Estimation of alkaline phosphatase in serum - liver function tests

    Liver Function Tests
    Estimation of alkaline phosphatase in serum

    Introduction
    • Phosphatase are enzymes which catalyze the splitting of phosphoric acid from certain mono phosphoric esters such as (glycerophosphates and phenyl phosphates)
    • Alkaline phosphatase with a maximum activity at about PH 10


    Principle
    • Alkaline phosphatase in serum acts on the substrate disodium phenyl phosphate  buffered at PH 10 at 37ᵒ to liberate phenol
    • This phenol condenses with 4- amino antipyrine in the presence of alkaline oxidizing agent potassium ferricyanide to give red colored complex which is measured at 520 nm
    Normal range                   
    • Alkaline phosphatase : 21 – 92 IU / L or 3 – 13 KA units
    • Note : one IU of ALP activity = 7.13 KA units
    Reagents
    • Buffered substrate PH 10
    • Phenol std
    • Chromogen reagent 4 – amino antipyrine 0.6 % , potassium ferricyanide 2.4 %


    Procedure
    Reagent
    Blank
    Standard
    Test
    Buffered substrate PH 10
    0.5 ml
    0.5 ml
    0.5 ml
    D / W
    1.55 ml
    1.55 ml
    1.55 ml
    Mix well and incubate at 37ᵒ for 15 min
    Serum
    -
    -
    50µ
    Phenol STD
    -
    50µ
    -
    Mix well and incubate at 37ᵒ for 15 min
    Colored reagent
    1 ml
    1 ml
    1 ml
    Mix well and read at 520 nm

    Calculation
    • ALP activity (IU/L) =


    Serum ALP levels are increased in:
    • Liver diseases: enzyme is produced by the hepatocytes canaliculi and hence marked increase is seen in condition of obstruction of bile flow
    • Extrahepatic biliary obstruction due to : stones in bile duct , cancer of head of pancreas
    • Intrahepatic biliary obstruction due to : viral / drug induced hepatitis or malignancy
    • Bone diseases: when osteoblastic activity in bone formation is take place like in:
    • Rickets : values of ALP more than 100 KA units can be seen
    • Osteomalacia : less rise than in rickets
    • Paget’s disease : very high values seen
    • Others: fanconi’s syndrome, hyperparathyroidism
    Serum ALP levels are decreased in:
    • Severe anemia
    • Malnutrition


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