Nephropathy in Diabetes
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POSITION STATEMENT Nephropathy in Diabetes AMERICAN DIABETES ASSOCIATION iabetes has become the most com- detection, prevention, and treatment of abetic patients with microalbuminuria mon single cause of end-stage renal early nephropathy. progress to overt nephropathy, but by 20 D disease (ESRD) in the U.S. and Eu- years after onset of overt nephropathy, ϳ rope; this is due to the facts that 1) dia- NATURAL HISTORY OF only 20% will have progressed to betes, particularly type 2, is increasing in DIABETIC NEPHROPATHY — ESRD. Once the GFR begins to fall, the prevalence; 2) diabetes patients now live The earliest clinical evidence of nephrop- rates of fall in GFR are again highly vari- longer; and 3) patients with diabetic ESRD athy is the appearance of low but abnor- able from one individual to another, but are now being accepted for treatment in mal levels (Ն 30 mg/day or 20 g/min) of overall, they may not be substantially dif- ESRD programs where formerly they had albumin in the urine, referred to as mi- ferent between patients with type 1 and been excluded. In the U.S., diabetic ne- croalbuminuria, and patients with mi- patients with type 2 diabetes. However, phropathy accounts for about 40% of new croalbuminuria are referred to as having the greater risk of dying from associated cases of ESRD, and in 1997, the cost for incipient nephropathy. Without specific coronary artery disease in the older pop- treatment of diabetic patients with ESRD interventions, ϳ80% of subjects with ulation with type 2 diabetes may prevent many with earlier stages of nephropathy was in excess of $15.6 billion. About 20– type 1 diabetes who develop sustained from progressing to ESRD. As therapies 30% of patients with type 1 or type 2 di- microalbuminuria have their urinary al- and interventions for coronary artery dis- abetes develop evidence of nephropathy, bumin excretion increase at a rate of ϳ10–20% per year to the stage of overt ease continue to improve, however, more but in type 2 diabetes, a considerably patients with type 2 diabetes may be ex- smaller fraction of these progress to nephropathy or clinical albuminuria Ն Ն pected to survive long enough to develop ESRD. However, because of the much ( 300 mg/24 h or 200 g/min) over a period of 10–15 years, with hypertension renal failure. greater prevalence of type 2 diabetes, such In addition to its being the earliest patients constitute over half of those dia- also developing along the way. Once overt nephropathy occurs, without specific in- manifestation of nephropathy, albumin- betic patients currently starting on dialy- uria is a marker of greatly increased car- sis. There is considerable racial/ethnic terventions, the glomerular filtration rate (GFR) gradually falls over a period of sev- diovascular morbidity and mortality for variability in this regard, with Native patients with either type 1 or type 2 dia- Americans, Hispanics (especially Mexi- eral years at a rate that is highly variable from individual to individual (2–20 ml ⅐ betes. Thus, the finding of microalbumin- can-Americans), and African-Americans Ϫ Ϫ min 1 ⅐ year 1). ESRD develops in 50% uria is an indication for screening for having much higher risks of developing of type 1 diabetic individuals with overt possible vascular disease and aggressive ESRD than non-Hispanic whites with nephropathy within 10 years and in intervention to reduce all cardiovascular type 2 diabetes. Recent studies have now Ͼ75% by 20 years. risk factors (e.g., lowering of LDL choles- demonstrated that the onset and course of A higher proportion of individuals terol, antihypertensive therapy, cessation diabetic nephropathy can be ameliorated with type 2 diabetes are found to have of smoking, institution of exercise, etc.). to a very significant degree by several in- microalbuminuria and overt nephropa- In addition, there is some preliminary ev- terventions, but these interventions have thy shortly after the diagnosis of their di- idence to suggest that lowering of choles- their greatest impact if instituted at a abetes, because diabetes is actually terol may also reduce the level of point very early in the course of the de- present for many years before the diagno- proteinuria. velopment of this complication. This po- sis is made and also because the presence sition statement is based on recent review of albuminuria may be less specific for the SCREENING FOR articles that discuss published research presence of diabetic nephropathy, as ALBUMINURIA — A test for the and issues that remain unresolved and shown by biopsy studies. Without spe- presence of microalbumin should be per- provides recommendations regarding the cific interventions, 20–40% of type 2 di- formed at diagnosis in patients with type 2 ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● diabetes. Microalbuminuria rarely occurs The recommendations in this paper are based on the evidence reviewed in the following publications: with short duration of type 1 diabetes; Diabetic nephropathy: etiologic and therapeutic considerations. Diabetes Rev 3:510–564, 1995; and Pre- therefore, screening in individuals with type vention of diabetic renal disease with special reference to microalbuminuria. Lancet 346:1080–1084, 1995. The initial draft of this paper was prepared by Mark E. Molitch, MD (chair); Ralph A. DeFronzo, MD; Marion 1 diabetes should begin after 5 years’ disease J. Franz, MS, RD, CDE; William F. Keane, MD; Carl Erik Mogensen, MD; Hans-Henrik Parving, MD; and Michael duration. Some evidence suggests that the W. Steffes, MD, PhD. The paper was peer-reviewed, modified, and approved by the Professional Practice Com- prepubertal duration of diabetes may be im- mittee and the Executive Committee, November 1996. Most recent review/revision, October 2001. portant in the development of microvascu- Abbreviations: ACE, angiotensin-converting enzyme; ARB, angiotensin receptor blocker; DCCB, dihy- dropyridine calcium channel blocker; ESRD, end-stage renal disease: GFR, glomerular filtration rate; lar complications; therefore, clinical UKPDS, United Kingdom Prospective Diabetes Study. judgement should be exercised when indi- © 2004 by the American Diabetes Association. vidualizing these recommendations. Be- DIABETES CARE, VOLUME 27, SUPPLEMENT 1, JANUARY 2004 S79 Position Statement Table 1—Definitions of abnormalities in albumin excretion tension is usually caused by underlying diabetic nephropathy and typically be- Spot collection 24-h collection Timed collection comes manifest about the time that pa- Category (g/mg creatinine) (mg/24 h) (g/min) tients develop microalbuminuria. In patients with type 2 diabetes, hyperten- Normal Ͻ30 Ͻ30 Ͻ20 sion is present at the time of diagnosis of Microalbuminuria 30–299 30–299 20–199 diabetes in about one-third of patients. Clinical albuminuria Ն300 Ն300 Ն200 The common coexistence of glucose in- Because of variability in urinary albumin excretion, two of three specimens collected within a 3- to 6-month tolerance, hypertension, elevated LDL period should be abnormal before considering a patient to have crossed one of these diagnostic thresholds. cholesterol and triglycerides, and a reduc- Exercise within 24 h, infection, fever, congestive heart failure, marked hyperglycemia, marked hypertension, tion in HDL cholesterol, obesity, and sus- pyuria, and hematuria may elevate urinary albumin excretion over baseline values. ceptibility to cardiovascular disease suggests that they may relate to common underlying mechanisms, such as insulin cause of the difficulty in precise dating of to-creatinine ratio does, they are subject resistance; and this complex is often re- the onset of type 2 diabetes, such screening to possible errors from alterations in urine ferred to as syndrome X and/or the meta- should begin at the time of diagnosis. After concentration. All positive tests by re- bolic syndrome. Hypertension in type 2 the initial screening and in the absence of agent strips or tablets should be con- diabetic patients may also be related to previously demonstrated microalbumin- firmed by more specific methods. There is underlying diabetic nephropathy, be due uria, a test for the presence of microalbumin also marked day-to-day variability in al- to coexisting “essential” hypertension, or should be performed annually. bumin excretion, so at least two of three be due to a myriad of other secondary Screening for microalbuminuria can collections done in a 3- to 6-month period causes, such as renal vascular disease. Iso- be performed by three methods: 1) mea- should show elevated levels before desig- lated systolic hypertension has been at- surement of the albumin-to-creatinine ra- nating a patient as having microalbumin- tributed to the loss of elastic compliance tio in a random spot collection; 2) 24-h uria. An algorithm for microalbuminuria of atherosclerotic large vessels. In general, collection with creatinine, allowing the si- screening is given in Fig. 1. the hypertension in patients with both multaneous measurement of creatinine The role of annual microalbuminuria types of diabetes is associated with an ex- clearance; and 3) timed (e.g., 4-h or over- assessment is less clear after diagnosis of panded plasma volume, increased pe- night) collection. The first method is often microalbuminuria and institution of an- ripheral vascular resistance, and low found to be the easiest to carry out in an giotensin-converting enzyme (ACE) in- renin activity. office setting, generally provides accurate hibitor or angiotensin receptor blocker Both systolic and diastolic hyperten- information,