10 Reasons Why Biochemistry Analyzer Reagents Interfere with Each Other

Using a fully automatic biochemistry analyzer often reveals a common issue: when tests are conducted individually, results are accurate, but when combined, abnormalities arise. This interference between reagents can affect the accuracy and reliability of test results, leading to significant deviations that may mislead clinicians, delay patient treatment, and cause serious consequences.

Understanding Reagent Interference in Biochemistry Analyzers

1. Contaminated Cleaning Systems

As the automatic biochemistry analyzer is used over time, the effectiveness of its cleaning system can decline. This increase in reagent cross-contamination affects subsequent tests, leading to inaccurate results.

2. Substrate Contamination

Reagents may contain substrates or components that interfere with subsequent reactions. For example, if a reagent contains a substance that reacts with the next test's substrate, it directly skews the measurement results.

3. Indirect Reaction Interference

Contaminated reagents can indirectly affect the reaction process of the next test. The results of subsequent tests can be compromised by the combined effects of previous and current reactions.

Common Types of Reagent Interference

4. pH Changes in Reaction Buffers

Reagent carryover can alter the pH of the reaction buffer, preventing optimal reaction conditions. For example, total serum protein measured by the bicinchoninic acid (BCA) method requires an alkaline pH (8-9). A lower pH results in underestimation, affecting globulin and albumin/globulin ratio assays.

5. Bile Acid Salts in Reagents

Reagents for triglycerides (TG), total cholesterol (T-CH), uric acid (UA), and magnesium (MG) contain bile acid salts. These can interfere with enzyme methods used for determining bile acids.

6. Lactate Dehydrogenase (LD) Components

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) reagents contain high-energy LD components, potentially interfering with LD determination.

7. Glucose Components in Creatine Kinase Reagents

Reagents for creatine kinase (CK) and CK-MB contain glucose components. The hexokinase (HK) reaction in these assays can interfere with glucose determinations, especially those using the HK method.

8. Magnesium and Copper Interference

Reagents for glucose, CK, CK-MB, triglycerides, HDL-C, and LDL-C contain magnesium salts. High concentrations of Cu2+ in total protein (TP) reagents can also interfere with magnesium determinations.

9. Potassium Interference

Reagents for ALT, AST, LDH, CK, CK-MB, UA, γ-GT, and TP contain potassium. This can interfere with enzymatic potassium determinations, affecting test accuracy.

10. Phosphate Buffer Interference

Reagents for butyrylcholinesterase (ChE), total cholesterol (TC), glucose (GOD-PAP), uric acid (UA), and α-HBDH use phosphate buffers. These can interfere with inorganic phosphorus determinations.

11. EGTA in Magnesium Reagents

Magnesium reagents containing EGTA, a calcium-complexing agent, can interfere with calcium determinations.

12. EDTA-Na in CK Assays

EDTA-Na in CK reaction solutions inhibits alkaline phosphatase (ALP) activity and binds calcium, leading to low ALP and calcium assay results.

13. NADH Consumption in BUN Assay

The BUN enzyme assay consumes NADH due to glutamate dehydrogenase (GLDH). Performing this test before assays requiring NADH (e.g., ALT, AST) can result in inaccuracies.

Conclusion

Understanding and mitigating reagent interference in biochemistry analyzers is crucial for ensuring accurate and reliable test results. Regular maintenance of the analyzer's cleaning system and careful consideration of reagent interactions can help prevent these issues, ensuring that clinicians receive the correct information for patient diagnosis and treatment.