Interviews with the Experts
Contributor: Dr. Gerald Berry - CHOP
Topic: Measurement of Galactitol in Urine
Measurement of galactitol in urine is accurate but is performed routinely in only a few laboratories around the world. Patients who have the severe or classic (not the variant type) type of galactosemia can be distinguished from non-affected infants, children, and adults even when they are receiving a lactose-free diet. The test is performed on a random sample of urine, a teaspoon-full or less. Patients with variant forms of galactosemia such as Q188R/N314D and S135L/S135L may have elevated urine galactitol levels but identification of the abnormality may depend on dietary lactose intake. Whether a newborn infant or adult, this is not the case with severe galactosemia (eg. Q188R/Q188R).
Urine galactitol can vary with age in patients, i.e. higher in infants and children than adolescents and adults. However, the values tend to remain stable in a patient during adolescence and adulthood.
The levels of galactitol in urine are as good as the levels of galactose-1-phosphate in red blood cells for following dietary compliance. To be specific, the urine galactitol level can rise above the range established in our laboratory for patients in different age groups if the patient ingests a lactose-containing formula, milk or dairy products. However, ingestion of small amounts of galactose may only cause the galactose-1-phosphate level, but not urine galactitol to rise. But it rises within hours or a few days after a single intake and then returns to the typical range (ie. 1-4 mg%) relatively quickly. The urine galactitol level may give a better indication of the effect of chronic ingestion of dietary galactose.
In my estimation, urine galactitol monitoring is just as good as galactose-1-phosphate to assess compliance.
The target ranges for galactitol/creatinine in urine for patients with a severe type depend on age and are:
| Age | Galactosemic | Non-Galactosemic |
| < 1 year | 183-800 | < 78 |
| 1-6 year | 194-620 | < 36 |
| > 6 years | 98-282 | < 19 |
There is no data that supports this type of observation. I suspect that chronic ingestion of a small amount of galactose, eg 100-200 mg galactose per day, may result in an elevation of urine galactitol (perhaps only after a few weeks) but no recognizable deviation of galactose-1-phosphate within the target range. We observed such an effect in 2 patients who volunteered for our fruits and vegetables study (Berry et al, ). Perhaps, under these circumstances only the red blood cell galactose-1-phosphate level will rise briefly and then return to the basal level.
Recommendations for blood and urine tests are as follows:
| Age | Gal-1-P | Urine Galactitol |
| At Diagnosis | At Diagnosis | At Diagnosis |
| 1st Year of Life | Every 3 Months | Every 3 Months |
| Age 1-2 | Every 6 Months | Every 6 Months |
| >Age 2-5 | Every 6-12 Months | Every 6-12 Months |
| >Age 5- Adulthood | Every 12 Months | Every 12 Months |
The formulas EleCare (Ross) and Neocate (SHS) contain no free or bound galactose, unlike the small content in Isomil or ProSobee. Because of our belief that endogenous synthesis of galactose is primarily responsible for galactose-1-phosphate and galactitol levels always being elevated compared to control subjects, I do not think this type of special formula is better for patients with galactosemia at any age. But this should be studied in a control fashion to prove this point.