Abstract
BackgroundAlkaline phosphatase (ALP) enzymes are widely used as signal amplifiers in immunoenzymatic methods. Conditions that cause ALP elevations, such as bone or liver diseases, can cause interference in immunoenzymatic methods. We aimed to examine ALP's effect on immunoenzymatic assay by adding isolated pure ALP to the prepared serum pool.MethodsWe prepared a serum pool and divided it into 4 groups. By adding isolated pure ALP at different concentrations to each group, we obtained sample groups containing ALP enzyme at concentrations of 85 U/L, 340 U/L, 870 U/L, and 1570 U/L. 20-repetition of bhCG, ferritin, FT4, TSH, troponin I, and Vit B12 tests were performed in each group. The coefficient of variation, bias, and total error was calculated. All groups were compared by using the Friedman test for paired samples.ResultsAfter ALP addition, the calculated total error values of FT4, bhCG and troponin I tests were above the acceptable error limits. There were statistically significant differences in bhCG, FT4, troponin I, and Vit B12 tests compared to the baseline ALP level (P<0.0125).ConclusionsIsolated ALP elevations can be a source of interference for immunoenzymatic methods.
Highlights
Alkaline phosphatases (ALP; orthophosphate mono-ester phosphohydrolase EC 3.1.3.1) are homodimeric and glycoprotein enzymes in the hydrolase group with a molecular weight of 86 kilodaltons
We created a serum pool with 20 patients’ sera who have previously consulted our laboratory in January 2020 and whose ALP, beta human chorionic gonadotropin (bhCG), ferritin, FT4, thyroid-stimulating hormone (TSH), troponin I, and Vit B12 tests were found to be within the reference range
After adding ALP, in bhCG, calculated Total error (TE) values at ALP concentrations of 340 U/L and 1590 U/L were found to be above the acceptable error limits
Summary
Alkaline phosphatases (ALP; orthophosphate mono-ester phosphohydrolase (alkaline optimum) EC 3.1.3.1) are homodimeric and glycoprotein enzymes in the hydrolase group with a molecular weight of 86 kilodaltons. These groups of enzymes are commonly found in nature in both eukaryotes and most prokaryotes. ALP mainly functions as bound by hydrophobic glucosyl-phosphatidylinositol to the cell membrane [2] It is mostly found in the canalicular membrane of hepatocytes and bile duct epithelium lumen, bone osteoblasts, brush border membrane of the intestinal mucosa, placenta, proximal kidney tubules, and breast tissue during lactation. A healthy human serum contains four different ALP isoenzymes under normal conditions These are Intestinal ALP, Placental ALP, Germ cell ALP and tissue nonspecific alkaline phosphatase. The difference between the isoenzymes stem from the sialic acid found in them at varying rates, and the protein amount of the placental isoenzyme is different [2, 3]
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