GLOMERULAR FILTRATION RATE ESTIMATED PROFILE

Lab Section Category

Clinical Biochemistry

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Description

With effect from 02/09/2024, all serum Creatinine results with the exception of serum Creatinine results as part of Creatinine Clearance tests, are reported together with an eGFR calculated using the 2009 CKD-EPI eGFR equation.

eGFR from Cockcroft Gault and MDRD equations will no longer be available and reported from 02/09/2024.

eGFR on the 2009 CKD-EPI equation is not available as a standalone test request. Please contact the Clinical Biochemistry Laboratory for further details.

Indications

Specimen Required

3 mL plain blood.

Required parameters:

For 2009 CKD-EPI Equation: Serum Creatinine (µmol/L), age (years), gender

Storage and Transport

Method

Calculated from measured parameters:
Creatinine (serum)*, age and gender

*Serum creatinine assay is traceable to isotope dilution mass spectrometry (IDMS) reference measurement procedure.

Test Results

Reference Interval / Value

CKDEPI eGFR reporting units are: mL/min/1.73m²

CKD-EPI eGFR is calculated using the 2009 CKD-EPI eGFR-creatinine equation (Levey AS et al. Ann Intern Med 2009;150:604-12). This equation is designed for patients with stable renal function.

eGFR results should be correlated clinically and interpretation can be guided by the KDIGO Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.

eGFR-creatinine calculations may be less reliable in certain situations (e.g. acute kidney injury, renal dialysis, acutely ill with haemodynamic instability, pregnancy, muscle wasting disorders, malnourishment, or extremes of body size or age).

Turnaround Time

Mean = 4 hrs, Range: 3 – 5 hrs

Day(s) Test Set up

Daily

Remarks

The 2009 CKD-EPI eGFR calculation uses the patient’s serum creatinine, age, sex and race to estimate the patient’s GFR.* For individuals less than 18 years of age, no eGFR will be calculated.

2009 CKD-EPI eGFR equation (Levey AS et al. Ann Intern Med 2009;150:604-12)

GFR = 141 × min(Scr /κ, 1)^α × max(Scr/κ, 1)^-1.209 × 0.993^Age × 1.018 [if female] × 1.159 [if black]*

where:

Scr is serum creatinine in µmol/L,

κ is 61.9 for females and 79.6 for males,

α is -0.329 for females and -0.411 for males,

min indicates the minimum of Scr /κ or 1, and

max indicates the maximum of Scr /κ or 1

*Our laboratory does not use the race correction factor in its calculation of CKD-EPI eGFR. A default factor of 1 is used.

Estimating equations are derived from large populations of patients and provide the best estimate of a patient’s GFR and not the patient’s actual GFR. These equations are designed for use in patients with stable renal function. Creatinine-based eGFR calculation may be less reliable in situations where renal function is rapidly changing/unstable or body weight/muscle mass deviates significantly from normal. These include:

• Acute kidney injury

• Critically ill

• Renal Dialysis

• Extremes of age (i.e. elderly)

• Extremes of muscle mass (i.e. bodybuilders, amputation)

• Malnourishment

• Muscle wasting disorders

• Pregnancy

In situations where creatinine-based eGFR is unreliable, one may consider the use of cystatin-based eGFR or measured GFR to assess renal function.

Glomerular filtration rate (GFR) is traditionally indexed to body surface area (BSA) to allow comparison among individuals of different body size. Definitions of chronic kidney disease are based on GFR indexed to BSA. Modern GFR estimating equations report estimated GFR (eGFR) indexed to BSA of 1.73m² .

For drug dosing purposes, please consult a pharmacist on the use of eGFR (vs estimated creatinine clearance).

Drug clearance is only related to GFR and not to body size or body surface area (BSA). In patients whose body sizes are very different from average, use of non-indexed eGFR (ml/min) may be preferrable.

Conversion of indexed eGFR (ml/min/1.73m2) to non-indexed eGFR (ml/min) can be performed by multiplying the indexed GFR result by the patient’s BSA (e.g. BSA = (Ht(in cm) x Wt(in kg)/3600)^0.5) and dividing by 1.73m² .

GLOMERULAR FILTRATION RATE, ESTIMATED, PROFILE