Today, in the complex diagnosis of many diseases, laboratory methods of examination are used. In this case, a biochemical blood test is performed.
Alkaline phosphatase: general characteristics of the enzyme
Alkaline phosphatase is one of the important indicators. This compound is an enzyme that exhibits phosphatase activity. It is present in almost all cells of the human body. Its maximum activity is manifested in an alkaline environment and is associated with cell membranes. The highest concentration of this compound is recorded in osteoblasts (bone tissue cells), in the cells of the liver and renal tubules, in the intestinal mucosa, and also in the placenta. Alkaline phosphatase, which is contained in the blood serum, usually comes from bone tissue or hepatocytes. Its high activity is observed mainly in liver diseases that occur with obstruction of the bile ducts, as well as in bone lesions, which are accompanied by bone tissue remodeling.
Alkaline phosphatase level is high. Why?
There are many pathological conditions in which increasedalkaline phosphatase. The norm of this indicator depends on age and gender, so this is taken into account when interpreting a biochemical blood test.
Among the etiological factors that can affect the level of enzymes, including alkaline phosphatase, are the following:
• pregnancy;
• post-menopause;
• inadequate dietary intake of calcium and phosphate;
• excess ascorbic acid in the body;
• Use of certain pharmacological drugs (eg, contraceptives containing estrogen and progesterone, and antibiotics).
In addition, alkaline phosphatase may be increased in the following conditions:
• hyperparathyroidism;
• kidney or lung tissue infarction;
• multiple myeloma;
• infectious mononucleosis;
• bone lesions, including cancer;
• lymphogranulomatosis, which occurs with the destruction of bones;
• rickets;
• malignant lesion of the biliary tract;
• inflammation of an infectious nature or cirrhosis of the liver, its tuberculous lesion.
Etiology of decreased alkaline phosphatase
There are a number of pathologies in which, on the contrary, alkaline phosphatase is reduced. So, the level of this enzyme is below normal in hypothyroidism. Bone dysplasia, zinc and magnesium deficiency, and anemia are etiological factors that can affectamount of alkaline phosphatase in blood serum. Taking certain medications also changes test results. In addition, the presence of scurvy, which develops due to a lack of ascorbic acid, leads to a decrease in this enzyme.
It should be noted that during pregnancy, alkaline phosphatase can increase due to an increase in the amount of placental isoenzyme. This is typical for the final stages of pregnancy and is associated with the maximum development of the placenta. This pattern has no diagnostic value, therefore, it is not used to assess the condition of the mother or fetus. In cases where a woman is diagnosed with placental insufficiency, the concentration of this enzyme compound decreases.
Features of changes in the level of alkaline phosphatase
Alkaline Phosphatase comes in the form of several isoenzymes. The degree of increase in the concentration of this compound correlates with osteoblastic activity (with the process of bone formation), therefore, the highest level of bone isoenzyme is observed in Paget's disease. If a patient develops pathologies with osteolytic activity (for example, multiple myeloma), then alkaline phosphatase increases, but only slightly.
With lesions of the hepatobiliary system, the hepatic isoenzyme increases. In clinical practice, it is used as a marker of cholestasis. In this case, direct damage to liver cells can occur against the background of a normal or even low level of alkaline phosphatase. This pattern is typical for mostclinical cases, although it may not be observed in a particular patient even with damage to the liver or biliary tract.
It is worth noting that the alkaline phosphatase in a child is elevated - a physiological phenomenon that is associated with active growth. So, the level of this enzyme in childhood can reach a level that exceeds the norm for an adult by 1.5-2 times (from 82 to 341 U/l).
Specificity of determining the level of alkaline phosphatase
Today, the optimal conditions for conducting an analysis for determining the concentration of alkaline phosphatase are different, since each laboratory has its own standards. There are several test methods that depend on the enzyme substrate and buffer system, as well as on the temperature at which the samples are taken. There are no uniform boundaries for the “alkaline phosphatase” indicator, so you should not compare the values of this enzyme, which were obtained in different laboratories. This is especially true in cases where it is not known what standards these laboratories set.
Blood serum is used for analysis. In most cases, the top layer is taken, which is formed in the separator tube. It is worth noting that the level of alkaline phosphatase may be erroneously increased if the tourniquet on the upper limb was applied for more than 30 seconds during blood sampling. In addition, the activity of this enzyme may change slightly if blood samples are stored at room temperature. At the same time, hemolysis in vitro does not affect the results of the analysis.
What to do with a pathological level of alkaline phosphatase?
When alkaline phosphatase is elevated, treatment should be etiological. So, in the presence of diseases of the liver or bile ducts, it is worth consulting with a gastroenterologist. Cholestasis, the presence of pancreatitis, alcoholic hepatitis or cirrhosis of the liver requires appropriate medical correction, the amount of which is determined only by a doctor. Self-medication in this case can lead to an exacerbation of the underlying disease.
Changes in the concentration of enzymes, including alkaline phosphatase, can be observed in heart failure, cancerous pathologies and severe kidney damage, as well as in diabetes mellitus, so you should consult a cardiologist, nephrologist or endocrinologist. The doctor will determine the therapeutic tactics depending on the clinical picture.
When the etiological factors are eliminated, the activity of alkaline phosphatase returns to normal. When prescribing therapy, it should be taken into account that, for example, a physiological increase in this indicator is possible with fractures, active growth of the skeletal system, and during gestation. It does not require medical intervention. The interpretation of the results of laboratory tests should be carried out comprehensively, taking into account other biochemical parameters and patient complaints.
