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HelpTest Code A124 Alpha-1-Microglobulin, 24 Hour, Urine
Necessary Information
24-Hour volume (in milliliters) is required.
Specimen Required
Container/Tube: Plastic, 5-mL tube
Specimen Volume: 4 mL
Collection Instructions:
1. Collect urine for 24 hours.
2. No preservative.
3. Mix well before taking 4-mL aliquot.
Additional Information: For multiple collections see Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens
Secondary ID
610363Useful For
Assessment of renal tubular injury or dysfunction using 24-hour urine collections
Screening for tubular abnormalities
Detecting chronic asymptomatic renal tubular dysfunction(2)
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| AIM | Alpha-1-Microglobulin, 24 HR, U | No | Yes |
| A1MCR | A1M/Creat Ratio | No | Yes |
| A1MC | Alpha-1-Microglobulin Concentration | No | Yes |
| CRT24 | Creatinine, 24 HR, U | Yes, (Order CTU) | Yes |
Special Instructions
Method Name
AIM, A1MCR: Calculation
A1MC: Immunonephelometry
CRT24: Enzymatic Colorimetric Assay
Reporting Name
Alpha-1-Microglobulin, 24 HR, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 7 days | |
| Ambient | 7 days | ||
| Frozen | 7 days |
Reject Due To
| Gross hemolysis | Reject |
Clinical Information
Alpha-1-microglobulin is a low-molecular-weight protein of 26 kDa and a member of the lipocalin protein superfamily.(1) It is synthesized in the liver, freely filtered by glomeruli, and reabsorbed by renal proximal tubules cells where it is catabolized.(1) Due to extensive tubular reabsorption, under normal conditions very little filtered alpha-1-microglobulin appears in the final excreted urine. Therefore, an increase in the urinary concentration of alpha-1-microglobulin indicates proximal tubule injury and/or impaired proximal tubular function.
Elevated excretion rates can indicate tubular damage associated with renal tubulointerstitial nephritis or tubular toxicity from heavy metal or nephrotoxic drug exposure. Glomerulonephropathies and renal vasculopathies also are often associated with coexisting tubular injury and so may result in elevated excretion. Elevated alpha-1-microglobulin in patients with urinary tract infections may indicate renal involvement (pyelonephritis).
Measurement of urinary excretion of retinol-binding protein, another low-molecular-weight protein, is an alternative to the measurement of alpha-1-microglobulin. To date, there are no convincing studies to indicate that one test has better clinical utility than the other.
Urinary excretion of alpha-1-microglobulin can be determined from either a 24-hour collection or from a random urine collection. The 24-hour collection is traditionally considered the gold standard. For random or spot collections, the concentration of alpha-1-microglobulin is divided by the urinary creatinine concentration. This corrected value adjusts alpha-1-microglobulin for variabilities in urine concentration.
Reference Values
≥18 years: <23 mg/24 hours
Reference values have not been established for patients who are less than 18 years of age.
Interpretation
Alpha-1-microglobulin above the reference values may be indicative of a proximal tubular dysfunction.
Cautions
Since this is a nephelometric assay, turbidity and particles (eg, cells, crystals) in the specimen can interfere with the test.
Clinical Reference
1. Akerstrom B, Logdberg L, Berggard T, Osmark P, Lindqvist A: Alpha(1)-microglobulin: a yellow-brown lipocalin. Biochim Biophys Acta. 2000 Oct 18;1482(1-2):172-184
2. Yu H, Yanagisawa Y, Forbes M, Cooper EH, Crockson RA, MacLennan RC: Alpha-1-microglobulin: an indicator protein for renal tubular function. J Clin Pathol. 1983 Mar;36(3):253-259
3. Hjorth L, Helin I, Grubb A: Age-related reference limits for urine levels of albumin, orosomucoid, immunoglobulin G, and protein HC in children. Scand J Clin Lab Invest. 2000 Feb;60(1):65-73
4. Pagana K, Pagana T, Papana T, eds: Mosby’s Diagnostic and Laboratory Test Reference. Mosby; 2020:632
Method Description
Alpha-1-Microglobulin:
In an immunochemical reaction, alpha-1-microglobulin present in the urine sample forms immune complexes with anti-alpha-1-microglobulin specific antibodies. These complexes scatter a beam of light passed through the sample. The intensity of the scattered light is proportional to the concentration of alpha-1-microglobulin in the sample. The result is evaluated by comparison with a standard of known concentration.(Package insert: N Alpha-1-Microglobulin. Siemens Healthcare Diagnostics Inc; V5, 05/2018)
Creatinine:
The enzymatic method is based on the determination of sarcosine from creatinine with the aid of creatininase, creatinase, and sarcosine oxidase. The liberated hydrogen peroxide is measured via a modified Trinder reaction using a colorimetric indicator. Optimization of the buffer system and the colorimetric indicator enables the creatinine concentration to be quantified both precisely and specifically.(Package insert: Creatinine plus ver 2. Roche Diagnostics; V 15.0, 03/2019)
Day(s) Performed
Varies
Report Available
1 to 7 daysSpecimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
83883
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| A124 | Alpha-1-Microglobulin, 24 HR, U | 99075-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CR_A | Creatinine, 24 HR, U | 2162-6 |
| AIM | Alpha-1-Microglobulin, 24 HR, U | 48414-7 |
| A1MC | Alpha-1-Microglobulin Concentration | 99076-2 |
| A1MCR | A1M/Creat Ratio | 99075-4 |
| TM27 | Collection Duration (h) | 13362-9 |
| VL69 | Urine Volume (mL) | 3167-4 |
| CR_24 | Creatinine Concentration, 24 HR, U | 20624-3 |
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.