
Alkaline phosphatase (ALP) is a protein found in all body tissues, with higher amounts present in the liver, bile ducts, and bones. A blood test is often used to measure ALP levels to diagnose liver or bone disease, evaluate the effectiveness of treatments, or check for medication side effects. Normal ALP values range from 44 to 147 international units per liter (IU/L) or 0.73 to 2.45 microkatal per liter (µkat/L), but these values can vary across laboratories and are typically higher in children experiencing growth spurts and pregnant women. While elevated ALP levels in infants may indicate bone disease or transient hyperphosphatasemia, further evaluation is often required to determine the underlying cause and establish a definitive diagnosis.
Characteristics | Values |
---|---|
Normal range | 44 to 147 international units per liter (IU/L) or 0.73 to 2.45 microkatal per liter (µkat/L) |
Normal value variations | Age and sex |
High levels of ALP | Children undergoing growth spurts and pregnant women |
What You'll Learn
Alkaline phosphatase (ALP) as an early biomarker for osteopenia of prematurity
Alkaline phosphatase (ALP) is an enzyme that can be found in the liver, bile duct, kidney, intestine, and bones. In newborns, ALP levels can be used as a biomarker for osteopenia of prematurity, which is a condition characterised by reduced bone mineral content. This condition is common in very low birth weight (VLBW) infants due to a lack of fetal mineralisation during the last trimester of pregnancy.
A study conducted on 120 newborn infants in Cairo, Egypt, aimed to assess serum ALP levels as an early biomarker for osteopenia in premature infants. The study found that infants with osteopenia had significantly higher mean ALP levels than those without. Additionally, birth weight and gestational age were inversely related to serum ALP levels. The optimal cutoff value of serum ALP for detecting osteopenia was found to be 500 IU/L, with 100% sensitivity and 80.77% specificity.
Another study in France also found that ALP levels greater than 500 UI/L at day 15 of life could be an early biomarker for metabolic bone disease in VLBW infants. This study concluded that early screening with ALP levels could be sufficient for the detection of metabolic bone disease and could help prevent osteopenia.
In summary, ALP levels can be a reliable biomarker to predict bone mineralisation status and the need for radiological evaluation in premature infants, especially those with low birth weight and gestational age.
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ALP levels in infants with hepatitis
Alkaline phosphatase (ALP) is an enzyme found throughout the body, with the highest concentrations in the bones, liver, and intestines. It is involved in various bodily processes, such as transporting nutrients and enzymes in the liver, aiding bone growth, and regulating cell growth during fetal development.
An ALP blood test is used to measure the level of ALP in the blood, and it is often included in a comprehensive metabolic panel (CMP) or liver panel. While an ALP test alone cannot diagnose a specific condition, high levels of ALP in the blood may indicate liver disease or certain bone disorders.
In infants with hepatitis, ALP levels can vary from normal to significantly elevated. A study found that infants with hepatitis who received daily doses of vitamin D exceeding 2,400 IU from the third to fourth weeks of age exhibited normal ALP values. In contrast, infants with hepatitis who received lower doses of vitamin D showed high serum ALP values. This suggests that elevated ALP levels in infants with hepatitis may be associated with secondary vitamin D deficiency.
It is important to note that ALP levels can be influenced by various factors, such as age, sex, and vitamin D supplementation. Therefore, healthcare providers consider an individual's overall health, symptoms, and results of additional tests when interpreting ALP levels.
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ALP levels in infants with biliary atresia
Alkaline phosphatase (ALP) is an enzyme found in the liver, bones, intestines, placenta, kidneys, and leukocytes. Normal ALP levels in newborns range from 8.7 to 28.3 King-Armstrong units, with a mean of 15.3 ± 5.9.
Biliary atresia (BA) is a rare disease that affects newborn infants and is characterised by an obstruction of the bile ducts. BA presents with persistent jaundice, hepatosplenomegaly, clay-coloured stool, and dark urine. Laboratory tests for BA reveal direct hyperbilirubinemia and variable levels of transaminases, gamma-glutamyl transpeptidase (GGT), and ALP.
