Special Quality Controls

Acute alcohol consumption can be detected by the direct detection of alcohol (ethanol) in the blood (serum or plasma). The measured blood alcohol level can be used to draw relatively reliable conclusions about alcohol levels over a few hours. Alcohol is broken down in the liver by alcohol dehydrogenase (ADH) via acetaldehyde to acetic acid. The rate of degradation varies from individual to individual, with women degrading on average 15 % more slowly than men. Endogenous alcohol does not exceed 0.012 ‰ (per thousand) and therefore need not be taken into account in measurements.

The concentration of ammonia (NH3) in the blood should be determined in cases of changes in consciousness or coma with unclear findings, as well as in infants who vomit constantly or are unusually lethargic. Ammonia is produced in the intestine with the help of bacteria by splitting proteins into amino acids and ammonia. Via the portal vein the ammonia is transported to the liver where it is broken down to urea and glutamine. The urea is then transported to the kidneys and excreted with urine. If this process does not function sufficiently, ammonia accumulates in the blood and can enter the brain, resulting in hepatic encephalopathy (liver-brain disorder). This is a functional disorder of the brain, which can lead to mental and neurological changes with deterioration of cognitive and motor skills up to epileptic seizures, loss of consciousness and coma. Causes of increased ammonia levels can be defects in the urea cycle, severe liver disease, reduced blood flow to the liver, Reye’s syndrome, kidney failure or hereditary hyperammonemia (hereditary ammonia excess).

Cystatin-C is produced endogenously at a constant rate by almost all nuclear cells in the human body. The serum concentration depends on the glomerular filtration capacity of the kidney. With a reduced GFR the concentration of cystatin C increases. Cystatin C concentration is not influenced by age, sex, muscle mass, nutrition and inflammatory processes (except immune diseases). Cystatin C is elevated in renal insufficiency and autoimmune diseases.