| Metabolism | A | B | C | D | F | G | H | K | L | M | N | O | P | S | A-Z |
| Specimen | Reference range | Dimension | Method * | ||||||||||||||||||||||||||||||||||||||||||||||||
| ORGSU | Organic acids in urine |
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see report |
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| General | Organic acidurias are inherited disorders resulting from a deficient enzyme or transport protein. Although most are autosomal recessive disorders, several are X-linked. The more than 60 described organic acidurias affect many metabolic pathways including amino acid metabolism, lipid metabolism, purine and pyrimidine metabolism, the urea cycle, the Krebs cycle, and fatty acid oxidation. These disorders are characterized by a wide variety of symptoms such as lethargy, coma, hypotonia, seizures, ataxia, vomiting, failure to thrive, developmental delay, liver disease, neutropenia, thrombocytopenia, osteomalacia, and osteoporosis. Severity of presentation is highly variable as is age of onset, and patients may not present with the most characteristic features. Laboratory results commonly indicate metabolic acidosis, increased anion gap, hyperammonemia, hypoglycemia, lactic acidemia, ketosis, or abnormal lipid patterns. Treatment may be based on dietary restrictions and/or supplementation with cofactors (e.g., riboflavin or cobalamin) or conjugating agents (e.g., carnitine or sodium benzoate); however, there is no effective therapy for some of the disorders. The following parameters will be investigated by LCMS: 2,3-dihydroxy-2-methylbutyric acid, 2,4-dihydroxybutyric acid, 3,4-dihydroxybutyric acid, 2-ethyl-3-hydroxypropionic acid, 2-hydroxybutyric acid, 2-hydroxyglutaric acid, 2-hydroxyisovaleric acid, 2-ketoglutaric acid, 2-methyl-3-hydroxybutyric acid, 2-methylsuccinic acid, 2-methyl citrate, 2-oxoadipic acid, 2-oxoisocaproic acid, 3-hydroxy-3-methylglutaric acid, 3-hydroxybutyric acid, 3-hydroxyglutaric acid, 3-hydroxyisobutyric acid, 3-hydroxyisovaleric acid, 3-hydroxypropionic acid, 3-methylglutaconic acid, 3-methylglutaric acid, 3-phenyllactic acid, 4-hydroxybutyric acid, 4-hydroxyphenylpyruvic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenyllactic acid, acetoacetate, adipic acid, succinic acid, pyruvate, ethylmalonic acid, Fumaric acid, glutaric acid, glyceric acid, glycolic acid, glyoxylic acid, homogentisic acid, lactate, malate, malonic acid, methylmalonic acid, mevalonic acid, N-acetylaspartic acid, N-acetyltyrosine, orotic acid, oxalic acid, phenylpyruvic acid, pyroglutamic acid (5-oxoproline), sebacic acid, suberic acid, succinylacetone, vanillic lactic acid, 2-methylbutyrylglycine, 3-methylcrotonylglycine, N-butyrylglycine, N-hexanoylglycine, N-isovaleroylglycine, phenylpropionylglycine, propionylglycine, suberylglycine, tiglylglycine. |
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| Indication | Suspicion of hypoglykemia, laktacidosis, ketosis | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Preanalytics | When collecting the spontaneous urine sample, bacterial contamination should be avoided as this can have a negative influence on the analysis.
It is therefore generally recommended: The preserved sample can be shipped at room temperature or refrigerated (stability at RT approximately 3 days and 2-8°C approximately 1 week). However, no data is available on whether these additives can act as a disturbing factor in case of strongly extended storage/transport times (>1 week). Thus, frozen native urine is the preferred sample type. Upon receiving unfrozen spontaneous urine, the laboratory assumes that this is a chemically preserved sample. When frozen spontaneous urine is received, on the other hand, a native urine is assumed and the sample is also forwarded to the performing laboratory on dry ice. |
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| Evaluation | Elevation of one or more organic acids is diagnostic for an organic aciduria; however, elevations should be interpreted in context with clinical findings and/or additional test results. Since many organic acidurias are episodic, the diagnostic efficacy is maximized when the patient is expressing symptoms at the time of specimen collection.
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| Specimen | Reference range | Dimension | Method * | ||||||||
| OLDL | Oxidated LDL |
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ng/mL |
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| General | Oxidation modification of LDL (OxLDL) is postulated to be one of the earliest events in the initiation of atherogenesis. OxLDL is present in aortas of human fetuses of hypercholesterolemic mothers, even prior to macrophage foam cell formation, in progressing atherosclerotic lesions of animal models and within human vulnerable plaques. OxLDL is found primarily in the atherosclerotic plaque and not in normal arteries. Conceptually, OxLDL is not a single defined chemical entity but represents a variety of modifications of both the lipid and protein components of LDL following initiation of lipid peroxidation. The resulting oxidized lipid and oxidized lipid-protein adducts are not only pro-inflammatory but are also recognized as foreign by the immune system and therefore are highly immunogenic. Circulating oxidized LDL does not originate from extensive metal ion-induced oxidation in the blood but from mild oxidation in the arterial wall by cell-associated lipoxygenase and/or myeloperoxidase. Oxidized LDL induces atherosclerosis by stimulating monocyte infiltration and smooth muscle cell migration and proliferation. It contributes to atherothrombosis by inducing endothelial cell apoptosis, and thus plaque erosion, by impairing the anticoagulant balance in endothelium, stimulating tissue factor production by smooth muscle cells, and inducing apoptosis in macrophages. However, oxLDL is also involved in triggering adaptive immunity pathways involved in the pathogenesis of atherosclerosis. T cell activation appears to be linked to LDL modification since peptides derived from oxLDL have been shown to be recognized by T cells. Most forms of modified LDL are immunogenic and induce the formation of autoantibodies in humans. A direct consequence of autoantibody synthesis against modified LDL is the formation of immune complexes. These immune complexes are detectable both in serum and in the atheromatous plaque, where both oxLDL and oxLDL antibodies have been found. Increased LDL oxidation is associated with coronary artery disease. The predictive value of circulating oxidized LDL is additive to the Global Risk Assessment Score for cardiovascular risk prediction based on age, gender, total and HDL cholesterol, diabetes, hypertension, and smoking. |
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| Indication | Risk assessment for cardiovacular diseases, arteriosclerotic plaques involvement, diet monitoring | ||||||||||
| Preanalytics | Stability of sample: Room temperature: 4-8 hours Refrigerated (4-8°C): 24 hours Frozen (-20°C): 2 years |
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