Interference in autoanalyzer analysis |
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Authors: | J J Fleming S Swaminathan |
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Institution: | (1) Department of Clinical Biochemistry, Christian Medical College and Hospital, 632 004 Vellore, Tamil Nadu |
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Abstract: | This paper presents certain simple procedures for assessing the most common types of interference, due to haemolysis, icterus
or lipaemic serum in 19 routine Clinical Chemistry tests and suggests steps to overcome the problem in some tests. A change
in the measured concentration, to be analytically significant, had to exceed 2.8 X % coefficient of variation (cv) of the
intra-assay analytical variation of each assay. Haemolysis caused interference in 10 of the 19 assays investigated. A haemolysate
haemoglobin concentration of 0.29 g/dl, visible to the eye, caused an analytically significant increase in creatinine kinase
MB subunit (CKMB), lactate dehydrogenase (LDH), total protein, triglyceride, uric acid and urea, and a significant decrease
in alkaline phosphatase (ALP), and total bilirubin. A higher concentration of haemoglobin (0.68 g/ dl) caused an additional
significant increase in CK, and a decrease in direct bilirubin. Addition of bilirubin caused interference in all the peroxidase
linked reactions as well as in the creatinine assay. At a serum concentration of 5.2 mg/dl it caused a decrease in creatinine,
glucose, triglyceride and uric acid. At a higher concentration (15.9 mg/dl) it also decreased cholesterol. Lipaemia interference
affected the least number of assays. An added triglyceride of 537–561 mg/dl caused an increase in glucose, uric acid, and
amylase. At a level of 1122 mg/dl it also increased CKMB, and at a value of 2244 mg/dl it increased total and direct bilirubin.
At the highest levels of haemolysis and lipaemia, the serum glutamate oxaloacetate transaminase (GOT) and giutamate pyruvate
transaminase (GPT) gave erratic results. Overall uric acid and CKMB were the analytes most susceptible to interference, while
serum caicium and phosphate did not suffer from any. The interference depends on the exact assay conditions used and the susceptibility
of each individual laboratory's tests should be determined by them. The reasons for the interferences described are discussed. |
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Keywords: | Bilirubin Haemolysis Icterus Assay interference |
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