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December 7, 1984

False Elevation in Serum Creatinine Levels

Author Affiliations

University of Maryland Hospital Baltimore

JAMA. 1984;252(21):2962. doi:10.1001/jama.1984.03350210018019

To the Editor.—  Flucytosine causes a falsely elevated serum creatinine measurement when an analytic method using creatinine iminohydrolase is employed.1 This enzymatic assay is being introduced into many hospital laboratories, replacing systems with which flucytosine did not interfere.

Report of a Case.—  A 53-year-old man with alcoholic cirrhosis and cryptococcal meningitis was receiving therapy with amphotericin B (0.3 mg/kg/day) and flucytosine (150 mg/kg/day). His serum creatinine level, which was 1.0 mg/dL prior to drug therapy, rose to 3.2 mg/dL on the fourth day of therapy. The dosing regimen was altered because of the possibility of amphotericin-related renal dysfunction and the consequent possibility of bone marrow toxic reaction from flucytosine. Serum creatinine values then fluctuated on a daily basis, with a high of 6.3 mg/dL, a low of 1.1 mg/dL, and a mean of 3.5 mg/dL. It was discovered that creatinine measurements were being determined on a Kodak Ektachem 400

Sundberg MW, Becka RW, Esders TW, et al:  An enzymic creatinine assay and a direct ammonia assay in coated thin films .  Clin Chem 1983;29:645-649.
Narayanan S, Appleton HD:  Creatinine: A review .  Clin Chem 1980;26:1119-1226.
Swain RR, Briggs SL:  Positive interference with the Jaffe reaction by cephalosporin antibiotics .  Clin Chem 1977;23:1340-1342.
Saah AJ, Koch TR, Drusano GL:  Cefoxitin falsely elevates creatinine levels .  JAMA 1982;247:205-206.Crossref
Toffaletti J, Blosser N, Hall T, et al:  An automated dry-slide enzymatic method evaluated for measurement of creatinine in serum .  Clin Chem 1983;29:684-687.