[Elevated serum creatinine without discernible kidney disease]

Area of Science:

• Biochemistry
• Clinical Chemistry
• Metabolic Disorders

Background:

• Elevated serum creatinine is a common indicator of kidney dysfunction.
• Dry chemical enzyme assays are widely used for routine laboratory testing.

Observation:

• A patient presented with incidentally elevated serum creatinine (2.7 mg/dl) on dry chemical testing.
• Subsequent tests revealed normal creatinine, but elevated plasma and urine sarcosine levels.
• Kidney function tests and imaging were unremarkable.

Findings:

• The elevated serum sarcosine levels interfered with the dry chemical creatinine assay, leading to a false positive result.
• Sarcosinemia, an inborn error of amino acid metabolism, was diagnosed.

Implications:

• Dry chemical enzyme assays may yield inaccurate creatinine results in patients with sarcosinemia.
• Alternative laboratory methods are recommended for creatinine measurement when sarcosinemia is suspected.
• This highlights the importance of considering metabolic disorders in unexplained laboratory abnormalities.