A researcher uses the Jaffe reaction to measure serum creatinine and notes that cephalosporins in the sample spuriously elevate the result. Which method best eliminates this interference for accurate RFT in patients on beta-lactam antibiotics?

• A Alkaline picrate with protein precipitation
• B Radioimmunoassay for creatinine
• C Enzymatic creatinine assay using creatininase-creatinase-sarcosine oxidase ✓
• D Jaffe method at acidic pH to reduce pseudochromogen formation

Explanation

The Jaffe (alkaline picrate) reaction is non-specific and produces a chromogen with acetoacetate, bilirubin, protein, and cephalosporins (pseudochromogens), all causing false elevation. Enzymatic methods using creatininase (converts creatinine → creatine), creatine amidinohydrolase (creatine → sarcosine + urea), and sarcosine oxidase are highly specific and unaffected by these interferents. RIA is not routinely used for creatinine. Acidic pH modification reduces some interferences but is insufficient for cephalosporins.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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