Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (873 page)

   Reduction of alkaline picrate (e.g., glucose, ascorbate, uric acid). Ketoacidosis may substantially increase serum creatinine results with alkaline picrate reaction.

   Formation of colored complexes (e.g., acetoacetate, pyruvate, other ketoacids, certain cephalosporins).

   Enzymatic reaction: 5-Fluorocytosine may increase serum creatinine ≤0.6 mg/dL.

   Other methodologic interference (e.g., ascorbic acid, phenolsulfonphthalein,
l
-dopa).

   Some medications inhibit tubular secretion of creatinine, thereby decreasing creatinine clearance and increasing serum creatinine without a change in GFR. These medications include the following:

   Cephalosporin and aminoglycoside antibiotics

   Flucytosine

   Cisplatin

   Cimetidine

   Trimethoprim

   The Cockcroft-Gault equation estimates creatinine clearance and is not adjusted for body surface area. The CKD-EPI and MDRD Study equations estimate GFR adjusted for body surface area. GFR estimates from the CKD-EPI and MDRD Study equations can therefore be applied to determine level of kidney function, regardless of a patient’s size. In contrast, estimates based on the Cockcroft-Gault equation can be used for drug dosage recommendations, whereas GFR estimates based on the MDRD Study should be “unadjusted” for body surface area.

   The Cockcroft-Gault equation appears to be less accurate than the MDRD Study equation, specifically in older and obese people.

   Modifications of the CKD-EPI and MDRD Study equations have been developed for Japanese and Chinese people. They have not yet been validated for Japanese or Chinese people living in other countries, including the United States. Studies in other ethnic groups have not yet been performed.