Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1054 page)

   SLE, in correlation with disease activity

   Various neoplasms (even without liver metastases) (e.g., breast, endometrium, and germ cell tumors)

   Preeclampsia, between 33 and 39 weeks of pregnancy

   Limitations

   Testing serum LAP is generally not as sensitive or as convenient as testing other liver enzymes to detect some liver problems. ALT, AST, ALP, LDH, and GGT are more commonly measured for the same purpose. Unlike other liver enzymes, LAP can be measured in the urine.

   Elevated LAP activity in serum usually indicates diseases of liver and bile ducts, and this elevation is less affected by damage of liver parenchyma than by active participation of biliary tract in the process.

LEUKOCYTE ALKALINE PHOSPHATASE (LAP)
*

   Definition

   LAP, or neutrophil alkaline phosphatase, refers to a staining reaction of peripheral blood smears. It reflects the presence of LAP in neutrophils and their precursors. Normally, about 20% of mature neutrophils show stainable leukocyte LAP activity.

   
Normal range:
score of 11–95. The scoring is based on counting 100 neutrophils and grading the stained granules from 0 to 4 on the basis of the intensity and appearance of the precipitated dye in the cytoplasm.

   Use

   LAP stain helps differentiate a severe neutrophilia (leukemoid reaction) and myeloproliferative neoplasms, where it is increased, from chronic myeloid leukemia, in which case it is decreased or absent.

   With the advent of modern diagnostic technologies, the use of LAP stains has diminished.

   Interpretation