Automatic biochemical analyzer in the measurement of routine blood items, is based on the colorimetric method, the main principle is the use of spectroscopic technology in the absorption of different atoms and the measurement of different, then for the realization of the function of the ISE module, there are two methods, one is colorimetric method, the second is the indirect method. Colorimetric method because of its measurement precision, accuracy, etc. and the required difference is too large, this method in the early medical laboratory examination in the use, is already belong to the elimination of the use of. Indirect method, the principle of its method and the existence of other instruments on the market used in the direct method is similar, but the vulnerability of the ACA due to the internal blockage of the instrument in order to prevent the instrument, the requirements of the sample is extremely stringent, need to be routinely separated and then by the dilution of the sample can be measured only after the general biochemical ISE module on the sample dilution times and most of them are in the 30-fold times or so, in such a large number of dilution times, on the pipeline is indeed beneficial, but from the perspective of statistical processing, such a measurement is not a good thing. However, from the point of view of statistical processing of data, such a measurement will amplify the error in the same proportion, then the results measured in this way, the accuracy and precision can not meet the requirements.
Additionally, the ACA indirect method used with other instruments currently used in the direct method of the differences between the test industry, citing an authoritative book "Clinical Biochemistry Tests," a book on this description: indirect potentiometric method: samples and standards to be used to specify the ionic strength and pH of the diluent dilution solution for the quantitative dilution, and then measured, the samples and standards of this time, the pH and the ionic strength of the standard solution converge, the measured ionic activity is equal to the ion concentration, indirectly, the ionic activity is equal to the ion concentration. At this time, the pH and ionic strength of the sample and the standard solution tend to be the same, and the measured ionic activity is equal to the ionic concentration. In the serum samples of hyperlipidemia or hyperproteinemia, due to the obvious reduction of water per unit volume of serum, if the quantitative sample is diluted and then measured by the indirect method, it will be pseudo-low blood sodium (or potassium), but the direct method can truly reflect the activity of ions in the serum, and it is reported that: the direct method is about 2~4% higher than the indirect method.
Through the understanding of the ACA, also found that the ACA is not enough to liberate the user's degree, think of mankind since embarking on the era of electronic and electrical appliances, auxiliary electronic products, one of the purposes is to liberate the person's time, and the ACA instrument, because of the huge and complex system, in the detection of the operation of the pre-warming, calibration, module testing, water testing, system reagent testing, and so on, many tedious work to be prepared, which is the norm! However, if the instrument malfunctions again, the workload is bound to increase dramatically. Despite the fully automated work of the instrument, but it is not conducive to the smooth progress of the work of the Laboratory, a large tertiary hospital, for example, the daily patient specimens more than hundreds, if only in the ACA spend as much time, the work carried out will make the efficiency of the greatly reduced.
From the cost side, imported equipment because of the monopoly of technology, there is no strong competitors in the domestic market, there is a certain degree of pricing power, there is a suspicion of market monopoly, the price of less than 100,000, more than hundreds of thousands, and for the ACA instrument with ISE module is in the same basis of the expensive out of about 5 to 80,000, and most of them can only detect the three indexes of K, Na, Cl, while the same The same product, the separation of different items single test, the domestic brand price is much lower, such as the domestic brand Myriad. In the reagent consumption, because most of the ACA is a complete set of supporting reagents, so for the determination of electrolytes, the corresponding cost will rise, for small and medium-sized hospitals, for a variety of reasons, can only be done for the treatment of common diseases, may be really needed only for the electrolyte test report, so that for the determination of a few items and the use of the ACA, the hospital, the utilization of the equipment is not high, resulting in a certain waste of resources.
The difference between the results of the indirect method and the direct method used by the automatic biochemical analyzer to measure electrolytes can be explained by the concept of error generation. First of all, a few concepts, first, the true value: the objective existence of the true value; second, the error: the measurement results and the difference between the true value of the measured. Indirect and direct methods of measurement results have error, but are fundamentally different. There are two causes of error, called systematic error and chance error. For the indirect method and direct method, because the measurement, calculation, results and other steps are completed by the instrument, the chance error can be approximated as the same, but the systematic error can not be ignored. Indirect method due to the limitations of the measurement method, so its systematic error is greater than the direct method, as used in the early clinical examination of the flame method, because of its own method of limitation, caused by the systematic error is larger, the systematic error is unavoidable, so the final result of the final results in the special serum will be pseudo hyponatremia (or potassium) appear.