In our ELISA Laboratory we have been using two Advia Centaur XPs for about a year. On both devices internal controls of low level of HBeAg with various lot numbers have improper Standard Deviations ( especially +2SD, +3 SD) through more than a six months period. My Lab Staff had to try several washes, use different lots of internal controls and repeat lots of tests. The local firm couldn't solve the problem and ask help from SIEMENS. We are still repeating our low level internal controls of HBeAg and it causes us spending plenty of time and sending the results later to the patients.
It is strange that it happens with commercial controls, in general with the diagnosis of Hepatitis B and with all the serological markers the results are reliable. My recommendation is this: If you have human controls sera that have all aspects of quality control covered (high titles and titles of patients without infection) use them for each plate individually, for example you can use 10 controls of high titles, perform a pool.The reading of a pool of sera prepared with equal quantity of each of the samples, must reproduce the algebraic average of the 10 previous determinations. With sera with low titers you can follow the same protocol and estimate cutoff with 3 standard deviations so as not to slow the delivery of results to patients. But remember each plate is unique and you could not use the cutoff for the patients you use on a second plate. What I can think of that could be happening with lots of commercial standards is the formation of antibody aggregates, a common thing in stored samples, should not be passed on samples of commercial house references. There may be problems with those particular lots.
Thanks for your kind and detailed answer.
I'll try the suggestion immediately.
Today, finally, local firm installed an updated software. I am looking forward to see how it will work.
help please..
anybody using quantitative ELISA for procalcitonin..kindly explain the last step , how to measure .... ??? by graph plot method ....or we have to use spectrophotometer..
how is interpretation of ELISA done.
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