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Constantinescu and associates studied serum angiotensin-converting enzyme (ACE) levels in 75 patients with multiple sclerosis (MS) and 31 matched healthy controls. Elevated ACE activity was found in 17 (23%) of the MS patients as compared with two (6%) of the controls. There was a loose correlation between increases in the ACE level and changes in total plaque volume.
Collard et al similarly found that of 71 MS patients, 22.5% had "false positive" antinuclear antibody (ANA) testing (vs 7.1% of controls). The ANA was not thought to have any pathologic significance but reflected "immune dysregulation." In serial testing of MS patients, the ANA occurrence was more frequently seen during clinical exacerbations rather than remissions.
In evaluating patients who present with symptoms and signs consistent with MS, many clinicians routinely send blood tests to exclude alternative disease processes. Included in a broad differential diagnosis are conditions such as systemic lupus erythematosus (SLE) or other collagen-vascular diseases and sarcoidosis. Not suprisingly, borderline high results can be encountered with the ANA, ESR, and the serum ACE level. Some physicians may then feel obligated to follow-up with a chest x-ray and gallium scan, which are invariably negative. As the authors reasonably suggest, a slightly elevated ANA or ACE level in a patient with otherwise typical MS need not lead to an extensive and expensive work-up for other diagnoses. ba