Preoperative ALP levels can be a potential predictor of the short-term outcome of surgery in infants with BA. Lower ALP levels are significantly associated with a successful surgical outcome. A cutoff level of 532.5 U/l or less can predict a successful Kasai hepatoportoenterostomy (HPE) with 75.9% sensitivity and 74.4% specificity.
In summary, while ALP levels can vary in infants with BA, lower levels are generally indicative of a better prognosis, and higher levels may predict a poor outcome.
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ALP levels in infants with parenteral nutrition-associated liver disease
Alkaline phosphatase (ALP) is an enzyme found throughout the body, with the liver and bones being the two main sources of ALP in the blood. Normal ALP levels vary with age and sex, with levels typically elevated during childhood and puberty due to bone growth and development.
Regarding ALP levels in infants with parenteral nutrition-associated liver disease (PNALD), elevated ALP levels can be observed. A study by Prathima Nandivada et al. found that in 15 infants with PNALD, the elevation in total ALP was due to marked elevations in bone-specific ALP rather than liver-specific ALP. This suggests that elevated ALP in these infants may reflect bone disease rather than liver disease alone.
Another study by S M Gabe and A Culkin investigated abnormal liver function tests in patients receiving parenteral nutrition, including neonates and infants. They found that abnormalities in liver function tests were common, with alkaline phosphatase being the most common abnormality. The incidence of abnormal liver function tests increased with the duration of parenteral nutrition, with 90% of neonates receiving parenteral nutrition for more than 3 months developing cholestasis.
It is important to note that the elevation of ALP levels in PNALD can be influenced by various factors, such as the duration of parenteral nutrition, birth weight, prematurity, and other nutritional and patient-related factors. Overall, elevated ALP levels in infants with PNALD may indicate underlying bone disease or liver disease, and further investigations are often needed to determine the specific cause.
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Transient hyperphosphatasemia (THP) in infants
Transient hyperphosphatasemia (THP) is a benign condition characterised by a marked, temporary elevation of serum alkaline phosphatase (ALP) without any associated diseases, such as those affecting the liver, bone or kidneys. THP mainly occurs in infants and children, and rarely in adults.
The condition is characterised by a return of ALP to normal levels within weeks or months of the initial observation. The exclusion of other causative illnesses before establishing a diagnosis of THP is paramount. Awareness of this condition is important for both parents and clinicians to avoid unnecessary concerns and investigations.
The prevalence of THP is not known in Saudi Arabia or worldwide. In a series of 260 healthy infants, 1.5% (n=3) had unexplained and transient elevations in ALP, with more than three times the upper limit of the normal range. In a prospective study of 316 healthy infants and toddlers, 2.8% had THP, with a serum AP >1000 U/L.
The childhood incidence of THP may exceed 2.8%, as 5.1% of infants in the study had an intermediate serum AP level between 400 and 1000 U/L. This intermediate group may represent children in whom THP is developing or resolving.
The mechanism of elevation in AP remains controversial. In THP, the liver and/or bone isoenzyme levels appear to be increased. The serum AP elevation might arise from a temporary increase in the release of AP from the liver and bone, or an increase in sialylation of the enzyme, resulting in reduced hepatic clearance from the circulation.
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Frequently asked questions
The normal range of alkaline phosphatase is 44 to 147 international units per liter (IU/L) or 0.73 to 2.45 microkatal per liter (µkat/L).
High levels of alkaline phosphatase in newborns can be caused by osteoblastic bone tumors, Paget disease of bone, or growth spurts.
Low levels of alkaline phosphatase in newborns can be caused by alcoholic liver disease, giant cell arteritis, or multiple endocrine neoplasia (MEN) II.
Alkaline phosphatase levels are measured through a blood test, usually by drawing blood from a vein located on the inside of the elbow or the back of the hand.
Alkaline phosphatase levels in newborns typically return to normal within a few months without any intervention.