The usefulness of serum amyloid A as a postoperative inflammatory marker after posterior lumbar interbody fusion

M. Deguchi, R. Shinjo, Y. Yoshioka, H. Seki
2010 Journal of Bone and Joint Surgery  
The post-operative changes in the serum levels of CRP and serum amyloid A (SAA) were investigated prospectively in 106 patients after posterior lumbar interbody fusion. In 96 patients who did not have complications related to infection within the first year after operation, the median levels of CRP before operation and on days 3, 7 and 13 after were 0.02 (0.01 to 0.03), 9.12 (2.36 to 19.82), 1.64 (0.19 to 6.10) and 0.53 (0.05 to 2.94) mg/dl, respectively and for SAA, 2.6 (2.0 to 3.8), 1312.1
more » ... .0 to 3579.8), 77.3 (1.8 to 478.4), 14.1 (0.5 to 71.9) μg/ml, respectively. The levels on day 3 were the highest for both CRP and SAA and significantly decreased (p < 0.01) by day 7 and day 13. In regard to CRP, no patient had less than the reference level (0.1 mg/dl) on day 7. In only three had the level decreased to the reference level, while in 93 it was above this on day 13. However, for SAA, the levels became normal on day 7 in 10 cases and on day 13 in 34 cases. The ratios relative to the levels on day 3 were significantly lower for SAA compared with CRP on day 7 and day 13. Of the ten patients with infection in the early stages, the level of CRP decreased slightly but an increase in SAA was observed in six. We concluded that SAA is better than CRP as a post-operative inflammatory marker. Posterior lumbar interbody fusion for degenerative or isthmic spondylolisthesis may simultaneously resolve both the stenosis and instability. It is important to prevent post-operative infection as the occurrence of surgical-site infection (SSI) requires removal of the implant and may lead to catastrophic results. Better results are obtained following early diagnosis and treatment with antbiotics and debridement. Changes in the levels of inflammatory markers in the serum assist in the diagnosis of SSI. Many reports indicate that CRP is the most sensitive inflammatory marker, and infection should be suspected when the serum CRP level increases again after returning to normal levels. 1-3 However, the CRP level may remain relatively high even when there is no infection. 3,4 Consequently, if there are inflammatory markers which increase and then become normal more rapidly, they would be useful for the early diagnosis of post-operative infection. Serum amyloid A (SAA) is a protein that is a precursor of amyloid A protein which is deposited in the tissues in amyloidosis in cases of chronic inflammatory disorder. It is an inflammatory protein with the highest growth ratio, and in situations of stimulation such as stress immediate increases of up to a factor of 1000 of the serum concentration have been observed. 5,6 This characteristic of the immediate increase is useful for the early diagnosis of an infection, and, in addition, SAA is of value for monitoring the effectiveness of treatment for infection because its half-life is short. 6 However, its use as a post-operative inflammatory marker has not been described. Our aim was to investigate the changes in the levels of SAA after posterior lumbar interbody fusion and to compare SAA with CRP as a post-operative inflammatory marker. Patients and Methods Our study was prospectively implemented from April 2006 in patients who had singlelevel posterior lumbar interbody fusion using pedicle screws and fusion cages. The operations were for degenerative or isthmic spondylolisthesis and herniated lumbar discs. We excluded patients with a pyogenic or nonpyogenic inflammatory disorder. After obtaining informed consent and entering patients into our study, we measured the white blood cell count, the serum CRP level (reference value, < 0.1 mg/dl) and the SAA level (reference value, < 8 μg/ml) before operation and on days 3, 7 and 13 after operation. We also recorded the daily body temperature before surgery up to day 14 after. The CRP and SAA levels were measured using a latex agglu-
doi:10.1302/0301-620x.92b4.22807 pmid:20357334 fatcat:6ppiwdxezba4vfdhibjfgj5i24