Assessment of renal function

Adults

To make best use of the recommendations in Table 2.33, it is necessary to calculate creatinine clearance (CrCl) if it has not been formally measured and to use this value as an estimate of the glomerular filtration rate (GFR). The most widely recommended method for doing this is to use the modified Cockcroft-Gault formula:

Adult males:
Adult females:	Multiply the above equation by 0.85

Use the patient’s height and Table 2.31 to determine the ideal weight. (The actual weight is usually satisfactory, except in the morbidly obese.) The above formula will not accurately predict clearance in patients with rapidly changing renal function. A guide to calculating creatinine clearance in children is shown in Table 2.32.

Click here for creatinine clearance and ideal body weight calculators.

Although automated reporting of the estimated glomerular filtration rate (eGFR) has been recommended practice in Australia since 2005, the eGFR has not been validated for drug dosing, and the dose modifications recommended in Table 2.33 are based on the assumption that clearance has been calculated using the Cockcroft-Gault formula.

Ideal body weight (Table 2.31)

Height		Ideal body weight (kg) [NB1]
cm	inches	female	male
155	61	48	53
160	63	53	57
165	65	57	62
170	67	62	66
175	69	66	71
180	71	71	75
185	73	75	80
190	75	80	84
195	77	84	89
200	79	89	93
205	81	93	98
210	83	98	102
215	85	102	107
220	87	107	111
NB1: Ideal weight for male = 50 kg + 0.9 kg/each cm over 152 cm (2.3 kg/each inch over 5 feet) Ideal weight for female = 45.5 kg + 0.9 kg/each cm over 152 cm (2.3 kg/each inch over 5 feet)

Children

When treating children, the appropriate dose for normal renal function should be calculated, then modified according to the guidelines in Table 2.33. A guide to calculating creatinine clearance in children is given in Table 2.32.

Guide to calculating creatinine clearance (mL/min) in patients under 21 years (Table 2.32)

Age	Formula
1 month to <2 years	40 x height (cm)/serum creatinine (micromol/L)
2 to <12 years	49 x height (cm)/serum creatinine (micromol/L)
12 to 20 years (female)	49 x height (cm)/serum creatinine (micromol/L)
12 to 20 years (male)	62 x height (cm)/serum creatinine (micromol/L)