Elevated creatinine in a patient on IVIG-therapy

Background: Intravenous immunoglobulin (IVIG) is prepared from the plasma of hundreds of blood donors and is used in the treatment of immunodeficiencies, autoimmune conditions, infections and inflammatory conditions. IVIG formulations contain one of a number of small molecule stabilizers, including sugars, polyols, and amino acids, some of which can cause acute renal failure. Case report: A 61 y-old woman was treated for paraneoplastic syndrome due to small cell lung cancer in which a creatinine measurement unexpectedly increased during IVIG therapy. This increased creatinine measurement was due to the proline stabilizer in the IVIG fluid that had inadvertently diluted the blood sample. Investigation revealed that proline causes a positive interference in enzymatic creatinine assays, likely due to the activity of sarcosine oxidase, a key component of the assay, on proline. Conclusions: Increased proline concentrations can occur after administration of high-dose proline (as was the case here) or in the rare metabolic disorders hyperprolinema types I and II.