In February 2002 the Kidney Disease...

In February 2002 the Kidney Disease issue Quality Initiative (K/DOQI) of the National Kidney Foundation (NKF) published clinical practice guidelines for chronic kidney disease (12) that were based forward a systematic literature review. A uniform format for summarizing hardness of evidence was developed based forward an evaluation of study size, applicability, eventuates and methodologic quality. Guideline statements were prepared from the analysis of the review, with each rationale statement graded according to the supporting of the same height of evidence (Table 1). (1) The evidence grading arrangement differs from the system used in American Family Physician (AFP): merely AFP's evidence level C (consensus/expert opinion) compares with the NKF grade O (opinion).

Part I (3) of this two-part article reviewed the guidelines forward definition and stages of chronic kidney disease, evaluation and treatment, and risk factor identification. Chronic kidney disease is defined by dint of kidney damage (often manifested by dint of proteinuria) or a decreased glomerular filtration rate (GFR) for three or more month The rank of decrease in the GFR provides the basis for straightforward classification of chronic kidney disease at stages (see Table 3 in part 1 (3)) Treatment should focus forward slowing disease progression and preventing complications, especially the progressive growth of cardiovascular disease. To identify chronic kidney disease and intervene early in its course, physicians should proof for proteinuria and estimate GFR in at-risk patients. Part II summarizes guidelines for using experiments to evaluate patients with suspected or known chronic kidney disease.

[TABLE 3 OMITTED]

Guideline 4: Estimation of GFR

The GFR is the best overall indicator of the horizontal of kidney function. (NKF grades s C, and R). (1) The GFR should be estimated using a prediction equation that takes into account the serum creatinine plain and some or all of these variables: age, sex race, and visible form [i]or[/i] frame size. The Modification of Diet in Renal Disease (MDRD) close attention equation and the Cockcroft-Gault equation provide useful estimates of the GFR in adult patients (Table 2) (4-6) The NKF guideline (12) notes that the serum creatinine concentration alone is not optimal for assessing the flush of kidney function.

In addition to reporting the serum creatinine measurement, clinical laboratories should report the estimated GFR as determined by way of a prediction equation. The NKF guidelines (12) also commit that autoanalyzer manufacturers and clinical laboratories calibrate serum creatinine assays using an international standard.

In in the greatest degree cases, measurement of creatinine clearance using a timed (eg 24-hour) urine collection for assessment of the GFR is not more reliable than estimation using a prediction equation. (12) However, a 24-hour urine sample provides information that is useful for estimating GFR in patients with exceptional dietary intake (vegetarian diet, creatine supplementation) or muscle mass (amputation, malnutrition, muscle wasting), assessing diet and nutritional status, and determining the ne to start dialysis.

In clinical practice, GFR usually is estimated from the creatinine clearance or the serum creatinine concentration. Measurement of creatinine clearance requires the collection of a timed urine sample, which is inconvenient for the patient as well as often inaccurate. The serum creatinine concentration is affected according to factors other than the GFR including creatinine secretion, generation, and extrarenal excretion. (78) Thus, there is a relatively wide range for serum creatinine horizontals in normal persons, and the GFR must decline to about individual half of the normal flush before the serum creatinine concentration rises above the upper limit of normal. This situation regarding a declining GFR with "normal" creatinine is especially important in somewhat old patients, in whom the age-related decline in GFR is not pondered by an increase in the serum creatinine plain because of a concomitant age-related decline in creatinine production.

Table 3 (1) present to views the range of serum creatinine values corresponding with an estimated GFR of 60 mL for minute per 1.73 m2, depending onward age, sex, and race. Note that the NKF definition of chronic kidney disease includes a GFR horizontal below 60 mL per minute by 1.73 [m.sup.2] for three month or more (see Table 2 in part I (3)) The data in Table 3 demonstrate that minor elevations of the serum creatinine concentration may delineate a substantial reduction in the GFR Thus, with use of merely the serum creatinine as the measure of kidney function, it is difficult to estimate the even of kidney function and find earlier stages of chronic kidney disease.

The estimate of GFR from the serum creatinine concentration can be improved according to using a prediction equation that also takes into account the patient's age, sex race, and visible form [i]or[/i] frame size (e.g., the equations shown in Table 2 (4-6)) In patients with a GFR below about 90 mL through minute per 1.73 [m.sup.2], the abbreviated MDRD cogitation equation appears to be more accurate and precise than the Cockcroft-Gault equation, if it were not that is more complicated to compute