Hi everyone,
I used Liaison instrument (by Diasorin) for measuring Parathyroid hormone (PTH) in serum samples. The principle is chemiluminescense immunoassay. However, the instrument is having a problem and no longer working. I found another instrument, named DXI 800 (by Beckman), that works with the same principle. I am planning to use the other instrument for measuring PTH in the rest of my samples. Can I find a way to ensure that both machines are going to give me similar results? I asked some technicians in the lab and they told me that I may plot a graph based on results got from few samples that are measured in both machines. Therefore, I can correct results of the rest of samples as if they were tested by one machine. Any ideas how to plot such graph? and how to use it for the correction?
Thank you.
Regards,
Manar
Hi there,
All you need is to perform the calibration of the apparatus from a PTH standard solution (trace the graphics light intensity=f(PTH), it should be linear or at least you may define the range of PTH for which the measured intensity varies linearly and then work within the corresponding range of light intensity). If you want to compare the results obtained from the two apparatus, you should use the same samples and run PTH calibration with the 2 devices. And for each sample (in the linear portion of the calibration curve), plot data device1=f(data device 2) (or the inverse), it should be linear. From this graph, starting from one data measured with device1, you will be able to calculate the data you would obtain with device2. And it also works the other way around.
Every chemiluminescense assay you ran on the old machine should of had a standard dilution curve on the plate with your samples. Run a few standard dilution curves on your new machine. You can then compare the linearity of your standards on the two machines and determine how the signal are correlated (i.e. linear, exponential, etc). You can then correct your old data using the correlation that was calculated.
Plotting of graph is applicable for individual instrument. Better method is check precision & IQC of instrument. If both are within permissible range, you need not spend extra cost on re-run.
the alignment of immunological results from different technologies and different immunoassy methodology is a unresolved problem. The critical points are not only the analyzers but, particularly in PTH mesurement, the antigen-antibody system employd. For these reasons the contemporary use of different analyser is hazardous. I suggest you to choose only one of your analyzer
Hello, I totally agree with A L Gioia.
You were asking about a graph.. are you using an external quality control for each? in addition to the internal? I would say that you use the Acceptable Range Limits for PTH (See Ricos 2014/2015) while you are using the same Chemiluminescence principle have you the same ranges anyhow for both? It can be like the repeatability admitted principle: the difference of the runs should be less than 2.8
Or you can build a graph after at least 30 runs on both (same conditions) instruments, using different values (distribution) and than calculate your own TE and CV.
Machine collection of results in genetic material in a liquid. Immune response material found in chemical spectral stimulation. Next instrument after previous instrument not working. Immune response material to be found in amounts in next instrument. Immune response material PTH. Each machine has different outcomes relevant to the research and results of each are useful. Samples found previously are to refer to in researching the next samples and similar variables can found with the next samples in finding results.
Kind Regards
Stephen Smith
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