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Biochemical analysis items should be set in this order. Have you ever paid attention to this problem?
Added:2019-05-21     Views:

The interference of reagents in the automatic biochemical analyzer affects the accuracy and reliability of the test results, which brings great deviation to the test results. Sometimes, it even mislead the clinician and delay the patient's condition, and cause serious consequences.Therefore, it is very important and urgent to avoid the interference between reagents in the daily biochemical test work.




Let's have a look or reference first

Common biochemical items can be detected in the following order


P、Alb、DBIL、TBIL、K、Ca、CK、TBA、TG、AFU、ALT、CK-MB、APOA1、T-CH、APOB、Cl、HDL-C、LP(a)、AST、GPDA、AMY、LDL-C、BUN、UA、CHE、ADA、r-GT、Mg、Na、ALP、LDH、GPDA、TP、Cr。


We usually pay attention to this problem. Maybe most of our colleagues don't pay much attention to it. Why do we do this? How do we check whether this problem exists and how to solve it when there is a problem? Let's have a look......



Types of interference between reagents



The reagent contains the substrate to be determined by the next test, or the reagent component contains the substrate of the next reaction, thus directly interfering with the determination result of the next reaction; the other is that the reaction led by the reagent has indirect interference with the reaction process of the next project, because in the case of reagent pollution, the next test determines the front and rear The results of the comprehensive action of the two project responses. The possible interference between some known common reagents is as follows:

1. PH change: the pH value of the next reaction is changed due to the contamination of the instrument between reaction buffer solutions in the reagent, so that the next reaction can not reach the optimal state. If the other conditions are the same, the peptide bond (CONH) can react with the alkaline copper solution to produce purple reaction, and the total amount of serum protein can be measured completely. If pH is less than 8, the total protein determination results are low, which directly affects the results of globulin and albumin / globulin. The enzyme activity was the fastest and the highest sensitivity when the optimum pH value was determined. However, because of the limited buffer capacity, the enzymatic reaction could be ineffective due to the pollution. The pH value of most enzyme reactions is between 6.0-7.5, ALP, γ - GT and LDH should be the most suitable in alkaline condition.

2. The TG, t-ch, UA, Mg reagents contain bile acid salts, which can cause serious interference to the determination of bile acids by cyclic enzyme method.

3. ALT (IFCC) and AST (IFC) reagents contain high activity LD components, which may interfere with the determination of LD.

4. The components of Glu are contained in CK (NAC activated) and CK MB (NAC activated) reagents. The principle of the analysis method includes the reaction process of Glu glycosylated kinase (HK), so it may interfere with the determination of Glu, especially the HK method of Glu.

5. Magnesium salt is used in Glu (HK), CK (NAC activated), CK MB (NAC activated), TG, HDL-C, LDL-C (direct method), which may interfere with the subsequent determination of mg2+; cu2+ with high concentration in TP reagent may also interfere with the determination of mg2+.

6. Alt, AST, LDH, CK, CK MB, UA, r-GT, TP, LDH and other reagents interfere with k+ enzymatic determination because they contain k+ or have the same or opposite process as k+ enzyme method.

7. The use of phosphoric acid buffer solution by Che (butyrylthiocoline), TC (ch-pap), Glu (got Pap), UA (Uricae), α -hbdh (dgkc) may interfere with the determination of inorganic phosphorus.

8. Mg2+ reagent (calmagite) contains EGTA, which may interfere with the determination of ca2+ for ca2+ complexing agent.

9. CK test should not be before ALP and Ca detection, because EDTA Na was added into CK reaction solution, which could inhibit ALP activity, and combined with Ca, the results were low.

10. Due to the consumption of NADH by GLDH, bun enzyme method cannot be put in the substrate NADH such as ALT and AST items for detection.



Investigation and discovery of interference



In fact, the product specifications provided by various manufacturers can not reflect the composition of reagents in a comprehensive way, and the factors affecting biochemical reaction are quite complex. Therefore, it is more important to find the interference that the cross contamination of reagents may bring. The following tests can be used to detect and find the possible interference between reagents.

1. Take a reagent as a sample to carry out a complete set of project measurement, investigate the results, and then determine the items causing direct interference when cross contamination occurs; both R1 and R2 of the double reagents should be done, so that it is targeted in solving the interference.

2. One sample is divided into two parts, one with normal saline or other appropriate diluent, and the other with equal amount of reagent. Meanwhile, the changes of the results are measured and inspected to determine the items that may cause interference when cross contamination of reagents occurs.

3. If it is suspected that item a reagent interferes with item B, the sample can be used to do item B several times, then item a and then item B several times. Through statistical analysis, we can know the interference degree of reagent a through reagent against item b.




Elimination of interference



Through the analysis of the causes of the interference between the above common reagents and the investigation test of reagent interference, some measures can be taken to eliminate the interference between reagents. The common methods are as follows:

1. In order to reduce the mutual interference between reagents, the instrument should be maintained regularly, such as replacing the pipeline, cleaning the colorimetric cup with detergent and acid lotion, cleaning the reagent needle with detergent, and scrubbing the stirring rod with benzyl alcohol.

2. Reasonable arrangement of the sequence of test items: generally, when arranging the sequence of items, it is required that there should be at least one non interfering item between two items, and the most thorough way is to put the interfered item before the interfering item, so as to eliminate the possibility of interference. At the same time, inspectors are required to know the working state of the instrument well, and consider the possibility of reagent cross contamination when selecting the item of a sample or the last item of a sample and the first item of the next sample, so as to arrange the item order reasonably, so as to get more reasonable results.

The common biochemical items can be detected in the following order:

P、Alb、DBIL、TBIL、K、Ca、CK、TBA、TG、AFU、ALT、CK-MB、APOA1、T-CH、APOB、Cl、HDL-C、LP(a)、AST、GPDA、AMY、LDL-C、BUN、UA、CHE、ADA、r-GT、Mg、Na、ALP、LDH、GPDA、TP、Cr。

3. Some biochemical analyzers also have additional flushing function, which can flush the reagent probe and colorimetric cup twice or several times with acidic or alkaline detergent before the detection of interfered items, so as to reduce the cross contamination between items.

4. Some full-automatic analytical instruments have different channels, and the interference items can be arranged in different channels for detection.

5. Select the kit with anti cross contamination: for example, add cholesterol ester inhibitor to free cholesterol reagent to reduce the contamination of free cholesterol determination caused by cholesterol ester hydrolysis by cholesterol esterase.





Through the above methods, most of the cross contamination between reagents can be solved, In practical work, it is difficult to detect the detailed process of each reaction by using the automatic biochemical analyzer for continuous determination of multiple items. Therefore, we must have a good understanding of the working principle, method, process and state of the biochemical analyzer in practical work, as well as in-depth analysis of the composition and reaction principle of the test agent, Only in this way can we find out a set of methods that are in line with the work of our unit.



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