Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (938 page)

   The within-subject variation for serum fructosamine is higher than that for HbA
_1C
; as a result, serum fructosamine concentrations must change more before a significant change can be said to have occurred.

GALACTOSE-1-PHOSPHATE URIDYLTRANSFERASE (GALT)

   Definition

   GALT is an enzyme responsible for converting ingested galactose to glucose. This measurement is used to identify in born errors of galactose metabolism, which can result in widespread tissue damage and abnormalities such as cataracts, liver disease, and renal disease. It also causes failure to thrive and mental retardation. The screening test should be done immediately to enable diet treatment if testing is positive.

   The deficiency of three enzymes, galactokinase (GALK), GALT or UDP, and galactose-4-epimerase (GALE), is clinically important and results in inborn errors of galactose metabolism.

   GALT deficiency, referred to as classical galactosemia or GG genotype, is the most commonly occurring of the three disorders.

   GALK deficiency is the second most common cause of galactosemia and results in a milder variant of galactosemia. GALK deficiency is very rare and usually is expressed by occurrence of juvenile cataracts in the absence of mental retardation (which occurs in transferase deficiency).

   GALE deficiency is an extremely rare cause of galactosemia.

   Other names: GPT, galactokinase, and galactose-1-phosphate.

   
Normal range:
14.7–25.4 U/g Hb.

   Use

   Diagnosis of GALT deficiency, the most common cause of galactosemia

   Confirmation of abnormal state newborn screening results

   Interpretation