GAL1P - Performance: Galactose-1-Phosphate (Gal-1-P), Erythrocytes

Test Catalog

Test Name

Test ID: GAL1P    
Galactose-1-Phosphate (Gal-1-P), Erythrocytes

Method Description Describes how the test is performed and provides a method-specific reference

Galactose-1-phosphate (Gal-1-P) levels in RBCs are measured enzymatically in a 2-part reaction. In the first reaction aliquot, galactose dehydrogenase converts the endogenous galactose in the specimen to a galactonolactone, with the simultaneous production of nicotinamide adenine dinucleotide (NADH; reduced form) from nicotinamide adenine dinucleotide (NAD). The absorbance of NADH at 340 nm is used to determine the amount of galactose present in the specimen. In the second reaction aliquot, both alkaline phosphatase and galactose dehydrogenase are added. The alkaline phosphatase converts Gal-1-P into galactose and the galactose dehydrogenase converts the galactose into the galactonolactone, while producing NADH. The absorbance of NADH at 340 nm represents the galactose and Gal-1-P present in the specimen. By subtracting the absorbance of the first reaction aliquot from that of the second reaction aliquot, the Gal-1-P level can be determined.


The Gal-1-P levels are reported per gram of hemoglobin. In the hemoglobin analysis, RBCs are combined with aqueous ammonia to form a compound that absorbs light at 540 nm. The Beer-Lambert Law is applied to calculate the hemoglobin concentration from the measured absorbance.(Gitzelmann R: Estimation of galactose-1-phosphate in erythrocytes; a rapid and simple enzymatic method. Clin Chim Acta 1969 November;26[2]:313-316)

PDF Report Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.

Tuesday; 8 a.m.

Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.

8 days

Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result

15 days

Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 month

Performing Laboratory Location The location of the laboratory that performs the test