Procalcitonin as marker of infection in patients with Goodpasture's syndrome is misleading.

BACKGROUND Procalcitonin (PCT) is routinely measured to differentiate autoimmune disorders from infection. There are reports, however, where PCT is high in the absence of infection, i.e. in vasculitis. To investigate the value of PCT in Goodpasture's syndrome, we reviewed the charts of patients with Goodpasture's syndrome who were treated from 1996 to 2006. METHODS PCT (normal range<0.5 ng/ml) was measured with an immunoluminometric assay, C-reactive protein (CRP; normal range<5 mg/l) with nephelometry. Anti-glomerular basement membrane antibodies (normal range<1:10) were measured with ELISA. RESULTS During the last 10 years we diagnosed seven patients with Goodpasture's syndrome. Six out of seven patients had biopsy proven crescentic and necrotizing glomerulonephritis. Five patients had a severe manifestation with pulmonary involvement (n=3) and/or severe renal insufficiency (n=4). Mean CRP levels were 145.7 mg/l, mean PCT levels were 34.1 ng/ml. Therapy consisted of plasmapheresis (n=3), pulse cyclophosphamide therapy (n=4) and glucocorticoids (n=6). Remarkably, all patients with elevated PCT levels had life-threatening disease (n=4) and remained dialysis-dependent (as compared to with only one out of three patients with normal PCT). In two out of five patients with severe Goodpasture's syndrome, PCT levels remained high. After thorough exclusion of infection, resumption of high dose glucocorticoids normalized PCT and CRP levels. CONCLUSIONS The measurement of PCT as a marker of infection in patients with Goodpasture's syndrome is misleading. High PCT values might rather point to a severe form of Goodpasture's syndrome with a more unfavourable prognosis. However, further studies with larger patient numbers are needed to prove this hypothesis.