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HelpTest Code SAU Sialic Acid, Free and Total, Random, Urine
Ordering Guidance
This is a recommended screening test for patients suspected to have a diagnosis of free sialic acid storage disease.
Urine oligosaccharides are also recommended for patients with a suspected diagnosis of sialidosis or galactosialidosis.
Necessary Information
Patient's age is required.
Specimen Required
Supplies: Sarstedt 5 mL Aliquot Tube (T914)
Container/Tube: Plastic, 5-mL urine tube
Specimen Volume: 1 mL
Pediatric Volume: 0.5 mL
Collection Instructions: Collect a random urine specimen (early morning preferred).
Forms
1. Biochemical Genetics Patient Information (T602)
2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Secondary ID
620916Useful For
Screening for sialic acid disorders
Special Instructions
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Specimen Type
UrineSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 90 days | |
| Frozen | 90 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
Free Sialic Acid:
≤4 weeks: ≤208 mmol/mol creatinine
5 weeks-12 months: ≤104 mmol/mol creatinine
13 months-18 years: ≤100 mmol/mol creatinine
≥19 years: ≤38 mmol/mol creatinine
Total Sialic Acid
≤4 weeks: ≤852 mmol/mol creatinine
5 weeks-12 months: ≤656 mmol/mol creatinine
13 months-18 years: ≤335 mmol/mol creatinine
≥19 years: ≤262 mmol/mol creatinine
Total/Free Ratio:
≤4 weeks: 1.94-18.68
5 weeks-12 months: 2.34-13.85
13 months-18 years: 2.63-9.18
≥19 years: 3.35-15.81
An interpretive report will also be provided.
Interpretation
An elevated result of total/free sialic acid ratio may be indicative of sialidosis or galactosialidosis.
A decreased result of total/free sialic acid ratio may be indicative of free sialic acid storage disorder.
Abnormal results or clinical suspicion should be confirmed with biochemical or molecular genetic analysis.
Method Description
Sialic acid is measured twice to give a free sialic acid and a total sialic acid value.
Free sialic acid is measured by drying down a 10 mcL aliquot from a random urine collection, reconstitution in 3M hydrochloric acid (HCl) in butanol to give the respective butyl ester. The butyl-ester sialic acid is reconstituted in eluent and submitted for liquid chromatography tandem mass spectrometry analysis.
Total sialic acid is measured by hydrolyzing a 10 mcL aliquot from a random urine collection with HCl. The hydrolyzed sialic acid is then converted to the respective butyl ester with 3M HCl in butanol. The butyl ester sialic acid is reconstituted in eluent and submitted for liquid chromatography tandem mass spectrometry analysis.
Both free and total sialic acid is quantitated using a commercially available stable isotope labeled internal standard from calibration over a concentration range 2.0 to 2000 mcM.(Tebani A, Schlemmer D, Imbard A, Rigal O, Porquet D, Benoist JF. Measurement of free and total sialic acid by isotopic dilution liquid chromatography tandem mass spectrometry method. J Chromatogr B Analyt Technol Biomed Life Sci. 2011;879(31):3694-3699. doi:10.1016/j.jchromb.2011.10.009; Li J, Wu T, Zhang X, Du Y, Wei B, Wang J. Clinical application of liver diseases diagnosis using ultrahigh-sensitive liquid chromatography-mass spectrometry for sialic acids detection. J Chromatogr A. 2022;1666:462837. doi:10.1016/j.chroma.2022.462837)
Day(s) Performed
Friday
Report Available
5 to 11 daysSpecimen Retention Time
1 monthPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
84275
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| SAU | Sialic Acid, Free and Total, U | 104657-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 621069 | Free Sialic Acid | 104658-0 |
| 621070 | Total Sialic Acid | 104659-8 |
| 621071 | Total/Free Sialic Acid Ratio | 104660-6 |
| 621072 | Interpretation | 94423-1 |
| 621073 | Reviewed By | 18771-6 |