PMN granulocyte elastase--an early indicator of postoperative spondylodiscitis?

The diagnosis of spondylodiscitis after lumbar disc surgery has been based so far on clinical abnormalities, non-specific changes in chemical laboratory parameters [erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)] and radiological examinations such as MRI. Such techniques do not enable any clear diagnosis to be made before the 3rd postoperative week. The PMN elastase released from stimulated polymorphonuclear granulocytes has been proved to be a good laboratory parameter by which it is possible to prognosticate bacterial and abacterial organ complications in surgical patients with a high degree of probability. Under investigation were 12 patients with spondylodiscitis out of 1162 operations on herniated lumbar discs. PMN elastase was determined on the 7th postoperative day. In patients with spondylodiscitis and a mean value of 110.5 micrograms/l, the elastase was on average higher by a factor of 2.6 as compared to 88 randomly selected control patients. Since spondylodiscitis is a rare complication, this results in a positive value of only 7%, which does not allow a reliable diagnosis of spondylodiscitis by the elastase assay. But because the negative predictive value is 100%, it is possible to exclude a postoperative spondylodiscitis already on the 7th postoperative day, if the elastase value is normal.