To ensure that work is performed safely and at a high level of quality, a medical laboratory must be of the highest possible calibre. By establishing a comprehensive quality control system that enables the monitoring and control of all phases of a process, we can provide high-quality laboratory services. A system must be established that is in line with our capacities and that can detect clinically significant errors. To verify whether the envisaged level of quality has been achieved, quality control processes are introduced and managed, whereby clear objectives must be set. One of the recommendations for setting objectives is the selection of suitable internal quality control rules based on selecting the appropriate control material, setting target values and acceptance intervals, selecting an implementation timeframe, using suitable statistical models and intervention techniques for quality control deviations.
The purpose of the master's thesis was to compare a variety of analytical criteria for the acceptability of internal quality control results in immunochemical methods for tumour markers CYFRA21-1, CA72–4, AFP, TESTO and fßHCG. We aimed to determine whether the control material used for the internal quality control of the manufacturer's average values differed from our values, and whether the number of rejected internal quality control results was higher when applying our limits for acceptable results. The data collected was statistically processed using the Acusera 24-7 program. We compared the results of the manufacturer’s average values and limits with the manufacturer’s average values and our limits, our average values and the manufacturer’s limits, our average values and limits, our average values, limits and rules, and the cumulative average values and limits, and assessed the distribution of the control results. By comparing the results using a single rule (13s) with the results where we used several additional rules simultaneously, we assessed the number of rejected control results.
We found that the manufacturer's average values differed only slightly from our own average values, but the differences were statistically significant and the number of rejected internal quality control results was higher when applying our own limits. The manufacturer's limits were set wider. Our limits are obtained within the laboratory, are defined for each individual concentration level and show the actual effectiveness of the method. Applying additional quality control rules increased the data rejection rate when using the manufacturer's values.
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