Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (759 page)

Decreased Ratio (
<
10:1) with Decreased BUN In

   Acute tubular necrosis

   Low-protein diet, starvation, severe liver disease, and other causes of decreased urea synthesis

   Repeated dialysis (urea rather than creatinine diffuses out of extracellular fluid)

   Inherited deficiency of urea cycle enzymes (e.g., hyperammonemias—urea is virtually absent in blood)

   SIADH (due to tubular secretion of urea)

   Pregnancy

Decreased Ratio (
<
10:1) with Increased Creatinine In

   Phenacemide therapy (accelerates conversion of creatine to creatinine)

   Rhabdomyolysis (releases muscle creatinine)

   Muscular patients who develop renal failure

   Limitations

   DKA (acetoacetate causes false increase in creatinine with certain methodologies, resulting in normal or decreased ratio when dehydration should produce an increased ratio)

   Cephalosporin therapy (interferes with creatinine measurement)

CALCITONIN

   Definition