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 an abnormally high permeability for albumin in the glomerulus of the kidney occurs. Normally, the kidneys filter albumin, so if albumin is found in the urine, then it is a marker of kidney disease. The term microalbuminuria is now discouraged by Kidney Disease Improving Global Outcomes^[1] and has been replaced by moderately increased albuminuria.

Microalbuminuria
Other names	Moderately Increased Albuminuria
Specialty	Nephrology

Causes

Higher dietary intake of animal protein, animal fat, and cholesterol may increase risk for microalbuminuria,^[2] and generally, diets higher in fruits, vegetables, and whole grains but lower in meat and sweets may be protective against kidney function decline.^[3][4][5]

Associations

• Marker of vascular endothelial dysfunction
• An important prognostic marker for kidney disease
  • in diabetes mellitus
  • in hypertension
  • in post-streptococcal glomerulonephritis
• Increasing microalbuminuria during the first 48 hours after admission to an intensive care unit predicts elevated risk for acute respiratory failure, multiple organ failure, and overall mortality
• A risk factor for venous thromboembolism^[6]

Microalbuminuria is an important adverse predictor of glycemic outcomes in prediabetes. Prediabetes 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.^[7]

Diagnosis and treatment

The level of albumin protein produced by microalbuminuria can be detected by special albumin-specific urine dipsticks, which have a lower detection threshold than standard 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 and 300 mg/24 hours) or, more commonly, from elevated concentration 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.^[8]

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.^[9]

Taurine in combination with N-acetylcysteine (Nefrosave Tablet) was useful in attenuating UACR in microalbuminuric type 2 diabetic patient as per Indian Journal of Nephrology 2008

To compensate for variations in urine concentration in spot-check samples, comparing the amount of albumin in the sample against its concentration of creatinine is helpful. This is termed the albumin/creatinine ratio (ACR)^[10] and microalbuminuria is defined as ACR ≥3.5 mg/mmol (female) or ≥2.5 mg/mmol (male),^[11] or with both substances measured by mass, as an ACR between 30 and 300 μg albumin/mg creatinine.^[12] 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 very high or very low muscle mass. This is due to the variation in creatinine level which is produced by the muscle.^[13]

Definitions of microalbuminuria

	Individual	Lower limit	Upper limit	Unit
24h urine collection		30[9]	300[9]	mg/24h (milligram albumin per 24 hours)
Short-time urine collection		20[9]	200[9]	μg/min (microgram albumin per minute)
Spot urine albumin sample		30[14]	300[14]	mg/L (milligram albumin per liter of urine)
Spot urine albumin/creatinine ratio	Women	3.5[15]	25[15] or 35[15]	mg/mmol (milligram albumin per millimole creatinine)
		30[15]	400[15]	μg/mg (microgram albumin per milligram creatinine)
	Men	2.5[15] or 3.5[15]	25[15] or 35[15]	mg/mmol
		30[15]	300[15]	μg/mg

References

• Abid O, Sun Q, Sugimoto K, Mercan D, Vincent JL (2001). "Predictive value of microalbuminuria in medical ICU patients: results of a pilot study". Chest. 120 (6): 1984–8. doi:10.1378/chest.120.6.1984. PMID 11742932.
• Andersen S, Blouch K, Bialek J, Deckert M, Parving HH, Myers BD (2000). "Glomerular permselectivity in early stages of overt diabetic nephropathy". Kidney Int. 58 (5): 2129–37. doi:10.1111/j.1523-1755.2000.00386.x. PMID 11044234.
• Heart Outcomes Prevention Evaluation Study Investigators (2000). "Effects of ramipril on cardiovascular and microvascular outcomes in people with diabetes mellitus: results of the HOPE study and MICRO-HOPE substudy". Lancet. 355 (9200): 253–9. doi:10.1016/S0140-6736(99)12323-7. PMID 10675071. S2CID 1863533.
• Lemley KV, Abdullah I, Myers BD, et al. (2000). "Evolution of incipient nephropathy in type 2 diabetes mellitus". Kidney Int. 58 (3): 1228–37. doi:10.1046/j.1523-1755.2000.00223.x. PMID 10972685.
• Lièvre M, Marre M, Chatellier G, et al. (2000). "The non-insulin-dependent diabetes, hypertension, microalbuminuria or proteinuria, cardiovascular events, and ramipril (DIABHYCAR) study: design, organization, and patient recruitment. DIABHYCAR Study Group". Controlled Clinical Trials. 21 (4): 383–96. doi:10.1016/S0197-2456(00)00060-X. PMID 10913814.
• Parving HH, Lehnert H, Bröchner-Mortensen J, Gomis R, Andersen S, Arner P (2001). "The effect of irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes". N. Engl. J. Med. 345 (12): 870–8. doi:10.1056/NEJMoa011489. PMID 11565519.
• Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney inter., Suppl. 2013; 3: 1–150.

Footnotes

1. "KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease" (PDF).
2. 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. 5 (5): 836–843. doi:10.2215/CJN.08001109. ISSN 1555-905X. PMC 2863979. PMID 20299364.
3. 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. 57 (2): 245–254. doi:10.1053/j.ajkd.2010.09.027. ISSN 1523-6838. PMC 3026604. PMID 21251540.
4. 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. doi:10.1159/000184293. ISSN 1660-8151. PMID 3600911.
5. 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. doi:10.1159/000189341. hdl:11382/374104. ISSN 1660-8151. PMID 8893161.
6. 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.
7. 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. S2CID 206117.
8. "Person—microalbumin level (measured), total micrograms per minute N[NNN].N". Retrieved 2007-07-05.
9. Mary Lee (2009-02-26). Basic Skills in Interpreting Laboratory Data. ASHP. pp. 291–. ISBN 978-1-58528-274-6.
10. 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.
11. "Proteinuria". UK Renal Association. December 15, 2005. Archived from the original on August 14, 2007.
12. clinlabnavigator.com > Test Interpretations Last Updated on Saturday, 19 June 2010
13. Microalbuminura in diabetes
14. Person—microalbumin level (measured) at Australian Institute of Health and Welfare. 01/03/2005
15. 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.

External links

• Microalbumin and Urine Albumin/Creatinine Ratio – Lab Tests Online