Microalbuminuria

Microalbuminuria
Classification and external resources
Specialty Nephrology
ICD-9-CM 791.0
MedlinePlus 003591
Patient UK Microalbuminuria

Microalbuminuria is a term to describe a moderate increase in the level of urine albumin. It occurs when the kidney leaks small amounts of albumin into the urine, in other words, when there is an abnormally high permeability for albumin in the glomerulus of the kidney. Normally the kidneys do not filter albumin, so if albumin is found in the urine it's then a marker of kidney disease. The term 'microalbuminuria' is now discouraged by KDIGO (Kidney Disease Improving Global Outcomes) and has been replaced by 'moderately increased albuminuria'.

Associations/Indications

Microalbuminuria is an important adverse predictor of glycemic outcomes in pre-diabetes. Pre-diabetes individuals with increased microalbuminuria even in the so-called normal range is associated with increased progression to diabetes and decreased reversal to normoglycemia. Hence prediabetes individuals with microalbuminuria warrant more aggressive intervention to prevent diabetes in them.[2]

Causes/Prevention

Higher dietary intake of animal protein, animal fat, and cholesterol may increase risk for microalbuminuria,[3] and generally, diets higher in fruits, vegetables, and whole grains but lower in meat and sweets may be protective against kidney function decline.[4][5][6]

Diagnosis

The level of albumin protein produced by microalbuminuria can be detected by special albumin-specific urine dipsticks. A microalbumin urine test determines the presence of the albumin in urine. In a properly functioning body, albumin is not normally present in urine because it is retained in the bloodstream by the kidneys.

Microalbuminuria can be diagnosed from a 24-hour urine collection (between 30–300 mg/24 hours) or, more commonly, from elevated concentrations in a spot sample (30 to 300 mg/L). Both must be measured on at least two of three measurements over a two- to three-month period.[7]

An albumin level above the upper limit values is called "macroalbuminuria", or sometimes just albuminuria. Sometimes, the upper limit value is given as one less (such as 300 being given as 299) to mark that the higher value (here 300) is defined as macroalbuminuria.[8]

To compensate for variations in urine concentration in spot-check samples, it is helpful to compare the amount of albumin in the sample against its concentration of creatinine. This is termed the albumin/creatinine ratio (ACR)[9] and microalbuminuria is defined as ACR ≥3.5 mg/mmol (female) or ≥2.5 mg/mmol (male),[10] or, with both substances measured by mass, as an ACR between 30 and 300 µg albumin/mg creatinine.[11] For the diagnosis of microalbuminuria, care must be taken when collecting sample for the urine ACR. An early morning sample is preferred. The patient should refrain from heavy exercises 24 hours before the test. A repeat test should be done 3 to 6 months after the first positive test for microalbuminuria. Lastly, the test is inaccurate in a person with too much or too little muscle mass. This is due to the variation in creatinine level which is produced by the muscle.[12]

Definitions of microalbuminuria
Individual Lower limit Upper limit Unit
24h urine collection 30[8] 300[8] mg/24h (milligram albumin per 24 hours)
Short-time urine collection 20[8] 200[8] µg/min (microgram albumin per minute)
Spot urine albumin sample 30[13] 300[13] mg/L (milligram albumin per liter of urine)
Spot urine albumin/creatinine ratio Women 3.5[14] 25[14] or 35[14] mg/mmol (milligram albumin per millimole creatinine)
30[14] 400[14] μg/mg (microgram albumin per milligram creatinine)
Men 2.5[14] or 3.5[14] 25[14] or 35[14] mg/mmol
30[14] 300[14] μg/mg

See also

References

Footnotes

  1. ↑ Mahmoodi, BK; Gansevoort, RT; Veeger, NJ; Matthews, AG; Navis, G; Hillege, HL; Van Der Meer, J; Prevention of Renal Vascular End-stage Disease (PREVEND) Study Group (2009). "Microalbuminuria and risk of venous thromboembolism". JAMA: the Journal of the American Medical Association. 301 (17): 1790–7. doi:10.1001/jama.2009.565. PMID 19417196.
  2. ↑ Dutta D, Choudhuri S, Mondal SA, Mukherjee S, Chowdhury S (2014). "Urinary albumin : creatinine ratio predicts prediabetes progression to diabetes and reversal to normoglycemia: role of associated insulin resistance, inflammatory cytokines and low vitamin D". Journal of Diabetes. 6 (4): 316–22. doi:10.1111/1753-0407.12112. PMID 24251376.
  3. ↑ Lin, Julie; Hu, Frank B.; Curhan, Gary C. (2010-05-01). "Associations of diet with albuminuria and kidney function decline". Clinical journal of the American Society of Nephrology: CJASN. 5 (5): 836–843. doi:10.2215/CJN.08001109. ISSN 1555-905X. PMC 2863979Freely accessible. PMID 20299364.
  4. ↑ Lin, Julie; Fung, Teresa T.; Hu, Frank B.; Curhan, Gary C. (2011-02-01). "Association of dietary patterns with albuminuria and kidney function decline in older white women: a subgroup analysis from the Nurses' Health Study". American Journal of Kidney Diseases: The Official Journal of the National Kidney Foundation. 57 (2): 245–254. doi:10.1053/j.ajkd.2010.09.027. ISSN 1523-6838. PMC 3026604Freely accessible. PMID 21251540.
  5. ↑ Wiseman, M. J.; Hunt, R.; Goodwin, A.; Gross, J. L.; Keen, H.; Viberti, G. C. (1987-01-01). "Dietary composition and renal function in healthy subjects". Nephron. 46 (1): 37–42. ISSN 1660-8151. PMID 3600911.
  6. ↑ Barsotti, G.; Morelli, E.; Cupisti, A.; Meola, M.; Dani, L.; Giovannetti, S. (1996-01-01). "A low-nitrogen low-phosphorus Vegan diet for patients with chronic renal failure". Nephron. 74 (2): 390–394. ISSN 1660-8151. PMID 8893161.
  7. ↑ "Person—microalbumin level (measured), total micrograms per minute N[NNN].N". Retrieved 2007-07-05.
  8. 1 2 3 4 5 Page 291 in: . ISBN 978-1-58528-180-0 Missing or empty |title= (help)
  9. ↑ Bakker AJ (February 1999). "Detection of microalbuminuria. Receiver operating characteristic curve analysis favors albumin-to-creatinine ratio over albumin concentration". Diabetes Care. 22 (2): 307–13. doi:10.2337/diacare.22.2.307. PMID 10333950.
  10. ↑ "Proteinuria". UK Renal Association. December 15, 2005.
  11. ↑ clinlabnavigator.com > Test Interpretations Last Updated on Saturday, 19 June 2010
  12. ↑ Microalbuminura in diabetes
  13. 1 2 Person—microalbumin level (measured) at Australian Institute of Health and Welfare. 01/03/2005
  14. 1 2 3 4 5 6 7 8 9 10 11 Justesen, T.; Petersen, J.; Ekbom, P.; Damm, P.; Mathiesen, E. (2006). "Albumin-to-creatinine ratio in random urine samples might replace 24-h urine collections in screening for micro- and macroalbuminuria in pregnant woman with type 1 diabetes". Diabetes Care. 29 (4): 924–925. doi:10.2337/diacare.29.04.06.dc06-1555. PMID 16567839.
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