Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (752 page)

   Increased utilization of protein for synthesis (e.g., late pregnancy, infancy, acromegaly, malnutrition, anabolic hormones)

   Diet (e.g., low-protein and high-carbohydrate, IV feedings only, impaired absorption [celiac disease], malnutrition)

   Nephrotic syndrome (some patients)

   SIADH

   Inherited hyperammonemias (urea is virtually absent in blood)

   Limitations

   Urea levels increase with age and protein content of the diet.

   Corticosteroids, tetracyclines, and drugs causing nephrotoxicity frequently increase BUN.

   The presence of ammonium ions in anticoagulants may produce falsely elevated results.

BONE MARROW ANALYSIS
*

   Definition

   Bone marrow analysis refers to studies of an
aspirate
or/and a
biopsy
with the objective of obtaining marrow samples. The bone marrow is usually obtained from the posterior iliac crest. The test is indicated when abnormalities in the peripheral blood are found that require additional etiologic, classification and prognostic details. The procedure can be performed at the bedside or in the office.

   
Normal range:
Cellularity-to-fat ratio is 100% at birth and declines ≈10% each decade; 9:1 in young children; 2:1 in young adults; 1:1 in middle-aged adults; gradually decreases to 1:9 in the elderly. Differential distribution tables of the various hematopoietic lineages can be found in hematology and pathology textbooks.

   Use