) was significantly higher than that in the group in which the symptom disappeared (21.8 micrograms/ml). On the initial consultation, there was a positive correlation between CRP and SAA (R = 0.77). The SAA level was more sensitive than the CRP level (y = 94.899 x -51.22). When the CRP level decreased, SAA was much more sensitive (y = 222.92 x +6.9121), suggesting the usefulness of SAA after the start of PSL treatment.

Conclusion: SAA may be a useful parameter of PMR activity.