Author: Shi Jianfei Li Qiao
Unit: Department of Clinical Laboratory, Xi'an Children's Hospital
The day's work has begun! We operate the AU5821 automatic biochemical analyzer every day as usual, this time due to the regular replacement and maintenance of the 1-unit module sample and reagent syringe the night before, and the retesting and calibration of the sample according to the situation. First of all, the AU5800 is maintained daily (check that the sample syringes, reagent syringes and cleaning water and ISE syringes replaced yesterday are leak-free, check that the cleaning agent peristaltic pump device has no leakage, etc.), the ISE unit is perfused and cleaned and calibrated, and after checking the sufficient number of all reagent units, everything is ready to start up.
The first item to be measured every day is the water gap detection to eliminate problems such as incorrect reagent addition, R1 and R2 position reversal, etc., this step is essential! When we thought that the reagent blank results were the same as before, the results were very different! It can be seen from the figure below that compared with the previous daily reagent water blank OD detection values, the detection values of 1 unit ALT and AST water blank OD all increased, the CK, TCHO, and TBA water blank OD detection values all decreased, and the UREA water blank OD detection values were not detected.
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Based on our work experience, this is definitely the result of systematic error, where is the reason?
Is it the problem with deionized water? AU5821 has 2 modules, immediately check the 2 unit reagent water blank OD detection value compared with before are normal, while the pure water electromechanical conductivity detected every day in the normal range, the filter element reverse osmosis membrane, etc. is also recently replaced, the morning instrument water is also newly taken deionized water, through the comparison to eliminate water quality problems, while to ensure bottle pollution, while re-taking water to select 1 unit of two reagents (Mg and ALB) items for computer detection, the results have not changed significantly, OD detection value is even lower.
At the same time as the above exclusion, we naturally thought that it was likely caused by the replacement of the syringe yesterday, and the syringe was checked before the start of the machine in the morning that there was no leakage and other problems, the syringe did not leak in the instrument work, the pressure spring in the syringe was stable, and there was no problem of insufficient suction and bubbles.
Look at the instrument alarm information in a display "sample probe clot", in order to eliminate the sample dosing needle blockage problem, in the instrument standby state, the sample dosing needle with a guide wire and ear wash bulbs are unblocked, while wiping the needle circumference with alcohol swabs, the sample dosing needle water circulation is not found clot and other impurities.
There is no error in the process of reagent addition, and the reagents such as Mg and ALB are single reagents, so the 1-unit reagent chamber is checked to eliminate the error of R1 and R2.
Observe the reaction curve of the reagent to see if the problem can be found.
The reaction of single reagent ALB and TP is detected by the endpoint method, and the absorbance will not be affected after adding water, and the detection value of the main wavelength and reaction OD in the detection range of the measurement point should not change much, and the secondary wavelength should not react. In the figure below, the main wavelength and secondary wavelength of the abnormal reaction curve in the morning show a wave shape, TP and ALB gradually decrease from the beginning of the addition of absorbance, and finally they all show a wave reaction, and the secondary wavelength is reacted; the double reagent UREA reduces the absorbance from the beginning and shows a wavy line, and after R2 joins the reaction, the sub-wavelength reaction disappears and the curve tends to be stable.
Observing the above changes, combined with the abnormal reaction curve of other reagents, after discussion with the engineer, we felt that the problem should still appear in the syringe problem, because the OD value after the reaction was abnormal from the beginning of the reaction, the stability of the reaction system was abnormal, if it was because of the problem of the long life of the light source, the secondary wavelength should not react, and the previous optical path calibration and the use time of the bulb were eliminated during the use period.