Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1046 page)

   No identified limitation.

   Methodologic interference (e.g., ascorbic acid).

   Proper specimen collection and processing techniques are critical for reliable results. Use of tourniquet or clenching hands increases lactate.

   This test does not measure
D
-lactate, an uncommon, often undiagnosed cause of lactic acidosis.

   A lactate/pyruvate ratio may be used to differentiate between causes of lactic acidosis. Certain congenital disorders in which pyruvate is not converted to lactate, for example, pyruvate dehydrogenase deficiency. In this case, pyruvate will accumulate, blood levels will be high, and the lactate/pyruvate ratio will be low.

LACTOFERRIN, STOOL

   Definition

   Glycoprotein, expressed by activated neutrophils. It is a sensitive and specific marker for detecting inflammation on chronic IBD. The lactoferrin stool assay offers a safe noninvasive, accurate method of differentiating IBD from IBS, once infectious causes of inflammation and colorectal cancer are ruled out. This assay is 86% sensitive and 100% specific in distinguishing IBD from IBS, making this an important diagnostic tool. Patients with IBD oscillate between active and inactive disease states, and fecal lactoferrin increases 2–3 weeks prior to onset of clinical symptoms. During remission and effective treatment, fecal lactoferrin decreases significantly.

   
Normal range:
negative.

   Use

   Screening for inflammation in patients presenting with abdominal pain and diarrhea

   Distinguish patients with active IBD from noninflammatory IBS

   Monitor IBD activity

   Interpretation