Ketones Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Ketones and links to relevant pages within the course.
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| Excessive carbohydrate loss that may occur due to vomiting, or rapid weight loss may result in the presence of which of following substances not normally contained in the urine? | View Page |
| Match the following reagent strip tests to the disease or disorder that would most likely cause a positive test result. | View Page |
| False Negative Results False negative results occur when elements present in the urine interfere with either the enzymatic reaction or prevent the oxidation of potassium iodide. Examples of such substances include: large quantities of ketones aspirin ascorbic acid > 50 mg/dL with some reagent strips levadopa 5-hydroxyindoleacetic acid homogentisic acid sodium fluoride ( a preservative)A specific gravity higher than 1.020 may lower glucose reagent sensitivity, especially in the presence of a high urine pH. Exposing reagent strips to excess humidity may also reduce glucose reagent reactivity.Check the package insert of the reagent strips used in your laboratory for interfering substances that may affect glucose results. | View Page |
| A copper reduction method (e.g. Clinitest® or Benedict's) is performed on pediatric specimens in order to check for the presence of: | View Page |
| Three Kinds of Ketones When the body breaks down fat for energy, three intermediate products are formed. These products, collectively referred to as ketones, are acetone, acetoacetic acid, and beta-hydroxybutyric acid. Normally, the body gets the energy it needs from carbohydrates in the diet. However, stored fat is broken down and ketones are produced and appear in the urine if the diet does not contain enough carbohydrate to supply the body with glucose for energy or if the body cannot use glucose properly. | View Page |
| Testing for Ketone Bodies Testing for ketone bodies is based on a nitroprusside reaction. Acetoacetic acid reacts with sodium nitroferricyanide and glycerine in an alkaline medium to produce a violet-to-purple colored complex. The reagent strip method can detect as little as 5 mg/dL acetoacetic acid in urine. It does not react with acetone unless glycine is present or B-hydroxybutyric acid. Since these two compounds are derived from acetoacetic acid, their presence can be assumed if the test for ketones is positive. Ketones are reported either as negative, small, moderate or large amounts; or negative, 1+, 2+, 3+, or 4+. In some severe cases of ketosis, it may be necessary to perform tests on serial dilutions to provide more information on the quantity of ketones present. | View Page |
| Ketone Bodies Ketone bodies are usually absent in urine, but low levels may be detected during conditions of physiological stress such as fasting, rapid weight loss, frequent strenuous exercise or prolonged vomiting. The presence of ketones in these situations is due to either inadequate intake or increased loss of carbohydrates. High levels of ketones are present in the urine of individuals with uncontrolled diabetes. In diabetes the ketones are present because the body's ability to metabolize carbohydrates is defective. | View Page |
| False Negative Results The presence of excess moisture/humidity can cause the ketone reagent to become nonreactive, resulting in a false negative test for ketones. Urine specimens should not remain at room temperature if testing is delayed because ketones are unstable at room temperature. | View Page |
| Clinical Significance of Positive Urine Ketone Result Ketone bodies are usually absent in urine. High levels of ketones are present in the urine of individuals with uncontrolled diabetes. In diabetes the ketones are present because the body's ability to metabolize carbohydrates is defective. Detecting the presence of ketones in the urine is a valuable aid to managing and monitoring individuals with diabetes mellitus. Ketonuria is an indication that the insulin dose needs to be increased. It is also an early indicator of insulin dosage problems in juvenile diabetes or in diabetics experiencing other medical problems. Electrolyte imbalance and dehydration occur when ketones accumulate in the blood. If these conditions are not corrected, the patient may develop acidosis and ultimately diabetic coma. Low levels may be detected during conditions of physiological stress such as fasting, rapid weight loss, frequent strenuous exercise or prolonged vomiting. The presence of ketones in these situations is due to either inadequate intake or increased loss of carbohydrates. | View Page |
| Which of the following substances can cause a false positive result for ketones? (Choose ALL of the correct answers) | View Page |
| Significantly increased levels of ketones are detected in the urine with which of the following conditions? (Choose ALL of the correct answers) | View Page |
| What is the largest constituent of plasma nonprotein nitrogen: | View Page |
| Causes of Ketonuria Under conditions of abnormal carbohydrate metabolism such as occurs in diabetes mellitus, ketones accumulate in the blood (ketonemia) and are excreted in the urine (ketonuria). The accumulation of ketone bodies is often the cause of acidosis and coma in diabetics. | View Page |
| Correlation of Urine Glucose and Ketones It is important to test for urinary (and plasma or serum) ketones when any patient shows a greater than normal excretion of sugar or reducing substances. Screening for ketonuria is useful in following the effects of treatment for diabetes and in judging the severity of acidosis. Large amounts of ketones will appear in the urine before serum ketone levels are elevated. | View Page |
| Urinary Ketones Ketone bodies are formed in the liver as intermediates in the catabolism of fatty acids. In normal, healthy individuals, ketone bodies are almost completely metabolized so that only negligible amounts appear in the urine. | View Page |
| The Acetest® Urine to be screened for ketone bodies should be tested immediately or refrigerated in a closed container since acetone is lost to the air if the sample is left standing at room temperature for any length of time.
The Acetest® can be used for the semiquantitation of ketones in urine, serum, or whole blood, however the reaction times differ depending on the type of specimen tested. The same substances which interfere with the dipstick tests for ketones will also interfere with Acetest® because the same reaction is involved.
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