Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1186 page)

   Investigating families with PK deficiency to determine inheritance pattern and for genetic counseling

   Interpretation

   Increased in patients with younger erythrocyte population

   Decreased in congenital nonspherocytic hemolytic anemia

   Limitations

   Patients who have recently received transfusions have normal donor cells that may mask PK-deficient erythrocytes.

   Most PK-deficient patients have 5–25% of normal activity.

   Leukocytes also contain PK, that is not decreased by hereditary erythrocyte PK deficiency, freeing the blood of WBC is critical for accuracy.

QUANTITATIVE PILOCARPINE IONTOPHORESIS SWEAT TEST

   Definition

   The sweat test consists of the quantitative analyses of sweat chloride with or without sodium. This procedure, often referred to as the quantitative pilocarpine iontophoresis test, involves collection and quantification of sweat after pilocarpine iontophoresis with the use of gauze, filter paper, or Macroduct coils and quantitative analyses of sweat chloride. The sweat test entails three consecutive procedures: sweat stimulation, sweat collection, and sweat analysis.

   
Normal range
(sweat chloride):

   Less than 40 mmol/L (>3 months)

   Greater than 30 mmol/L (<3 months)