Procalcitonin in SLE

Procalcitonin (PCT), the precursor of the calcitonin, is synthesized in the parafollicular C-cells of the thyroid. It has been used to detect and to differentiate systemic bacterial infections from flares of systemic lupus erythematosus (SLE).
PCT in serum increases in severe bacterial and fungal infections, but not, or only slightly in viral infections.

In this case controlled study published in Journal of Clinical Rheumatology authors looked at PCT levels in patients with active and withous lupus activity. They conclude that there is no association between activity of SLE and PCT.