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Biochemical Calculations

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Renal
Calculations
Creatinine Clearance
Calculated Creatinine Clearance (Cockcroft & Gault)            On-line Calculator (umol/L)
Calculated Creatinine Clearance (Lean Body Mass est'd from height)  On-line Calculator (umol/L)
Fractional Excretion of Sodium (FENA)
Creatinine Clearance - correction for body surface area

 

General
Calculations
LDL Cholesterol
Transferrin Saturation
Indirect Bilirubin
Calcium corrected for albumin
Half-Life Calculator
Unit Conversions

Web Chemistry calculator
 

Renal Calculations


 

 

 


Creatinine Clearance

(calculated from creatinine measured in 24 hours urine and plasma collections)

Creatinine Clearance (mL/s) = {U Creat x Vol x 1000} / {Pl Creat x Time x 60 x 60}

Urine and plasma creatinine concentrations in mmol/L; Volume in mL

For serum creatinine measurements in umol/L:

Creatinine Clearance (mL/s) = {U Creat x Vol x 1000 x 1000} / {Pl Creat x Time x 60 x 60}

Urine creatinine concentration in mmol/L and serum creatinine concentrations in umol/L; Volume in mL


Reference Interval: 1.5 - 2.5 mL/s

Notes:
Creatinine excretions >20 mmol/d or <5 mmol/d may indicate prolonged or incomplete collections.
Plasma creatinine should be collected within the period of urine collection. Plasma creatinine from outside this period may be acceptable if renal function is stable.

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Calculated Creatinine Clearance (Cockcroft and Gault)

(estimated from plasma creatinine, age, wt and sex)

Creatinine Clearance (mL/s) = {(140 - Age)} x Wt x F}/ {P CREAT x 48816}

F= 1 (males); F=0.85 (females)
Age in years
Plasma creatinine concentration in mmol/L
Weight in kg

For serum creatinine measurements in umol/L:

Creatinine Clearance (mL/s) = {(140 - Age)} x Wt x F}/ {P CREAT x 48.816}

F= 1 (males); F=0.85 (females)
Age in years
Plasma creatinine concentration in umol/L
Weight in kg


Reference Interval: 1.5 - 2.5 mL/s

Notes:
Extremes of body composition may affect accuracy of estimation.
On-line Calculator for Cockcroft and Gault Equation

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Calculated Creatinine Clearance (Cockcroft and Gault) with
Lean body Mass estimated from patient height

(estimated from plasma creatinine, age, height and sex)

Creatinine Clearance (mL/s) = {(140 - Age)} x Wt x F}/ {P CREAT x 48816}

F= 1 (males); F=0.85 (females)
Age in years
Plasma creatinine concentration in mmol/L
Weight in kg

For serum creatinine measurements in umol/L:

Creatinine Clearance (mL/s) = {(140 - Age)} x Wt x F}/ {P CREAT x 48.816}

F= 1 (males); F=0.85 (females)
Age in years
Plasma creatinine concentration in umol/L
Weight in kg


Reference Interval: 1.5 - 2.5 mL/s

Estimated Lean Body Mass from patient's height:
Males (kg) = 50 kg plus 0.9 kg for every cm of height > 150 cm
Females (kg) = 45 kg plus 0.9 kg for every cm of height > 150 cm

Notes:
Extremes of body composition may affect accuracy of estimation.

On-line Calculator for Cockcroft and Gault Equation

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Fractional Excretion Of Sodium (FENA)

FENA(%) = {U Na / Pl Na x 100} / {U Cr / Pl Cr}

All concentrations in mmol/L

Interpretation:
In pre-renal renal failure FENA is generally <1%.

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Creatinine Clearance Per M2 Body Surface Area (BSA)

BSA(m2) = 0.0235 x Ht(cm)0.42246 x wt(kg)0.51456

CrCl(mL/s/1.73m2) = U CRCL(mL/s) x 1.73/BSA(m2)

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General Calculations


LDL Cholesterol (LDLC)

LDLC (mmol/L) = Total Cholesterol - HDLCholesterol - (Triglycerides / 2.2)

All values in mmol/L

Notes:
If the triglyceride concentration is > 4.5 the calculation is not valid and cannot be used.

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Transferrin Saturation (%SAT)

%SAT = 3.982  x  Iron (umol/L) / Transferrin (g/L)

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Indirect Bilirubin

Indirect Bilirubin (umol/L) = Total Bilirubin (umol/L) - Direct Bilirubin (umol/L)

Indirect bilirubin is a measure of unconjugated bilirubin
Direct bilirubin is a measure of conjugated bilirubin

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Calcium Corrected for Albumin

Used to correct plasma total calcium measurements for effects of changes in albumin concentration. Corrected calcium can then be compared with usual reference intervals.

Calcium (corrected, mmol/L) = Calcium (measured, mmol/L) + {(40 - albumin (g/L)) x 0.02}

Notes:

  • The correction can be applied to elevated as well as decreased serum albumin
  • The correction only applies to total calcium
  • The correction is a guide only.

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Last Updated 16/12/2004
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