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Principle: The detection is based on the pseudoperoxidative activity of hemoglobin and myoglobin, which catalyze the oxidation of an indicator by an organic hydroperoxide, producing a green colour.
Evaluation: The minimum sensitivity of the test strip is 5 to 10 erythrocytes/μl urine corresponding to approx. 0.015 mg hemoglobin or myoglobin/dl urine. Intact erythrocytes are indicated by flecked discolourations of the test field. The colour fields correspond to the following values:
0 (negative), ca. 5-10, ca. 50, ca. 250 Ery/μl,
or a hemoglobin concentration out of ca. 10, ca. 50, ca. 250 Ery/μl.
The blood test on Medi-Test urine test strips is optimally protected against interferences by ascorbic acid. Even with 40 mg/dl of ascorbic acid the tests provide safe results. Only for Combi 11 ascorbic acid in the sample may lead to false negative readings. For Combi 10® SGL and URYXXON® Stick 10 normal concentrations of ascorbic acid (< 40 mg/dl) do not influence the test result. However gentisic acid still shows an inhibitory effect. Falsely positive reactions can be produced by a residue of peroxide-containing cleansing agents.
Diagnosis: Every positive reaction should be taken as a pathological finding requiring further diagnostic examinations. Hematuria (hemolysis of intact erythrocytes occurs on the test field), hemoglobinuria or myoglobinuria are frequently caused by: Serious infections of the kidneys and urinary tract, kidney and bladder calculi, serious poisonings (e. g. benzene and aniline derivatives, chlorate, bacteria toxins, poisonous mushrooms and snake poison), heart attack, hemolysis after transfusion incident, cold hemoglobinuria or march hemoglobinuria (after strong physical exertion), different paroxysmal hemoglobinurias and serious hemolytic anemias.
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